This is only a preview of the August 2020 issue of Silicon Chip. You can view 38 of the 112 pages in the full issue, including the advertisments. For full access, purchase the issue for $10.00 or subscribe for access to the latest issues. Items relevant to "USB SuperCodec":
Items relevant to "A homemade Switchmode 78XX replacement":
Items relevant to "1MHz-6GHz Arduino-based Digital RF Power Meter":
Items relevant to "Velco 1937 'kit' radio restoration":
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Contents
Vol.33, No.8 August 2020
SILICON
CHIP
www.siliconchip.com.au
Features & Reviews
10 Measuring distance & motion with lidar and SODAR
While radar has been a staple for use in detecting stationary or moving objects
over large distances, sometimes precise measurements need to be made over
much smaller ranges. This is where light (lidar) and sound (SODAR) are much
more useful – by Dr David Maddison
31 Microchip’s new Hello FPGA kit
The Hello FPGA (Field Programmable Gate Array) is an evaluation kit from
Microchip intended to be a gentle introduction to FPGAs. It costs approximately
$250 and includes a 480 x 320 LCD display (similar to the one in our Micromite
BackPack V3), colour camera, 8GB of RAM and more – by Tim Blythman
Lidar can be used to make detailed
3D maps or track moving objects,
while SODAR is mainly used to
remotely monitor the movement of
water or air – Page 10
Constructional Projects
24 SuperCodec: the ultimate in computer sound cards
With performance so good our Audio Precision test gear has difficulty measuring
it, we believe the USB SuperCodec is better than nearly everything on the
market. If you’re serious about your computer audio, you’ll want to build this one!
- by Phil Prosser
38 A homemade Switchmode 78XX replacement
Here’s an efficient drop-in replacement to the well-used 78XX series of regulators
that you can easily build yourself for a variety of voltages – by Tim Blythman
This USB SuperCodec
is a must-have multi-function
audio device, with high-fidelity audio
recording and playback – Page 24
66 1MHz-6GHz Arduino-based Digital RF Power Meter
This RF power meter uses an Arduino Nano and measures from 1MHz-6GHz at
power levels up to 3mW (5dBm), and its range can be easily extended by using
low-cost fixed attentuators – by Jim Rowe
88 The Colour Maximite 2 – part two
The final part of this series covers assembly, setup and writing your own BASIC
programs with this miniature computer – by Geoff Graham and Peter Mather
Your Favourite Columns
46 Serviceman’s Log
Fixing heaters – it’s a gas – by Dave Thompson
These DIY switchmode regulators
can replace 78XX linear regulators
with better efficiency (no heatsink
required!), and can be built for 3.3V
all the way to 24V – Page 38
61 Circuit Notebook
(1)
(2)
(3)
(4)
(5)
Four USB power supplies from a laptop charger
Preamplifier power supply runs from 5V DC
Modifying the Ultra-LD Mk.2 to drive a hearing loop
Altitude readout for the Boat Computer
Heelometer for boats
83 Vintage Radio
Velco 1937 ‘kit’ radio restoration – by Ken Kranz
98 Vintage Workbench
Tektronix T130 LC Meter, Part 3 – by Alan Hampel
Everything Else
2 Editorial Viewpoint
4 Mailbag – Your Feedback
65 Product Showcase
siliconchip.com.au
87 SILICON CHIP ONLINE SHOP
106 Ask SILICON CHIP
111 Market Centre
112
Notes
and Errata
Australia’s
electronics
magazine
112 Advertising Index
A Wideband RF Power Meter has
never been simpler to build. It goes
up to 6GHz, and is powered by an
Arduino Nano – Page 66
August 2020 1
www.facebook.com/siliconchipmagazine
SILICON
SILIC
CHIP
www.siliconchip.com.au
Publisher/Editor
Nicholas Vinen
Technical Editor
John Clarke, B.E.(Elec.)
Technical Staff
Jim Rowe, B.A., B.Sc
Bao Smith, B.Sc
Tim Blythman, B.E., B.Sc
Technical Contributor
Duraid Madina, B.Sc, M.Sc, PhD
Art Director & Production Manager
Ross Tester
Reader Services
Ann Morris
Advertising Enquiries
Glyn Smith
Phone (02) 9939 3295
Mobile 0431 792 293
glyn<at>siliconchip.com.au
Regular Contributors
Dave Thompson
David Maddison B.App.Sc. (Hons 1),
PhD, Grad.Dip.Entr.Innov.
Geoff Graham
Associate Professor Graham Parslow
Ian Batty
Cartoonist
Brendan Akhurst
Founding Editor (retired)
Leo Simpson, B.Bus., FAICD
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Editorial Viewpoint
Businesses need to handle
‘black swan’ events better
Some businesses have clearly handled the COVID-19
crisis better than others. In some cases, they continue
to operate as usual; you would never know that their
workforce has been relocated and their internal operations disrupted.
Others have significantly reduced their quality of service since early this year, and are obviously struggling to adjust to the current
situation. I think that those who have reacted by cancelling (or ignoring) contracts, and have cut back on their activities, are making a long-term mistake.
There is that saying that “every dark cloud has a silver lining”, and perhaps the
silver lining of the current situation is the fact that it’s forcing us to re-evaluate
what is really important and perhaps focus a bit more on our long-term goals.
Sure, times are tough, but life has to go on, and businesses need to continue to operate. Clearly, many ‘bricks and mortar’ retail operations have suffered
badly (with some exceptions, like supermarkets). But for the most part, at least
in Australia, mail-order businesses are doing very well, and many service-based
companies have remained open.
I do feel very sorry for those businesses which were forced to close by government edict and many will probably never re-open; eg, restaurants, bars, pubs,
clubs etc. I think the situation could have been handled in such a way to avoid
much of that pain and suffering (but that’s a discussion for another day).
Nobody knows how long this situation will last; it could be years. Life can’t
just stop in the meantime. We have to adapt and find ways to keep the economy running, and continue to supply the goods and services that people want
and need. We certainly haven’t let COVID-19 interfere with SILICON CHIP (apart
from some mailing disruptions, which are unfortunately out of our control).
Over the last few months, I have dealt with several organisations that have
seemingly seen increased demand for their products and services. While it’s understandable that they are busy, the lack of communication and resulting poor
service are not justified.
Lots of people are out of work, so if your business is booming and you can’t
cope with the demand, why not hire some extra people? With all that extra
money coming in, plus government stimulus support, surely they can afford to
hire new employees. And I would imagine there are plenty of people looking for
work at the moment. (On a related topic, we are hiring; see the ad on page 37).
Many companies are now refusing even to answer the phone and take weeks
to answer e-mails (if they ever do). That is not the way to conduct business. We
are still answering the phone and replying to e-mails as best we can, although
our office occasionally closes a bit earlier than usual due to reduced staff presence. But at least you can get a hold of us.
Even if you have many employees working from home, it is not hard to forward e-mails and redirect phone calls. So I think that those companies which
have closed their phone lines are really just using the crisis as an excuse to avoid
dealing with customers (except for new sales, of course).
In fact, I get the impression that many businesses and individuals are exploiting the crisis by crying poor and trying to shirk their responsibility when really,
they are not doing that badly. Some are also taking advantage of the situation
to reduce after-sales support and prioritise on making sales, which is not likely
to lead to happy customers.
So let’s keep the economy going and find ways to work around the voluntary or
enforced isolation we are currently experiencing. It may go on for a while yet. We
can keep the country and the economy going, despite the unfortunate situation.
Nicholas Vinen
24-26 Lilian Fowler Pl, Marrickville 2204
2 Silicon Chip
Australia’s electronics magazine
siliconchip.com.au
MAILBAG
your feedback
Letters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that
Silicon Chip Publications Pty Ltd may edit and has the right to reproduce in electronic form and communicate these letters. This also applies to
submissions to “Ask Silicon Chip”, “Circuit Notebook” and “Serviceman”.
New Zealand delivery delay
I’m happy with the result and they and the silicone recommended in the
work well. My old A/V amp/receiver article hardened in a day. For a VicThanks for your explanation of why
my June 2020 issue was so late. Ironi- has a subwoofer output, so I am con- torian winter (don’t forget Tassie and
cally, it arrived today, just after I read sidering adding a single subwoofer NZ), you will probably need more
than a week.
your e-mail (about a month late). I eventually.
Also, the bricks need to be perfectI used the Altronics drivers. I debatthink you people must have waved
RAYMING TECHNOLOGY
ed whether to recess the drivers into ly dry; it will not adhere well to old,
your magic wand.
mossy bricks. Once the silicone is dry,
the cabinet
as IPCB
thought
that they were
I would like to pass on
my thanks
PCB
Manufacturing
and
Assembly
Services
it is almost impossible to remove and
susceptible
to
damage
if
mounted
on
and appreciation to you and
your
staff
Fuyong Bao'an Shenzhen China
therefore would require destruction to
for producing such an excellent and the outside.
0086-0755-27348087
Some comments against mounting replace an internally mounted speaker
informative technical publication.
I
Sales<at>raypcb.com
purchased my first issue of
Electronics them inside were that the acoustics should it fail.
Gaps can be the result of irregular
Australia in 1971, and built
the Delta- would be compromised, but surely
www.raypcb.com
het receiver, which is still operation- only an acoustic pedant would notice concrete, so spend some time selecting
your bricks and ensuring that the sural. I stayed with EA, purchasing each the difference.
Anyway, if they were mounted in- face is smooth and true. It helps to rub
monthly edition until Jamieson Rowe
side, the ports would have to be per- two blocks together to remove small
moved to Silicon Chip. I followed.
I always look forward to receiving fect, and mine were not. so I mount- chunks or just run an angle grinder
my monthly dose of Silicon Chip. Well ed them outside. I used the silicone lightly over it. Also, check that the
sealant, as suggested, but I found that timber is not warped and only select
done to all of you.
there is small side-slip still possible the best timber.
Ray Clarkson,
You can mount the Altronics drivwith pressure. It might harden with
Dunedin, New Zealand.
time, however; maybe Liquid Nails ers inside the larger concrete block,
and it will help the bass end without
would be better.
Feedback on Concreto speakers
having to buy the more expensive subAlso, I may have overdone the
I endeavour to keep an interest in
woofer drivers.
things electronic, mainly via your mag- amount required for adhesion, as there
Use the same dimensions for the
azine. I have been an Amateur Radio is a small gap between the timber and
port as shown in the sub diagram, and
licence holder for some 40+ years, and brick in one of the “cabinets”.
reduce the driver mounting hole diRaymond Reaburn,
I am a musician (still playing). So I was
ameter to suit. Our original prototype
Mont Albert North, Vic.
interested enough in your Besser brick
used this configuration, and it worked
bookshelf speaker project (June 2020; Allan Linton-Smith responds: Thanks
siliconchip.com.au/Article/14463) to for your comments! I built the pro- well, but our final setup with the small
totype speakers during hot weather, and large bricks worked better.
have a go.
RAYMING TECHNOLOGY
Fuyong Bao'an ,Shenzhen, China Tel: 0086-0755-27348087
email: sales<at>raypcb.com web: www.raypcb.com
PCB Manufacturing and PCB Assembly Services
4 Silicon Chip
Australia’s electronics magazine
siliconchip.com.au
Use neutral-cure silicone with concrete
I have enjoyed many projects provided and read all articles with interest. I am one of the silent majority.
The Concreto Speaker System,
June 2020 edition, is impressive for
its simplicity and reported good performance. It is on the list of projects I
want to undertake.
In the assembly instructions, you
mention Parfix Kitchen & Bathroom
silicone sealant was used. This is an
acetic cure silicone suitable for glass,
tile and stainless steel surfaces. The
blocks used as the base structure of
the speakers are concrete and so are
alkaline in nature.
Acetic cure silicone is unsuitable for
concrete as the acetic acid produced in
the curing process will react with the
concrete and degrade the “adhesion
surface” interface, causing the sealant
to release from the blocks in time. It
often takes months to manifest itself
as a problem.
For adhesion to concrete surfaces, it is best to use one of the many
neutral-cure silicones on the market,
nominally called “concrete” or “roofing” silicone.
Charles Camenzuli,
Wentworthville, NSW.
Concern over chemical spill handling
I have some concern in your article
on anodising aluminium (May 2020;
siliconchip.com.au/Article/14423).
You are using suggesting the use of
sodium bicarbonate to neutralise sodium hydroxide spills. Both of these
are basic (alkaline), not acidic.
Sodium hydroxide (NaOH) is extremely dangerous when not carefully
used. Basic (alkaline) burns usually are
much more severe (rapid-acting) than
acidic burns. Get it in your eye, and
you will be permanently blind. With
acid, you have a small chance if you
are quick enough to wash it out.
NaOH has a pH of 14 while sodium
bicarbonate (NaHCO3) is a weak base
with a pH of 8.4. On the pH side of
things, you are better off using water
with a pH near 7.0 to weaken NaOH.
Ideally, a weak acid should be used to
neutralise sodium hydroxide.
For example, citric acid (lemon
juice), acetic acid (vinegar) or dilute
hydrochloric acid could be used. Boric acid or ammonium chloride are
sometimes used.
For non-industrial situations, vinegar or lemon juice are the easiest
6 Silicon Chip
to obtain and safe to use. Remember
that mixing acids and bases will create an exothermic reaction with likely
splattering consequences, the degree
of which is determined by the way,
quantity and rate of mixing. Be sure
to wear the appropriate protective
equipment.
The above information is based on
safety processes learned while working for a major chemical company,
starting as an instrument technician
and then as an engineer.
Wolf-Dieter Kuenne,
Bayswater, Vic.
Response: you are right that NaHCO3
would be of no use in the case of a
NaOH spill. The bicarbonate of soda
was only intended to be used to clean
up any spilled acid (specifically, the
sulfuric acid), and that is the only purpose that we mentioned for it.
The reason why we did not suggest
keeping a weak acid on hand is that
NaOH is only used in that process in
a very weak solution (one spoonful in
a tub of water). It might still be possible to create a hazard by accidentally dropping a large number of NaOH
granules into the water while making
that solution. In that case, you are right
that having a jug of vinegar on hand
would be a good idea.
Preamp for acoustic guitar
I would like to suggest that you
design an acoustic guitar preamp in
pedal format. Commercially available
guitar preamps are expensive for what
they are (well, the good ones anyway).
I don’t think the circuits are all that
complex. LR Baggs makes some popular ones.
The ideal list of features would include a DI (direct injection) output,
six-band graphic equaliser, phase
switch, volume and gain controls. It
could also include a notch filter, if
there is room. (J. C., Point Cook, Vic)
Comment: thanks for the suggestion;
it is a good one.
Thumbs up for Colour Maximite 2
Thanks for producing another Silicon Chip with great content under the
somewhat difficult global conditions
we are currently experiencing. I am
pleased that I can keep up by having a
combined print & online subscription,
because the June printed issue has yet
to arrive in New Zealand.
I perused my online version of Silicon Chip earlier today and am pleased
Australia’s electronics magazine
to see Geoff Graham’s and Peter
Mather’s Colour Maximite 2 included.
I look forward to more on it in the
future. I am fortunate to have a singleboard version of the CMM2 sitting on
my bench, and am awed by its performance. It is a huge step up from the
original Maximite, so I must congratulate the originators of this design.
The future for the CMM2 and
Micromite is now really only limited
by our imaginations.
Warwick Guild,
Dunedin, New Zealand.
Response: the CMM2 is a potent little computer, and pleasingly easy to
build. Sorry about the delays for New
Zealand subscribers; it took around
six weeks for the June issues to arrive.
Unfortunately, there isn’t much we can
do about it. We hope the postal system
will recover soon.
Fire and inversion layers affect radio
signals
I was prompted to write in by the letter about radio communications during bushfire emergencies in the June
2020 issue (pages 10 & 11). I read a Scientific American article in late 1968/
early 1969 with comments from a fire
chief (from memory, in New York) on
what he experienced at the scene of a
very intense fire.
He said that the department had
introduced new UHF portables and
were using them at this fire when he
attempted to communicate with one
of his men that he could see through
the shimmering air.
There was no response from his radio, even though he could see his man
using his portable. He, the fire chief,
had no reception of those signals obviously being transmitted, so he assumed his radio was faulty.
At the end of the day, he had a technician check both radios, and they
worked OK, both one-to-one and as
part of the whole system.
Investigations were ordered, and
after extensive tests, it was assumed
that the intense fire had created a
vertical air shear, like a mirror wall,
that deflected the radio signals at the
shear between the two radios. The
lower frequency (longer wavelength)
of their earlier low-band VHF was assessed side-by-side through the tests,
and VHF worked OK.
We know that horizontal layering
(inversion layer), temperature and air
density go hand-in-hand.
siliconchip.com.au
A further anecdote, if I may, is that
long hop HiBand VHF over about
100km between Barrow Island and
Onslow on the mainland of WA was
problematic when the sea was calm,
and there was no wind.
When the sea was rough, we assumed that scatter was occurring to
give a path between the inversion layer and the sea surface through ducting
– a perfect mirror on top and bottom
causing the radio wavefront to move
past or fall short (skip).
A similar effect was experienced
when I set up a HiBand VHF link between a high building in Fremantle
and an oil rig being serviced in Gage
Roads. When the rig floated higher on
the tide, the antenna set on the top of
the derrick would move above the low
inversion layer, and comms failed until the tide lowered or after sundown
when we assumed the inversion layer
disappeared.
My point here is that this effect
must be considered for any proposed
upgrade in fire comms. It also might
explain why short-wavelength mobile
phones and the current UHF radios
issued to firefighters failed at times
during the last Black Summer events.
Some HF manufacturers might be
approached to create a small HF portable, particularly as both Australian
manufacturers of HF have created almost FM-like clarity using HF.
I also recall setting up some AM-HF
at around 2MHz for the CFA at Werribee while I was at the RAAF radio
school in 1967 (in my spare time of
course) and that seemed to work well,
despite the cumbersome equipment.
Robert Sherwood,
Perth, WA.
Properly aligning AM radio dial low end
In Dr Hugo Holden’s article on his
H-Field Transanalyser, he gives some
instructions on how to use it to align an
AM radio (June 2020, p90; siliconchip.
com.au/Article/14471). Hugo observes
that the low-end antenna alignment
can be done by sliding a ferrite rod’s
coil one way or the other.
As he points out, many cannot be
so adjusted. When it was possible, I
have not found a case where this adjustment was sufficient for optimal
alignment. This is a method that lots
of folks repeat, without having challenged its usefulness.
The preferred method is to adjust
the oscillator coil for maximum output
siliconchip.com.au
at 600kHz, while ‘rocking’ the gang. In
effect, the adjustable oscillator circuit
is being brought into alignment with
the unadjustable/limited-adjustable
antenna circuit. I have detailed this
method in my articles.
Also, the accepted top-end alignment consists of (i) setting the oscillator trimmer for 1600kHz with the gang
fully open, (ii) re-checking the bottom
end, then (iii) setting the signal generator to 1400kHz, tuning to that signal,
and adjusting the antenna trimmer for
max output.
There are sound and accepted theoretical and practical reasons for the
above procedures, in that they consistently deliver the best performance
figures from broadcast-band radios of
all kinds.
Ian Batty,
Rosebud, Vic.
Clarification of H-fields
Based on some of the feedback I’ve
received on my H-Field Transanalyser
design (May & June 2020; siliconchip.
com.au/Series/344), I realised that I
could have done a better job of explaining some aspects of the design,
and how the unit got its name.
Generally, a transistor radio with
a ferrite rod responds to the magnetic component of the electromagnetic
wave, or the H-field as it is known. The
E-field is the electric component of the
field, not received to any great extent
unless the radio has an external wire
antenna. So the idea of the Transanalyser was to produce a controlled and
known near H-field to apply to the radio’s ferrite rod.
This field is produced by the current
in the one-turn loop. This current is
set by the open circuit source voltage
from the attenuator output applied
across a 150W resistance, 75W being
the generator output impedance and
the other 75W being a series resistor.
The loop is on the “ground” side, as
capacitively coupled voltages to the
rod’s coils are to be avoided.
The point is that the loop which
generates the H-field has a controlled
current. The loop voltage is not important. Therefore, the controlled H-field
at the radio’s ferrite rod is reduced by
the attenuator to very low values, analogous to the H-field from a far off, or
weak, radio station. And this amount
of field is the same for each radio tested, as the loop passes directly around
the radio’s ferrite rod.
Australia’s electronics magazine
August 2020 7
One problem with external loops some distance away
from the radio is that the near-field H-radiation depends
on the spacing of the loop from the radio and the rotational axis of the loop, with respect to the radio’s rod, and the
other factors I noted in the article. My direct loop avoids
that, and helps with comparisons and uniformity between
testing different radios.
But of course, seeing a wire loop around the ferrite
rod being fed by an RF source, one is tempted to think of
transformers and the efficiency of the coupling. But the
voltage on the one turn loop and the voltages on the tuned
circuit or other secondary windings on the radio’s ferrite
rod (due to turns ratios etc) will vary by radio.
This does not matter, because it is the radio’s overall
response to the H-field applied to the ferrite rod that is
important – just as it is in use, when the radio is responding to the H-far-field of the electromagnetic wave from a
radio station.
Also, the noise performance of the radio is better assessed on a listening test. As the audible modulation on
the carrier of the received H-field drops, you can hear
into the noise floor, which is exactly what happens with
weak and far off radio stations as you get further away
from them. This is the main reason why any RF test generator, however it is coupled to the radio, requires a decent attenuator.
One other thing I could have mentioned was that if a
thin wire is used to make the loop, the wire pair can be
twisted together for a considerable length (30cm or more).
Then the radio’s PCB can be flipped around for repairs and
adjustments without being hindered by the presence of
the loop. Teflon-covered hookup wire or enamelled copper wire is fine.
When finished, the small loop near the rod can just be
cut to remove it, and the wire discarded.
Dr Hugo Holden,
Minyama, Qld.
Hazards swapping Active & Neutral
I was delighted to read your article on assembling “Concreto” speaker enclosures. I still use my 3-foot Humes
concrete pipe with an 8-inch Wharfedale speaker on top,
standing on two timber slats to provide an air vent, assembled around 1960.
In the same issue (June 2020), a correspondent asked
why it was dangerous to swap Active and Neutral wires
in domestic power points, and I would like to comment.
I spent many years living in rental accommodation, in
old buildings that had (presumably) been wired before a
standard existed for the orientation of Active and Neutral pins.
One day, a friend visited and offered to prepare a meal.
She brought her electric frypan, one which she had used
for years. We discovered that it worked with some of my
power points but not with others. I checked and found that
Neutral and Earth had been swapped inside the frying pan.
Since Earth and Neutral leads are joined at the switchboard, the appliance worked correctly with no indication
to the user that anything was wrong -- provided it was
plugged into a correctly-wired powerpoint. When the incoming Active and Neutral were reversed, the element was
connected between Neutral and Earth, while the body of
the pan was connected directly to 240V!
8 Silicon Chip
I have come across the same behaviour with an extension cord in which Neutral and Earth were inadvertently
swapped at one end. Appliances worked (with and without
the extension cord) when plugged into a correctly worked
socket, but failed – and had a live outer casing – when
plugged into outlets that had Active and Neutral reversed.
If ever an appliance works with some power points and
not others, switch off and beware!
Congratulations on an excellent magazine.
Mike Emery,
Fern Tree, Tas.
Flywheels are not to be trifled with
I was interested to read John Walker’s account of flywheel storage in your June 2020 issue (Mailbag, p4). It
brought to mind a similar situation I encountered many
years ago.
As a young graduate student, I used to spend my summers working at Culham Laboratory in Oxfordshire, on the
fringes of nuclear fusion research. During my first month,
I joined a tour to see JET (the Joint European Torus) and
some of its ancillary research tools.
One that stuck in my mind was an enormous flywheel
weighing many tons. I believe it was spun up over several hours, then connected to a generator that would bring
it to a halt in a matter of seconds, thereby delivering a
huge pulse of current to one of the particle accelerators.
The flywheel was mounted in a shallow pit with its axle
vertical, and one of the party asked why. Surely the bearings would be easier to maintain if the axle was horizontal?
The tour guide agreed, but pointed out that the designer had considered a range of risks, one of which was the
bearings failing and the flywheel tearing itself loose when
spun up to full speed.
If this had happened, some back-of-the-envelope calculations had shown that the flywheel would break its way
out of the building and roll as far as London, destroying
everything in its path before it came to a halt! Hence the
pit, which would at least contain the damage in the case
of a failure.
I greatly enjoy your magazine and look forward to reading many more issues.
Andrew Colin,
Brisbane, Qld.
Adding altitude display to Touchscreen Boat Computer
The speedo in my elderly LandCruiser went berserk,
and the pointer broke off. I solved this problem by building the April 2016 Touchscreen Boat Computer with GPS
(siliconchip.com.au/Article/9887) and installing it in a bespoke (3D-printed) ABS case above the dashboard. With
the software upgrade published soon after, it has served
well for nearly four years.
One addition I would have liked would be to show the
altitude – not a great need for this as a Boat Computer,
but inspired by your Car Altimeter in the May 2020 issue
(siliconchip.com.au/Article/14431).
I wondered if the boat computer software could be
tweaked to extract the current altitude from either the
GGA or GSN lines or the NMEA messages.
It could then be shown on the screen along with the
latitude and longitude, assuming a spot could be found
for it.
Australia’s electronics magazine
siliconchip.com.au
One change I did make that could be of interest to the
current project; I have a transistor shorting across the
trimpot, which adjusts the screen brightness for maximum daytime driving.
When the headlights are turned on, a wire from that relay activates to turn the transistor off, so the screen brightness is at the trimpot setting for night driving. Maybe this
is only possible on older cars where you can access this
sort of wiring.
Ron Walker,
King Creek, NSW.
Response: As luck would have it, we’ve actually finished
the modifications for the Altimeter, and it can be viewed
on page 64 of this issue.
Combining block control with DCC
UG85-W LoRaWAN Gateway (Wi-Fi)
The Ursalink UG85 is an intelligent, performant
and configurable LoRaWAN indoor gateway for
smart IoT applications. The UG85 is based on the
Semtech SX1301 chipset, allowing to operate on
multiple channels at the same time.
SKU: ULC-014
Price: $560.50 ea + GST
UC11-N1 LoRaWAN Sensor Node
I found your article on an Arduino DCC system interesting (January 2020; siliconchip.com.au/Article/12220).
However, not all model railway enthusiasts want to use
DCC. Many of us are happy to stick with block control,
which for many prototypes is more practical. But there
are DCC features we would like such as constant lighting,
switchable lighting in coaches/trains, on/off loco traction
and switchable sound.
Constant lighting is possible using low-voltage lamps,
LEDs or 12V intermittent pulses plus capacitors, or highfrequency AC. (However, locos are now appearing with
Faulhaber coreless motors which don’t like AC).
It would seem to me to be possible to use an imposed
track DCC signal (once) to switch on/off a latching decoder to achieve most of the above features. That shouldn’t
damage existing motors.
Greg Procter,
Hukerenui, NZ.
Tim responds: I certainly do see the benefits on block control, but do not see it as mutually exclusive with DCC. A
layout set up with block control is well suited to making
the most of conversion to DCC. Most DCC decoders are
‘backwards-compatible’ with analog DC tracks.
The blocks can be configured into ‘power districts’ to
ensure that electrical faults are isolated. The blocks can
also be connected to individual track current sensors to
provide inputs to a signalling system, opening up the possibility of automatic train control.
Current sensing is easier to do in a DCC system as there
is always power present, which is not the case in a basic
analog DC system.
We’ve looked at designing our own DCC decoders, and
while we think it would be interesting to create a ‘hackable’ design which can be customised by the end-user,
there is no way we can compete with existing commercial
decoders on price point or miniaturisation.
Presuming that you do not want to simply install DCC
for motor control, which would give the desired features,
you could consider what was suggested in Mailbag in
March 2018 (p7, “WiFi model railway control is already
available”).
Such a system could sit alongside existing analog DC
hardware. The problem of getting steady power still exists,
and there doesn’t appear to be a broadly accepted standard to work with (another of DCC’s benefits). A miniature
WiFi controller would also be handy for many applications
outside of model railways.
SC
siliconchip.com.au
Helping to put you in Control
The UC11-N1 is a fully integrated,
battery powered LoRaWAN node with
multiple communication interfaces for
connecting to a wide range of external
sensors.
SKU: ULC-015
Price: $258.00 ea + GST
AM100 Ambience Monitoring LoRaWan Sensor
Ursalink AM100 Series consists of multiple smart sensors that
are built specifically for indoor ambient
measurements. It has a clean and modern
design that makes it discrete in indoor
ambience.
SKU: ULC-019
Price: $285.00 ea + GST
ITP14 Universal Process Indicator 0-10 V / 4-20 mA
Easy to mount the ITP14 fits into a standard
22.5 mm borehole for signal lamps and can
be connected to 0-10V or 4-20mA signals.
The measured values are scalable and there
is NPN output for control or alarm function.
SKU: AKI-010
Price: $149.95 ea + GST
TCW122B-RR - Remote relay control across a LAN
Each TCW122B-RR is an Ethernet based I/O
module that has two digital inputs and two
relay outputs. Two units can be paired in
order to seamlessly send digital IO data to
the other paired device.
SKU: TCC-003
Price: $144.70 ea + GST
Slim Multi-Function Timer SPCO MINI-1M
Slim Line, DIN Rail mount, multi-function timer.
SPCO output, dual LEDs indication. Multiple time
range 0.1 s to 100 hours. 12 to 240 VAC/VDC
powered.
SKU: NTR-101
Price: $74.95 ea + GST
Relayduino USB/RS-485 IO Module 8-28VDC
Arduino-compatible controller with eight relay outputs, four optoisolated inputs and three 4 to 20 mA or 0
to 5 VDC analog inputs. USB and RS-485
serial interfaces. Windows, Mac OS X and
Linux compatible. 8~28VDC powered.
SKU: KTA-223
Price: $164.95 ea + GST
For Wholesale prices
Contact Ocean Controls
Ph: (03) 9708 2390
oceancontrols.com.au
Prices are subjected to change without notice.
Australia’s electronics magazine
August 2020 9
Measuring distance & motion
with Lidar & Sodar
Radar has been used for more than a century to detect moving or
stationary objects at great distances. But sometimes you need to make
precise measurements over much smaller distances – mapping a building
or a crime scene, for example. Or you may want to measure wind or
water currents. For these tasks, light and sound are more useful than
radio waves. Hence, the invention of lidar and SODAR.
D
istance and motion can be measured using radio
waves, light or sound. Radar (RAdio Detection And
Ranging) is the most well known of such technologies,
and the use of sound for sonar (SOund Navigation Ranging)
on ships and submarines is also well known.
In this article, we look at the use of light and sound waves
for sensing technologies and how they differ from radar and
sonar.
Experiments with radar started in the late 19th century, but
it wasn’t fully developed until the early 20th century, with
rapid advances occurring between 1935
and 1945. It was used mainly to detect
by Dr David
10
Silicon Chip
ships and later, aircraft at great distances. Sonar developed
over a similar period, and was used both for marine navigation and to detect submarines.
We previously described Airborne Weather Radar in
the April 2015 issue (siliconchip.com.au/Article/8449)
and Broadband Marine Radar in the November 2010 issue
(siliconchip.com.au/Article/343). Plus, we discussed sonar
in the context of bathymetry in June 2019 (siliconchip.com.
au/Article/11664).
More recent developments include SODAR (SOnic Detection And Ranging) and ultrasonic ranging, both of which utilise sound waves,
Maddison
Australia’s electronics magazine
siliconchip.com.au
but they operate quite differently to sonar. You may have
also heard of lidar (LIght Detection And Ranging), which
uses light rather than radio waves.
We’ll also briefly discuss infrasound detection, which is
at the opposite end of the frequency spectrum to ultrasound.
We previously discussed some uses of lidar, for Google
Street View and Apple Look Around mapping, in the SILICON CHIP article on Digital Cartography in the March 2020
issue (siliconchip.com.au/Article/12577). Many autonomous
ground vehicles also carry lidar units to sense their surroundings, and some such vehicles also use pre-scanned 3D maps
for safe navigation.
Radar vs lidar and SODAR
The main differences between radar, lidar, SODAR and
ultrasonic ranging are as follows:
Compared to radar, SODAR and ultrasonic ranging, lidar gives much-improved object detail because of its shorter wavelength (in the hundreds of nanometres). Similarly,
smaller objects can be detected, such as dust particles.
Lidar and SODAR can be used to measure wind strength
and direction at a distance. Lidar senses the motion of aerosol
particles in the air, while SODAR is sensitive to air density
differences. For example, the Windfinder AQ500 (siliconchip.
com.au/link/ab2q) SODAR unit is designed for meteorological measurements.
Ultrasonic ranging is superficially similar to SODAR, in
that ultrasound is used to determine the range in both cases.
But SODAR uses an array of microphones and sound ‘beams’,
while ultrasonic ranging uses a single microphone and beam.
It is often used in older autofocus cameras, and also small
robots, for obstacle detection and avoidance.
Radar gives a much greater detection range than lidar or
SODAR. The laser beams used for lidar are readily absorbed
by atmospheric particles like fog, smoke or dust, whereas
Fig.1: lidar measurements taken as Apollo 15 orbited the
Moon on two different orbits (numbers 15 and 22) in 1971.
The lines indicate elevations and depression relative to a
sphere 1738km from the centre of mass of the Moon.
those hardly affect radar or SODAR.
Radar detection distances are generally limited by lineof-sight considerations. Airborne radar can have a range of
several hundred kilometres, while over-the-horizon radars
(which reflects a beam off the ionosphere) can have a range
of several thousand kilometres.
One example of the latter is Australia’s Jindalee Operational Radar Network (JORN).
Lidar can have a range of tens to hundreds of metres, or
in extreme cases, up to about 4km. SODAR typically operates over a maximum range of about 200-2000m. Ultrasonic
ranging is typically is used at distances between centimetres and a few metres.
Fig.2: a lidar image of a forest. Source: Oregon State University.
siliconchip.com.au
Australia’s electronics magazine
August 2020 11
Fig.3: a lidar-derived flood model for an area in South
Carolina along the Saluda River. Source: USGS.
Note that lidar will work through a glass window, but ultrasonic ranging will not, since sound waves will bounce
off the glass but light waves can pass through. This was a
limitation of early ultrasonic autofocus cameras such as the
SX-70 (described below).
Operating principles
In all cases, the operating principles of radar, lidar and
SODAR are essentially the same. A pulse of radio energy,
light or sound waves is emitted. That pulse is reflected off
an object or objects and the reflected pulse returns to the receiver. The elapsed time between emission and the detection of the reflected pulse is recorded and, in some cases, so
is the frequency difference.
The distance to the object is determined by multiplying
the elapsed time by the speed of light or sound, and dividing
the result by two. This accounts for the fact it has to travel
there and back. For example, if a pulse of radio waves or
light takes 3 microseconds to return to the place of emission, then the range, R = 3µs x 300,000,000m/s ÷ 2 = 450m.
300,000,000m/s is approximately the speed of light.
The object’s velocity can be determined by the Doppler
shift (if measured), and the angle from the transmitter/receiver can also be determined by knowing the direction of
the strongest return.
Lidar usually uses a single beam. It may be fixed, to measure a distance, or scanned in two or three dimensions to establish a 2D or 3D map of an area. SODAR generally uses
multiple beams to develop a 2D or 3D map.
In contrast, ultrasonic ranging typically uses a single beam
Fig.5: a 2D (horizontal) DIAL map showing methane
emissions above a landfill area. Source: Innocenti et al.
(https://doi.org/10.3390/rs9090953)
12
Silicon Chip
Fig.4: a photograph (left) and lidar image (right) revealing
otherwise almost invisible remains from an archeological
site in New England, USA. Source: Kate Johnson, University
of Connecticut.
to establish distance, but it is possible to move the beam to
create a 2D or 3D map of an area.
So why use lidar rather than a camera, as both sense visible light? A single lidar sensor can have a 360° field of view
(360° cameras exist, but are composed of multiple cameras).
But its main advantage is that the distance to each ‘pixel’
in the image is accurately known. Our brains are good at extracting approximate range information from a photo, but it’s
very hard for a computer to do that.
With a lidar image, though, it is clear to the computer exactly where each sensed object is located relative to the lidar
device, as the result is a 3D ‘point cloud’. That’s much easier
to use for tasks like obstacle avoidance. The point cloud can
also be shown as a 2D image and rotated in place; something
you can’t easily do with still images without using multiple
cameras and a lot of image processing.
Uses for lidar
The idea of using a laser to measure distance came about
in 1960, just after the laser was invented. It was then used by
the US National Centre for Atmospheric Research to measure
clouds. It was later used in 1971 by Apollo 15 to make topographic measurements of the Moon (Fig.1) and by Apollo 16
and 17, both in 1972.
Earlier measurements with lidar were relatively simple
distance measurements, or small collections of distance
measurements, because of limited computer storage capabilities. But now, highly-detailed and complex 3D ‘point
clouds’ representing detailed photo-like models of the environment can be produced.
Fig.6: a partial photo and drawing of the Apollo 15 laser
ranging retroreflector. This was the largest reflector left
during the Apollo missions and is still in use.
Australia’s electronics magazine
siliconchip.com.au
Fig.7: the NASA Clementine topographic map of the Moon
from 1994. The colours indicate elevation, as shown on the
scale. This data was gathered from an altitude of ~500m.
Fig.8: lidar observations of Martian clouds on 3rd September
2008 from NASA’s Phoenix Mars Lander. Fall streaks are
suggestive of falling of water snow (not CO2 snow).
Lidar can be used from the air or space, with topography
mapped as the terrain is traversed, or it can be performed
at ground level, either in a fixed location or on a moving
platform. Examples of the latter are Google and Apple cars
making 3D maps of entire cities from a ground perspective.
Airborne or ground-based lidar can be used in forestry
to measure the height of trees, their rate of grown and their
volume (to estimate when to harvest or for fire management
purposes) – see Fig.2 overleaf.
Airborne lidar can also be used to make accurate 3D maps,
for example, to determine where flooding will occur (Fig.3).
Lidar can be used for pollution modelling, by detecting
particles in the air that are approximately the same size as
the wavelength of the light used.
Lidar has several uses in digital mapping and urban planning; these were described in our March 2020 article on
Digital Cartography (siliconchip.com.au/Article/12577).
Coastlines can be accurately mapped with lidar, and with
special lidar that penetrates water calls LADS (Laser Airborne Depth Sounder), the submarine environment can also
be mapped. LADS was described in our June 2019 article
on sonar (siliconchip.com.au/Article/11664).
Lidar is also useful for mobile phone network planning,
so that line of sight locations from proposed towers can be
determined. This is particularly important for 5G because
of poor building and foliage signal penetration.
In mineral exploration and mine management, lidar can
be used for high-accuracy surveys of existing and proposed
mine sites, and also to measure dust and pollutants.
In archeology, lidar can be used to map ruins beneath
jungle canopies, where they would otherwise be invisible,
or to reveal micro-topography in other areas suggestive of
buried remains (see Fig.4).
Lidar can be used in architecture and building restoration to make precise models of buildings, and in the case
of restorations, parts can be scanned and reproduced if
necessary.
It can also be used for geology; for example, to study
changes in topography due to a volcanic eruption or ground
movements such as landslides or avalanches.
stances in the atmosphere such as pollution, or natural
emissions such as from hydrocarbon deposits. The latter
can be used to locate such deposits (see Fig.5).
This technique was developed in the late 1970s by BP
and the National Physical Laboratory in the UK. In DIAL,
laser beams of two specific frequencies are emitted. One
frequency is tuned to a known absorption band of a molecule of interest, and the other is at a slightly different wavelength which is not absorbed by the molecule of interest.
Both beams are backscattered by atmospheric dust etc.
The beam that is tuned to the absorption band will be absorbed more than the other, indicating the amount of gas of
interest and its location. A map can then be drawn showing
the concentration of the gas of interest as a function of range.
This technique can also be used to find trace emissions
of gases from hydrocarbon deposits, thus locating them,
even if they are under the surface.
Differential Absorption Lidar (DIAL)
DIAL is a remote sensing technique and a form of lidar.
It is used to determine the chemical composition of subsiliconchip.com.au
Lunar laser ranging experiments
On several trips to the Moon, laser retroreflectors were
left behind, providing a reflective surface from which a laser could be bounced. This allows the distance from the
Earth to the Moon to be measured accurately.
Reflectors were placed by Apollos 11, 14 and 15 (Fig.6)
and the two Soviet Lunokhod missions. All five arrays are
Human echolocation
Some people with visual impairments have taught themselves
to echolocate similarly to bats, whales and dolphins. They use
natural “passive” environmental echos while others actively produce clicks with their mouth and listen to the echos from those.
Research has shown that in such
people, the brain uses the visual
cortex to process this information,
since it is not being used for its
normal function of eye vision. See
the video titled “Daniel Kish: How
I use sonar to navigate the world”
at https://youtu.be/uH0aihGWB8U
and read about the organisation he
established to promote and teach
this technique, World Access for
the Blind at https://waftb.net
Australia’s electronics magazine
August 2020 13
Fig.9: the RPLIDAR A1 360° laser range scanner.
still being used today to make measurements. To determine
the lunar distance, a laser pulse is fired from Earth and the
round trip time measured. The range is computed, based
on the known speed of light. Measurements can be made
with millimetre-level accuracy.
When a laser is fired from Earth, the beam diameter is
6.5km on the Moon’s surface and on average, about three
photons per laser pulse return to the detector on Earth.
The precise calculation of the distance is not as simple
as it sounds. Many variables have to be taken into account.
These factors include the very slight variations of the
speed of light in different parts of the atmosphere (which
also have to be taken into account for satellite navigation
systems) and the motion of the observing station due to
tides in the Earth’s crust. The “crustal tide” due to the
Moon’s gravitational pull can be as much as 384mm. Relativistic effects and many other small effects also have to
be accounted for.
Some facts established from the measurements are: the
Moon is becoming more distant from Earth at the rate of
3.8cm per year; the Moon has a liquid core; Newton’s
gravitational constant has changed less than 1 part in 100
billion in the last 50 years; and Einstein’s general theory
Fig.10: this shows how the RPLIDAR A1 can scan a room
in and make a 2D map of the area.
of relativity is correct within the accuracy allowed by the
measurements.
There was a plan to install a new reflector on the Moon
(called MoonLIGHT) in July 2020. This was to be placed
by the MX-1E lander being built by Moon Express, but the
mission was cancelled and the fate of this experiment is
unknown. It would have improved the measurement accuracy by about 100 times.
Lunar and Martian lidar
The Moon surface has been mapped from orbit using lidar
(Fig.7), and Martian cloud patterns have been observed by
the Phoenix lander (Fig.8). There are also proposals by the
SETI Institute to use robotic vehicles to map the surfaces of
the Moon and Mars using lidar, to map interior structures
such as possible caves or lava tubes.
Inexpensive hobbyist or consumer lidar
There are several inexpensive lidar devices available that
SILICON CHIP readers may wish to use or experiment with.
One example is the US$150 GARMIN LIDAR-Lite v3HP
(siliconchip.com.au/link/ab2l). This has a range of 5cm to
40m, an accuracy of ±2.5cm, an update rate of more than
Fig.11: a 3D map of the Jenolan Caves (near Sydney)
created with the Zebedee lidar device. Source: CSIRO.
See the video titled “Real science from caves to the
classroom” at https://youtu.be/jt38pF_TJvY
14
Silicon Chip
Australia’s electronics magazine
siliconchip.com.au
Fig.13: the 20-20 Ultralyte 100LR with DBC or “distance
between cars” feature, showing the distance in feet on
the left and time in seconds on the right, as well as speed
in miles per hour. The DBC feature is used to enforce
‘tailgating’ laws.
1kHz and an I2C or PWM interface. The GARMIN LIDARLite V3 for US$130 is similar; the main difference is that
the maximum update rate is lower, at 500Hz.
The Seeedstudio Grove TF Mini LiDAR (siliconchip.com.
au/link/ab2m) is a US$40 device with a range of 0.3m to 12m,
an accuracy of 1-2% depending on range, and a UART (serial) interface.
The devices mentioned above establish range only and
cannot produce a two-dimensional map unless they are rotated and scanned on a mount.
The Slamtec RPLIDAR A1 (see Figs.9 & 10 and www.
slamtec.com/en/Lidar/A1) is a 360° laser range scanner
with a sampling rate of 8kHz and a scan rate (rotation rate)
of 2-10Hz, a range of 12m and an accuracy of 2mm with a
serial and USB interface. It can produce a two-dimensional
map and costs about US$115.
Note that there are some devices marketed as “lidar” which
do not use a laser but rather a regular LED, and therefore are
not true lidar devices. For example, the US$60 GARMIN LIDAR-Lite V4 LED, with a 5cm to 10m range and accuracy of
±1cm to ±5cm depending on range, an update rate of around
200Hz and I2C or ANT wireless interfaces.
Lidar mapping of confined spaces
Lidar can be used to map the inside of caves and other enclosed spaces. If the lidar unit is stationary, then one room
can be easily captured (see Fig.11). But if a “walk through”
is required such as in a cave, mine or large building, a location reference is needed.
It is usually not possible to use GPS as the signal does not
work in such places, so the location of the lidar as it moves
is determined by SLAM or Simultaneous Location and Mapping. This is where the location is determined by the use
of three-axis accelerometers, which provide data about the
movement of the device.
siliconchip.com.au
Fig.14: the Remtech PA-XS, a small SODAR unit weighing
only 7kg, with a range of 400m.
Lidar sensors for consumer drones
Relatively inexpensive lidar devices are now available for
consumer-level drones. As an example, the Livox Mid-40 LIDAR can be purchased in Australia for A$899.
Lidar for crash investigation
In Australia, the NSW and Victorian police forces are both
known to use lidar to map vehicle crash scenes; specifically,
they use the RIEGL VZ-400i, as shown on page 10.
Lidar police speed enforcement
Police in many countries use lidar for speed limit enforcement. One advantage of lidar over radar is that there is much
less beam divergence with lidar, so theoretically, if the equipment is used correctly, it is possible to measure the speed of
a specific vehicle in a stream of traffic.
Speed-detecting radar, on the other hand, has difficulty
in distinguishing between nearby vehicles. When used incorrectly, it has even been known to measure the speed of
other objects such as windmills, aircraft and tree branches
blowing in the wind! Very high levels of operator attention
and training are required to ensure the accurate operation
of police radar.
Models of police handheld lidar used in Australia and New
Zealand include the LTI TruCAM, LTI TruSpeed, LTI 20-20
Ultralyte 100 LR, LTI TruSpeed SE, LTI Ultralyte Compact,
Australia’s electronics magazine
August 2020 15
Fig.15: a SODAR
result for Niwot Ridge
in Colorado, USA,
showing how the wind
speed and direction
vary with the height
above ground level
and time of day. The
arrow colour indicates
the wind speed while
the arrow orientation
shows the direction.
Kustom Signals ProLaser III, Kustom Signals ProLaser 4 and
Kustom Signals Pro-Lite+. See www.lasertech.com/default.
aspx and https://kustomsignals.com for more details.
Note that while lidar for speed enforcement is theoretically
accurate (within error margins), its use in Australia has been
successfully challenged, reported by the ABC at siliconchip.
com.au/link/ab2n
Lidar is also used by police in some areas to measure the
distance between vehicles as they travel down a road (see
Fig.13).
SODAR
SODAR is a meteorological instrument that uses sound
in a similar way that lidar uses light. SODAR is generally
designed to determine wind speeds as a function of height
above the instrument. This type of device is also known as
Fig.16: a Metek Doppler SODAR PCS.2000 with RASS
temperature profiler operating at 482MHz, 915MHz or
1290MHz. This setup is used for vertical profiling of
temperatures, temperature gradients and inversion layers
synchronously with the SODAR wind profiling. The RASS
antennae are placed on either side of the SODAR unit. The
vertical range for RASS is up to 500m.
16
Silicon Chip
a wind profiler (see Fig.14).
They take advantage of the Doppler effect, where the frequency of an echo is altered by the motion of the object it
bounces off. This is related to the effect where a moving vehicle with sirens or a horn blaring appears to change in pitch
as it passes you. Apart from sound waves, wind profiler instruments can also use radar or lidar to perform measurements using the same basic principle.
Applications of SODAR include: assessment of sites for
wind generators, to prove there is a suitable wind speed
profile throughout the height of the windmill; wind shear
detection at airports; wind studies to examine dispersal of
Fig.17: how RASS works. A radio beam is reflected
off acoustic waves from the SODAR unit, and the
backscattered signal can be used to determine the speed
of sound as a function of altitude, which can be then be
converted to temperature.
Australia’s electronics magazine
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Fig.18: lidar measurements from an aircraft over the
Atlantic on 27th September 2016, testing the ALADIN
Airborne Demonstrator (A2D) prototype lidar. This was
used on the European Space Agency Aeolus satellite,
launched on 22nd August 2018. It shows wind speed as a
function of height along the flight path. Aeolus is the first
satellite capable of making global wind measurements and
can measure from the surface to an altitude of 30km.
pollutants from smokestacks etc; and determining existing
wind patterns for environmental impact studies.
The ‘echo’ of the sound wave returning to a receiver from
the atmosphere is known as backscatter. Backscatter can occur from substances such as atmospheric dust or rain. But
due to the way SODAR operates, it generally arises from
small changes in the ‘sonic refractive index’ due to the
changes in wind speed or temperature.
A change in wind speed of 1m/s corresponds to a change
in the sonic refractive index of 0.3%; for a change in temperature of 1°C, the change is 0.17%. For radio frequency
signals, the change in refractive index due to a 1°C temperature change is 1ppm (part per million) and radio waves are
unaffected by changes in wind speed.Therefore, it is best to
use sound to measure wind speed, as RF is very insensitive.
See siliconchip.com.au/link/ab2o for more details on this.
A SODAR system may be mono-static or bi-static. In a
mono-static system, both the transmitted and received beam
use the same ‘antenna’ (one transducer is used as both a
microphone and a speaker). Backscattering is thus due to
temperature fluctuations, which are carried along with the
wind, enabling its speed to be determined (Fig.15).
In a bi-static system, separate transmitting and receiving
devices are used, and backscatter occurs from both temperature and speed fluctuations; however, all commercial
SODARs are mono-static.
Mono-static SODAR systems use a series of antennas
pointed upward in different directions, or they may have
a phased-array arrangement with the ‘beam’ electronically steered. A minimum of three beams are required to resolve the three components of wind speed, being in the x,
y and z directions.
More beams give better results, as with ADCP, which is
discussed later. Usually, there is a vertical beam and two
beams at right angles, offset from the vertical by about 15-30°.
In operation, multiple transmitted pulses are backscattered (reflected) from a moving turbulent patch of air. The
reflected pulses incur a Doppler shift according to the
speed of the air patch, and the shift of consecutive pulses
will change as the patch moves along. When the data from
multiple different beams are analysed, the individual vesiliconchip.com.au
Fig.19: Japan’s National Institute of Advanced Industrial
Science and Technology (AIST) mounted a lidar wind
profiler on a windmill to measure upwind speed and
direction, for optimising the windmill’s yaw angle and
blade pitch for maximum power and service life.
locity components can be calculated.
The sound a SODAR unit makes in operation can be heard
in the video titled “Sound from SODAR wind measurements”
at https://youtu.be/8HUyExuFMFI
Looking at a range of typical SODAR devices such as those
from Remtech, Inc (www.remtechinc.com), the audio frequency is from 1-5.5kHz with an acoustic power level from
5-150W, giving a maximum analysis altitude of 400-3000m.
A single unit may use multiple frequencies.
SODAR and RASS
A RASS or radio acoustic sounding system may be used in
conjunction with SODAR to measure the atmospheric lapse
rate, which is the measure of how temperature changes with
altitude. A radio signal, typically in the UHF frequency range,
is directed vertically into the SODAR beam (see Figs. 16 & 17).
When certain conditions are met, due to the way the acoustic beam changes the dielectric properties of the atmosphere
(it causes either compression or rarefaction), this alters the
amount of the radio beam which is backscattered.
This provides a measure of the Doppler shift due to vertical motion of the air caused by the acoustic beam. The speed
of sound in the air can be determined from this, and thus the
temperature, as it alters the speed of sound.
As an example of how the speed of sound varies with temperature, between -10°C and 30°C at standard sea-level atmospheric pressure, the speed of sound varies from 325m/s
to 350m/s. Measurements are made at different altitudes,
so the “pressure altitude” also has to be taken into account.
Lidar for wind profiling
Doppler lidar can also be used for wind profiling. As with
SODAR, the light is backscattered, and the Doppler shift is
measured to determine wind speed. Data obtained can be
used to optimise windmill performance or for meteorological applications (see Figs.18 & 19).
ADCP in water
An equivalent device to SODAR for use in water is the
acoustic doppler current profiler (ADCP). It uses the same
basic principles as SODAR. The frequency range used is
Australia’s electronics magazine
August 2020 17
Fig.20 (above): a variety of ADCP and DVL instruments
from Rowe Technologies, Inc. Note the differing numbers of
transducers, as some units utilise more beams than others.
typically from 38kHz to several megahertz. Figs.20, 21 &
23 show various ADCP units, while Figs.22 & 24 show how
they can be used. The results are visible in Figs.25 & 26.
The predecessor to the ADCP was the Doppler speed log,
used to measure the speed of a ship through the water. The
first commercial ADCP produced in the mid-1970s was an
adaption of that system.
ADCP works by sending out pulses of ultrasound which
are backscattered from particles in the water column of
interest. The backscattered signal yields two main pieces
of information: the Doppler frequency shift, which gives
information about the speed of the particle and the time
delay to receive the backscattered signal, giving the range
of the particle.
An ADCP can also yield information about the distribution of particles in the water column, such as sediments
or plankton. When the ADCP is attached to a ship or other maritime platform, the depth of the water and platform
speed are also known. When the ADCP is on the seafloor,
information about surface waves can be obtained.
An ADCP uses two beams for horizontal measurements
(2D H-ADCP) or three or more beams (3D case) to resolve
water motion in two or three directions. In the 3D case, a
fourth beam provides more accuracy. Additional beams
Fig.21: the Teledyne RD
Instruments ChannelMaster
H-ADCP. It uses two
beams to produce a
2D velocity profile
for a water channel.
Different versions
can measure across
a channel with a
width from 20m to
300m. Such devices
are often permanently
mounted.
can be used to make measurements at other frequencies to
provide either better accuracy (high frequency) or greater
range (low frequency).
Three is the minimum number of beams needed for
measuring the three velocity components of flow in the
x, y and z directions. But the standard configuration uses
four beams, as this provides redundancy plus an estimate
of the measurement error. A five-beam system is a fourbeam system with an additional vertical beam for measuring waves and ice when upward-looking or depth when
downward-looking.
Some dual-frequency systems have seven beams; three
beams per frequency plus a vertical beam, while there are
also eight-beam dual-frequency systems with four beams
per frequency.
An ADCP can measure the flow of water current through
a column. Fig.22 shows a variety of ways in which this
is useful. It may be mounted horizontally, such as on the
shore of a river, to measure the flow of water from shore to
shore. Or it can be mounted on bridge pilings or seawalls to
measure flow in streams and irrigation channels (H-ADCP).
Alternatively, it may be mounted on the seafloor to look
vertically through a column of water all the way to the surface, or on a ship’s hull to take measurements of current
Fig.22: the variety of ways in which ACDP can be used, on mobile or fixed platforms. The direction of the multiple beams
is shown. DVL refers to Doppler Velocity Logging, for measuring vehicle speed relative to the seafloor. Source: Rowe
Technologies, Inc.
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Silicon Chip
Australia’s electronics magazine
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Fig.24: a StreamPro ADCP
attached to a small flotation
device is dragged across
the Boise River in the
USA to measure the flow
volume and speed. The
velocity profile is measured
continuously on the laptop
computer. The device is
usually connected to the
computer via Bluetooth,
plus the data is recorded
onboard as a backup.
Source: Tim Merrick, USGS.
Also see the video at https://
youtu.be/E69Y3JaBIiQ
Fig.23: the popular Teledyne RD Instruments StreamPro
ADCP for measuring velocity and discharge in shallow
streams. It is designed for measurements in water 15225cm deep and uses four beams at 2MHz. The whole
system weighs just 5kg and is powered by AA cells. The
transducer head overhangs the front of the float while the
electronics package is in the other blue housing.
flow along the path of the vessel (a transect).
In H-ADCP, the instrument is set horizontally looking
across a stream, irrigational channel etc at a fixed height.
Current profiling is often done in two dimensions, rather
than three – see Fig.25.
If only a 2D slice is measured, then the total flow can be
inferred by using an appropriate velocity model for rectangular, circular, trapezoidal, multi-point, or polynomial
shaped channels. Relevant dimensions are entered into the
measurement software.
Three-dimensional ACDP readings are typically in the
form of measurements for North-South, East-West and vertical flows.
Ultrasonic ranging
Ultrasonic or ultrasound ranging uses an ultrasonic pulse
to measure the distance to an object. It can also detect if an
object has moved in front of a beam. Ultrasonic ranging is
used for camera autofocus systems, motion detection, robotics guidance, proximity sensing, measurement of tank
liquid levels, measurement of wind speed and direction
and object ranging.
Parking sensors in cars are an everyday use of ultrasonic
ranging. These help motorists manoeuvre vehicles without
striking cars or other objects which they may not be able to
see, or cannot easily estimate the distance to (Fig.28). The
sensors are built into the bumpers of cars, and typically,
Fig.25: measurements of the Antarctic Circumpolar
Current with velocity profiles as a function of time
in the N-S, E-W and vertical directions (left) with the
measurement path (above). These were taken with an
ADCP attached to an SD 1020 Saildrone USV (unmanned
surface vehicle) at 300kHz, 90m deep. Six days of data are
shown. Source: Saildrone.
siliconchip.com.au
Australia’s electronics magazine
August 2020 19
Fig.26: typical data that can be obtained from the StreamPro. The middle image shows the measurement
matrix while the measurements are at the bottom, with the flow rate indicated by colour. This 3D measurement
determines the velocity profile at all depths. Source: Kyutae Lee.
20
Silicon Chip
Australia’s electronics magazine
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Fig.27: an ultrasonic
anemometer, the
Gill Instruments Ltd
WindObserver II. An
advantage of this type
of instrument is that it
contains no moving parts.
there are four in the front and four in the back, although
some vehicles have twelve sensors in total.
Similar sensors may also be used to provide automatic
parking features, for example, to measure the distance from
the vehicle to the curb, or an already parked vehicle.
Wind speed and direction can also be measured with an
ultrasonic anemometer (see Fig.27). The time of flight of an
ultrasonic pulse depends on the speed of the wind passing
in front of it. With two pairs of ultrasonic sensors, the individual velocity components can be resolved to give speed
and direction.
Ultrasound is typically defined as sound waves with a
frequency above 20kHz, which is the upper limit that any
human can hear (some people have a much lower bound;
it generally drops as we age). Dogs can hear up to 45kHz,
cats 64kHz. Some animals such as porpoises can detect frequencies up to 160kHz.
At average sea-level atmospheric pressure, 20kHz sound
waves have a wavelength of 1.9cm and higher frequencies
will be less than that. Ultrasound is used because it gives
a more accurate range measurement due to its shorter
wavelength than
lower sound frequencies.
Fig.29: the
Polaroid SX70 camera
with “Sonar”
autofocus
from 1978.
The ultrasonic
transducer is the
large perforated
disc above the lens.
It is a valuable
collector’s item
today, and has a
niche following.
siliconchip.com.au
Fig.28: a range of Bosch ultrasonic sensors for automated
car parking, parking assistance and manoeuvering
systems, including emergency braking. They can detect a
7.5cm “standard pole” from 15cm to 5.5m (depending on
model), have a horizontal field of view of ±70°, a vertical
field of view of ±35°, use frequency modulation and have
dedicated ICs to make interfacing easier.
The Polaroid Sonar Ranging Module
In 1978, Polaroid introduced the SX-70 instant camera
which featured an innovative ultrasonic rangefinding system
to focus the camera automatically (see Fig.29). The technology was licensed to other users for different applications,
and Polaroid built a business around the supply of this ultrasonic transducer circuit board.
It was known as the 6500 Series Sonar Ranging Module
(Fig.30), and it was suitable for use with a range of Polaroid
transducers such as the 600 Series Instrument Grade Electrostatic Transducer (Fig.32). It was intended for use by experimenters and commercial developers alike. Its data sheet
can be seen at www.robotstorehk.com/6500.pdf
These modules were prized by robotics experimenters,
and possibly still are, judging by the amount written about
them. Some people have sourced modules from old Polaroid cameras, although the modules are not the same as those
that were sold separately. There are notes (last updated
2005) on salvaging them from old cameras at www.uoxray.
uoregon.edu/polamod/
Before salvaging these from old cameras, be aware of the
possible value of the camera as a collector’s item – especially the SX-70!
Fig.30: the Polaroid 6500 Ultrasonic Ranging Module with
600-series transducer. The scale is in inches. Note the
discrete components and DIP (dual in-line package) ICs.
Australia’s electronics magazine
August 2020 21
Experimenting with ultrasonic distance sensors
Jaycar and Altronics both sell ultrasonic sensor modules.
Jaycar has Cat AU5550 (an all-in-one transmitter/receiver) and
also the very popular dual HC-SR04 module, Cat XC4442. Altronics also has the HC-SR04, Cat Z6322.
One interesting way to experiment with the HC-SR04 ultrasonic rangefinder module is to build the Jaycar Cat KR9292
“Duinotech Mini Smart Car Robot Kit”.
The HC-SR04 module is elementary to drive, as demonstrated
by our March 2016 project, the Ultrasonic Garage Parking Assistant (siliconchip.com.au/Article/9848). That was one of our
first projects based on Geoff Graham’s Micromite LCD BackPack,
which has built-in support for the HC-SR04 sensor module.
It requires just two connections to the microcontroller: one
digital output to trigger a pulse and a digital input, to determine
when the echo is received. Measuring the time between one
changing state and then the other tells you the distance from
the front of the sensor to the closest object.
The 6500 module was capable of driving a transducer
such as the 600 Series at 50kHz. This provides range detection over about 2-17m, with 1% accuracy.
SensComp (www.senscomp.com) bought Polaroid’s portfolio of ultrasonic ranging modules and transducers and
remarkably, a modern SMT (surface mount) version of the
6500 module is still available today (Fig.31).
Fig.31: the SensComp 615078LF SMT 6500 Ranging
Module, a derivative of the original Polaroid 6500 module
but using surface-mount components. It has the same
specifications as the original Polaroid device and the parts
appear to correspond directly to those shown in Fig.30.
Infrasound is at the opposite end of the acoustic spectrum
to ultrasound, and is defined as being acoustic frequencies
less than 20Hz, the typical lower limit of human hearing. Infrasound arises in nature from some animals such as whales
and elephants and natural phenomena such as earthquakes,
ocean waves and aurorae.
Infrasound listening arrays have been used to locate avalanches, nuclear detonations and tornadoes.
The volcanic explosion of Krakatoa in 1883 was detected as small pressure fluctuations on traditional barometers
around the world, as infrasonic waves circled the Earth three
to four times in each direction.
The low-frequency array or LOFAR is a radio astronomy
observatory in the Netherlands, but the infrastructure of
LOFAR is also used for sensors to perform infrasound observations.
According to KNMI’s website (they are a member organisation), the observatory consists of “a temporary 80 element
high density array, a permanent 30 element microbarometer
array with an aperture of 100km and, at the same locations,
a 20 to 30 element seismological component”.
The microbarometers can be used to probe processes in
the upper atmosphere above 30km and other infrasound
phenomena, and also to study seismo-acoustic phenomena
since seismic events are also measured at the same site. See
http://siliconchip.com.au/link/ab2p
Infrasound is also used by the comprehensive nucleartest-ban treaty organization (or CTBTO, of which Australia is a member) to monitor for unauthorised nuclear tests.
Australia has infrasound stations located Warramunga, NT;
Hobart, TAS; Shannon, WA; Cocos Islands and Davis Station, Antarctica (see Fig.33).
For more information on this network, see the video titled “The Infrasound Network and how it works” at https://
youtu.be/GVWOA5pZG6o
SC
Fig.32: a SensCorp 604142 Series 600 Instrument Grade
Ultrasonic Sensor for use with the 6500 module. This is a
modern version of Polaroid’s original 600 sensor.
Fig.33: the Australian infrasound monitoring station
“IS03” at Davis Base, Antarctica. This is one of about 300
stations around the world maintained by CTBTO member
states. Apart from infrasound, Australia monitors seismic,
radionuclide and hydroacoustic phenomena to detect
unauthorised nuclear tests as part of the International
Monitoring System (IMS).
Infrasound
22
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Australia’s electronics magazine
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Part 1 –
By Phil Prosser
• 192kHz
• 24-bit
USB
This beauty is the ultimate in high-fidelity
audio recording and playback. You could use the SuperCodec
for digitising LPs, recording your own music or playing music with a
very high-quality stereo amplifier driving excellent speakers.
It can also turn your PC into an advanced audio analyser, capable of
measuring harmonic distortion down to 0.0001% and signal-to-noise
ratios up to 110dB (or even more, with suitable attenuators).
T
his project was inspired by a
reader who wanted to digitise
his LP collection, and asked if
we had a USB sound interface that
would let him record with very high
fidelity.
If you want better quality audio for
your PC, including the ability to record and playback at high sampling
rates and bit depths (up to 192kHz,
24-bit), read on.
In addition to recording and playback of music or other audio, this
project enables your PC to become an
advanced audio quality analyser. You
24
Silicon Chip
just need the right software; we’ll get
to that later.
With the addition of the SILICON
CHIP Balanced Input Attenuator for
Audio Analysers and Scopes from the
May 2015 issue (siliconchip.com.au/
Article/8560), you will have a potent
measurement tool indeed.
It allows you to measure the distortion performance of the very best amplifiers, preamps, equalisers and other
audio devices.
In designing this project we started
by looking for a simple IC CODEC as
the solution. There are some all-in-one
Australia’s electronics magazine
USB audio chips available, but they
fall short on several fronts. They generally limit you to the use of 48kHz, 16bit audio but more importantly, they
generally have quite high distortion
figures of around 0.1%, with signal-tonoise ratios topping out at about 85dB.
We need better performance than that.
The first prototype for this project
used the same analog-to-digital converter (ADC) and digital-to-analog
converter (DAC) boards from the DSP
Active Crossover (May-July 2019;
siliconchip.com.au/Series/335).
Those boards use the Cirrus Logic
siliconchip.com.au
CS5381 and CS4398 chips respectively.
While they are a few years old, their
performance is phenomenal.
The CS4398 DAC has a dynamic
range of 120dB and signal-to-noise
ratio (SNR) of 107dB; the CS5381
ADC achieves an SNR of 110dB, or
0.0003%.
So we decided to stick with those
chips but put as much as possible onto
one board, to make it easier to build
and give a nice, compact result. The
performance this USB Sound Card delivers should fulfil even the most ardent hifi enthusiasts’ desires.
We did make several changes and
improvements compared to that earlier project, though. This design teases
the maximum performance from these
parts, in a ‘no-compromise’ approach
to low noise and low distortion.
Plus it provides ‘plug-and-play’
operation for Windows, Mac and Android computers. We tested it on Windows, but trust the vendor’s promise
of Mac and Android compatibility.
During the development process, we
made several key decisions:
• To get the best performance, we need
to isolate the PC’s ground from the
USB Sound Card. Computers are
noisy things, so we must break the
ground loop.
• It must be supported by proper drivers in Windows and ideally, all other
common operating systems.
• The ability to handle different sampling rates is important, though once
set, it will generally be left alone.
• The PCB layout must minimise
noise, plus we need to be able to
connect the inputs and outputs in
a variety of ways.
Features
•
•
•
•
•
•
•
•
Stereo input & output with very low distortion and noise
Connects to computer via USB
Windows, macOS & Android driver support
Asynchronous sampling rate conversion (completely transparent)
Full galvanic isolation between computer and audio connectors
Housed in a sleek aluminium instrument case
Power by 12V DC (eg, from plugpack)
Power and clipping indicator LEDs
• Putting a transformer in the box
would introduce measurable 50Hz
related noise, even if we took measures to minimise it. Since we don’t
want a complicated power supply
arrangement, we chose a DC plugpack.
• For the cleanest project for SILICON
CHIP constructors, everything should
be on one PCB.
As we have noted in the past, the
use of some surface-mount components is unavoidable in projects like
this. We need to use specific parts to
get this level of performance, and in
many cases, they only come in SMD
versions. In this case, that includes
the USB interface and the ADC and
the DAC chips.
Where possible, though, we have
used through-hole components. This
has resulted in the PCB being a bit
larger than an all-SMD version would
be, but we have found a very nice case
that fits it neatly.
Principle of operation
Fig.1 shows the block diagram of
the SuperCodec. It consists of a USB
to I2S (serial digital audio) interface
with galvanic isolation to the remainder of the circuit, a local clock generator for the ADC and DAC with bidi-
rectional asynchronous sampling rate
conversion (ASRC), the power supply
section and the aforementioned ADC
and DAC sections.
We have chosen to use a MiniDSP
MCHStreamer to provide the USB interface. This is a pre-built device that
we have integrated into our design.
This avoids us having to develop
the hardware and USB driver software for the PC which is complex,
expensive and needs to be done very
well to deliver you an easy-to-use
product.
It is essential that constructors can
reliably install the sound driver software for this project and have it work
with a minimum of fuss. The investment in this component is well worth
the ease of use it will deliver you.
This project appears to a Windows
computer as a sound interface that you
select and use just like any other – we
show you how to in the box titled “Setting up the MCHStreamer”. This is essentially a regular audio device then,
just one of very high quality.
The MCHStreamer is a very clever
device that can provide 10 input and
output channels (five stereo pairs)
with sampling rates of 32-384kHz at
24 bits. It supports I2S as well as TDM
and other audio formats.
We are using it as a two-channel
Fig.1: the concept of the USB SuperCodec is deceptively simple, since much of the complexity is hidden in the prebuilt MiniDSP MCHStreamer module. That USB interface module produces a serial digital audio stream which passes
through a galvanic isolation section and onto the ASRC, then the separate ADC and DAC sections. It’s all powered
from the PC USB 5V and a 12V DC plugpack.
siliconchip.com.au
Australia’s electronics magazine
August 2020 25
Fig.2: spectral analysis (large window FFT) of the data
from the SuperCodec’s ADC when fed a sinewave from
a Stamford Research Ultralow Distortion Function
Generator. This gives an excellent result of 0.0001% THD
(-121.4dB). That’s despite an Earth loop causing a largerthan-normal spike at 50Hz, which was fixed with some
extra isolation in the final version of the Sound Card.
Fig.3: a close-up of the 980-1020Hz portion of the spectral
analysis, showing very little evidence of clock jitter in the
ADC system. That’s because the crystal oscillator, digital
isolators and ASRCs are all low-jitter devices. High jitter
can distort signals since the sampling rate effectively
changes between samples.
(stereo) audio interface. This leaves pack, along with power for the rest of download the PC driver software.
We have laid out our sound card so
many channels unused, but that is the circuit.
You can buy the MCHStreamer from that the MCHStreamer plugs straight
not the aim of this project. If you want
onto the underside of
to use this design as
the board. This avoids
the basis of a multiSpecifications
having to send highchannel recorder, be
• Sampling rate: 32-192kHz
speed digital signals
our guest!
• Resolution: 16-32 bits (24 bits actual)
over a ribbon cable.
The MCHStreamer
• Loopback total harmonic distortion (THD): 0.0001% (-120dB)
When purchasing parts
is powered from the
• DAC THD+N: 0.00050% (-106dB)
for this, be very careful
USB cable and breaks
to get the header speciout the I2S audio in• ADC THD+N: 0.00063% (-104dB)
fied in the parts list.
terface that we need
• Loopback THD+N, no attenuator: 0.00085% (-101.4dB)
Any alternative needs
on a pair of headers.
• Loopback THD+N, 8dB resistive attenuator: 0.00076% (-102.5dB)
a pin pitch of 2mm and
The chip we’re us• Recording signal-to-noise ratio (SNR): 110dB
a minimum height of
ing for galvanic isola• Playback SNR: 107dB
10mm; otherwise, you
tion requires a pow• Dynamic range: 120dB
will not be able to seat
er supply on both
• Input signal level: up to 1V RMS
the MCHStreamer fully.
sides of the barrier.
• Output signal level: up to 2.4V RMS; 2.0-2.2V RMS
Luckily, the MCHPerformance
(-1.5 to -0.75dB) for best performance
Streamer has a 3.3V
measurements
output available on
We used three methan expansion header
which we can use to power the com- www.minidsp.com/products/usb- ods to measure the performance of the
puter side of that chip. The audio side audio-interface/mchstreamer Once USB SuperCodec, and these measurepower supply is derived from the plug- you register and order it, you can ments aided us in improving it over
Fig.6: the noise floor of the complete DAC+ADC system.
It’s higher than the ADC alone, but still very low at around
-130dB.
26
Silicon Chip
Fig.7: here the 1kHz test signal has been reduced in amplitude
by 10dB, dropping from around 1V RMS to around 0.1V
(100mV) RMS. That’s below most normal ‘line level’ signals,
but despite this, distortion performance is still excellent, with
THD measuring as -112dB/0.0002%.
Australia’s electronics magazine
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Fig.4: the first loopback test, measuring the performance
of the complete DAC+ADC system. Performance is still
excellent with only slightly higher harmonic distortion than
the ADC alone, at -118dB (still rounding to 0.0001%).
To verify that clock jitter is not a
problem, we then ‘zoomed in’ to the
1kHz fundamental, as shown in Fig.3.
This plot shows spectral data for 1kHz
±20Hz. This shows that the fundamental is 120dB down at about ±2Hz from
the fundamental. That’s about as good
as you can expect, and suggests that
jitter in the clock source and digital
signal path is minimal and has little
effect on performance.
Loopback testing
Importantly, there is no spike at
25kHz, 12.5kHz or related frequencies,
suggesting that the switchmode regulators are not squegging, ie, are free from
subharmonic oscillation that could affect audible frequencies.
The harmonics of the very slightly
distorted 1kHz fundamental are visible at 2kHz, 3kHz etc up to 8kHz,
then 11kHz and 12kHz. The strongest
harmonic is 2kHz (second harmonic),
at around -118dB. The result is a very
low THD figure of -118dB/0.00013%.
Remember that this now includes any
distortion from the DAC plus the ADC,
so this is very impressive. But this
measurement does not include noise.
To calculate the THD+N figure and
signal-to-noise ratio, the inputs to the
The second test method was to connect the unit’s outputs to its inputs via
a stereo RCA-RCA cable. This lets us
conduct ‘loopback’ tests using PC audio
analysis software. The result of the first
such test is shown in Fig.4. You can see
that we’ve solved the
SuperCodec DAC THD+N vs Frequency
Earth loop now as the
.01
50Hz peak is at -130dB!
22kHz BW 0dB
You can also see the
22kHz BW -1dB
.005
50kHz spike from the
22kHz BW -2dB
22kHz BW -7.5dB
switchmode circuitry.
Total Harmonic Distortion (%)
several iterations until we arrived at
the final design.
The first method was to feed in a
very low distortion sinewave from a
Stamford Research DS360 Ultralow
Distortion Function Generator. Very
large sample sets were run through an
FFT so we could inspect the close-in
phase noise.
The reason for doing this (rather
than merely looping the output back
to the input) is that we need independent clocks for the signal generator and
ADC to pick up any distortion caused
by clock jitter. With both devices running off the same clock, those effects
are liable to cancel each other out, at
least partially.
The results of this first test are shown
in Fig.2. Note that we had an Earth
loop during this test, leading to a greater than usual spike at 50Hz (this was
fixed later); despite this, the reading is
extremely promising with just a THD
figure of just 0.0001% (-118dB) THD.
Fig.5: the noise floor of the ADC, measured with the inputs
shorted. The biggest spike in the audible range is at 50Hz
due to mains hum pickup, but this is hardly a problem,
being below -140dB.
19/05/20 14:37:19
80kHz BW 0dB
.002
.001
.0005
.0002
.0001
Fig.8: the 1kHz test signal has been increased to the
maximum DAC output level of a bit more than 2V RMS. You
can see that in this case, more isn’t necessarily better, as the
THD figure is slightly worse than the 1V test case, yielding a
THD figure of -111dB/0.0003%. That’s still excellent, though!
siliconchip.com.au
20
50
100
200
500 1k
2k
Frequency (Hz)
5k
10k
20k
Fig.9: THD+N (not THD) at four different signal levels
for the SuperCodec’s DAC, asFig.9
measured with our Audio
Precision System Two. The fifth curve has a wider
measurement bandwidth of 20Hz-80kHz, to get a more
realistic idea of distortion levels at higher frequencies.
Unfortunately, measurements with 80kHz bandwidth
also have an unrealistically high noise level.
Australia’s electronics magazine
August 2020 27
.01
SuperCodec ADC THD+N vs Frequency
19/05/20 14:51:30
.01
Total Harmonic Distortion (%)
Total Harmonic Distortion (%)
19/05/20 15:20:11
.005
.005
1V RMS (0dB)
0.5V RMS (-6dB)
.002
.001
.0005
No attenuator
8.0dB attenuator
.002
.001
.0005
.0002
.0002
.0001
SuperCodec loopback THD+N vs Freq.
20
50
100
200
500 1k
2k
Frequency (Hz)
5k
10k
20k
Fig.10: THD+N (not THD) at two different signal levels for
Fig.10Audio Precision System
the SuperCodec’s ADC, using our
Two as the signal source. The rise in distortion with
increasing frequency seems to be an artefact of the way the
audioTester software calculates THD+N. We don’t think it
is a real effect. The true THD+N level for the ADC is well
below 0.001% across the whole frequency range.
.0001
20
50
100
200
500 1k
2k
Frequency (Hz)
5k
10k
20k
Fig.11: THD+N (not THD) calculated in a loopback manner,
ie, using just the SuperCodec with its outputs feeding its
inputs. As the nominal DAC output level is 2.4V RMS and
the maximum input level is 1V RMS, its performance is
best with an 8dB resistive attenuator (1.5k/1k) between
the outputs and inputs. Otherwise, the SNR is degraded by
an additional 7dB or so.
ADC were shorted out, and a new spec- other test frequencies ranging from decent results at the maximum output
trum captured (Fig.5). We then rein- 20Hz up to 19kHz, all with virtual- signal level, if that’s what you need.
stated the loopback cables and meas- ly identical results, so the plots are
ured the input level with the DAC si- not worth reproducing. We also ran Audio Precision testing
lent (Fig.6). These give us an idea of 1kHz tests with lower and higher sigThe third measurement method we
the noise floor, which is around -104dB nal levels.
used was to hook the SuperCodec up
for the ADC alone and -102dB for the
Fig.7 shows the results with the to an Audio Precision System Two anDAC+ADC. Both figures are limited by output level reduced by 10dB. This alyser. This was mainly to verify that
50Hz hum pickup.
only increases the THD figure to
the above results were all correct, and
Since these levels are significantly -112dB/0.0002%, indicating that you we weren’t somehow fooling ourselves
higher than the THD alone, that means aren’t sacrificing much performance by using the Sound Card to measure
that the THD+N performance figures by operating the codec at lower signal its own performance.
for the Sound Card are determined just levels when necessary.
We ran three tests: one to test the
by the noise levels.
Fig.8 is at the maximum output sig- DAC in isolation, one to test the ADC
By the way, since the DAC has to nal level, which increases second and in isolation, and one to test the whole
have its output level set no higher third harmonic distortion so that the system.
than -7.5dB to avoid overloading the THD figure is -111dB/0.0003%. This
The first test involved feeding digital
ADC in the loopback test, we could indicates that the optimal signal lev- sinewaves to the SuperCodec’s DAC,
have gotten better results by inserting el for low distortion is a few decibels with its outputs then fed into the AP2’s
a resistive divider between the output below maximum. But you’ll still get distortion analyser. This yielded SNR
and input. Indeed, if you are
and THD+N measurements
using this device as part of
both of 106dB, and the distora measurement system, you
tion vs frequency and level
would need resistive dividplot of Fig.9.
ers, especially if the device
These figures match the exyou are measuring has gain
pected performance given in
(eg, an audio amplifier).
the CS4398 IC data sheet pretSo when used as a measty much precisely, suggesting
urement system, you can
we’ve built the circuit around
expect slightly better perforit correctly!
mance than the figures givThe second test involved
en here suggest. Essentially,
feeding the AP2’s low distorthe loopback THD+N (and
tion sinewave generator into
thus the measurement limit)
the SuperCodec’s ADC and
will approach the 0.00063%
plotting similar curves, shown
(-104dB) figure given for the
in Fig.10.
ADC alone.
These curves are a bit ‘wonky’
The back end of the SuperCodec has all the input and
We made many other output connectors (the RCA sockets) along with the USB
due to the weird way that the
loopback measurements at connector and the 12V DC power socket.
software we used (audioTester)
28
Silicon Chip
Australia’s electronics magazine
siliconchip.com.au
Parts list – USB SuperCodec
1 PCB assembly – see below
1 Hammond 1455N2201BK extruded aluminium instrument case
with black panels [Altronics H9125, Mouser 546-1455N2201BK]
1 MiniDSP MCHStreamer USB-to-I2S interface
[www.minidsp.com/products/usb-audio-interface/mchstreamer]
1 12V DC plugpack, 1.5A+ [Altronics M8936D, Jaycar MP3486]
2 white (or black) insulated panel-mount RCA sockets
(CON6a,CON7a) [Altronics P0220, Jaycar PS0496]
2 red insulated panel-mount RCA sockets (CON6b,CON7b)
[Altronics P0218, Jaycar PS0495]
2 plastic TO-220 insulating bushes
2 M3 x 6mm panhead machine screws
1 M3 x 10mm panhead machine screw
2 M3 flat washers
3 M3 shakeproof washers
1 M3 hex nut
2 3mm inner diameter solder lugs
2 3mm inner diameter fibre washers
1 8mm tall adhesive rubber foot [Altronics H0930, Jaycar HP0825]
4 12mm round slim adhesive rubber feet [Altronics H0896]
1 1m length of heavy-duty figure-8 shielded audio cable
[Altronics W2995, Jaycar WB1506]
1 30cm length of 2.4-3mm diameter black or clear heatshrink
tubing
1 30cm length of 5mm diameter black or clear heatshrink tubing
PCB assembly parts
1 double-sided PCB coded 01106201, 99.5 x 247.5mm
1 150µH 5A toroidal inductor (L1) [Altronics L6623]
2 47µH 0.5A bobbin-style inductors (L2,L4) [Altronics L6217]
1 100µH 5A toroidal inductor (L3) [Altronics L6622, Jaycar LF1270]
13 4-5mm ferrite suppression beads (FB1-FB13)
[Altronics L5250A, Jaycar LF1250]
2 M205 fuse clips (F1)
1 5A fast-blow M205 fuse (F1)
3 16x22mm TO-220 PCB-mount heatsinks (HS1-HS3)
[Altronics H0650, Jaycar HH8516]
1 PCB-mount DC barrel socket, 2.1mm ID (or to suit plugpack)
(CON1) [Altronics P0620, Jaycar PS0519]
2 tall 6x2-pin header sockets, 2.0mm pitch (CON2,CON3)
[Samtec ESQT-106-03-F-D-360; available from Mouser]
2 4-pin polarised headers with matching plugs, 2.54mm pitch
(CON4,CON5) [Altronics P5494+P5474+P5471, Jaycar HM3414+HM3404]
3 mica or rubber TO-220 insulating washers
3 plastic TO-220 insulating bushes
3 M3 x 6mm panhead machine screws
3 M3 flat washers
3 M3 shakeproof washers
3 M3 hex nuts
1 60 x 70mm rectangle of Presspahn, Elephantide or similar
insulating material
Semiconductors
1 CS5381-KZZ stereo 192kHz ADC, TSSOP-24 (IC1) [#]
7 NE5532AP or NE5532P dual low-noise op amps, DIP-8
(IC2-IC5,IC8,IC10,IC11)
2 CS8421-CZZ stereo audio sample rate converters, TSSOP-20
(IC6,IC7) [#]
1 CS4398-CZZ stereo 192kHz DAC, TSSOP-28 (IC9) [#]
1 MAX22345SAAP+ 4-channel high-speed digital isolator,
SSOP20 (IC12) [#]
siliconchip.com.au
1 DS1233A-10+ 3.3V supply supervisor, TO-92 (IC13) [#]
1 4N28 optocoupler, DIP-6 (OPTO1) [Altronics Z1645]
1 ACHL-25.000MHZ-EK 25MHz clock oscillator module (XO1)
[#]
2 LM2575T-ADJG 1A buck regulators, TO-220-5 (REG1,REG2) [#]
3 LM317T 1A positive adjustable regulators, TO-220
(REG3,REG6,REG8) [Altronics Z0545, Jaycar ZV1615]
1 LM337T 1A negative adjustable regulator, TO-220 (REG4)
[Altronics Z0562, Jaycar ZV1620]
1 LP2950ACZ-3.3 100mA 3.3V low-dropout regulator, TO-92
(REG5) [Altronics Z1025]
1 AZ1117H-ADJ 1A adjustable low-dropout regulator, SOT-223
(REG7) [Altronics Y1880]
1 BC547 or BC549 100mA NPN transistor (Q1)
2 high-brightness 5mm LEDs (LED1,LED2)
9 1N4004 400V 1A diodes (D1,D22-D29)
2 1N5822 40V 3A schottky diodes (D2,D3)
12 BAT85 30V 200mA schottky diodes (D5-D16) [Altronics Z0044]
Capacitors
1 2200µF 25V low-ESR electrolytic [Altronics R6204, Jaycar RE6330]
1 2200µF 10V low-ESR electrolytic [Altronics R6238, Jaycar RE6306]
4 470µF 25V low-ESR electrolytic [Altronics R6164, Jaycar RE6326]
1 470µF 6.3V low-ESR organic polymer electrolytic
[Panasonic 6SEPC470MW] [#]
1 220µF 25V low-ESR electrolytic [Altronics R6144, Jaycar RE6324]
4 100µF 25V low-ESR electrolytic [Altronics R6124, Jaycar RE6322]
8 47µF 50V low-ESR electrolytic [Altronics R6107, Jaycar RE6344]
1 33µF 25V low-ESR electrolytic [Altronics R6084, Jaycar RE6095]
4 22µF 50V bipolar electrolytic [Altronics R6570A, Jaycar RY6816]
14 10µF 50V low-ESR electrolytic [Altronics R6067, Jaycar RE6075]
1 1µF 63V electrolytic [Altronics R4718, Jaycar RE6032]
2 1µF 25V X7R SMD ceramic, 2012/0805 size
[Vishay VJ0805Y105KXXTW1BC or VJ0805Y105KXXTW1BC] [#]
1 220nF 63V MKT
19 100nF 63V MKT
17 100nF 25V X7R SMD ceramic, 2012/0805 size
[Kemet C0805C104M3RACTU] [#]
4 22nF 63V MKT
7 10nF 63V MKT
9 10nF 50V X7R SMD ceramic, 2012/0805 size
[Kemet C0805C103J5RACTU] [#]
2 2.7nF 100V NP0/C0G SMD ceramic, 2012/0805 size
[TDK C2012C0G2A272J125AA] [#]
4 1.5nF 63V MKT
8 470pF 50V NP0/C0G ceramic [TDK FG28C0G1H471JNT00] [#]
1 220pF X7R SMD ceramic, 2012/0805 size
[AVX 08052C221K4T2A] [#]
2 100pF NP0/C0G/SL ceramic [Altronics R2822, Jaycar RC5324]
2 33pF NP0/C0G ceramic [Altronics R2816, Jaycar RC5318]
Resistors (1/4W 1% metal film types)
5 47k 6 10k
2 5.6k 4 2.4k 2 1.5k
14 1.2k 3 1k
4 750 4 680 1 560
2 330 2 270 4 240 2 220 4 91
1 0 (or 0.7mm diameter tinned copper wire)
4 10
Resistors (1/10W 1% SMD types, 2012/0805 size) [#]
2 47k 5 2k
2 1k 1 220 1 22
1 10
All components marked with [#] are available from Mouser.
Australia’s electronics magazine
August 2020 29
To whet your appetites
for the construction
details to be presented
next month, here’s the
“naked” SuperCodec
PCB before it was
placed in its case.
As we explained in
the text, there are
mainly through-hole
components but also
a few SMDs, mainly
because they’re not
available in throughhole versions.
calculates THD+N, as we will explain
in a later article. But despite this, they
confirm that the ADC performance is
just slightly worse than the DAC performance, mainly to do with its lower
signal levels.
The final test involved running more
loopback tests, but this time using
the audioTester software to measure
THD+N, so that we can make a direct
comparison to the Audio Precision figures. This yielded the curves shown
in Fig.11.
This time, there appears to be an artificial drop at higher frequencies, which
we think can be ignored. Our assumed
real performance is pretty much flat, as
shown by the dashed lines.
So it seems that a measurement system based around a personal computer, the SuperCodec and some low-cost
software has performance approaching that of our Audio Precision System Two, which cost many thousands
when new.
Even good used AP2s are priced at
four figures.
Plus, you gain some additional
functions and features with this solution compared to the AP2, such as
THD-only measurements (rather than
THD+N).
SC
Next month:
As the USB SuperCodec circuit is fairly
complicated, we don’t have enough room
left to describe it in this article. So we’ll
be presenting all the circuit diagrams
next month, along with an in-depth description of how it all works. Following
that, we’ll describe how to build and test
it in detail, along with some tips on how
best to use it.
In the meantime, if you’re interested in
building the USB Sound Card, we suggest
that you get busy ordering all the parts
that you will need, as per the parts list.
Our test setup. We initially built a version of this card without the asynchronous sample rate conversion (ASRC) components,
shown at right. The performance is pretty much identical but it’s less flexible, so we decided to stick with the design that
included ASRC.
30
Silicon Chip
Australia’s electronics magazine
siliconchip.com.au
“First look” at Microchip’s new FPGA kit . . . by Tim Blythman
Hello
FPGA
Field Programmable Gate Arrays (FPGAs) are
powerful chips which are getting easier to use all the
time. This Microchip Hello FPGA Kit is targeted towards
entry-level users. It comes with demonstration software for image processing,
signal processing and artificial intelligence. We took one for a test-drive, to
see what’s possible for even those with minimal knowledge of FPGAs.
F
ield programmable gate arrays
are incredibly powerful and
useful. They are regularly used
to simulate many microchip designs
before they are committed to ASICs
(application-specific integrated circuits).
Making custom chips is a very costly
process, so you want to be sure your
chip will work before pulling the trigger! FPGAs are one of the essential
tools to achieve that.
An FPGA is effectively a lot of configurable logic gates; it’s a bit like the
old 300-in-1 electronics kits with the
spring connectors and wires, but more
like 1,000,000-in-1, much smaller in
size and electronically configurable.
Having basic elements equivalent
to individual logic gates and flip-flops
means that they can emulate almost
any chip.
Most modern FPGAs also have specialised functional blocks to provide,
siliconchip.com.au
for example, RAM, adders, multipliers, DSP functions and even complete
microprocessor cores!
In some respects, they are a counterpoint to microcontrollers and microprocessors. Microcontrollers and
microprocessors typically work in a
linear fashion, processing instructions
one at a time.
On the other hand, the gates in an
FPGA can all work in a massively
parallel manner, doing many things
simultaneously.
We’ve described some FPGA boards
previously. The Arduino Vidor MKR
utilises an FPGA to produce HDMI
video (amongst other things). We
reviewed this in March 2019; see
siliconchip.com.au/Article/11448
The Vidor also allows the FPGA to
be configured to provide custom peripherals, although, for the most part,
it is a microcontroller board.
We also reviewed the Lattice iceAustralia’s electronics magazine
Stick in April 2019 (siliconchip.com.
au/Article/11521). That is a development board that can be programmed
using the open-source IceStorm software and even the block-based IceStudio software.
The iceStick combined with the
IceStudio software is one of the cheapest and easiest ways to get an introduction to FPGAs.
We even showed our readers how
to turn the iceStick into a VGA Terminal for displaying retro computer text
and graphics in that issue (siliconchip.
com.au/Article/11525).
So to sum up, FPGAs are incredibly
powerful but also very complicated
and sometimes difficult to work with.
The Hello FPGA Kit
The Hello FPGA Kit is an evaluation board, originally from a company called Microsemi. For many years,
they were known as a supplier of elecAugust 2020 31
The Hello FPGA Kit consists of an LCD board, a main FPGA board and a camera board which are usually sandwiched
together, as seen on page 31.
tronics for military, aerospace and other high-reliability applications.
Some of their products were used
in the Mars Curiosity rover and unsurprisingly, one of their key product
lines is FPGAs; their PolarFire FPGA
was named Product of the Year in
2017 by Electronic Products China
and 21ic.com.
In 2018, they were taken over by Microchip Technology, better known as
manufacturers of PIC microcontrollers
(and now also Atmel AVR microcontrollers since their takeover of Atmel).
The Hello FPGA Kit reviewed here
was kindly loaned to us by Microchip
Technology Australia.
The Hello FPGA Kit is a set of
three boards which are sandwiched
together. One board has a camera
lens poking out and a set of headers; it is fitted with an OmniVision
OV7725 camera.
There aren’t many electronic components on that board; a switchmode
regulator and its associated passives
take 5V in to provide a 1.8V rail for
the camera. Its underside has headers
to attach to the FPGA motherboard, labelled as “Expansion” and “Arduino”.
Its top sports a MikroBus socket.
The second outer board features an
LCD panel. The PCB itself is not much
larger than the LCD, although neither
the board nor schematics give any indication about the model or capabilities of the LCD controller.
It measures 3.5in (89mm) diagonally, and the documentation states that
it has a resolution of 480 x 320 pixels.
32
Silicon Chip
A solitary DFN-6 package and two
passives provide PWM control of the
display’s LCD backlighting. The schematic indicates that the LCD uses a parallel 8-bit bus. It connects to the FPGA
board via an “Expansion” header.
The LCD panel appears to be similar to the type used in our Micromite
LCD Backpack V3 (siliconchip.com.
au/Article/11764).
The main board (see below), sandwiched and normally hidden in between the other two, carries the FPGA
and a microcontroller. But the block
User Push Buttons
Power LEDs
20-pin Expansion
Header
diagram, Fig.2, shows that there’s a
lot more on the board than just those
two chips.
The PIC32MX795F512 micro provides an interface for uploading of
the demonstration software to the
FPGA and monitoring its operation.
The PIC32MX795F512 is the same
chip that we used for both the Maximite and Colour Maximite computers (see siliconchip.com.au/Series/30
and siliconchip.com.au/Series/22 for
more information).
The FPGA is a Microsemi SmartUser LEDs
FPGA JTAG
Header
PICkit
Header
SmartFusion
FPGA
PIC32MX79SFS12L
USB 2.0
20-pin Expansion
Header
Arduino Compatible
Interface
Australia’s electronics magazine
Fig.1: there is no shortage of
connectivity on the Hello FPGA main
board. USB, JTAG and even Arduinocompatible headers are provided.
siliconchip.com.au
Fig.2: the Hello FPGA main board consists of an M2S010VF256 FPGA communicating with a PIC32MX795F512
micro. The PIC32MX795F512 communicates with
the GUI app over a USB-serial link, while the FPGA
connects with the camera and LCD board via headers.
Fusion2 M2S010-VF256 in a BGA
(ball grid array) package, with 256
‘pins’ (actually lands).
Microsemi M2S010-VF256
FPGA
The M2S010-VF256 is described
as an SoC (system on a chip). It incorporates a 166MHz 32-bit ARM Cortex
M3 processor, which has 64KB of integrated RAM and 512KB of embedded
non-volatile memory.
The processor also has, among other typical microcontroller peripherals
such as SPI, I2C and UART, a USB OTG
controller, an Ethernet controller and
a CAN bus controller. It can interface
directly to the FPGA as well, since
they are on the same die.
Such an arrangement appears to be
typical of many modern FPGA devices.
While it is certainly possible to create
a processor in the ‘FPGA fabric’, to do
so is less efficient in terms of power
and FPGA resources than having dedicated silicon for this purpose.
And since the processor is on the
same die as the FPGA, communication is much faster than if the processor was a separate chip.
In terms of ‘power’, it is interesting
to compare the M2S010-VF256 to the
Lattice iCE40HX1K chip used in the
iceStick that we previously reviewed.
It isn’t always easy to make a direct
comparison between FPGAs from different brands or even families, as their
siliconchip.com.au
Fig.3: the GUI app is simple and easy to use. The main
things to remember are to use the controls at top right to
connect to the Hello FPGA Kit and ensure that the correct
Action is selected before clicking Run.
internal structures can be quite different, even though they achieve a similar result.
Nonetheless, we can say that the
M2S010-VF256 has roughly 9.5 times
the logic elements of the Lattice FPGA,
at 12,084 total, compared to 1280. It
also has many more Logic Array Blocks
(1007 vs 160).
Its maximum operating frequency is
not given, but we suspect that it will be
lower than the 1066MHz for the iCE40HX1K, given that the M2S010 series
is designed for power efficiency. Low
power normally does not translate to
blistering clock speeds.
Despite that, its large number of logic
blocks means that it can be configured
to do a lot of work per clock cycle.
One of the interesting features of the
Hello FPGA Kit is that it can measure
and report its own power consumption. So it’s clear that making the best
use of power is a focus of the SmartFusion2 range.
Their power analysis tool can estimate and evaluate power usage before
committing to a design.
The FPGA component of the
M2S010-VF256 also has several
‘SerDes’ interfaces. SerDes is an abbreviation for “Serialiser-Deserialiser”, and as the name suggests, they
convert data between serial and parallel formats.
For example, the SerDes on the
M2S010-VF256 can be configured to
Australia’s electronics magazine
provide a 10Gbps Ethernet interface.
Many modern high-speed buses are
serial in nature; HDMI and USB are
other examples.
The SerDes may include features
such as clocking, encoding and framing. Data is processed internally in
parallel and then serialised for output.
Beyond this, there are many socalled ‘IP cores’ that can add further
configurable peripherals to the chip.
Their page also notes some potential
applications in fields such as medical
imaging, radar processing, automotive
and military systems.
Medical imaging and radar processing are examples of applications which
require a large amount of data to be
processed; the parallel nature of an
FPGA allows it to process this data in
parallel and the results to be then fed to
the processor for storage and display.
See siliconchip.com.au/link/ab3o
for more information on the FPGA
chip. A guide for the Hello FPGA Kit
can be found at siliconchip.com.au/
link/ab3p
Now let’s have a look at some features on the Hello FPGA Kit’s main
PCB (see Fig.1).
The block diagram for the FPGA
board is shown in Fig.2. The FPGA
itself is labelled U1 while the PIC microcontroller is labelled U13. The latter has an 8MHz crystal (Y1), while a
50MHz oscillator (X1) provides the
clock signal for the FPGA.
August 2020 33
Fig.4: the FPGA Demo tab for the AI Demo offers several
sample digit sets to test out the AI recognition system, and
displays the output from the FPGA too.
Four regulators are present: U9, U10,
U11 and U16. U16 derives 3.3V from
the 5V rail. This feeds into U9, providing 1.2V for the FPGA core; and U10,
supplying 1.5V for a DRAM chip. U11
provides the VTT (terminator voltage)
for the DDR DRAM.
U2 is a current-monitoring device
with an I2C interface; it is used to
measure the FPGA current via a current sense resistor connected to the
output of the 1.2V regulator which
powers the FPGA core.
The USB function is not provided by
the PIC (although it is capable of doing so), but by a dedicated USB-serial
IC (U5; MCP2221A). This can also interface to an I2C bus.
There are also a great many passive devices on this side of the PCB;
the power decoupling section shows
over 50 bypass capacitors connecting
across several rails.
The underside of the board is not
quite as busy, although still littered
with many tiny parts, including the
8Gb MT41K1G8RKB DRAM IC (U4),
in a BGA package.
There is also non-volatile storage in
the form of U8, a 64Mb SST26VF064B
serial flash IC. Many FPGAs are designed to load their configuration from
a flash IC during startup.
On the other hand, the Microsemi
M2S010 has its own internal flash,
which reduces power consumption
and is more secure in that the flash
34
Silicon Chip
Fig.5: the Image Processing Demo is simple enough, offering
some sliders to change the way the image from the camera is
displayed on the LCD screen.
memory cannot be easily read by unauthorised persons.
The remaining ICs on this side of
the PCB are U14 (a 74CBTLV3257
four-channel multiplexer) and U15
(a 74LVC1G157 single-channel multiplexer), which combine into a fivechannel multiplexer to switch the
JTAG programming lines between the
PIC and a set of header pins.
This is controlled from the PIC and
defaults to the header pins, allowing
the PIC to take control of these lines
if needed, but allowing connection to
the JTAG header when it is not.
Software
While we earlier alluded to the fact
that some FPGAs are hard to work
with, the demonstration software for
the Hello FPGA Kit is the opposite.
We could only see downloads for
the Windows operating system; our
test system used Windows 10.
You will need a Microsemi account
to download the software. Registration is simple and does not require a
confirmation email (but does need an
email address).
This is done at the following web
page: https://soc.microsemi.com/
Portal/Default.aspx?v=2
You can then go to www.microsemi.
com/existing-parts/parts/150925 and
click on the Resources tab and download the Hello FPGA GUI Application.
The design project files are listed
Australia’s electronics magazine
separately, but the necessary demonstration files are included with the
GUI application. You can download
the various user guides too.
The installer is packaged in a zip
file, so you should extract the entire
file and then run the installer. While
the zip file was around 250MB, the install only appears to be 9MB.
After installing the software, we
were prompted to disable fast-start,
which we did not do. But we did need
to reboot the computer to complete the
installation.
A copy of the MCP2221 drivers is included. We found the files at C:\Microchip\Hello_FPGA_GUI\MCP2221_
Drivers on our system, although they
installed automatically. It appears
that a copy of the PIC firmware image
(HEX file) is also installed along with
the software.
Fig.3 shows the rather terse screen
you are greeted with when you open
the GUI app (it has an “M” icon). At
upper right, connecting to the Hello
FPGA Kit requires selecting its COM
port and pressing the connect/disconnect button next to it.
If it lights up green, then you have
successfully connected.
AI digit recognition
We found the AI Digit Recognition
demonstration to be the most interesting. Once the Hello FPGA Kit is
connected to the host application,
siliconchip.com.au
Fig.6: the FIR demo shows several stages in the signal
processing sequence, from defining and selecting a filter to
testing it and validating the result through FFT analysis of
the output.
the demo firmware is easy to upload.
Under “DAT File”, browse to the
file named “Demo3_HF10_DIGIT_
CNN_FF_V1.1.dat”. On our system,
this was located at C:\Microchip\
Hello_FPGA_GUI\DatFiles. Ensure
“PROGRAM” is selected under the
“Action” drop-down and then click
Run.
The process takes almost a minute,
and prompts you to unplug and replug
the board; this appeared to be unnecessary, although we did need to press
the “Connect” button to restart communication.
One upside of this demo is that it
doesn’t need the GUI app to work, as
much information is displayed on the
onboard LCD screen. The LCD should
show what the camera sees, with some
other information overlaid.
The centre of the LCD is marked by a
green square, which indicates the area
that the FPGA is processing. This is
scaled down to a 28x28 greyscale image, a preview of which is shown in the
LCD’s upper-left corner. It shows the
AI Digit Recognition output at lower
left, as a digit between 0 and 9.
You can click on the FPGA Demo
tab of the GUI app to see some more
information (Fig.4). Some testing digit
sets are available. It is a simple case of
pointing the camera at the digits in the
GUI app to see that it recognises them.
The Hello FPGA Kit had no trouble
identifying the sample digits shown,
siliconchip.com.au
Fig.7: a major focus of the Hello FPGA Kit is on power
consumption, and the Power Graph tab allows this
to be seen in real time, including during and after
applying the Flash Freeze mode.
as long as the camera was correctly
aligned with the image. Since this is
how the ‘AI’ has been trained, that is
to be expected.
The More Info button and CNN
Structure tab both show some background about how the neural network
in the AI is organised.
AI and neural networks are a field
which is seeing more interest of late.
The demo on the Hello FPGA kit is
impressive, but also telling of how
narrow its capabilities are.
Other demos
There are two other demos included
with the Hello FPGA GUI App. These
are the FIR Filter demo (found by loading and programming the “Demo1_
FIR_FILTER_V1.3.dat” file) and the
CAM LCD demo (“Demo2_HF10_
CAM_LCD_FF_V1.1.dat”).
These both rely on the GUI App
to control and interface to the Hello
The LCD screen on the Hello FPGA Kit displays the number that it recognises,
so the AI demo can be used without the GUI app or even a computer connected.
Australia’s electronics magazine
August 2020 35
Fig.8: the Libero design software allows graphical editing of advanced functional blocks. The design files for the three
supplied demos can be viewed and edited, so you can see how they work. That makes it much easier to design your own
firmware, rather than starting from scratch.
FPGA Kit. Select the appropriate DAT
file, select “PROGRAM” and click Run.
The CAM LCD demo (Fig.5) shows
some basic image processing; the controls are seen in the accompanying image and include brightness, contrast
and colour balance. The image from
the camera is processed by the FPGA
and then displayed on the LCD.
The FIR filter demo (Fig.6) shows
how the Hello FPGA Kit can be used
in a signal processing application. FIR
stands for Finite Impulse Response
and is a technique usually used to implement a digital filter.
An FIR filter consists of several coefficients which are applied to a window of samples to produce the output.
The important thing is that the process
involves a large number of multiplications (by coefficients) happening almost simultaneously.
Since the Smartfusion2 FPGA has
many hardware multipliers, this becomes a lot easier to implement in
real-time. Having the multipliers in
hardware means the processing is fast,
which can be critical if the processing
needs to occur with low latency.
An FIR filter has advantages over
discrete filters in that the characteristics are set by the coefficients.
The same hardware can be set to
behave as low-pass, high-pass, bandpass or band-stop by changing the coefficients.
The cut-off frequencies can be
changed, and the filter may even be
Fig.9: 16 sets of
digits are supplied
for use with the
AI Demo. They
shows that it can
recognise digits
regardless of how
they are drawn. You
could test it with
your own writing,
too!
36
Silicon Chip
something that is not even possible
with discrete components.
With the FIR Filter demo, a filter is
generated and the coefficients can be
seen. This filter can then be applied to
a signal to see its effect; the FFT (Fast
Fourier Transform) is also displayed
so that the frequency response of the
filter can be validated.
Power and Flash Freeze
As we noted earlier, power use and
monitoring is an important feature
of the Hello FPGA Kit. The app provides a Power tab to explore this. A
time vs power graph dominates this
view (Fig.7), with a live power reading at lower left.
There are also buttons to switch the
Flash Freeze feature on and off. Flash
Freeze is akin to sleep or suspend
modes in microcontrollers, and the
demos allow users not only to see the
standby power levels, but also measure how long it takes for the unit to
wake up from Flash Freeze.
Libero design software
The demonstration programs are
quite interesting, but somewhat limited in scope. To develop further applications requires the Libero design
Australia’s electronics magazine
siliconchip.com.au
software. To program and debug a device requires a licence, but it’s also possible to get a 60-day free licence which
allows you to see how the Libero design software works.
As mentioned earlier, we tested on
Windows 10, although there are also
versions for Linux.
The Libero design software is a 7GB
download from the Microsemi website,
at http://siliconchip.com.au/link/ab3q
You will need to register to do this.
The install involves unzipping the file
and then installing it, which requires
another 15GB of hard drive space. During the install, you’ll also be prompted
to provide a license; the trial license
can be requested as part of this process,
although it may take up to 45 minutes
to be processed.
Once granted, follow the instructions to install the license; this involves setting an environment variable to a path.
We also downloaded the design files for the three demos from
www.microsemi.com/existing-parts/
parts/150925#resources
There is even a design guide for using the Libero software with the Hello
FPGA hardware, at siliconchip.com.
au/link/ab3r You’ll need to unzip
these to work with them. The actual
project is another compressed archive
inside this.
We opened the Image Processing
demo project (“HF10_OV7725_LCD_
FF.prjx”).
As shown in Fig.8, the overall view
is a similar block-based editor to
what we saw when we reviewed the
iceStick hardware and tested the IceStudio software (siliconchip.com.au/
Article/11521).
So even if you have minimal experience with FPGAs or coding in HDL,
it is possible to create a custom design
using the Hello FPGA hardware, al-
though you will need a different license
to do so, on top of the cost of the board.
Conclusion
The Hello FPGA Kit is simple to use
and demonstrates several diverse features and applications. The GUI app
is straightforward to use. The free trial
license of the Libero design software
is a good way to investigate its suitability for designing for your custom
applications.
The Hello FPGA Kit is well-provisioned; it is currently listed for sale at
around AU$300. The FPGA chip costs
around AU$50 by itself, in multiples
of 119 (in a 7 x 17 chip tray).
You can order a Kit from Digi-key
(siliconchip.com.au/link/ab3s) or
Mouser (siliconchip.com.au/link/ab3t).
Both companies offer free international
express (courier) delivery for this item
(and any other items you order at the
SC
same time).
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Australia’s electronics magazine
August 2020 37
A Switchmode
Replacement
for 78xx
regulators
By
Tim Blythman
The 78xx series of three-terminal linear regulators started as the
LM109/309 in 1969. So they’ve been around for about 50 years, and
they are undeniably still useful today. Their biggest disadvantage is
inefficiency, especially with a large input/output voltage difference.
If only there was an efficient, drop-in alternative!
W
Of course, there are plenty of switch- efficiency at higher currents and volte have been using 78xx series
linear regulators since the mode ICs which do a similar job, but age differentials. It’s built on a board
first issue of SILICON CHIP in they almost always require quite a few that’s roughly the same size as a TONovember 1987 and we still use them extra ‘support’ components, possibly 220 package and has the same three
including a bulky inductor. And some- connecting leads. And it’s relativeextensively today.
There is no doubt that they are a times selecting the right components ly inexpensive and doesn’t use very
simple and effective way of getting is a bit of a ‘black art’. Even then, the many components.
However, we must point out that
a well-controlled fixed voltage sup- result may not match the performance
ply between 3.3V and 24V. They’re of a 78xx; for example, the allowable sometimes, a linear regulator is precheap, they’re available everywhere range of input voltages may be more ferred, mainly because its output does
limited.
not have switching artefacts (such as
and they’re easy to use.
This article describes a switchmode
high-frequency ripple). Linear regulaFor example, our 45V Bench Supply from October and November 2019 regulator that can be used as a direct tors may also have better line and load
(siliconchip.com.au/Article/12014) replacement for a 78xx type regulator regulation. Switchmode regulators are
used three 78xx series positive regula- in most cases, but with much greater continually improving in this regard,
but we understand that there
tors and one 7905 -5V regulawill always be cases where a
tor to provide regulated rails
Features & specifications
linear regulator is required.
for its circuitry.
The ideal solution is often
But being linear devices, • Input voltage: 4-30V
to combine a switchmode
they can be inefficient, and • Output voltage: 2-24V
pre-regulator with a lowthis causes two major prob- • Output current: up to 1A
dropout linear post-regulalems. Not only is much of • Quiescent current: around 80µA
tor. That gives you the best
the supplied energy wasted, • Efficiency: typically 90-96%
of both worlds. Our Hybrid
but it must be adequately • Dropout voltage: 0.5V
Bench Supply from Aprilremoved from the device to • Size: equivalent to a TO-220 package semiconductor device
June 2014 used this apprevent overheating. In oth- • Heatsinking: not required
proach; see siliconchip.com.
er words, more inefficiency • PWM frequency: 500kHz; lower at light loads
au/Series/241
means more dissipation and • External capacitance required: 1µF+ at input, 22µF+ at output
Thus, in the space taken up
more dissipation means more • Other features: under-voltage lockout (4V), thermal shutdown,
over-current/short circuit protection
by two TO-220 parts, you can
heatsinking is required.
38
Silicon Chip
Australia’s electronics magazine
siliconchip.com.au
even implement such a hybrid regulator arrangement by using
our design and then passing its output to a discrete
linear regulator.
The latter should ideally
be a low-dropout type, but a
78xx could be used if maximum
efficiency is not required.
The IC at the centre of this
design can deliver any voltage from 2V to 24V, with the
output voltage of our Regulator set by just one resistor value. So this design can replace
not just one part, but many.
You might also be wondering about parts like the ubiquitous LM317 adjustable regulators.
They have a different pinout
to the 78xx series, so it isn’t possible
to make a one-size-fits-all solution
that addresses both of these families.
While it is possible to fit this device in place of an LM317 in many
cases, you would need to make some
changes to the surrounding circuitry,
including deleting the external resistors which set its voltage.
Our replacement device
The 78xx we know and love is the
one we find in a TO-220 package. This
version alone appeared in half a dozen
circuits that we published last year.
There are also variants in the smaller
TO-92 package (the 78Lxx) and SMD
TO-252 (78Mxx in surface-mounting
D-PAK) packages.
It’s the TO-220 package that we’re
targeting, because if you can get away
with one of the smaller variants, the
chances are that you don’t have too
much dissipation to worry about. Also,
it’s harder to cram the necessary parts
into the smaller spaces that these packages offer.
If your intended application has a
78xx bolted onto a chunky heatsink,
then you’re going to benefit most from
our upgrade. And that’s precisely what
this project is; a drop-in replacement
regulator for the hot, inefficient IC
that’s wasting energy on your design.
Our design is easily adaptable for
Our switchmode Regulator
has a very similar outline to the 78xx
linear regulator it is intended to replace.
With careful choice of parts, the thickness The design
can be kept much the same too. If you
We wanted our Regulator to be as
have space available, you may wish to
close
as possible to a direct substiuse a larger inductor or larger capacitors
tute for the 78XX in a TO-220 packto improve its performance.
many voltages; it can be used in place
of a 7833 (3.3V), 7805, 7806, 7808,
7809, 7810, 7812, 7815 or 7824. It
might also be suitable to replace one
of the many low-dropout three-terminal fixed regulators on the market
(although their pinouts don’t always
match the 78xx).
age, and the first item we considered
was the size.
The body of a TO-220 part is around
10mm x 15mm; a minuscule size for
a PCB. But it would not be a dropin replacement if it doesn’t fit in the
same space.
We decided to leave off the tab
mounting hole, since our design will
How switchmode regulators work
There are many types of switchmode regulators in use today.
This includes step-down (buck), boost, flyback, buck/boost, SEPIC,
resonant and fully isolated types.
But step-down/buck is probably the most common configuration and is also, in a sense, the simplest (with boost not far behind). This is a step-down/buck design.
A linear regulator reduces its output voltage by simply introducing a controlled resistance in series with the load. If the input
voltage is twice the output voltage, this means that 50% of the
power going into the regulator is turned into heat. That means
poor efficiency.
If your aim was to vary the power to something like a LED or
lamp, which only responds to the average current, you could get
much greater efficiency by applying the full input voltage to it but
only doing so 50% of the time. This could be done using pulse
width modulation (PWM), and indeed that is how most DC lamp
dimmers and simple motor speed controllers work.
The voltage is normally switched by a transistor, with the transistor either fully off (and passing no current) or fully on (dropping no voltage). Little power is lost in the switching element, with
real-world efficiencies coming quite close to 100%.
But such an arrangement is not suitable for powering ICs or
other devices which expect a more-or-less constant supply voltage. Thus, to get a similar efficiency to the PWM approach when
siliconchip.com.au
powering such devices, we need to ‘filter out’ the rapidly changing part of the waveform (the AC component), giving us just an
average voltage level (the DC component).
An LC low-pass filter is a simple way to do this. We can’t use
an RC filter since we would have half the voltage across the resistor, so efficiency would be no better than a linear regulator. But
with an LC filter, energy is stored in both elements (the inductor
and the capacitor). Most of that is returned later, so losses and
heating are minimal.
In the case of the inductor, excess energy is briefly stored in
its magnetic field.
One way to think of this approach is that applying pulses of
voltage to an inductor forms something like a constant current
source. At the same time, the capacitor makes the load impedance
very low at high frequencies, resulting in a fairly unchanging voltage across the load, despite the pulses applied by the transistor.
There will still be some amount of ripple present at the load, but
with the correct choice of components, it can be reduced to a manageable amount. In fact, the amount of tolerable ripple dictates the
required switchmode frequency and capacitor and inductor values.
The best way to reduce ripple is to use the largest inductor and
capacitor values possible. In practice, size is an issue, particularly
with inductors, so we are forced to compromise (too large an inductor can also affect the regulator’s response to load transients).
Australia’s electronics magazine
August 2020 39
CON1
OUTPUT
GND
INPUT
3
2
L1 22 H /1A
4
1
3
1 F
35V
2
1 F
6.3V
X7R
SC
2020
VIN
EN
VOUT
6
7
REG1
BOOST
MCP16311
VFB
VCC
AGND
8
100nF
R1
52.3k
1 F
1
6.3V
X7R
PGND
5
10k
HIGH EFFICIENCY SWITCHMODE REGULATOR (5V)
Fig.1: the circuit of the Regulator is just about straight out of the MCP16311 data
sheet, except that the input and output capacitors are lower than recommended.
That’s because these are supplemented by external capacitance on the host
board. The values in red need to change for a different output voltage.
40
Silicon Chip
package (eight-pin micro small outline package). We found a device that
came in this package, with a good
compromise of most of the features
we wanted.
By the way, MSOP packages
have varying pin pitch, sometimes
0.635mm (the same as SSOP and
TSSOP) and sometimes even smaller,
at 0.5mm. But they’re also narrower
than SSOP and TSSOP, so are one of
the most compact packages that can
be hand-soldered without too much
difficulty.
Switchmode operation
If you aren’t familiar with the operation of switchmode regulators, see
our panel “How switchmode regulators work”. This also explains some
6
5
OUTPUT VOLTS
not need to dissipate anywhere near
as much heat. So there is no need to
attach it to a heatsink.
While this does also remove the
option of using a mounting screw to
secure the part, our Regulator uses
sturdy pin headers which are thicker
than the leads on most discrete parts.
If absolutely necessary, silicone sealant or other adhesive can be used to
provide mechanical support.
In any case, the Regulator PCB with
all its parts is typically around half the
weight of a TO-220 device, so the mechanical stresses will be less.
With a PCB size set, we started looking for the best switchmode regulator
IC to use. We needed to choose one
which we could fit on this small PCB,
including all the required supporting
components.
We found it difficult to find suitable
parts that could work up to the nominal 35V input that the 78xx series can
tolerate. In the end, we settled for a
part with a 30V rating, as this covers
most use cases.
We considered using a device in
a user-friendly SOIC-8 SMD package, but one of these would take up
around a quarter of the available space
on the PCB.
Other parts we found came in QFN
(quad flat no-lead) and DFN (dual flat
no-lead) packages, but we decided that
these would be too difficult for many
people to solder.
You need a reflow oven or hot air
station to have much chance of success. So we limited our search to parts
with leads.
A decent compromise between size
and ease of soldering is the MSOP-8
of the other design considerations we
had to take into account.
While sorting through the (huge
number of) switchmode regulator ICs
that are available, we looked at several features. Firstly, high-frequency
operation is necessary. This means
that a lower inductor value is needed, which reduces its physical size. A
higher frequency also means less ripple and noise.
We also looked for parts which operate synchronously, rather than requiring an external diode. While it is
only one extra part, the diode does carry a fair amount of current, so choosing a synchronous part means that
some space and dissipation is saved.
The voltage drop across the low-side
Mosfet (which replaces the diode’s
function in synchronous designs) is
less than that of the diode.
Ultimately, we settled on the Microchip MCP16311. It has a switching
frequency of 500kHz and operates synchronously with a minimum number
of external components for an adjustable output. As noted earlier, it can
operate with up to 30V on its input.
We initially tried to lay out the
PCB using 3216-size (1206 imperial)
passive components. These measure
3.2mm x 1.6mm, but were too large,
so we switched to 2012-size (0805 imperial) parts measuring 2.0 x 1.2mm.
These save a significant amount of
space on the PCB, but aren’t too much
harder than 3216-size parts to solder.
The footprints that we’ve provided
on the PCB are actually a tiny bit larg-
SWITCHMODE
4
7805
3
2
1
0
0
1
2
3
4
5
6
7
8
9
INPUT VOLTS
Fig.2: the Switchmode Regulator does not operate with an input supply below
4V. At 4V and above, though, it has a much lower dropout voltage than the 7805
and attains a 5V output with only 5.5V at its input (ie, 0.5V dropout). The 7805
needs nearly 7V on its input before it is in regulation.
Australia’s electronics magazine
siliconchip.com.au
er than 3216/1206 parts, so you might
be able to use the slightly larger 1206
parts anyway.
The circuit
The circuit for our design is shown
in Fig.1, with the components for a
5V output. IC1 is the MCP16311 integrated switchmode controller. It
works with 4.4-30V at its input (pin
4, VIN) and can deliver 2-24V at up
to 1A. Pin 3, the enable (EN) input, is
tied to VIN so that the IC is enabled
as long as there is a sufficiently high
supply voltage.
The input supply is bypassed by a
1µF capacitor. While this is less than
the recommended capacitance in IC1’s
data sheet, any application using a
7805 requires an external bypass capacitor anyway, which will supplement the capacitance fitted to the PCB.
Pins 5 and 8 are connected to
ground, with pin 5 being the highcurrent return for the synchronous
switch, while pin 8 is the low-current
reference ground to which the output
voltage is referred. Both are connected to large copper pours on the PCB.
IC1 has an internal low-voltage regulator for its control circuitry, which
should be bypassed by a 1µF capacitor
connected between pin 2 and ground.
This pin sits around 5V, so a 6.3V capacitor is adequate.
Pin 1 is connected to IC1’s internal
regulator feedback circuitry. The voltage at pin 1 is compared to a precision
0.8V reference, so this pin should be
Desired
Vout
R1
(E96)
Nominal
Vout
R1
(E24)
L1
3.3V
31.6k 3.328V
30k
3.2V
15µH
(eg, SRN6028-150M)
5V
52.3k 4.984V
51kV
4.88V
22µH
(eg, SRN6028-220M)
6V
64.9k 5.992V
62k
5.76V
27µH
(eg, ASPI-6045S-270M)
8V
88.7k 7.896V
91k
8.08V
39µH
(eg, ASPI-6045S-390M)
9V
102k
8.96V
100k
8.8V
39µH
(eg, ASPI-6045S-390M)
10V
115k
10V
110k
9.6V
47µH
(eg, SRN6028-470M)
12V
140k
12V
130k
11.2V
56µH
(eg, SRN6045TA-560M)
15V
178k
15.04V
180k
15.2V
68µH
(eg, TYS6045680M-10)
24V
287k
23.76V
300k
24.8V
120µH
(eg, SRN6045TA-121M*)
* current rating is 850mA, so don’t draw more than this (the output voltage may drop before reaching that level). For more current, you can probably get away with a 100µH inductor, part code ASPIAIG-S6055-101M.
Table 1: Component choices
connected to the midpoint of a voltage divider between the output and
ground. The ratio of this divider sets
what fraction of the output voltage
is seen at pin 1 and thus dictates the
output voltage.
The MCP16311 data sheet recommends a 10k resistor for the lower
part of the divider, so changing the
output voltage is simply a case of setting the upper resistor.
For a 5V output, the upper resistor should ideally be 52.5k. While
From left to right, a 3.3V Regulator, a 5V Regulator and a 12V Regulator. Note
that the inductor needed is much larger for higher voltage versions. This version
is only 6mm thick, which is more than the 5mm of many 78xx regulators, but
still slim enough to fit in most places where one would be used, especially as no
heatsink is normally required.
siliconchip.com.au
Nominal
Vout
Australia’s electronics magazine
changing this resistance will set a different output voltage, for optimum
performance, other components must
be adjusted too.
In practice, 52.3kis the closest
commonly available value, from the
E96 (96 values per decade) series. This
gives a nominal 4.984V output. For
comparison, a 51k resistor (found in
the more common E24 series) would
give a nominal 4.88V output.
Unless you need a precision voltage reference, either of these would
be close enough for most 5V supplies.
You probably should not use a switchmode device as a precision reference
anyway!
Pin 6 is the switch (SW) terminal,
which is connected to the two internal
Mosfets. One switches the output to
ground (pin 5), the other to VIN (pin
4). A non-synchronous part would
require an external diode (typically a
schottky diode) in place of the lower
transistor, to allow inductor current to
circulate while the upper Mosfet is off.
Between the switch terminal and
the output is an LC low-pass filter
comprising a series inductor and a capacitor to ground. Like the input capacitor, we’re using a lower capacitor
value than recommended in the view
that more external capacitance will be
fitted. However, it would be possible
to fit a higher capacitance in the space
available if necessary.
The output of the LC filter is fed to
August 2020 41
Setting the output voltage
The MCP16311 data sheet recommends different inductors for different
output voltages. The rule-of-thumb
value is 4.5µH per volt at the output.
In choosing an inductor, keep an
eye on the DC resistance specification
too. Values around 100mare recommended, meaning that the inductor
will drop 0.1V, dissipating 100mW
when the regulator is supplying 1A.
If you are planning to run your regulator near 1A, this will probably be
the biggest loss.
Another critical point is the voltage
rating of the output filter capacitor.
You need a 6.3V or higher rating for a
5V output, but we’ve specified 50V for
all capacitors to keep things simple.
Advanced constructors may wish to
use devices with a lower voltage rating but higher capacitance, as long as
they still have a sufficient voltage rating for their particular role.
Table 1 shows some choices for both
the top resistor value (from both the
42
Silicon Chip
TOP VIEW
1 F
18105201
1
BOTTOM VIEW
L1
1
52.3k 10k
1 F
100nF
REG1
1
1 F
REG1
1
1 F
CON1
100nF
L1
1
R1
R1
52.3k 10k
1 F
18105201
CON1
the output pin of CON1, which forms
the interface with the external circuitry; its other two pins are connected
to the VIN pin of IC1 and the ground
pour. This output voltage is also fed
to the upper resistor in the feedback
voltage divider mentioned earlier.
The final component on the board
is a 100nF capacitor between pins 6
(switch or SW) and pin 7 (BOOST).
Because the internal high-side Mosfet is an N-channel device for maximum efficiency, it needs its gate to be
brought above its source to conduct.
As the source is connected to the SW
pin, a voltage above SW (and possibly
above VIN) is required to drive its gate.
An internal charge pump provides
this higher voltage, which is stored in
this 100nF capacitor until it is needed
to switch the Mosfet.
The overall operation is as follows.
IC1 produces a pulse-width modulated (PWM) square wave at the SW pin
(pin 6) which is filtered by the LC circuit. The output voltage is monitored
by the voltage divider connected to
pin 1, which causes IC1 to change its
PWM duty cycle to maintain the desired output voltage.
With a light load at its output, IC1
can also ‘drop’ or skip PWM cycles,
reducing power consumption.
Three-pin header CON1 has 0.1in
(2.54mm) spacing, to match a TO-220
package.
1 F
1
(WITHOUT LABELS)
Fig.3: we’ve shown the component
overlays same size (above) as we
IN GND OUT
OUT GND IN
normally do but thought a veryBOTTOM VIEW (300%)
TOP VIEW (300%)
much-enlarged view (at right)
would help you with assembly.
Inductor L1 is fitted to the top side of the PCB, opposite to the other parts. It is
easiest to solder IC1 first, as access to its pins is not as good once the surrounding
parts are in place. The part that controls the output voltage is resistor R1 at upper
left. Here it is a 52.3kresistor, to give a 5V output. Pin header CON1 can be fitted
to either side, depending on the needs of your application. This can be fitted last,
so you can test fit the board before soldering it.
E24 and E96 series) and also a suggested inductor value.
Note that the E24 resistor values do
not allow for a high level of accuracy,
but may still be close enough, depending on your application.
Performance
Naturally, we ran some tests to ensure that the Regulator has equivalent
performance to its linear predecessor.
As per the data sheet recommendations, we connected around 10µF extra capacitance at the input and 22µF
at the output.
Efficiency is very high compared
to a linear device. We connected our
prototype 5V Regulator to an 8 load
(a wirewound power resistor), drawing a nominal 625mA. For low values of input voltage (up to around
12V), efficiency was 96%, dropping
off above 12V.
This agrees well with the information in the MCP16311 data sheet. Our
calculations suggest that well over half
of these losses are simply due to dissipation in the inductor’s DC resistance. Hence, the importance of low
DC resistance in this part.
During this test, we noted the Regulator was warming up above ambient,
but was never too hot to touch.
Another quick measurement indicated that the quiescent current of
the Regulator (under no-load conditions) is around 80µA, close to the
Australia’s electronics magazine
value from the data sheet, and a lot
less than a 78xx regulator at around
5mA (60 times higher!).
Fig.2 shows how the output voltage
varies with the input voltage, comparing the Regulator with the expected
performance of a standard 7805. This
also indicates the dropout voltage. Interestingly, the 7805 passes more voltage at very low input voltages.
This is not unexpected, as the
MCP16311 does not even come out
of the under-voltage lockout until
its input reaches around 4V. Once it
starts up, it has a much lower dropout, needing an input of only 5.5V to
supply 5V at the output; a dropout
voltage of around 0.5V.
On the other hand, the 7805 is not
regulating correctly until its input
reaches around 7V; a 2V dropout.
In battery-powered applications,
both the lower quiescent current and
the low dropout voltages are big advantages. Not only does the higher
efficiency mean that less energy is
wasted, but the Regulator is also capable of operating with much lower
input voltages, making better use of
the same battery.
One advantage of the MCP16311’s
low-voltage shutdown feature is that
in a battery situation, the 7805 would
continue to pass current, completely
flattening the battery (which could be
fatal if it’s a rechargeable type), while
the MCP16311 will switch off when
siliconchip.com.au
Again reproduced very much larger
than in real life, these photos show
front and back of the regulator – in
this case set up to replace a 7805 (5V)
regulator. Changing the regulation
voltage is as simple as changing R1
and L1 to suit.
its input gets too low, preventing this.
Since the output is below 5V by the
time the input reaches 4V, the connected circuit will probably not be operating to specification anyway.
Scope1-Scope4 show more details
of the circuit’s performance. Scope1
shows that the Regulator takes around
350µs to start up, which is quick
enough for most applications. Scope2
shows output ripple.
This is one area in which the 7805
will be superior, although this small
amount of ripple is tolerable for most
applications.
Scope3 and Scope4 show the response to load and line changes; the
output varies by around ±150mV for a
625mA load step, recovering in less than
100µs, while line regulation is around
1%, ie, an output variation of around
17mV for an input ripple of 1.88V.
Construction
Taking note of what is described
above, choose your components before starting construction. Many of
the components are quite small, and
their marking will be barely legible.
The capacitors will probably be unmarked, so take care not to mix them
up (or lose them!).
Check that you have the appropriate
tools for working with small surfacemounted components.
At a minimum, we recommend a
fine-tipped soldering iron (preferably
siliconchip.com.au
with adjustable temperature), a pair
of fine-tipped tweezers, a magnifier
as well as some flux paste and solder braid (wick).
Something to secure the very
small PCB would be handy. If you
don’t have a PCB clamping tool,
then Blu-Tack may be sufficient.
The Regulator is built on a double-sided PCB coded 18105201
which measures 15 x 10mm and
is 0.6mm thick (a standard PCB is
1.6mm thick, which would make
the device 1mm thicker). Refer to the
PCB overlay diagram (Fig.3) during
construction, to see which parts go
where.
IC1 has the finest pins, so start by
fitting it. Check and confirm where the
pin 1 dot is and align it with the markings on the PCB. If you have CON1 at
the bottom then IC1’s pin 1 is at lower left. If you cannot find a dot, then
the part may have a chamfer along
one edge; this edge should be closest
to CON1.
IC1’s pins are on a 0.65mm pitch
with only a 0.2mm spacing. You will
probably bridge some pins while soldering it, so the solder braid is essential.
Apply some flux to the pads and
hold the IC in place with the tweezers. Solder one pad down (or one
even one side if your iron tip is broad).
Check and double-check that all the
pins are entirely within their pads; if
they are not, then they may short to
adjacent pads even after any solder
bridges are removed. Also check that
the part is flat.
Once you are sure of this, solder the
pins on the other side. Don’t be concerned about bridges; in this case, they
are almost inevitable. Just ensure that
each pin is soldered to its correct pad
in some fashion.
With the IC soldered in place on
both sides, you can clean up any bridges. Apply some more flux paste to the
pins and press the braid against the
pins with the soldering iron on one
side. Gently draw the braid away from
the part. It should draw up any excess
solder, leaving a clean fillet.
Inspect this with the magnifier and
compare it to our photo above.
Apart from IC1, none of the parts
are polarised, so do not be concerned
about the orientation after IC1 is installed. Follow with the 100nF capacitor which goes near IC1’s pins 1 and
8. Apply flux to the pads and solder
Australia’s electronics magazine
Parts list – ‘78XX’
1 double-sided PCB coded
18105201, 15 x 10 x 0.6mm
1 3-pin right-angle header, 2.54mm
pitch (or straight header,
depending on application) (CON1)
1 22µH 6mm x 6mm 1.1A inductor*
(eg, BOURNS SRN6028-220M)
1 MCP16311 switchmode IC, MSOP8 package (Digi-key, Mouser)
Capacitors (all X7R SMD ceramics,
size 2012/0805)
3 1µF 50V^
1 100nF 50V
(code 105)
(code 104)
Resistors (all 1% SMD size 2012/0805)
1 52.3kW (R1)* (code 5232)
1 10kW
(code 1002)
* parts for 5V output; see Table 1 for
other voltages
^ increase to 2.2µF if an external lowESR input bypass capacitor of at
least 1µF is not possible
one lead only. Confirm that the part is
flat and square within the pads before
soldering the other lead. Go back and
retouch the first lead with some fresh
solder or a bit of extra flux.
Use the same technique to fit the
three 1µF capacitors. While they don’t
all need to be 50V types, the price difference is small, so it’s easier to just
use 50V types for all three as stated
in the parts list. That also makes assembly easier since you don’t have to
worry about which one goes where.
The two remaining parts on this side
are the resistors. Fortunately, these are
usually marked so are more difficult
to mix up. The 10kresistor will be
marked as 103 or 1002. The other resistor value will vary depending on
your selected output voltage. For the
52.3kresistor we’ve recommended
for a 5V output, expect a code of 5232.
The last component, inductor L1, is
on the other side of the PCB. So now is
a good time to clean up any flux residue on the top before flipping the PCB
over. If you don’t have a dedicated flux
solvent, isopropyl alcohol may work
(assuming you can get some at a reasonable price… even metho is getting
hard to find!).
In any case, take care, as many of
these cleaning substances are flammable. Allow the PCB to thoroughly dry
before resuming soldering.
L1 is a larger part and will generally have more thermal mass, so may
August 2020 43
Scope1: this shows the response of the Regulator to having
8V applied with an 8
load (625mA). Its startup time is
limited mostly by having to charge the output capacitance,
which would be the case for most regulator circuits.
require more heat. We’ve sized the
pads for a nominal 6mm x 6mm part
although up to 8mm x 8mm may fit. In
this case, you may need to apply heat
to the inductor leads.
The technique is much the same as
for other two-lead parts. Apply flux,
solder one lead, check that the part is
where you would like it and then solder the remaining lead. Then clean
up the flux that’s been applied to this
side of the PCB.
You may need to install straight or
right-angle headers for CON1, depending on how you wish to use the Regulator. We’ve fitted right-angle headers
to our units to make them install just
like a TO-220 device. This is also ideal
for use on a breadboard.
If using right-angle headers, check
which side is the best fit (they can be
soldered on either side), in case space
is tight in your application.
We fitted the headers at the rear (IC1
side) of the PCB by removing the pins
from the plastic frame and threading
them into the frame from the other
side. This allows the pins to be held
in position while soldering.
This arrangement can also be used
to mount the Regulator flat against the
PCB by bending the leads a further 90°,
just as you would for a discrete part,
but a more rigid option would be to
mount a straight header at the back.
This may not work if you have components very close to where the Regu44
Silicon Chip
Scope2: under the same test conditions as Scope1, we’ve
zoomed into the output waveform after it has had time to
stabilise to show the output ripple. We see around 50mV
of ripple at the MCP16311’s 500kHz PWM frequency; more
output filter capacitance would reduce this. This ripple is
the main downside of using a switchmode regulator.
lator will need to mount, but will be
a lot more secure as the shorter leads
will not be able to flex as much.
Testing
One of the worst things that could
happen is that R1 is open circuit,
which would mean that IC1 is not
able to regulate the output as it cannot see any voltage at its output; effectively, the input voltage will appear at
the output.
If this is your first foray into surface
mounted parts, you might want to double-check your soldering against our
photos. You should ideally also test
that the Regulator works correctly before deploying it to your circuit. 3-pin
header CON1 will make it easy to plug
into a breadboard or use jumper wires
to rig up a test circuit.
Note that the front of the Regulator
is the side with the inductor and the
CON1 header and pin 1 markings are
on this side.
Apply 4-30V to pin 1 of CON1 (with
respect to GND at pin 2). Use a currentlimited supply if possible (eg, a bench
supply) or series resistor to limit the
current; this will minimise damage in
the event of a fault with the circuit.
You should be able to measure the
desired output voltage at pin 3. You
may also like to load the output (for
example, with a resistor) to check
that the circuit works under load. If
it works as expected, you are ready to
Australia’s electronics magazine
solder it into your final circuit.
Installation
Because it is intended to replace a
single component, the Regulator could
be used in any number of designs, so
we can only offer general advice.
Any design using a 78xx or similar
should have separate bypass and filter
capacitors already included.
We’ve put some modest capacitance
on the Regulator PCB, but as mentioned earlier, not as much as recommended by the MCP16311 datasheet;
mostly due to space considerations.
The MCP16311 should ideally have
at least 2µF at its input and 20µF at
its output; we’ve provided around 1µF
For some
variants, we
squeezed
in slightly
larger 3216/
1206-sized
capacitors
across the
input and
output pins.
It’s generally
easier to get
these larger
valued or
higher-rated
parts in the larger
part sizes, so it is
worth considering
if space
is not critical.
siliconchip.com.au
Scope3: here we connected a 68
load to the Regulator
and switched a second 8
load in and out using a Mosfet
(gate voltage in blue, the yellow trace is the supply voltage).
Thus the output current jumps from 75mA to 700mA and
back. The green trace shows the output voltage, which in
all cases stays within 200mV of the setpoint. More output
capacitance will stabilise this further.
for each. Thus an extra 1µF on the input and at least 22µF at the output is
recommended.
One option to add more capacitance directly to the Regulator PCB is
to stack capacitors vertically. We’ve
even seen part manufacturers do this
to create discrete capacitors with more
capacitance!
You might also be able to get discrete
capacitors with a higher value that
will fit onto the board, depending on
the actual input and output voltages
you’ll be using.
Check what parts are available in
the 2012/0805 size (or 3216/1206 size,
if you’re willing to jam them in). We
recommend that you stick with types
having an X5R, X6S or X7R dielectric.
For example, 2.2µF 50V X5R capacitors are available in 2012/0805 size,
if you can’t fit a 1µF external ceramic
bypass capacitor on your host board.
We’ve also built some variants with
larger 1206 (3216 metric) sized input
and output capacitors; you can see
these in the photos.
On the other hand, if your design
can tolerate some ripple at the output,
then you may be able to reduce the
output capacitance below the recommended value.
Just be careful to check that this
doesn’t affect stability under the range
of load conditions the regulator will
experience.
When fitting the Regulator to your
siliconchip.com.au
Scope4: the same 8
load as before but with the input
supply being fed from an AC transformer and bridge
rectifier with a 1000µ
µF filter capacitor. Around 2V of ripple
(at 100Hz) from the supply produces less than 20mV of
ripple at the Regulator’s output, an attenuation of around
100 times.
PCB, keep in mind that there are
bare component leads on the back of
the Regulator PCB which may short
against (for example) the existing 78xx
mounting hole. Some insulating tape
(eg, polyimide) applied to the PCB
should be sufficient to avoid problems here.
Under low load conditions, thermal
dissipation will be quite low, so you
could probably even seal the entire
part in heatshrink tubing, although
we haven’t tested this.
Alternatively, if you have space, extend the headers pins of CON1 so that
there is clearance between the Regulator PCB and the PCB underneath.
If your design is subject to vibration,
some neutral-cure silicone sealant between the two will reduce mechanical fatigue.
If you are using the right-angle
mounting arrangement, then you will
also lose the option to mechanically
secure the Regulator PCB because it
lacks a mounting hole. You should also
ensure clearance between the Regulator PCB and any case parts that might
short against the components on the
Regulator PCB.
Again, some tape and sealant may
be required to maintain clearance and
insulation. If you have space, the right
angle connector CON1 can be mounted
at the front (rather than the back) of
the PCB. This will increase the clearance behind it.
SC
Australia’s electronics magazine
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AUGUST 2020
45
SERVICEMAN'S LOG
Fixing heaters – it’s a gas
Dave Thompson
I usually only repair electronic and mechanical devices, not gas
appliances. But when our heater started acting up in the middle of
winter, I thought I’d better look into it. It turned out to be an electrical
problem after all, so it was up my alley!
It’s almost the middle of winter here
in Christchurch, and as is usual for this
time of year, the weather is gloomy and
cold. Because of the ‘lockdown’, we are
spending a lot more time inside than
we usually would, and subsequently
spending a lot more on keeping the
house warm as well! Then again, as we
aren’t driving our cars that much, the
money saved and extra money spent
probably cancel out.
I know what you are thinking; LPG
isn’t the most efficient way to heat a
46
Silicon Chip
home. I agree, but the 6.5kW Masport
gas stove (or fire, depending on where
you went to school) installed in our
lounge was already here when we
moved in. And given that we no longer
have a reticulated natural gas supply
in town, it is bottled gas or nothing.
We never actually intended to keep
this fire; we knew the people we purchased this house from and spent
many nights enjoying dinners here, but
because they didn’t use the fire much,
we thought it wasn’t much chop.
Australia’s electronics magazine
We planned to replace the gas fire
with a pellet fire (or stove, depending
on where you went to school). We’d
used a pellet fire in our old home for
the previous decade or so and we were
very happy with it. While some love
and some loathe pellet fires, for efficiency, they’re tough to beat.
The fuel is simply compressed
sawdust, which is cheap to make and
widely available, and emissions are
next-to-nothing. The ash pot only
needs emptying once every few weeks
siliconchip.com.au
when the fire is used all day, every
day. Our old Canadian-made Evolution 2 pellet stove (which replaced a
log burner) could throw out around
10kW, but we only ever used it on the
lowest of five heat settings; otherwise,
we’d have melted!
Before we moved in, I purchased
an identical, almost-new Evolution 2
pellet fire salvaged from a quake-damaged home. It was a bargain, and all
we’d need to do was swap out the gas
fire with this one, although I’d have to
get resource consent and a registered
installer to do that work. I could do
it, of course; but I had to pay a professional to do it, to satisfy the insurance company.
But once we moved in, we discovered that the gas fire could produce
some decent heat (about 6.5kW worth),
so it wasn’t worthwhile to replace it.
That spare pellet fire is now taking up
valuable bench and power tool space
in my workshop, so if anyone is looking for a cheap, good-condition Evolution 2, drop me a line!
fires is the noise of the fan and auger
motor. On the low setting, the auger
runs for about three seconds twice per
minute; on high, more often. It isn’t
that loud, and we found after the first
few nights we no longer heard it, but
visitors would often ask what it was.
The fan noise is similar to a small
fan heater; not too intrusive but certainly audible. Many people think they
couldn’t put up with these noises, but
it really isn’t that intrusive, and we
soon got used to it.
Another downside is that a pellet
stove needs electricity, so it was initially rendered useless in the quakes,
when we had prolonged periods without mains power. However, I soon had
it rigged it up to our generator, so we
could at least keep warm if the power failed.
And that is pretty much it as far as
operation goes. Keeping it as dustfree inside as possible, and emptying
the ash pan once in a while is about
all that is required; plus a flue clean
every couple of years.
An introductory course on
pellet heaters
The problems begin
For those who don’t know what a
pellet stove is, or how they work, they
are actually very clever. Most work
similarly, regardless of make or model.
(Don’t worry, this is leading to a repair
story, I promise…)
The top part of the machine is a
hopper into which pellets are poured.
Pellets are available from supermarkets and hardware stores in 10, 15 or
20-kilo bags, with the largest bags being the hardest to carry, but also the
best value. Thankfully, since we usually ran our heater on low, it would
only burn through about 15kg of pellets each week.
A motorised auger system in the bottom of the pellet hopper periodically
feeds pellets into a burn pot, usually
within a sealed burn chamber in the
bottom half of the fire. You can generally see this burn pot through the glass
front door of the chamber, and this is
where the visible flames sprout from
as well, giving that cosy ‘fireplace’ effect. A blower fan spreads the hot air
outwards from the fire.
Once the fire is alight, the more pellets you feed in, the hotter it burns.
Drop in the pellets less-frequently, and
the heat output is reduced.
Besides having to feed the hungry
fire, the other main gripe with pellet
siliconchip.com.au
As you’d expect, there are lots of
moving parts in a pellet heater, and
they need to be in good condition to
ensure they are operating effectively.
The first problem I had with our Evolution stove was a common one: a
failed igniter.
Usually, to get the fire going, you just
push a button. It starts the auger motor
and an internal fan. The auger drops
pellets into the burn pot. When they
have built up into a small pile, the igniter, which protrudes slightly into the
burn pot, glows red-hot and sets the
pellets burning. It’s helped along by
the calibrated airflow in the chamber.
When the chamber temperature
rises to a set level, the main blower
fan kicks in, and it’s away. This usually takes about 10 minutes or so, but
after a few years, it took increasingly
longer, and eventually failed to ignite
altogether.
This wasn’t as disastrous as you’d
think, because I could easily start the
fire by opening the door, manually igniting a small number of metho-soaked
pellets in the burn pot and then closing the door; the stove would then be
going almost instantly. However, this
took away some of the convenience,
so I looked into replacing that igniter.
I ended up getting the supplier to
send out their maintenance guy who
Australia’s electronics magazine
Items Covered This Month
•
•
•
•
Fixing a pellet heater
Upgrading a Labtech Q1590
frequency counter
Asus monitor repair
LG TV power board repair
*Dave Thompson runs PC Anytime
in Christchurch, NZ.
Website: www.pcanytime.co.nz
Email: dave<at>pcanytime.co.nz
replaced it, telling me that poor design meant that as long as the stove
was ‘on’, the igniter was powered
and glowing red hot. This makes little
sense, as once the thing was alight, it
didn’t need any other ignition source
and all this did was considerably
shorten the life of the igniter.
It went again after another two years
and that time I replaced it, at considerably less cost. When it failed again two
years after that, I left it as-is and simply used the metho starting method.
After about 10 years, the auger motor bearings failed, and that made a really nasty noise. Fortunately, they are
standard bearings and easily replaced,
but it goes to show that the more complex a system, the more breakdownprone it becomes.
All this influenced our decision not
to replace the Masport gas fire/stove.
For one, it is relatively cheap to run
(compared to electricity) and as we use
the gas for cooking as well, it makes
no real sense to replace it.
Even the fire is sick of the
lockdown
So it was a bit ironic that barely a
few weeks into the lockdown, the fire
would periodically go out. I never saw
it going out; I just noticed that while
the built-in fan was still running, there
was no fire on the fake logs. Re-lighting
it was also difficult.
At first, I thought that the 45kg bottle was empty and needed swapping
(I use a manual switching system, so
I know when one of the bottles needs
replacing). Usually, all I have to do is
open the tap on the fresh bottle and
flick the gas switch over, and all is
well. But this time, I could see the
go/no-go indicator in the gas line was
still showing green, so the tank wasn’t
empty after all.
August 2020 47
I went back inside and tried to ignite
the fire to no avail. To start it, I push
and turn the main gas valve to ‘light’
and hold it down while I press the
piezo igniter. Typically, it takes a few
strikes to light the pilot lamp, and after
about five seconds I can let up on the
valve and the pilot stays alight while
I hear gas enter the burn chamber, beneath the fake rocks. A few ‘WOOFS’
later and the thing is going.
We rarely have to turn this one up either, with level one or two sufficient to
warm our space. However, this time I
needed to keep the valve pressed much
longer, and even then the pilot barely
lit up. Once going, we needed to run
it on level five just to keep it alight.
Something was obviously wrong…
While I know a little about a lot of
things, I know next to nothing about
how gas fires work. But a quick internet search gave me all the information I needed, as well as an excellent
service manual for the appliance. At
least that allowed me to investigate
what could be wrong.
I know one thing though; messing
around with gas and fittings is something that absolutely should be left to
48
Silicon Chip
the professionals. I can still clearly
recall sitting at my workshop desk a
few months back, and feeling/hearing
the massive bang as a house about four
kilometres from me literally blew to
bits because of a gas fire leak. Lesson
learned! Gas is not to be trifled with.
Editor’s note: as detailed in this column in the past, just because you get a
professional to do the job doesn’t necessarily mean that you will get a good
result. Our newly-built house had a
recurring gas leak (as did our neighbours, in the other half of the duplex).
That was despite it being checked and
approved by the relevant authorities!
The good news is that as there was
some electronics involved, I had a legitimate reason to at least have a poke
around.
These fires are actually very clever;
all gas fires must have a fail-safe system
that shuts off the flow if either the pilot
light goes out or the main gas valve is
opened without lighting the fire. This
stops the room filling up with gas and
suffocating anyone, or converting the
home into a bomb.
The gas-flow system is controlled
by a solenoid which is held open (and
Australia’s electronics magazine
thus allows gas to flow) only while a
flame heats a thermocouple (or thermopile). If the pilot flame goes out, the
thermocouple cools, its output voltage
drops and the solenoid closes, stopping the gas flow. It’s simple and highly
effective, as long as all the components
in the system are working.
So based on the symptoms, I could
at least start to troubleshoot this problem without having to take any gas
lines apart.
The first possibility was a blocked or
partially blocked gas line. If the blockage was further up the line, towards
the bottles and the fittings, I wouldn’t
be able to do anything without a gasfitter’s ticket.
However, we use the same system
for cooking, and our gas hob rings all
burned at full noise, so it was unlikely
to be a problem with the lines, at least
to the junction where the fire and gas
hob feeds split off – which is situated
handily right behind the heater.
That meant that it was unlikely
that the gas lines to the heater were
blocked. But we could have simply
had a blocked pilot light, and that assembly is readily accessible after removing the escutcheon and one glass
panel from the front of the heater.
Once exposed, I used a bent piece of
copper wire that just fit into the pilotlight jet to clear any potential blockage. It felt clear, and a quick puff with
one of my rubber-bulb circuit-board
dusters ensured that it was clear of
obstructions.
The pilot light on this fire has three
flame paths: one towards the bare-copper igniter wire, one to the thermocouple, positioned opposite the igniter
wire, and one into the main part of
the fire. I used a pipe-cleaner soaked
in white spirit to clean these out, and
as they came out remarkably clean,
that was likely not the fault.
I could hold the gas valve down
and turn the main gas input tap at
the back of the fire on and off, and
could hear a decent gas flow through
the system. So I doubted that it was
a flow problem.
The next thing to check was the thermocouple. These are a known consumable, and replacements are widely and
cheaply available. After removing the
rear access panel, I could see where
the thermocouple connected into the
main valve. This is a plumbing-type
fitting that is easily removed/undone
with an open-ended spanner.
siliconchip.com.au
Once free, the copper tube-like
electric lead can be unfurled to bring
the connection out so I could get my
multimeter probes onto it. The tube is
grounded, while the internal wire is
the ‘hot’ lead (LOL!).
With the meter set to volts, I played
the flame of my small gas torch over
the thermocouple tip, where the pilot flame usually hits it. I measured
just on 9mV. According to the book,
I should read at least 15mV, so this
was a potential (haha!) problem; 9mV
may be barely enough to hold the solenoid in.
A replacement M9x1 thermocouple
was only $39 including delivery, so it
made sense to replace it and see what
happened. I tested the new one when
it arrived, and got a reading of 16mV.
Fitting it was as easy as loosening a
retaining nut and bolt, removing the
old one and threading the new one
in. I re-connected it to the main valve,
and the fire’s been going perfectly for a
month now, so I think that’s job done!
Labtech Q1590 frequency counter
upgrade
C. K., of Croydon, Vic, went a bit beyond the usual remit in this column of
making something that’s broken work
again. Instead, he took an older test instrument that was functional but a bit
inaccurate, and modernised it so that
it is super-accurate. As you can imagine, it took a bit of doing...
What can we do with test equipment, years old but still functional,
The interior view of the Q1590 frequency counter. There is an oscillator module
inside the centre metal enclosure.
that is well off the pace in regards to
accuracy and stability? This was my
dilemma when I tried to calibrate a
Labtech Q1590 multi-function counter.
I bought it probably in 1989, and it
has never failed me. But these days,
digital communication technology
requires extreme frequency accuracy.
Only a few Hertz out, and digital messages cannot be decoded.
I tried to calibrate the counter using
a GPS-disciplined source of 10MHz,
but the readout was about 150Hz
too low. Taking the case off revealed
an oscillator module inside a metal
case, with two trimcaps which can
be accessed through holes in the top
(shown above). One trimmer is for a
10MHz crystal, and the other is for a
3.906250MHz crystal, the purpose of
which is not clear to me.
As the readout was low, the 10MHz
oscillator frequency was too high. But
adjusting the trimmer still did not give
me a correct reading. Adding an 18pF
capacitor across it helped, but the adjustment was difficult and tended to
jump.
By replacing the trimmer capacitor
and the parallel fixed capacitor with
new ones, and with very careful adjustment, I could get to within about
3Hz. But I wasn’t satisfied with that.
Fig.1: the small circuit designed to utilise a cheap
TCXO found online as a replacement oscillator
module in the Q1590.
siliconchip.com.au
Australia’s electronics magazine
August 2020 49
The original oscillator module shown without the metal cover (left) and with the
oven and NPN transistor removed (right)
Also, on turning the counter on, the
reading started about 50Hz low and
after a couple of minutes overshot by
about 8Hz, then over several hours, it
gradually crept to within 3Hz.
Both crystals are wrapped in a piece
of copper that is heated by an NPN
power transistor (shown above). A
thermistor glued to the copper sheath
provides feedback so that it maintains
a more-or-less constant temperature.
But apparently, the temperature still
was not stable enough.
Since I hate to throw things out, I
decided to come up with an improved
oscillator design using a TCXO (Temperature Compensated Crystal Oscillator). These can be expensive, but I
found a 10MHz model on AliExpress
for less than $20. That seemed suspiciously cheap, but I decided to take a
punt anyway.
The 3.906250MHz crystal was a
problem – I couldn’t find a TCXO
at that frequency. So I decided to
use a DDS (Direct Digital Synthesis) chip like the Analog Devices
AD9850 (as described in the September 2017 issue; siliconchip.com.au/
Article/10805).
Modules using this chip are available cheaply on eBay and elsewhere,
but there was not enough space in the
Frequency Counter to fit such a module and associated micro.
Fortunately, I had a couple of the
bare chips in my stock of parts. Virtually any microcontroller can be used
to load the tuning word into this chip,
and as I have heaps of Atmel AVRs on
hand, I decided to use an ATtiny2313.
The circuit I came up with is shown
on the previous page. If it looks familiar, that might be because it’s quite
similar to my Circuit Notebook entry on pages 96-97 of January 2020
(siliconchip.com.au/Article/12231).
But that circuit used an Arduino and
an AD9850-based module, compared
to the more basic approach taken here.
There is a small problem in that
when the AD9850 has a 10MHz input
frequency, the 3.90625MHz we want
at the output is a bit too close to the
The fixed frequency counter with new oscillator module – the repair cost
totalled less than $50.
50
SILICON CHIP
Australia’s electronics magazine
siliconchip.com.au
The finished replacement module was
made using a custom PCB.
Nyquist frequency of 5MHz, resulting
in a very distorted output with many
spurs that could read as false edges. I
solved this with a tuned circuit that
cleans up the waveform, based on
transformer T1 plus one fixed and one
variable capacitor.
I managed to locate the original
counter schematic and discovered that
the 3.90625MHz crystal is driven by
one stage of a 74HC04 hex inverter, operating as an oscillator amplifier. So I
just had to remove the old crystal and
feed the output of the AD9850 chip
into pin 13 of the 74HC04.
All that the ATtiny2313 does is load
five bytes into the AD9850 to set up the
correct output frequency. The tuning
word is 0x64000000 (hex). Obviously,
there is some magic power-of-two relationship between the two frequencies
to get such a simple number (and this
hints at why a seemingly odd frequency was chosen).
Designing the PCB was a bit tricky,
as there is not much room available,
so I mostly used surface-mount components. Some resistors and capacitors are on the underside of the board.
It was fortunate that the pins connecting the oscillator board to the
motherboard were at 5.08mm (0.2in)
centres. I used socket strips on the
motherboard and matching pins on
the oscillator board so that it became
a plug-in module.
Once the custom PCB arrived, I
loaded the components and plugged
the module in (shown at left). Holding my breath, I connected the 10MHz
reference to the input. And up came
10000000 – spot on! I decided to leave
it running several hours, in which time
there was the rare jump to 10000001,
but only for one count period. I was
quite surprised and pleased that the
cheap TCXO is so accurate.
There is a sticky label on the oscillator which gives access to an adjustsiliconchip.com.au
ment, but I am rather glad that I did
not have to fiddle with that.
I still don’t know what the
3.96250MHz frequency is used for. I
believe it has to do with the 100MHz
to 1GHz range of the counter. Having
spent considerable time on this repair/
upgrade, I did not feel inclined to do
a full analysis of the original design.
Has the exercise been worth it? Not
if I count the (unpaid) hours I spent on
it. As I already had most of the components, I spent less than $50 in total.
But the satisfaction of extending the
life of an otherwise useless instrument
certainly made it worthwhile.
Asus monitor repair
Poor, innocent bugs are often unfairly targeted as the cause of electronics
misbehaving. But in the case of one
particular monitor, B. P., of Dundathu,
Qld, found the culprit to be of the reptilian variety instead...
We’ve been using an Asus computer
monitor in our camper as a TV, with
it connected to a personal video recorder (PVR). Recently, my wife told
me that the monitor was dead. I found
that she was right, so I had to take it
apart to see if it could be repaired. Often something that is totally dead is
easier to repair than something that
partly works; I was hoping that would
be the case here.
Opening the monitor up proved to
be quite tricky. Computer monitors, in
general, don’t seem to be built with repair in mind, as they are clipped and
Australia’s electronics magazine
not screwed together. So it’s often difficult to get them apart without damage.
The usual way of opening them is to
pull the front plastic surround away
from the screen carefully, making sure
not to damage the screen in the process. I’ve opened up quite a few monitors over time, but this one proved to
be a lot more difficult than most of the
others I’ve worked on. Still, I eventually got it open.
I then sat the monitor face-down on
a towel and lifted the back off. I could
then see why the monitor had stopped
working; there was a blown-up gecko
at the side of the metal housing. I could
see that the gecko had been burnt by
high voltage electricity. Despite that,
it had clearly crawled some distance
from where it had been zapped.
After removing the gecko, I proceeded to disconnect the cables necessary to turn the metal housing over
so I could access the circuit boards
on the other side. While doing this, I
found a dead cockroach in the corner
of the video board. I’ve previously had
a computer power supply blown up
by a roach, but this time, the culprit
was the gecko.
There was a considerable carbon deposit between the two tracks where the
gecko had come in contact. I’ve seen
other devices where tracks have been
shorted by some wildlife, but this is
the first time I’ve seen this carbon between the tracks. I would need to rectify this before I looked into what else
might have been destroyed.
August 2020 51
I started by scraping all the carbon
out of the burnt section of the PCB
until it was back to clean fibreglass.
This was to ensure that it would not
arc when voltage was applied. Next, I
touched up the corner of the blown-off
pad with solder, although this may not
have been entirely necessary.
I checked the fuse next, and it had
blown. That was potentially a good
sign, but it didn’t rule out damage to
other components.
I searched for a replacement fuse,
but as this fuse was a leaded type that
was soldered to the PCB, I was unable
to find a suitable replacement. I then
thought of fitting fuse clips, so that I
could use a regular fuse, but I didn’t
have any clips of a suitable size.
I wondered what junk circuit board
I might have that I could salvage some
smaller fuse clips from, and I located
an old CRT TV board that I hadn’t yet
stripped of components.
It had suitable clips and even a fuse
with the correct rating, so I removed
them from the board and considered
how I could fit them to the monitor
PCB.
Because the replacement fuse was
shorter than the original fuse, I decided
to re-use one of the original fuse pads
and fit the other clip to a section of
the PCB with no tracks. I drilled 1/16in holes for the clips, fitted them and
bent the pins over, then soldered the
first one to the pad.
It was then just a matter of soldering a wire from the pins on the other
clip to the original track. This would
save me effort in future if the fuse ever
blew again.
It’s always hit and miss replacing a
blown fuse, as it might just blow again
the instant that power is applied, or
perhaps it wouldn’t blow but something else would.
So before applying power, I decided
The dead gecko and the damage done
shown below.
52
Silicon Chip
Australia’s electronics magazine
to make some further checks. I checked
the bridge rectifier, and it tested good.
I then checked across the power terminals and as there was no short circuit
apparent, I decided to apply power to
see what would happen. I plugged in
a power cable and turned the monitor
over, then pressed the power button
and the monitor came to life.
That was a good sign; it appears that
the fuse had done its job in protecting
the circuit from the killer gecko. I just
had to reassemble the monitor and put
it back into service. It has been working well since the repair and I’m hoping for no more wildlife invasions. Unfortunately, there are large openings in
the monitor for ventilation, so that is
still a possibility.
This was another successful repair
at no cost, which was a win-win situation. It saved the monitor from landfill and avoided us having to find a
replacement. It’s worth having a go at
repairing devices, but always remember that electricity kills, so proceed
with extreme care.
LG TV power board repair
R. S., of Fig Tree Pocket, Qld found
some damaged parts on a TV power
supply PCB and replaced them. But
it seems that the damage was more
widespread than he thought...
This LG TV power supply board had
a strange fault on the 5V standby supply. It uses a 3B0365 IC (IC500) with
an internal high-voltage FET, which
shorted out.
When this and the 1.2W currentsense resistor (which I found to be
open circuit) were replaced, the 5V
supply would still not power up.
The circuit (siliconchip.com.au/
link/ab3a and siliconchip.com.au/
link/ab3b) shows that the auxiliary supply generated for the 3B0365
comes from an extra winding on the
transformer. This also supplies two
other integrated circuits on the board,
via a transistor controlled by a powerup signal from the main board.
This transistor was shorted out, as
was the L6599 IC (IC100), so the auxiliary supply for the 3B0365 was being shunted, stopping it from working.
Once these additional faulty parts
were replaced, the board sprang to life.
What I am not sure about is whether
the L6599 failed first and damaged
the other components, or whether the
3B0365 failed first and caused the other problems.
SC
siliconchip.com.au
Test and
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TEMPERATURE /
ENVIRONMENT MONITOR
to detect humidIty, temperature,
and air quality
AIR QUALITY SENSOR
WITH CO2+TEMPERATURE
DUST SENSOR MODULE
Detect a wide range of volatile organic
compounds (TVOCs), including equivalent
carbon dioxide (eCO2) and metal oxide
(MOX) levels.
ONLY
• 5V Input Power
• CCS811B chip
• Precision NTC thermistor
• Board Measures 36 x 20mm
XC3782
Detect airborn micro-particulate particles
as small as 0.8μm with this photoelectric
dust sensor module. Sensitive enough to
detect cigarrette smoke.
• Sharp GP2Y1014AU optical sensor
• Ultra low power consumption
• 0.5V/(0.1mg/m3) Sensitivity
XC3780
34
$
$
TEMPERATURE AND HUMIDITY
SENSOR MODULE
DIGITAL TEMPERATURE
SENSOR MODULE
Measure both temperature and humidity. Features
resistive-type humidity measurement.
• 0 ºC - 50 ºC +/- 2 ºC temp range
• 20 – 80% +/- 5% humidity
• 1Hz sample rate
XC4520
ONLY
Provides up to 12 bits of resolution and 0.5°
accuracy through a single digital IO pin.
Multiple devices can even be
connected to the same pin.
XC3700
ONLY
9
$
ONLY
2395
95
695
95
TEMPERATURE
SENSOR MODULE
Provides simple way to measure
temperature. The module outputs an
analogue voltage that varies directly
with temperature. Connect it straight
to one of your Duinotech analogue
inputs. Max 100°C.
• 21cm breakout
ONLY
cable included
XC4494
695
$
$
BLUETOOTH® V4.0
BLE MODULE
2 X 16 LCD
CONTROLLER MODULE
JUMPER LEAD - 100 PIECE
ACTIVE BUZZER MODULE
ONLY
ONLY
ONLY
ONLY
Brings the latest Bluetooth® 4.0 standards to
your Arduino® project. Configurable as master
or slave. Provides a serial communication
channel. Serial interface with AT commands.
XC4382
29
$
Allows you to create a user friendly interface
for your project. Comes with a built-in 16
character by 2 line LCD display with backlight.
• Contrast adjust knob
• 4 Bit Arduino® LCD Library
XC4454
19
95
$
14
95
$
SMART WI-FI RELAY KIT
SCREW TERMINAL SHIELDS
ONLY
FROM
An ESP8266 Wi-Fi controlled SPDT
relay that you can trigger with an
App from anywhere in the world.
5VDC Input power or 9-12VDC via
regulator.
• 10A <at> 250VAC Contact rating
• ESP8266 Module and microcontroller
• Screw terminal blocks
• 45(L) x 28(W) x 20(H)mm
XC3804
17
$
$
BREADBOARD LAYOUT
PROTOTYPING BOARDS
HP95
70
4
95
In the Trade?
9
$
95
$
Over 200 parts to get your new Arduino®
project up and running with a minimum
of fuss. Includes wires, components,
400 point breadboard and a 170 page
instruction book to get you started.
• Classic Arduino® Uno board
• Includes a buzzer, motor and servo
for interactive output
• Light sensors, pushbuttons,
LEDs and more!
XC9200
ONLY
169
$
XC3
8
90
Strip of eight RGB LEDs which can
be controlled by a single Arduino®
pin. Up to 1000 LEDs can be daisy
chained and run from one pin.
• Each channel has 256 brightness
levels
• Current draw 500mA per module
maximum
XC4380
JUST
495
95
See website for details
RGB LED STRIP MODULE
A prototyping board that lets you transfer
your breadboard design without having
to rework it. Includes five holes on each
side per row and power rails running the
length of the board.
Small 400 Hole HP9570 $4.95 (Shown)
Large 862 Hole HP9572 $9.95
$
95
The easy way to add sound to your
project. Hook up a digital pin and
ground, and use the tone() function
to get your Arduino® beeping.
XC4424
ARDUINO® STARTER KIT
A screw terminal block to simplify
wiring for your Arduino® Uno & Nano
boards. Includes a large prototyping
area with through-plated holes
for any components that require
soldering.
Suits Nano XC3892 $9.95
Suits Uno XC3890 $15.95
9
95
FROM
A mixed pack of jumper leads for
your Arduino®, breadboarding and
prototyping projects.
WC6027
BREADBOARD
POWER MODULE
BREADBOARD
WITH 830 TIE POINTS
ONLY
JUST
Adds a compact power supply to
your breadboard. Power from a USB
socket or DC. 3.3V or 5V switchable.
XC4606
9
$
95
With labeled rows and columns and adhesive
back for mounting, it is ideal for electronic
prototyping and Arduino® projects. 200
distribution holes.
• 630 terminal holes
PB8815
1495
$
55
YOUR DESTINATION FOR ENCLOSURES, ELECTROMECH & MORE.
Think. Possible.
NEMA-4 IP65 waterproof sealed enclosures
Jaycar stocks a comprehensive range of enclosures suitable for professional
applications in harsh environments, prototyping or even general utility uses.
Excellent value for money!* More than 120 enclosures available.
• Sealed lid with recessed neoprene gasket
• Protects against the ingress of moisture and dust
LISTED ARE SOME OF OUR POPULAR SELLERS.
*See in-store for details.
DIECAST ALUMINIUM (METAL):
ABS (DARK GREY):
POLYCARBONATE (LIGHT GREY):
• Operating temperature: -40°C to +125°C
• Lid fixing screws are M4 stainless steel
(non-magnetic) into threaded brass inserts
• Some sizes available with flange or clear lid
Small
82 x 80 x 55mm
HB6230 $14.95
Medium
115 x 90 x 55mm HB6216 $17.95
Large
171 x 121 x 80mm HB6224 $26.95
Extra Large 222 x 146 x 55mm HB6220 $34.95
HB5050
HB6230
• Operating temperature: Up to +400°C
• Screw holes for lid fixing are roll threaded
• Captive recessed lid screws
• Some sizes available with flange mount
Small
64 x 58 x 35mm
HB5030 $13.95
Medium
115 x 90 x 55mm HB5042 $25.95
Large
171 x 121 x 55mm HB5046 $36.95
Extra Large 222 x 146 x 55mm HB5050 $39.95
• Operating temperature: -20°C to +80°C
• Lid fixing screws are M4 stainless steel
(non-magnetic) into threaded brass inserts
• Some sizes available with flange mount
Small
64 x 58 x 35mm
HB6120 $6.95
Medium
115 x 65 x 55mm HB6124 $13.95
Large
171 x 121 x 80mm HB6129 $23.95
Extra Large 240 x 160 x 90mm HB6134 $39.95
SEE OUR WEBSITE
FOR A FULL RANGE OF
ENCLOSURES!
HB
FROM
9
612
SELF-POWERED
LED PANEL METERS
20%
OFF
SELECTED
PANEL METERS
& ACCESSORIES
1495
95
$
HEAVY DUTY CURRENT SHUNTS
Super simple to install, these units connect
straight up, with no fuss! Auto zero calibration
and easy to read red LED display.
• Automatic polarity sensing
Voltmeter 4.5-30V QP5581
WAS $14.95 NOW $11.95
Ammeter 0-50A QP5588
WAS $39.95 NOW $31.95
These shunt bars allow you to measure high
current draw without needing a high current
ammeter. 50mV max current.
5A 10.0mΩ
QP5410
WAS $14.95 NOW $11.95
50A 1.0mΩ QP5412
WAS $14.95 NOW $11.95
100A 0.5mΩ QP5415
WAS $19.95 NOW $15.95
200A 0.25mΩ QP5417
WAS $19.95 NOW $15.95
10
NOW FROM
11
95
19MM IP67
METAL
PUSHBUTTON
SWITCHES
Durable and stylish stainless steel switch with
LED ring illumination.
• 12V LED illumination
• DPDT momentary action
• Spade or solder connection
Red DPDT SP0800 $19.95
Blue DPDT SP0802 $19.95
Green DPDT SP0804 $19.95
Blue SPDT SP0810 $20.95
SP
08
04
$
SP0810 (Front)
1995
click & collect
Moving Coil Type.
• 44mm meter hole
• MU45
• 59(W) x 52(H)mm
WAS $17.95 EA
0-1mA QP5010
0-50μA QP5012
0-1A
QP5013
0-5A
QP5014
0-10A QP5015
0-20A QP5016
0-20V QP5020
0-30V QP5022
QP5016
QP5022
7
1395
$
EA.
SAVE 20%
IP67/65 waterproof switches
Jaycar stocks a great range of high quality
electromechanical switches to suit every application
and every budget. Our range is so huge that it would
be impossible to feature all of them here. So if you
are looking for any of these features for your project,
talk to us now. *See in-store for details.
• Heavy duty plastic or metal body
• SPST, SPDT or DPDT configurations
• Momentary or On/Off action
• Round, square or rectangular bezels
• Black, red, green, blue or metal silver buttons
• lluminated or non-illuminated LED status
• Spade or solder lugs connection
PUSHBUTTON SWITCHES
SPST IP67
SEALED MINI TOGGLE
SWITCHES IP67
ROCKER SWITCH
SPDT IP65
ONLY
FROM
ONLY
4
SP0810 (Back)
PANEL METERS
NOW
1
QP54
SAVE 20%
$
FROM
$
95
• Contact rating: 100mA <at>50VAC
• Momentary action
Black Button SP0656
Red Button SP0657
(with Power Symbol)
QP54
NOW FROM
11
$
SAVE 20%
56
FROM
13
$
HB
95
4
6
$
613
FROM
• Contact rating: 2A <at>250VAC
• On-On action
SPDT ST0554 $6.95
DPDT ST0555 $7.95
6
$
95
EA
95
• Contact rating: 21A<at>14VDC
• On-Off-On action
• Red/green illumination
SK0999
1695
$
YOUR ONE-STOP-SHOP! HEAD TO OUR WEBSITE
FOR ALL YOUR MECHANICAL SWITCH REQUIREMENTS.
Buy online & collect in store
ON SALE 24.07.2020 - 23.08.2020
YOUR DESTINATION FOR COMPONENTS & MORE.
Exclusive
club offer
Think. Possible.
15A 2 CORE TINNED
POWER CABLE
25A 2 CORE TINNED
POWER CABLE
Suitable for automotive and marine
applications. Double insulated.
• Resistance (20°C): 0.0123 ohm/m
• Max Temp: 80°C
Per Metre WH3079
RRP $2.85 CLUB $2.40
CLUB
Per 30m Roll WH3077
FROM
RRP $74.95 CLUB $62.95
2
$
Suitable for auto, marine or
general purpose wiring.
• Resistance (20°C):
0.0053 ohm/m
• Max Temp: 80°C
WH3087 RRP $4.95/m
$
/m
CRIMPING TOOL
FOR NONINSULATED LUGS
ONLY
95
RESISTOR PACKS
CLUB
5
$
NOW FROM
SAVE 20%
SAVE 20%
15 AMP DC POWER CABLE
HANDY PACK
7.5A TINNED HEAVY DUTY
HANDY PACKS
CLUB
CLUB
Suitable for general purpose
automotive and marine applications.
15A rated current.
• 10m roll black cable
WH3055 RRP $12.95
$
EA
Quality connectors
Whether you’re working with micro power
digital signals, or high current automotive
equipment, we’ve got the connectors to
suit your application. Solder, crimp or screw
terminals, Jaycar is your one stop shop for
everything electrical.
HEAVY DUTY
WIRE STRIPPER /
CUTTER / CRIMPER
WITH WIRE GUIDE
Strip all types of cable
from AWG 10-24 gauge
(0.13-6.0mm). TH1827
ONLY
32
$
More ways to pay:
95
1995
FROM
FROM
TERMINAL STRIPS
D' BACKSHELLS
12 way & capable of being divided
with a sharp knife. Supplied with a
sturdy retention hole.
• Temperature: -35°C to 110°C
6A HM3194 $2.15
10A HM3196 $2.45
FROM
215
$
20%
OFF
SAVE 20%
‘D’ CONNECTORS
1
EA
SELECTED
PROTOTYPING
PACKS
$
WEIDMULLER PCB MOUNT
SCREW TERMINALS
$ 35
$
NOW
95
These are 5.08mm spacing.
Interlocking. 10A rated.
2-Way HM3130 $1.35
3-Way HM3132 $1.75
1270
00
100 pieces. Contains 3mm and 5mm LEDs
of mixed colours. Even includes 10 x 5mm
mounting hardware FREE!
ZD1694 WAS $24.95
7
9
$
95
Silicone rubber insulation, very
flexible with high temperature rating.
Suitable for 250V wiring and general
heavy duty work. 10m roll length.
• Resistance (20°C): 0.0237 ohm/m
• Max Temp: 80°C
RRP $14.95 EA
Red
WH3035
Black WH3037
ASSORTED LED PACK
Ceramic 10pF - 100nF - 60 Pieces
RC5399 WAS $9.95 NOW $7.95
Greencap 0.001μF - 0.22μF - 60 Pieces
RG5199 WAS $14.95 NOW $11.95
Electrolytic 1μF - 470μF - 55 Pieces
RE6250 WAS $13.50 NOW $10.80
NOW FROM
/m
11
00
CAPACITOR PACKS
0.25W 5% Carbon Film - 300 Pieces
RR1680 WAS $12.95 NOW $9.95
0.50W 1% Metal Film - 300 Pieces
RR0680 WAS $19.95 NOW $15.95
SELECTED HIGH CURRENT
GENERAL PURPOSE
POWER CABLES.
840
$
/m
Flexible heavy duty cable suitable for
general purpose wiring up to 250V.
10m roll length.
• Resistance (20°C): 0.0237 ohm/m
• Max Temp: 80°C
RRP $5.95 EA
Red
WH3045
Black WH3046
Green WH3047
16
$
For even higher current
applications where twin core
cabling is required.
• Resistance (20°C):
0.0024 ohm/m
• Max Temp: 80°C
WH3063 RRP $9.95/m
CLUB
7.5A TINNED HANDY PACKS
Comfortable handles and
spring-loaded.14-18 AWG
and 22-26 AWG.
TH1834
$
CLUB
420
40
15%
OFF
56A 2 CORE TINNED
POWER CABLE
Quality solder-type connectors with
gold plated contacts and nickel
plated shells.
9-Pin Plug
PP0800 $1.45
9-Pin Socket PS0804 $1.95
15-Pin Plug
PP0820 $1.95
15-Pin Socket PS0824 $1.95
1
$ 45
Quality range of backshells in plastic,
metal & ABS flameproof. 9-pin to 25pin available. See website for details.
9-Pin Plastic PM0808 $2.25
9-Pin ABS
PM0810 $2.95
9-Pin Metal
PM0812 $3.95
FROM
2
$
25
METAL BANANA PLUGS
Gold plated, designed for monster type
speaker cable. The hole will accept another
banana plug or a thick cable.
Red
PP0426 $4.95
Black
PP0427 $4.95
Red Locking PP0416 $7.95
Black Locking PP0417 $7.95
FROM
495
$
BANANA SOCKET
- SCREW TYPE
Top quality speaker terminal with gold
banana sockets which also have a huge hole
(6mm) to accept high gauge speaker cable.
• Suppled with gasket.
PT3008
ONLY
1095
$
57
YOUR DESTINATION FOR THE BEST REWARDS & PERKS
love jaycar? you're going to love our rewards!
SHOP
In store & online
EARN
POINTS
For dollars spent
1 point = $1
CLUB OFFER
GET
REWARDS
eCoupons for future shops in store
200 points = $10 eCoupon
CLUB OFFER
139
249
$
SAVE $20
account profile and more...
CLUB OFFER
139
$
+
PERKS
offers, event invitations,
$
SAVE $30
300W HOT AIR
REWORK STATION
SAVE $50
PROFESSIONAL
400K LUX METER
• Temp range: 100-500°C
• Air flow control:
Rotary dial
• 240V powered
TS1645 RRP $159
PROFESSIONAL
SOUND LEVEL METER
WITH CALIBRATOR
• Selectable Lux or
fc scale
• Data hold
• Relative mode
• Includes
carry case.
QM1584 RRP $169
• Wide dynamic range from
30dB to 130dB.
• Min, Max & Data hold
• A & C Weighting* Fast
(125ms) or Slow (1s)
response.
• USB connectivity
QM1598 RRP $299
CLUB
OFFER
SAVE
CLUB
OFFER
SAVE
CLUB
OFFER
SAVE
CLUB
OFFER
SAVE
RATCHET CRIMPING TOOL
TRANSISTOR CLAMPS
CORROSION BUSTER PEN
20A 6.5-100V DC POWER
METER WITH BUILT-IN SHUNT
25%
Heavy duty. Crimp F-type CAT-V
connectors onto RG6 or RG59 coax.
TH1831 RRP $39.95 CLUB $29.95
20%
Clamp TO-220 devices to a heatsink.
Pack of 100.
HH8602 RRP $24.95 CLUB $19.95
20%
Remove rust, wax and dirt.
NA1410 RRP $24.95 CLUB $19.95
20%
Display power, voltage, energy, current.
QP2320 RRP $29.95 CLUB $22.95
CLUB
OFFER
SAVE
CLUB
OFFER
SAVE
CLUB
OFFER
SAVE
ANALOGUE BENCH
VOLTMETER 0-15V
TINNED COPPER WIRE
REVERSIBLE GEARHEAD MOTOR BATTERY SECURING TRAYS
25%
Quick and easy to read display of volts.
QP5040 RRP $19.95 CLUB $14.95
25%
Tin plated. 100g.
WW4030 RRP $19.95 CLUB $14.95
CLUB
OFFER
SAVE
20%
25%
50kg.cm torque at 55RPM at load and up
to 160RPM at No load.
YG2738 RRP $43.95 CLUB $34.95
Heavy duty. 2 sizes available.
Small HB8104 RRP $14.95 CLUB $10.95
Large HB8106 RRP $16.95 CLUB $11.95
CLUB
OFFER
SAVE
CLUB
OFFER
SAVE
CLUB
OFFER
SAVE
CLUB
OFFER
SAVE
BENCH ENCLOSURE
4-IN-1 USB TYPE-C
CONNECTION LEAD
10 WAY BLADE FUSE
BLOCKS
4P/6P/8P MODULAR CRIMP TOOL
WITH NETWORK/POE TESTER
10%
Comply with standard IEC297 rack
heights. 88(H) x 279(D) x 304(W)mm.
HB5556 RRP $69.95 CLUB $59.95
20%
Connects most portable USB devices.
1m long.
WC7764 RRP $24.95 CLUB $19.95
15%
Screw or spade terminals with LED
indicator. SZ2097 or SZ2098
RRP $26.95EA. CLUB $21.95EA.
10% OFF
EXCLUSIVE CLUB OFFER
DESKTOP MAGNIFIERS*
*See T&Cs for details.
58
click & collect
Buy online & collect in store
15%
Tests both UTP and STP cable. Detachable
cable tester.
TH1939 RRP $74.95 CLUB $62.95
YOUR CLUB, YOUR PERKS
KEEP UP TO DATE WITH THE LATEST OFFERS & WHAT'S ON!
Visit www.jaycar.com.au/makerhub
ON SALE 24.07.2020 - 23.08.2020
YOUR DESTINATION FOR WORKBENCH ESSENTIALS
Think. Possible.
1. VACUUM BENCH VICE
WITH 75MM JAW
• Made from hard-wearing diecast
aluminium
• Vacuum base and ball joint clamp
• 75mm opening jaw
• 160mm tall (approx)
TH1766
ONLY
39
$
95
2. MAGNETIC PICKUP
TOOL
• Magnetic tip with claw
• Flexible spring steel shaft
• LED illumination
TH1864
ONLY
1495
$
4. 100MHZ DUAL CHANNEL
OSCILLOSCOPE
WITH DIGITAL STORAGE
849
$
1795
$
Contains wash-free RMA
flux and conforms to
MIL- F- 14256F.
• Plastic reels
• 1.5m long
1.5mm NS3026
3.0mm NS3028
139
SAVE $20
6. DIGITAL MICROSCOPE
• Suitable for laboratory work, jewellers etc.
• Up to 600X Magnification
USB with 3MP Camera QC3191 (Shown)
WAS $99.95 NOW $69.95 SAVE $30
1080P with 4.3" Screen QC3193
WAS $129 NOW $99 SAVE $30
EA
ELECTRONIC CLEANING
SOLVENT 175G
Highly efficient fast drying solvent for
use on delicate electronic, electrical
equipment. NA1004
ONLY
1150
$
SAVE $30
Easy and inexpensive alternative to
welding, soldering and brazing. Two
part epoxy resin. Bonds to almost any
surface. NA1518
ONLY
1695
$
Bond, build, fix and fill anything in seconds. A
solvent free formula stays liquid until cured with
the included UV LED Light. NA1530
44
$
• Temp range up to
320°C
• Exceptional heat
recovery
• High insulation,
low current leakage
• Electrically safety
approved
TS1430
ONLY
89
$
95
95
More ways to pay:
95
10% OFF
SELECTED WATCH TOOLS.
• 08mm punch
• 2 spare pin punches
• Assortment of 2 pins
TH2014 WAS $10.95
NOW
950
$
JEWELLER'S
SCREWDRIVER SET
BONDIC LIQUID PLASTIC
WELDING KIT
2
15W 240V
SOLDERING IRON
PIN EXTRACTOR PRESS
J-B WELD EPOXY
JUST
6995
$
Japanese built quality, with a large
vacuum chamber for strong suction.
• 330mm long.
TH1856
31
95
3
NOW FROM
DESOLDERING TOOL
$
5
$
4
$
ONLY
ONLY
1
• Up to 5A current
• Input Voltage: 100-240VAC <at> 50/60Hz
• Output voltage: 0-16V/5A, 0-27V/3A, 0-36V/2.2A
• Constant current and voltage options
• Includes banana to alligator clamp leads NOW
• 53(W) x 300(D) x 138(H)mm
MP3842 WAS $159
Quality soldering irons & accessories by goot.
DESOLDER BRAID
6
5. 80W SLIMLINE LAB POWER
SUPPLY
3. VERNIER CALIPERS
• 5-digit LCD
• 0-150mm (0-6”) measurement range
• Metric & imperial measurement
Budget
TD2081 $17.95
Stainless Steel TD2082 $39.95
FROM
5
• Lightweight and compact unit for greater control
and data storage options
• 7" colour LCD
• Built-in waveform generator
NOW
• High accuracy
• PC connection via USB
• SD card support
SAVE $50
QC1936 WAS $899
Set of six, housed in a handy
storage case
• Slotted: 1.0, 1.2 & 1.6mm
• Phillips: #00, #0 & #1
TD2023 WAS $9.95
NOW
8
$
95
65W 240V TEMPERATURE
CONTROLLED SOLDERING STATION
• Adjustable temperature (200-480°C)
• Excellent temperature stability and anti-static
characteristics
• Electrically safety approved
• 146(L) x 115(W) x 98(H)mm
TS1440 WAS $329
NOW
299
$
SAVE $30
2 PIECE WATCH CASE
OPENER KIT
Consists of an adjustable opener
that engages the little
recesses on the back of
a watch. Also includes
an oyster shucker style NOW
opening tool.
TH1929 WAS $24.95
2195
$
4 PIECE WATCHMAKER'S KIT
Case retainer with 18 retaining lugs,
a large dusting bulb pump, No. 7
tweezers and fine dusting brush.
TH1932 WAS $34.95
NOW
3095
$
WATCH CASE HOLDER
TH1934 WAS $15.95
NOW
1395
$
59
What’s
DUINOTECH LEONARDO
ATMEGA32U4
DEVELOPMENT BOARD
DUINOTECH ATTINY85 MICRO
USB DEVELOPMENT BOARD
4 X 4 X 4 LED
CUBE KIT
Take your soldering skills to the next level by building a dazzling array of ultra-bright
blue LEDs. Using the supplied template, you will arrange this 4 x 4 x 4 matrix into a
work of art. Fifteen different psychedelic patterns are included, with instructions on
how to create your own. With some ingenuity, you could even create a 3D version of
your favourite retro platform game!
• 64 Ultra-Bright LEDs
ONLY
• 65(W) x 88(H) x 65(D)mm
KM1097
1395
95
$
Suit Windows and
Android Smartphones.
Omnidirectional with
a 2m long cable.
Includes wind sock
to reduce noise and
a convenient carry
pouch.
• 35Hz - 18kHz
frequency response
• Electrostatic pickup
• -30dB sensitivity
AM4015
Components may differ slightly to the one shown.
12V 850A
DON'T FORGET
YOUR BATTERIES!
179
CR123A 3V LITHIUM BATTERIES
- 6 PACK
Commonly used in LED torches and
cameras.
• 1600mAh capacity
• Not rechargeable
SB2324
Jaycar stock a huge range
of batteries from tiny
button cells to rechargeable
batteries to suit your
requirement. See in-store or
online for our full range!
Extremely light and portable.
Capable of jump starting just
about anything. Charges via
USB C socket.
• 850A cranking current
• Qi Charger
• Lithium rechargeable
battery
• 2 x USB ports
• LED torch with SOS function
MB3764
$
2995
$
JUMP STARTER
& POWERBANK
Send high definition AV
signals to a screen in
another room up to 150m
away using a Cat5e/6 cable
through a common router
or Ethernet switch.
• 100m (Cat5e), 150m
INCLUDES TRANSMITTER,
(Cat6)
RECEIVER AND POWER
Transmission distance
SUPPLIES
• HDMI pass-through
ONLY
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CIRCUIT NOTEBOOK
Interesting circuit ideas which we have checked but not built and tested. Contributions will be
paid for at standard rates. All submissions should include full name, address & phone number.
Four USB power supplies from laptop charger
AC/DC adaptors for notebooks and
laptops are widely available at low
prices. These usually have an output
voltage of 19-20V and output current
between 3.5A and 7A. They are reliable, compact, have low RFI/EMI emissions and do not dissipate much heat.
There are also many devices designed to run from a USB +5V power
supply. Also, many devices designed
to be powered from 6V or 4.5V work
well when powered from +5V. So it
is handy to have a way to power such
devices from the laptop supplies previously mentioned. This circuit accomplishes that.
It’s based on four identical sub-circuits built around MIC4576-5.0 fixed
output voltage buck regulator chips.
These can deliver up to 3A at 5V.
Their switching frequency is nominally 200kHz.
The circuit is protected with a fuse
at the input and diode D9 will cause
the fuse to blow immediately if the
supply polarity is accidentally reversed. LED5 lights up to indicate
when power is applied.
The output of a switchmode laptop
supply can have some noise and ripple, so this is reduced by the CLC pi
filter comprising numerous capacitors
on the input side, a 220µH choke and
the bypass capacitors for REG1-REG4
which are all effectively in parallel.
This filter also helps to prevent switching noise from REG1-REG4 being radiated out of the input supply leads.
Each regulator has three input bypass capacitors of various values, to
provide a low-impedance supply over
a wide range of frequencies.
They also require freewheeling
schottky diodes (D1-D4), filter inductors (L1-L4) and output filter capacitors,
which each comprise a parallel pair,
100µF and 1000µF. LEDs1-4 indicate
the presence of voltage at each output,
while diodes D5-D8 protects the circuit against back-fed negative voltages.
With up to 15W delivered to each
USB output, the total maximum power
is 60W. If we assume that efficiency is
around 80%, we need an adaptor that
can deliver 72W. If the output voltage
is 19V, this means a current draw of up
to 4A, hence the value chosen for F1.
Most laptop supplies can handle that.
REG1 to REG4 need to be connected
to large copper areas to help remove
heat from them. For output currents
above about 1.5-2A, it would also be a
good idea to attach small finned heatsinks to each regulator.
If you can’t get the MIC4576-5.0 regulators, you could substitute LM25965.0 or LM2576-5.0 regulators, but then
the values of inductors L1-L4 might
have to change.
Petre Petrov,
Sofia, Bulgaria. ($75)
61
Preamplifier power supply runs from 5V DC
I wanted to build the Ultra-Low Distortion Preamp with Tone Controls
and Six-input Preamp published in
the March, April & September 2019
issues (siliconchip.com.au/Series/333
& siliconchip.com.au/Article/11917).
However, I decided that I wanted to
run my preamp from a single 5V DC
supply. So I started researching the use
of a Linear Technology LT1930 power
converter chip. From their application
sheet, I built up a supply that could
deliver ±15V at 70mA per side from
a 5V DC input. The chip switches at
1.2MHz, which means the inductor
and capacitors can be physically small.
One problem with the chip is its surface-mount footprint which makes it
a bit difficult to design the board and
solder the 5-pin chip. In the application notes, they mentioned using the
copper PCB to provide heatsinking
since the chip is switching a lot of
power for its size.
It works like a boost converter feeding into a charge pump. When REG1’s
pin 4 shutdown input (SHDN) is high,
it periodically sinks current into its
switch pin (SW, pin 1). This causes
current to flow through inductor L1,
charging up its magnetic field.
When REG1’s internal switch turns
off, the voltage at pin 1 shoots up. This
rise is coupled through capacitor C1,
forward-biasing schottky diode D2,
charging up output filter capacitor C3.
When pin 1 of REG1 goes low again,
C1 discharges through D1, so it’s ready
to repeat the cycle.
When the voltage at pin 1 goes up,
capacitor C2 is also charged up via
diode D3. When pin 1 goes low, the
negative transition is coupled through
C2, pulling the cathode of diode D4
negative and charging up output filter capacitor C4.
The +15V output voltage is divided
down and applied to REG1’s feedback
pin (FB, pin 3) so that it can adjust its
duty cycle to maintain a constant +15V
output regardless of load. The load on
the -15V output is assumed to be similar, and so the -15V output should be
reasonably close to the desired voltage.
I have run the supply for more than
three months without any problems. I
measured its efficiency at 75%. I used
the recommended 2.2µF multi-layer
ceramic capacitors and a 22µF tantalum capacitor for input bypassing.
Although I have no means of measuring the audio quality from the
preamp, it sounds fine to me. Since
the chip runs at 1.2MHz, I doubt it will
have much effect on audio frequency
signals, although it may interfere with
RF tuners. But I have never noticed
any such problem.
The inductor I used is an SMD 10µH
ferrite-core type from Altronics, Cat
L8200, which is rated at 2.3A with a
DC resistance of 70mW. The LT1930 is
available from element14. The diodes
must be schottky devices to keep up
with the high switching frequency.
Although I haven’t tried it, the circuit should run from a 3.7V lithiumion rechargeable battery.
Bob Temple,
Churchill, Vic. ($80)
The LT1930 regulator is soldered
to the copper side of the PCB.
Modifying the Ultra-LD Mk.2 to drive a hearing loop
As shown here, it’s quite easy to
modify one of our Ultra-LD amplifier
modules (or indeed, just about any
discrete amplifier published in Silicon Chip in the last 10 years) to drive
a hearing loop. The additional components can be mounted on a piece
of protoboard, with the double-pole
switch mounted on a panel or bracket.
There are three connections to the
amplifier labelled X, Y and Z. Connec62
Silicon Chip
tion X can be made by carefully soldering a wire to a pad on the top side
of the PCB while Y and Z are made
through the speaker output connector. The switch is included to allow
the amplifier to be switched from constant current back to constant voltage
mode if desired.
With switch S1 in the position
shown here, the current through the
external loop is sensed by a 0.5W
Australia’s electronics magazine
shunt resistor and the voltage developed across this resistor is AC-coupled
back to the base of PNP transistor Q2,
in the input pair of the amplifier. This
overrides the normal voltage feedback
signal because it has a much lower impedance of around 12.5W compared to
the original 489W (510W ∥ 12kW).
The two added 1N4148 diodes are
to protect the electrolytic coupling capacitor from damage under overload
siliconchip.com.au
conditions. The 2.5W resistor limits
the peak loop current. This must be a
high-wattage resistor.
With S1 in the alternative position,
the shunt resistor is shorted out so that
the negative terminal of the speaker
connects to ground as it usually would,
and the current feedback path is disconnected, allowing the usual voltage
feedback to resume. You still have the
2.5W resistor in series with the speaker,
but that won’t stop the speaker from
working. It will reduce the maximum
power and damping factor, however.
The hearing loop comprises two
turns of figure-8 light-duty cable, 25
AWG (14 x 0.12mm). I’ve mounted it
in the ceiling of a room measuring 5.2
x 5.0 meters. The two turns of the figure-8 cable provide a four-turn loop.
An under-carpet loop may work too,
but there would be some attenuation
and field distortion from the steel in
a concrete floor.
The amplifier sensitivity is 0.5V
peak input for a 5A peak output, or 20
amp-turns in the loop. I’m also using
a PreChamp preamplifier (July 1994;
siliconchip.com.au/Article/5252) provides a small amount of gain to accommodate typical auxiliary line-level
inputs. I also added a volume control
potentiometer to the preamp.
I am very grateful to Associate Professor Catherine Birman, director of
the Sydney Cochlear Implant Centre,
and numerous others who gave me the
ability to hear again. From a technical
perspective, Cochlear implants are
mind-blowing, particularly for someone who started in the days of vacuum
tube technology.
Anthony Leo,
Cecil Park, NSW. ($80)
siliconchip.com.au
Australia’s electronics magazine
August 2020 63
Altitude readout for the Boat Computer
We had a request to add an altitude display to the Touch-Screen Boat
Computer project from April 2016
(siliconchip.com.au/Article/9887).
We briefly pondered what this chap
might be doing with his boat that
would require an altimeter, but he
noted that he was using the unit in his
four-wheel drive. The apparent utility
of an altimeter readout is now obvious!
As the data from the GPS module includes an altitude reading, we figured
that it would not be too hard to arrange.
If you have already built the Boat
Computer, the update is easy to perform and does not require hardware
changes. With the revised software,
the altitude is shown (in metres) on
the latitude/longitude display screen,
as shown in the photo.
Using MMedit or similar (eg, TeraTerm and the XMODEM command),
simply load the “BoatComputerV7altitude.bas” file in place of the existing BASIC file. You can download
this new code from siliconchip.com.
au/Shop/6/3372 After the program has
been run once, it will run automatically whenever power is applied.
If you are starting from a blank Micromite (loaded only with the BASIC
interpreter), then you will still need to
configure the LCD and load the fonts
before loading the BASIC program. See
the original article for details.
Alternatively, you can use a PIC32
programmer to load the HEX file directly into the PIC’s flash memory.
This will work whether or not you already had the Boat Computer up and
running.
Our correspondent also noted a
small hardware modification he has
made to his Boat Computer (which
can be applied to just about any Micromite BackPack project). He added
a transistor across the trimpot which
adjusts the screen brightness.
When the headlights are on, a wire
from that relay activates to turn the
transistor off, so the screen brightness
is at the trimpot setting for night driving. The rest of the time, this added
transistor is on, enabling maximum
display brightness.
Tim Blythman,
SILICON CHIP.
Heelometer (heel meter) for boats
Once upon a time, the heel or lean
of a boat was measured with a passive,
gravity-powered device like the one
shown in the photo below. Nowadays,
we can use an accelerometer instead.
I realised that the Digital Spirit Level
project from August 2011 (siliconchip.
com.au/Article/1122) could easily be
modified to perform this task.
So I modified the software, as follows. It only measures the angle with
A classic style heel meter which
uses gravity to determine angles.
64
Silicon Chip
a resolution of 1° and prefixes the
reading with “P” for port or “S” for
starboard, depending on which way
it is leaning. For readings beyond 90°,
it displays “OOPS”. This provides a
handy way of knowing whether your
boat has capsized!
It also records the maximum heel
encountered, which is displayed for
a couple of seconds the next time it
is turned on.
The original software was written in
C and compiled with Microchip’s C18
compiler. It has been migrated to the
current Microchip XC8 compiler and
modified to give the above facilities.
The revised source code and HEX file
are available as a free download from
the Silicon Chip website (siliconchip.
com.au/Shop/6/5507).
Geoff Champion,
Mount Dandenong, Vic. ($80)
The heel meter showing a reading of port 19°
19°.
Australia’s electronics magazine
siliconchip.com.au
PRODUCT SHOWCASE
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summer.shen<at>maximintegrated.com
Designers of compact consumer devices can now slash solution size by
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management IC (PMIC) from Maxim.
This next-generation SIMO PMIC
delivers 3 outputs with just one insiliconchip.com.au
ductor at 91% efficiency, which is
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Australia’s electronics magazine
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Digital Transistor
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MAX77654 builds on Maxim’s robust
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current and 6µA supply current, this
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compared to discrete solutions.
The MAX77654 is available at
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The MAX77654EVKIT evaluation
kit is available for $119 US.
August 2020 65
by
Jim Rowe
Low-cost,
Wideband
Digital RF
Power Meter
Simple to build and low in cost, this RF Power Meter will be very useful
for anyone who needs to measure radio frequency signals from 1MHz
to 6GHz. By itself, it can only handle power levels up to about 3mW
(5dBm), but its range can easily be extended using fixed attenuators.
W
hile reviewing Banggood’s little RF Power Meter to extend its power range. I freely admit this last idea was
that was published last month (siliconchip.com. copied from Banggood’s RF Power Meter...
au/Article/14498), it occurred to me that we could
design a similar device that wouldn’t cost much more to The Meter’s heart
The Analog Devices AD8313 demodulating logarithmic
build, but would handle much higher frequency signals.
I also realised that its construction could be made easy amplifier chip in the RF Detector module forms the heart
by using other low-cost prebuilt modules that I had re- of the Meter. It accurately converts an RF signal into a corresponding decibel-scaled DC output voltage. It maintains
viewed recently.
The concept quickly solidified around using an Arduino accurate log conformance for signals from 1MHz to 6GHz
Nano module as the ‘brains’, together with the Banggood and provides useful operation to 8GHz.
The input range is typically 60dB (referenced to 50),
RF Detector module I reviewed in the March 2018 issue
with errors less than ±1dB up to 5.8GHz.
(siliconchip.com.au/Article/11005).
Fig.1 shows how the AD8318 works. It has nine cascaded
In a sense, this is a simpler and lower-cost replacement
for my Digital RF Level and Power Meter from the October amplifier/limiter stages, each with a gain of 8.7dB. The outputs of each amplifier
2008 issue.
stage are connected to
At the same
a full-wave detector
time, it offers some
cell, and the output
worthwhile encurrents of the detechancements, like
tor cells are summed
a much wider freand fed to a currentquency range (from
to-voltage converter
1MHz up to above
S
which produces out6GHz), the ability
put voltage VOUT.
to send the results
The voltage-to-curof each measurerent converter at upment to your PC for
per right allows addata logging, and
Fig.1: an internal block diagram for the AD8318 log detector IC. The
justment of the slope
an allowance for
differential input signal passes through a string of nine amplifiers/limits and
of VOUT. For example,
fixed attenuators at
the outputs of each one go to full-wave detectors. The direct currents from
the Meter’s input,
each detector are summed and converted to a voltage which appears at VOUT. when the VSET and
66
Silicon Chip
Australia’s electronics magazine
siliconchip.com.au
Features and
Specifications
Function:
A compact, low-cost RF power
and level meter with LCD screen
and USB interface
Frequency range:
from 1MHz to over 6.0GHz
Input impedance:
50 nominal
Maximum input power level:
+5dBm (3.2mW/398mV RMS)
Minimum input power level:
-60dBm (1nW/224µV RMS)
Measurement range:
-60dBm (224µV RMS) to +33dBm
(10V RMS) with recommended
attenuators
Measurement linearity:
about ±1dBm, 10MHz to 1GHz,
+6dBm/-4dBm, 1MHz to 4.0GHz
(see measurement plots)
Measurement resolution:
approximately ±0.1%
Power supply:
5V DC at less than 120mA via
USB micro-B socket
SC
Ó
VOUT pins are tied
together, this sets
the output slope to
a nominal -25mV/
dB.
The AD8318 also
includes an internal temperature sensor and bias stabilisation on the cascaded gain stages, so that changes in ambient temperature
do not unduly affect accuracy. And all of this impressive
technology is squeezed into a tiny 4 x 4mm 16-lead LFCSP
surface-mount package.
Fig.2 shows the measured transfer characteristic of an AD8318 at four
different frequencies: 100MHz, 1GHz,
2GHz and 4GHz. It’s very close to linear
at -25mV/dB at all four frequencies, between 0dBm and -60dBm.
Fig.3 is the full circuit of the Banggood
log detector module we are using. There’s
very little in it apart from the AD8318
and a 78L05 regulator, which provides
the AD8318 with a regulated +5V supply.
(We are actually bypassing the 78L05 in
this project, as you’ll learn shortly.)
The full circuit
The full circuit for our new RF Power
Meter is shown in Fig.4. The Banggood
AD8318-based log detector module is at
upper left, connected to the rest of the circuit via CON2. The Arduino Nano MCU
‘brain’ is on the right. IC1 in the centre
an LTC2400CS8 high-resolution (24-bit)
ADC (analog-to-digital converter) used to
digitise the output voltage from the log
detector module.
siliconchip.com.au
Fig.2: a plot of
VOUT vs input
signal level for
the AD8318 at
four different
frequencies (with
the default slope
setting of -25mV/
dB). As you can
see, the linearity
is excellent, and
the frequency has
minimal effect on
the measured RF
power level.
This ADC requires a reference voltage to set its input
scaling, and this is provided by accurate 2.500V reference
REF1, an LT1019ACS8.
IC1 digitises its input voltage under the control of the Arduino MCU via an SPI interface using Nano pins 1 (SCK),
30 (MISO) and 28 (SS-bar). After the MCU processes the
digitised sample data, it displays the calculated RF power and voltage levels on the 16x2 LCD module via CON1.
This is via an I2C interface using MCU pins 8 (SDA) and 9
(SCL) – the LCD module is an I2C serial type.
Three pushbutton switches (S1-S3) are connected to MCU
pins 25, 23 and 21. These are used to tell the unit when
SC 1MHZ – 8GHZ LOGARITHMIC DETECTOR MODULE
Fig.3: the circuit of the pre-assembled log detector module is very simple. The
RF signal is terminated with a 51Ω resistor (52.3Ω might be better) and coupled
to the inputs of IC1 via a pair of 1nF capacitors. The output from IC1 is fed
to a pin header, while power is supplied via a 2-way terminal block. We’re
bypassing 5V regulator REG1 in this project.
Australia’s electronics magazine
August 2020 67
16 x 2 LCD
SC
WIDEBAND DIGITAL RF POWER METER
Fig.4: thanks to the use of three prebuilt modules, the circuit of the RF Power Meter is not too complicated. The
Arduino Nano uses 24-bit analog-to-digital converter IC1 to read the output of the log detector with high precision.
2.5V reference REF1 ensures that IC1 measures that signal with reference to a very stable voltage. The whole circuit
is powered from the 5V pin of the Nano, which gets its power from a USB charger or computer.
you have connected one or more external RF attenuators
ahead of the Meter’s RF input, to increase its measurement
range. It then adjusts its display to give correct readings.
Since the Meter is designed to operate from a 5V DC supply derived via the USB cable connected to the Arduino
Nano, the supply for the rest of the Meter circuitry is taken
from MCU pin 12. This goes directly to the LCD module
(again via CON1). For the rest of the circuitry, it is filtered
by inductor RFC1 and several bypass capacitors.
We are making a few minor modifications to the Banggood
Log Detector module to simplify using it in the RF Meter
project. The 78L05 regulator on the module needs an input
of at least 7V for proper regulation, but we don’t have that.
Instead, we have a well-filtered 4.75V rail after the 4.7
series resistor. So we are bypassing the 78L05 in
the module by connecting the supply wire from
CON2 directly to its output pin 1.
To make sure that the 78L05 isn’t damaged by
reverse current, it’s a good idea to remove the 10k
resistor in series with the LED at the input of the 78L05.
It’s pretty unlikely that such a small current would damage the regulator, but the LED won’t be visible once the
case is on anyway, so it just wastes power if left in-circuit.
The only other modification needed is to fit a 1nF SMD
ceramic capacitor (2012/0805-size) across the two pads just
to the left of the 2-pin output connector on the log detector
68
Silicon Chip
PCB. This provides additional filtering for the AD8318’s
internal feedback loop – it’s shown as COBP on Fig.4.
All of these modifications should be clear from both the
notes on the circuit (Fig.3) and the close-up photo of the
log detector module PCB below.
CONNECT +5V WIRE
TO THESE PADS
REMOVE
THIS RESISTOR
ADD 1nF CAPACITOR
ACROSS THESE PADS
A few minor modifications need to be made to the
Banggood module before fitting it to the PCB.
Australia’s electronics magazine
siliconchip.com.au
Pin 8 of IC1 (the LTC2400 ADC) is taken to
the centre pin of JP1, a three-pin header. This
allows the sampling frequency of IC1 to be set
for optimum rejection of any power line frequency components in its input signal.
When the jumper shunt fitted to JP1 is in
the lower position, the sampling frequency is
set to reject 60Hz components (as you’d need
in the USA), but if the jumper shunt is fitted
in the upper position, the sampling frequency
is set to reject 50Hz components. So the latter
position is the best one for use in Australia,
New Zealand or the UK.
What the firmware does
The firmware sketch for the RF Power Meter is called “RF_Power_Meter_sketch.ino”
and is available for free downloading from
the SILICON CHIP website. When uploaded to
the Arduino Nano’s ATmega328P micro, it
does several things.
Its main task is to direct IC1, the ADC,
to take a sequence of 10 measurements of
the output voltage VOUT from the log detector module. It then averages each group of
measurements and calculates from that the
corresponding RF power level in dBm and
the equivalent voltage level in millivolts or
microvolts.
These figures are then sent to the LCD module for display, and are also sent out via the
Meter’s USB data line for display and possible logging on a computer.
The firmware’s other main task is to check
between measurement cycles for any presses
of the Select Attenuation pushbutton switch,
S1. If S1 has been pressed, it then swings into
‘change attenuation’ setting mode and it monitors any presses of switches S3 (‘Increase’) or
S2 (‘Decrease’) and adjusts its setting for the
external attenuation in steps of 1dB.
Then when S1 is pressed again, it saves
the new external attenuation figures and returns to its normal measurement mode. The
attenuation value is set to zero each time the
unit is powered up.
SILICON
CHIP
Fig.5: this PCB overlay diagram and the photo below
shows which parts go where. The only polarised
parts are IC1, REF1 and the Arduino Nano module.
Pushbutton switches S1-S3 are mounted on the lid and wired back to the
board using flying leads, while the header on the LCD screen (also mounted
on the lid) is soldered directly to the pins of CON1 as the last step in the
assembly.
Construction
The complete RF Power Meter is housed
in a diecast aluminium box measuring 119 x
93.5 x 56.5mm. Pushbutton switches S1-S3
and the LCD module all mount on or behind
the box lid/front panel.
All of the other modules and components are mounted
on a double-sided PCB measuring 109 x 83mm and coded
04106201. This also mounts behind the box lid/front panel, via four pairs of spacers.
Begin construction by first fitting the passive SMD components to the main PCB, using the overlay diagram of Fig.5
and the matching photo as a guide.
Then fit RFC1, which is larger and will probably need a
hotter iron. It’s best to smear a thin layer of flux paste on
its pads before soldering it in place. After this, install IC1
siliconchip.com.au
and REF1, which are both in SOIC-8 SMD packages.
Next mount 4-pin SIL headers CON1 and CON2, along
with the 3-pin header for JP1. Then you can fit the four
PCB terminal pins, which all push through their matching
holes in the main PCB and are soldered to the pads underneath. Two are to the left of RFC1 (TPGND and TP5V), while
a third pin (TP2.5V) is to the right of REF1 and the fourth
(TP VOUT) is to the right of CON2.
You should then be able to fit the Arduino Nano module to the PCB, with its 30 pins passing down through the
Australia’s electronics magazine
August 2020 69
matching holes and soldered to the
pads underneath.
The final step in assembling the
main PCB is to fit the AD8318 log detector module. It mounts on the top of
the main PCB using four 10mm long
M3 machine screws, with an M3 nut
used on each screw as a spacer, and
then further M3 nuts underneath to
complete the job.
Once it has been secured, plug a
4-pin SIL socket into header CON2
and solder four short lengths of lightduty hookup wire to its pins, then to
the matching points on the module
using Fig.5 as a guide.
By the way, although the log detector module shown in the photos and
diagrams is fitted with a small two-way
terminal block power and a two-pin
header for Vout, the module as supplied may not have these.
Neither connector is required in this
application, as you can simply solder
the wires to the pads on the PCB.
Case preparation
There are only two holes to be cut
in the box proper: an 11mm diamFig.6: only two holes need to be made in the main part of the case, with the
eter round hole in the front, and a 9
locations and sizes shown here. The round hole is for the SMA RF input
x 11mm rectangular hole in the rear.
connector while the rectangular cutout allows a USB micro-B plug to be inserted
The location of each of these holes is
into the socket on the Nano board
shown in Fig.6.
There are 12 holes to be cut in the
box lid, which becomes the Meter’s
front panel. The locations and sizes of these holes are shown in Fig.7.
There are three 12.5mm holes for the
three pushbutton switches and a 65
x 15mm rectangular hole for the LCD
‘window’. The remaining small holes
are for mounting the LCD module and
the main PCB.
After you have made and deburred
all the holes in the lid/front panel,
it’s a good idea to attach a dress front
panel to the front for a professional
appearance.
We have prepared an actual-size
artwork for this, which can be downloaded from the SILICON CHIP website
as a PDF file.
You can print this out in colour and
then hot-laminate it in an A5 laminating pouch. After this you can cut it to
size, punch four 3mm holes (one in
each corner) and then attach it to the
front of the lid using either thin double-sided cellulose tape or contact adFig.7: most of the holes that need to be made are actually in the case lid, including
hesive. Once it is securely attached,
a large rectangular cutout for the LCD screen. This is best made by drilling a
cut out the remaining holes using a
series of small (say 2mm) holes around the inside of the perimeter, knocking the
inside part out, then filing the edges to shape. You can use a similar technique for sharp hobby knife.
For other options to make a panel
the USB socket hole in the base.
70
Silicon Chip
Australia’s electronics magazine
siliconchip.com.au
Photos of the front (above) and rear (at right) of the assembled project showing the holes required, These photos match
Fig.6, opposite.
label, see siliconchip.com.au/Help/FrontPanels
The next step is to attach an 80 x 25mm rectangle of thin
clear plastic (say, 0.4mm thick) behind the LCD window
cutout, to protect the screen from dirt and damage. This
can be attached using standard cellulose tape, taking care
not to cover the LCD module mounting holes.
The lid assembly can now be finished. Mount the LCD
module behind the window using four 16mm-long M2.5
countersunk screws, four 9mm-long untapped spacers,
three or four Nylon washers and then four M2.5 nuts as
shown in Fig.8 and the photos.
Then you can mount the three pushbutton switches using the supplied plastic nuts, and finally attach a 25mmlong M3 tapped spacer near each corner using a 6mm long
M3 machine screw. The rear of your lid/front panel should
now look like the photo.
Next, cut six 25mm lengths of single-core hookup wire
(three red and three black) and strip off about 4-5mm of
the insulation at both ends of each. Then solder one end
of each red and black pair of wires to the connection lugs
at the rear of each pushbutton switch. These are to connect the switches to their matching pads on the main PCB.
After plugging a four-pin SIL socket into CON1, attach
the main PCB using four 12mm M3 screws through each
corner of the PCB, with a 6mm long untapped spacer between the PCB and each 25mm long tapped spacer – see
Fig.8. The only trick is making sure that the wires from
each pushbutton pass through their matching holes in the
main PCB, although you can adjust them later if necessary.
Once all the switch wires are through their corresponding PCB pads, upend the assembly and solder the wires
to those pads.
The final step is to solder the four pins of the SIL header
on the LCD module to the corresponding pins at the top of
the SIL socket you fitted to CON1.
You may need to slightly bend the LCD header pins using a pair of needle-nose pliers, so that they are close to the
pins of the SIL socket, allowing them to be soldered together. If this proves a little tricky, it can help to temporarily
remove the nearby tapped spacers, which can be replaced
easily once the connections have been made.
Don’t fit this assembly into the box just yet, since it’s a
good idea to check a few key voltages at this stage. It may
also be necessary to adjust the contrast of the LCD to get the
clearest display once the Meter firmware has been uploaded.
Testing and setup
First, connect the Meter up to a USB 5V power supply
siliconchip.com.au
using a mini-B cable. As soon as power is applied, the
LCD’s backlight should illuminate. Get out your DMM and
check a few voltages relative to the TPGND pin at the left
Parts list – Wideband Digital
RF Power Meter
1 diecast aluminium box, 119 x 93.5 x 56.5mm [Jaycar
HB5064 or similar]
1 double-sided PCB coded 04106201, 109 x 83.5mm
1 Arduino Nano or compatible module
1 1-8000MHz AD8318-based RF Logarithmic Detector
module [eBay, AliExpress, Banggood]
1 16x2 LCD module with LED backlight and I2C serial
interface [SILICON CHIP Cat SC4198]
3 panel-mounting SPST pushbutton switches (S1-S3)
[Jaycar SP0700 or similar]
1 100µH RF choke, SMD 12 x 12 x 8mm
[Jaycar LF1402 or similar]
4 25mm-long M3 tapped spacers
4 9mm-long untapped spacers
4 6mm-long untapped spacers
4 M3 x 12mm panhead machine screws
4 M3 x 10mm panhead machine screws
4 M3 x 6mm panhead machine screws
8 M3 hex nuts
4 M2.5 x 16mm countersunk machine screws
4 M2.5 hex nuts
4 Nylon flat washers, 3mm inner diameter
2 4-pin SIL headers, 2.54mm pitch
1 3-pin SIL header, 2.54mm pitch
2 4-pin SIL header sockets, 2.54mm pitch
1 2-pin SIL header socket, 2.54mm pitch
1 jumper shunt/shorting block
2 100mm lengths of light-duty hookup wire (red & black)
Semiconductors
1 LTC2400-CS8 24-bit ADC, SOIC-8 (IC1)
[Digi-Key LTC2400CS8#PBF-ND]
1 LT1019ACS8-2.5 voltage reference (REF1)
[Digi-Key LT1019ACS8-2.5#TRPBFCT-ND]
Capacitors
2 100µF 10V X5R SMD ceramic, 3216/1206-size
2 10µF 16V X7R SMD ceramic, 3216/1206-size
7 100nF 50V X7R SMD ceramic, 3216/1206-size
2 1nF 50V C0G or NP0 SMD ceramic, 2012/0805-size
Resistors (all SMD 1%, 3216/1206 size)
1 5.6Ω (code 5R6 or 5R60) 1 4.7Ω (code 4R7 or 4R70)
Australia’s electronics magazine
August 2020 71
Fig.8: this side profile
view shows how it all
goes together and fits
into the case. If you
don’t have untapped
6mm spacers, you
could use tapped
6.3mm spacers
instead. Note how the
log detector module is spaced
off the main PCB using nuts.
The last step before dropping
the whole thing into the case
is to bend the 4-pin header on
the LCD over to make contact
with CON4 on the main
board, then solder the pins
together.
rear of the main PCB. You should measure close to 5V on
the adjacent TP5V pin, around 4.75V on the VCC pin of the
socket plugged into CON2, and very close to 2.5V at TP2.5V.
If you get all of these readings, remove the power and
download the Meter’s Arduino sketch from the SILICON
CHIP website.
You will need the Arduino IDE (Integrated Development
Environment) to compile and upload the sketch. If you
don’t have it already installed, it’s a free download from
www.arduino.cc/en/Main/Software
Our sketch, “RF_Power_Meter_sketch.ino”, uses libraries: SPI.h, Wire.h and LiquidCrystal_I2C.h. The first two
come as standard with the Arduino IDE, but you’ll probably have to install the last one via the Library Manager or
download it from siliconchip.com.au/link/ab2k
Once ready, plug the Meter’s USB cable into a free port
of your PC. If you are running Windows 10, go into Settings
-> Bluetooth & Other Devices and then go down to Other
devices. You should find an entry like USB-SERIAL CH340
(COMxx), where the digits after “COM” indicate the virtual
COM port that Windows has assigned the Meter’s Nano –
or strictly, its CH340 USB-serial interface chip.
Next, start up the Arduino IDE, and go into the Tools
menu. Then click on Board, which will produce a list of
possible Arduino modules; select Arduino Nano from that
list. Then click on Processor and select “ATmega328P (old
Bootloader)”, since this is the appropriate one to communicate with the Meter’s Nano MCU via its CH340 serial
interface.
After this, click on Port, which should give a listing of
any virtual COM ports that IDE has found available. Select the COM port address that corresponds to the Meter.
If you didn’t already load the LiquidCrystal_I2C library
via the Library Manager, do so now. If you downloaded the
ZIP file instead, add it via the “Add .ZIP Library” option
near the top of the Sketch -> Included Library list.
Now open the downloaded sketch file and click Sketch
-> Verify/Compile, After 20 or 30 seconds, you should get
the message “Done compiling” in the box near the bottom of the IDE window, plus some statistics regarding the
compilation.
If all has gone well, the final step is to go into the Sketch
menu again and click on Upload. When this is completed,
the Meter should spring into life. The LCD should first display the initial greeting:
This photo is from the same direction as Fig.8 above . . .
. . . while this shot is from the opposite direction.
72
Silicon Chip
Silicon Chip
RF Power Meter
Then, after a few seconds, it should begin displaying
the results of its RF input sampling and calculations. With
nothing connected to the Meter’s RF input, you should get
a display like this:
RF Pwr= -68.5dBm
=83.2uV At=00dB
If the display on the LCD is not clear and well defined
– perhaps just two lines of blocks – that indicates that the
contrast trimpot on the back of the LCD module needs to
be adjusted. Rotate the trimpot in one direction or the other
using a small screwdriver. The trimpot is just above RFC1
and the TP5V and TPGND terminal pins.
The last thing to test before fitting the Meter assembly
into its box is to make sure it is sending the test readings
back to the PC.
Australia’s electronics magazine
siliconchip.com.au
An end-on photo (above) with a shot showing the display
board and pushbuttons, obviously before they were wired
in! Note how the standoffs are lengthened to make the
required spacing between the main board and front panel.
To do this, go to the Arduino IDE and open the Tools menu.
Click on Serial Monitor and it will open up another window.
This should show the Meter’s virtual COM port address at
the top, and at the top of the centre area you should see:
Silicon Chip Digital RF Power Meter
Then, after a few seconds, you should see the results
of the first reading on a single line:
RF Pwr= -68.6dBm = 82.6uV At=00dB
Further readings will appear every few seconds. If you
don’t see this display in the Serial Monitor window, or
if all you see is a string of weird graphic symbols, check
at the bottom right of the window to make sure that the
serial data rate is set to 115,200 baud (bits per second).
This is the data rate at which the Meter’s Arduino Nano
sends the reading data.
If you click on the “Show timestamp” checkbox at bottom left of the same window, a timestamp will be added
to the start of each line of readings to allow data logging.
If you have access to the equipment necessary to finetune the Meter’s calibration, as described at the start of
the section below, you may wish to do that now.
Otherwise, you can accept the default calibration we
have built into the firmware. In that case, unplug the USB
cable and lower the Meter assembly it into the box, securing it with the four supplied mounting screws. Your
Digital RF Power Meter is then ready for use.
Calibration
To fine-tune the Power Meter’s calibration, you’ll need
a DMM able to measure DC voltages up to 2.5V with high
accuracy, and a UHF signal generator which can be set to
provide CW signals at 1GHz (1000MHz) with an accurate
amplitude of between +5dBm and -65dBm.
The first step is to remove the Meter assembly from its
box (if you’ve already finished the assembly) and apply
5V power via the USB cable. After allowing a few minutes for it to stabilise, use the DMM to measure the reference voltage at TP2.5V, up near the right rear corner of
the main PCB, relative to the TPGND pin.
This should be very close to 2.5000V, but whatever the
siliconchip.com.au
reading you get, record it carefully as VREF.
Next, transfer the positive test lead of the DMM to
monitor the voltage at the TP VOUT terminal pin, just to
the right of CON2 at the rear of the log detector module.
Then connect the input of the Power Meter to the output
of the signal generator via a short length (say 150mm)
of SMA-SMA cable. The short length is to minimise cable losses.
Set the generator to provide a CW (continuous wave,
ie, unmodulated) signal at 1.000GHz, with an initial level
of +5dBm (1.78V RMS).
The DMM should show the log detector’s VOUT voltage
to be around 0.5V. Record the actual value of this reading, this time with the label “Vo5dBm”.
Next, reduce the generator output level to 0dBm (224mV
RMS), and again record the DMM reading (it should be
around 0.56V) with the label “Vo0dBm”.
Repeat this exercise with the generator set to -55dBm
(398µV), which should give a reading of around 1.9V, and
-65dBm (126µV), which should give a reading of around
2.1V. These figures should be recorded as “Von55dBm”
and Von65dBm” respectively.
Now remove the DMM test leads and go back to the
Arduino IDE, which presumably still has the RF Power
Meter sketch open. Scroll down about 50 or so lines from
the top, where you’ll find three lines reading:
byte S1 = 0;
byte S2 = 0;
byte S3 = 0;
then you’ll see a blank line, followed by a line reading:
const float Von65dBm = 2.0451;
In place of that figure of 2.0451, type in the reading
you recorded for Von65dBm. Similarly, replace the values on the next four lines with the other readings that
you noted earlier.
Make sure that, in replacing these figures, you don’t
remove the semicolons after each one. Otherwise, the
sketch won’t compile.
Save the modified sketch file and recompile it by going
to the Sketch menu and clicking on Verify/Compile. Then
Australia’s electronics magazine
August 2020 73
+20
Even with a longer cable between
the generator and the Meter (allowing
for the cable losses), there was still a
peak at 2.5GHz. But if you know the
frequency of the signal you are measuring (as you usually would), you can
use Fig.9 to make allowances for this
behaviour.
+10
+5
398mV
0
224mV
–10
71mV
Suitable attenuators
To make the Meter truly useful, you
should ideally also get a few inline attenuators.
These can be used to extend its meas–30
7.1mV
urement range above +5dBm. Banggood has a range of very compact SMA–40
SMA fixed coaxial attenuators, for the
2.24mV
reasonable price of A$10.65 each or
A$28.11 for three. They are rated at
–50
2W and 0-6GHz, and are available with
710mV
attenuation figures of 3dB, 6dB, 10dB,
20dB and 30dB.
–60
224mV
The 10dB attenuator could be used
to extend the range of the RF Pow–70
er Meter to +15dBm (1.26V RMS, or
71mV
32mW), while the 20dB unit would
extend its range to +25dBm (3.98V
–80
RMS or 316mW). Similarly, the 30dB
5
5
2
2
500 1GHz
50
200
20
10
10
100
1
unit would extend its range to at least
FREQUENCY
+33dBm (10.0V RMS or 2W into 50Ω).
Fig.9: the measured performance of the finished product for nine different
I ordered the 10dB, 20dB and 30dB
input levels over a range of frequencies from 1MHz to 4GHz. The readings are
units,
and thanks to the COVID-19 pangenerally within about ±1dB up to 1GHz, but a peak at around 2.5GHz makes
demic they took about seven weeks to
readings from higher frequencies less accurate. You can use this diagram to
arrive. But they did turn up eventucompensate the readings, as long as you know the signal frequency.
ally, and they seem to be well made.
if it compiles correctly as before, click on Sketch→Upload They’re pictured in the photo below.
to load the revised firmware to flash memory on the PowAs mentioned earlier, when you power up the Meter,
er Meter’s Nano.
the external attenuation figure is set to zero – displayed
Your Power Meter should now be calibrated. Just to as “00dB” at the right-hand end of the second line of the
verify that this has been achieved, you can set the signal LCD. When you change the attenuation figure to allow
generator output to say -40dBm (2.24mV RMS), where- for any attenuator(s) you are using via buttons S1-S3,
upon the Meter should give a reading very close to this the Meter will display this new figure on the LCD in the
figure; within ±1dBm.
same position.
The calibration is then complete. You can remove the
If at a later stage you remove the external attenuator(s)
power from the Meter assembly and reinstall it in its box, and wish to reset the Meter’s attenuation figure to zero,
so it’s ready for use.
this can be done either by using the trio of pushbuttons
again, or simply by removing power from the Meter for
Typical response plot
about 10 seconds and then reapplying it.
SC
After calibrating the prototype RF Power Meter shown
in the photos, we measured its response over a range of
signal levels and between 1MHz and 4.0GHz (the upper A selection of
attenuators, in
limit of the Gratten GA1484B Signal Generator).
The results are shown in Fig.9. This shows that the this case 10,
Meter response at most signal levels is within ±2dB up 20 and 30dB,
to 1.0GHz, rising to a peak of around +6dB at 2.5GHz, which will rather
significantly
before falling away again.
increase the
The peak at 2.5GHz is presumably related to the com- power handling
ponents (and possibly the PCB tracks) at the input of the of your RF meter.
log detector module. We wondered whether the 51Ω in- These were also
put load resistor was responsible, as the AD8318 data sheet sourced from
suggests 52.3Ω intead. But swapping that resistor out with Banggood, at less
some 52.3Ω samples we bought did not eliminate the peak. than $30 for the
three.
So it’s probably a PCB layout problem.
RF INPUT LEVEL in dBm
–20
22.4mV
74
Silicon Chip
Australia’s electronics magazine
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Offers support for batteries up to 300Ah with an output current up to 12A.
7 stage charging delivers the appropriate charge current to maintain best performance
& battery life. Can also recover deeply discharged cells. Suits permanent connection,
making it great for seldom used vehicles. Auto reconnect starts charging again as soon
as you connect the unit to mains!
Provides everything you need to wire up a secondary
battery in your vehicle - vital for powering appliances at
campsites, inverters etc, and isolating the primary battery
so you have enough juice to start your car! Instructions
included.
Do-It-All
Battery Charger
SAVE 32%
44
$
Powered by USB,
allowing you to
stay powered up Charges: Li-Ion, Ni-Mh & Ni-Cd
anywhere. Works
with 10440 to 26650
size lithium and
AAAA to C size
.95
$
Ni-MH/Ni-Cd.
22
M 8881
Super saving!
Charge 8 USB devices at once.
Got a family full of devices? This handy charger
produces up to 12A of charging current to keep all your
tablets and phones juiced up! Includes power cord.
A 0289A
Huge range of vehicle DC power products available
NEW!
High Current DC Power
Distribution Posts
High current DC power distribution posts with reinforced nylon
base. Available in single, dual and
bridging types. 48V DC max.
Model
Type
NEW!
P 2172
Single M8 Red
P 2173
Single M8 Black
$10.95
$10.95
$14.95
$14.95
$10.95
$10.95
$14.95
$14.95
$13.75
$13.75
P 2175
Dual M8 Red
P 2176
Dual M8 Black
P 2182
Single M10 Red
P 2183
Single M10 Black
P 2177
Dual M10 Red
P 2179
Dual M10 Black
P 2180
Bridging M8 Red
P 2181
Bridging M8 Black
SAVE 20%
26
$
SAVE 22%
19
per roll
$
P 0690
Dual USB
Charging Socket
3.1A max output. Suits
standard switch recesses.
W 2120
Must have for
portable solar
power systems
SAVE 22%
Q 0589
35
$
Figure 8 Power Cable
Easy Read DC Energy Meter
The cable of a million uses!
A great general purpose electronics
cable - don’t let your workshop run
out. 7.5A rated. 24/0.20. 30m roll.
Simultaneous display of voltage, current,
power and energy (Wh) readings. Ideal for DC
battery monitoring and small solar systems.
Requires 85x45mm cutout. 20A max.
See last page for store locations or visit altronics.com.au
Sale pricing ends August 31st 2020.
Expand your AV system & save.
C 5285
C 0876
Magnetic
‘edge to
edge’ grilles.
355
$
229/pr
$
160
/pr
/pr
$
SAVE $100
NEW!
SAVE $80
C 0881
8”
C 0871
6.5”
Includes
easy to mount
ball joint
bracket
Opus One® 2x30W
Bluetooth® Wireless Ceiling Speakers
179/pr
$
SAVE $80
Built to stream the best content from your favourite music streaming
service, app or podcast player. Bluetooth 5.0 technology offers superb
audio performance and range. Each speaker pair has an in-built high
performance 2x30W RMS amplifier. The ideal way to add permanent
wireless sound to any room in the house. A modern, low profile finish is
provided by frameless magnetic fit grilles. Includes power supply.
Sold in pairs.
Premium sound in a tiny package.
Stunning hi-fi clarity by Opus One®
Redback® 2.75” Mini Satellite Speakers. Deliver full and
rich sound you’d hardly believe these speakers are only 10cm
tall! They’re the perfect home and small commercial sound
solution - especially when paired with our C 5210 subwoofer
and A 4860 bluetooth amplifier. 8Ω 10W rated.
Suits flat
TVs up to
84”
The perfect partner for our A 1116 Bluetooth amplifier
(see below). Can be installed yourself, fliplock brackets
secure each speaker for flush mount screwless finish.
Sold in pairs.
Broken remote?
No problem!
With USB
connection
in base!
SAVE $80
209
$
SAVE
UP TO
$50
H 8232A Dual
SAVE
$50
H 8126B
225
109
$
Cantilever Arm
TV Bracket
Active Optical
HDMI Cables
SAVE $20
$
H 8230 Single
Desk Monitor Mounts
Silky smooth cantilever adjustment, stays just where
you want it to. It even has 14° of tilt adjustment!
Engineered for flat screens up to 84” using 600 x
400mm VESA. Max weight, 45kg.
Regain precious desk space! • Single or dual
models with easy adjust arms • USB ports for
easy peripheral connection • Monitors up to
30” • Desk clamp installation. • Max 9kg.
SAVE 20%
SAVE 25%
59
A 3089
A 3133B
50
$
$
2 Way HDMI Splitter
A handy switcher for
connecting up to 5 HDMI
sources to a 4k/2k or HD
display. Includes plugpack.
Sends one HDMI signal to two HDMI
outputs (ie show the same on two
TVs). 4K ready.
Dynalink®
F2 Pro Gaming
Headset
Multi-platform ready! Suits PC,
Playstation, Xbox and Switch with
included TRRS adaptor. Offers
excellent comfort for long gaming
sessions with RGB lighting effects
(when USB is plugged in). 2m
cable.
C 9042
68.95
$
NEW!
Cutting edge Active Optical Cable
(AOC) HDMI technology supporting 4K
resolutions at longer lengths than copper
cable. Plus, it’s thinner, lighter & more
flexible!
Why use HDMI AOC?
These cables totally eliminate the need
for long distance baluns, UTP conversion
and boosters for HDMI signals - get full
4K <at> 60Hz over the full distance!
42
$
A 3127
5 Way HDMI Switcher
SAVE 25%
Mini
HDMI Repeater
Extends HDMI leads up to
50m. Inline connection.
Supports 4K <at> 60Hz.
Model
Length
Normally
NOW
P 7427
10m
$240
P 7428
12m
$265
P 7429
15m
$275
P 7430
20m
$289
P 7432
30m
$299
P 7434
50m
$345
$185
$189
$199
$225
$235
$295
Listen
while you
walk, run
or ride!
NEW!
C 9044
63.25
$
Flexible Wireless Sports Headphones
Great sound and even better battery life! These over ear
style headphones offer up to 16 hours listening time in a
super comfortable & compact design. Bluetooth 5.0 for
great range and audio quality.
Buying for business? Save with a VIP-Trade Card
Dog ate your remote?
Enthusiastic toddler
binged too hard on
Paw Patrol? This handy
replacement features
IR learning plus preprogrammed codes
for 100’s of popular
equipment brands.
A 1012A
34.50
$
SAVE $50
199
$
A 4201
Bluetooth® 2x50W Amp
Stream audio directly from your device to
your speakers in the study or entertaining
area. 3.5mm and RCA inputs. Class D
design. Includes power supply, banana
speaker plugs & 3.5mm to RCA cable.
Amazing
Bluetooth
Sound For
Less!
The perfect every day
commuter earphones
with top notch
wireless sound,
compact folding
design and up to
18 hours of listening
between recharges.
50
$
C 9034
SAVE 12%
Sale pricing ends August 31st 2020.
Upgrade the tool kit this month...
FEATURE
PACKED
SAVE $39
41
$
.50
19 Range DMM
With in-built AC mains
detection. Featuring true
RMS measurement, transistor
and diode testing and backlit
display. Q 1126A
SAVE $25
50
READS
AC & DC
SAVE $21
80
$
28
MANUAL
RANGES
NEW
MODEL!
ULTRA
SLIM
CASE
SAVE $25
70
$
$
$
9999 Count True
RMS Multimeter
Feature Packed
28 Range DMM
600A AC & DC
Clamp Meter
Not much bigger than your
average mobile phone
(16mm thickness), this auto
ranging meter saves space
in your tool box. Easy to use
with volts, current, amps and
resistance. Q 1064
With in-built AC mains
detection. Featuring a
striking easy to read reverse
backlit screen and a massive
9999 count readout. Auto
ranging with easy push
button operation. Q 1090
Includes temperature probe
at no extra cost! Excellent
for service technicians or
enthusiasts. Easy to use with
an on screen guide for test lead
connection. Massive 20A rating
AC/DC to 1000V. Q 1067
Safe and easy measurement
of AC & DC voltage/current.
In-built non contact voltage
detection indicates live AC
wiring. Includes test probes,
temperature probe & carry
case. Q 0965
RCD Mains
GPO Tester
SAVE 23%
Q 3003
35
$
Detect lethal AC voltages instantly.
This non-contact probe detects cabling and power outlets
with live AC power (100-1000V). An essential preventative
tool for trades people. Waterproof case with in-built torch.
Do-It-All Multimeter
With in-built AC mains detection.
This is one of the best DMMs we have
evaluated when it comes to build
quality and features. Its perfect for the
serious enthusiast or tradesperson
• LCD bargraph • 3.75 digit display
• Mode assistance indicators.
• Includes case, temp probe &
insulated test leads. Q 1068
Powerful
diagnosis tools
in the palm of
your hand.
Tests mains power
points for correct
operation with
simulation of an
earth leakage to test
your household RCD.
Indicates unsafe
wiring. A must have for
P 8142
electricians.
Measure and map UTP
cable networks - simply!
SAVE $40
105
80
$
Space Saver
Multimeter
Waterproof design for field use!
TOP
FEATURE
SET
NEW!
40
$
SAVE $44
Q 1347
The must have diagnostic tool kit for any
IT technician or data installer
Measures cable length up to 1000m,
continuity testing and trace cable locations
all with the one unit. Kit includes 8 remote
identifiers for connection to cable runs, a
‘sniffer’ probe and main tester with easy
to see backlit screen. Includes carry case,
batteries and various connection adaptors
185
$
All the power of a benchtop
oscilloscope in the palm of
your hand. This compact digital
storage oscilloscope and digital
multimeter makes field testing
easy, even when working in
tight spaces or with equipment
on site. Offers 2 channels
with real time sampling of
125MSa/s per channel with
waveform comparison tools
and a full range of accessories
(plus carry case).
Q 0102
SAVE $81
319
$
310
$
M 8205
0-30V 5A
Network
Cable
Tracer
SAVE $20
Q 1341
105
$
A must have for IT
technicians!
Combines a cable
tracer & tester in
one unit. Injects an
audible signal down
the line, making it
easy to find specific
lead. Requires 3 x AA
and 1 x 9V batteries.
239
$
SAVE
$80
D 3006A
SAVE 12%
40
$
Linear Lab Power Supplies
Our most popular models! Fully adjustable with LCD meters for precision
adjustments. Great for R&D and workshops. • Precision linear toroidal
design • Fixed 12V & 5V output rails • Fully regulated • Short circuit &
overload protection.
LAN Network Tester
Instantly displays the status of all data cable
conductors (shorted pins, straight or crossover
cable identification).
M 8200A
0-30V 3A
er supply?
Why choose a linear toroidal pow
mode designs
compared to switch
Linear power supplies offer far lower noise
s or analog circuits. They are
device
ve
sensiti
ing
power
to
and are well suited
or medical equipment.
ions
unicat
comm
ideal for use in labs, with
See last page for store locations or visit altronics.com.au
Sale pricing ends August 31st 2020.
Electronics workbench essentials.
Torque adjustment
prevents chewed
out screw heads!
375
SAVE $80
$
Not just for
desoldering works great as a
regular hot air gun!
SAVE
$30
T 2052
NEW!
160
$
99
$
T 1289
SMD Hot Air Re-Work
Desoldering Gun
T 2128
Repair faster with
a lithium screwdriver.
Super fast
desoldering for
quick repairs or
recycling parts
Soldering & Vacuum Desoldering Station
Provides 300W of hot air for quick and easy
desolder and re-work of surface mount boards.
Melts solder in seconds allowing you to remove
devices easily. 200-500°C adjustable. Includes
desk stand - plus narrow, medium and wide
nozzles for different tasks.
This USB rechargeable screwdriver features a fully
adjustable torque drive for fast and accurate driving
of precision screws found in modern high tech
devices. Two way direction control. Standard 4mm
driver bits (14 included). 3 hours use per charge.
See web for full contents list.
Save space on your bench with this top performing 60W soldering iron and
90W vacuum desoldering station. Removes a 16 pin through hole IC in 30
seconds! Sucks molten solder away from components & pads in no time and
is easily cleaned. 160° to 480°C adjustable. Includes 0.2mm soldering tip
and three desoldering tips.
NEW!
49.95
Includes hard to find bit types
for latest phones & laptops
$
T 2164A
SAVE 15%
SAVE 15%
29
$
Pro 72pc Repair / Servicing Tool Set
A premium finish aluminium driver handle with silent ball bearing ferrule
top. Contains a huge variety of driver 4x28mm driver bits, double ended
opening tools, spudger, curved tip tweezers and flexible drive extension. It
makes servicing high tech devices easy!
SAVE 30%
SAVE 19%
16
T 2748A
Superb
build
quality!
T 2749
Stay
sharp
longer!
10
$
Rust free
stainless
steel!
T 2741
T 2865A Side Cutter
T 2870A Long Nose Plier
T 2860A Bull Nose Plier
SAVE 13%
$
T 1490A
T 2185A
An aluminium driver handle with 48 4mm bits to
open and repair all types of devices. Housed in
an ultra slimline aluminium casing. Great for field
repairs. See web for kit contents.
A 35x26cm heat resistant silicon work mat to keep screws and materials organised while you work. Also includes a separate 25x20cm
magnetic mat for keeping tiny metal parts from rolling away.
20
$
48pc Compact Servicing Kit
Never lose a tiny screw again!
SAVE 18%
60
$
29
$
T 4015A
Must
have for
any tool
kit
SAVE 16%
22ea
$
5” Carbon Steel
Side Cutters
Tungsten Carbide
Side Cutters
Stainless Steel
Long Nose Pliers
Super Sharp Stainless
Steel Scissor Snips
1000V Rated Electrical Tools
Tough carbon steel blades, stay
sharp longer. Ideal for cutting
solid core wires. 130mm.
Tough HRC 72° tungsten carbide
construction for 5 times the life of
standard side cutters. 130mm.
Rust Resistant - great for the
tackle box or use in moisture
prone environments. 125mm.
Multi-purpose snippers made from
SK4 carbon steel. Spring loaded
with comfort grip. 160mm.
VDE 1000V rated electrical hand tools constructed
from quality drop forged steel with comfort grip
insulated handles.
T 1499
SAVE 20%
No more eye strain!
50
NEW!
$
11.50
$
T 2168A
Screen Removal Suction Cup Pliers
For removing outer glass from phones tablets &
laptops. Cups rotate for larger screens.
Pick Prying
Set
A handy
plastic tool set
for prying open adhesive surfaces on
phones, laptops etc.
SAVE $9.95
SAVE 23%
7
$
T 1498
Get a crisp
close up view.
Features
1/4” and
4mm drive
handles
SAVE 22%
36
25
$
$
X 0432
5x magnifier with LED backlight.
Great for reading fine print,
sewing etc. USB rechargeable.
Includes carry case.
69pc Dual Ratchet Driver Kit
11 Pc Screwdriver Set
T 2198B
Quality set of flat blade and phillips screwdrivers for general repairs. Chrome vanadium.
Buying for business? Save with a VIP-Trade Card
Superb quality ratchet driver with a wide selection of bits
for most electronic jobs. Includes both a 1/4” adjustable
angle (<90°) ratchet handle and a smaller 4mm ratchet
handle. Great for the home handyman or enthusiast.
Sale pricing ends August 31st 2020.
Print your own parts, models & more!
K 8600
559
$
30 x 30 x 40cm
build volume for
larger prints
FREE!
1kg roll of PLA filament
with every CR-10 or Ender
3 sold this month. Valued
at $49.95
K 8606
1095
$
Print bigger with the Creality® CR-10 V2 3D Printer
Creality® ‘Ender 3’ 3D Printer
The CR-10 offers reliable large volume printing up to 30Wx30Dx40Hcm!
The dual port fan cooled hot end offers reliable and precise print quality whilst the triangular design provides
excellent stability. Heated print bed reduces warping, ensuring great prints every time. This printer is great for
anyone who needs to print larger designs such as cosplay parts, architectural models & replacement parts.
Creality’s top selling 3D printer is here! The Ender 3 is a compact 3D
printer offering excellent print quality with a build volume of 22Wx22Dx25Hcm
and is compatible with ABS, PLA and TPU filaments. Supplied mostly
assembled and can be up and running within an hour.
Creality® Premium
PLA Filament
ABS Filament
We’re now stocking Creality’s premium 1.75mm
PLA designed for use in many brands of 3D
printer on the market. Creality have focused on
making top quality non toxic filaments with a
tolerance of just 0.02mm. Each filament is 100%
bubble free and offers excellent tensile strength
& fluidity. This all adds up to more reliable prints
and less waste!
Made from high quality
materials for less brittle
filament breakages.
49
$
.95
per kg.
NEW!
T 2370
T 2745A
18
$
.50
n K 8387A Silver
n K 8388A Gold
n K 8389A Pink
n K 8391A Orange
n K 8392A Green
n K 8393A Yellow
n K 8394A Purple
n K 8395A Blue
n K 8396A Red
n K 8397A Black
n K 8398A Grey
n K 8399A White
35
$
Comfy Precision Snippers
Remove rough edges and neaten up prints
with this comfort grip external chamfer tool.
Ideal for trimming plastic supports
from prints.
SAVE 24% T 1296
SAVE 12%
15
$
5 Piece Needle File Set
T 2352
Fine edge files for smoothing 3D prints.
SAVE 15%
Blow Brush
16
$
T 1480
Remove fine debris from
prints when smoothing or reworking.
44.95
n K 8383A White
n K 8384A Black
$
Fluoro Filament
A translucent fluoro yellow
coloured PLA for brightly
coloured prints! 1kg roll.
57
$
.95
K 8390A
Cut, Polish,
Grind, Sand
& Carve.
SAVE 16%
Deburring Hand Tool
Printing with ABS instead of PLA.
We’ve also added to the range
Creality ABS. 1kg rolls.
60
$
Fume Extractor & Fan
Whisk away solder/print fumes
from your workspace! Also works
as a fan. Adjustable speed.
Great for finishing and
smoothing your 3D
prints!
Perfect for odd jobs and
hobbies. Powerful 130W
motor with variable speed
between 8000 and 33000
RPM. Included is a 172pc
accessory kit of grinding
wheels, drills, cutters,
sanding discs, polishing
pads and more.
See last page for store locations or visit altronics.com.au
T 2120
SAVE 13%
75
$
Sale pricing ends August 31st 2020.
Top deals for makers & builders.
Raspberry Pi® 4
The latest Pi 4 is now capable
of running two monitors at
once - in 4K resolution too! It’s
also equipped with USB 3.0,
upgraded CPU and a choice of
4GB or 8GB RAM.
Micro sized desktop
computing has arrived!
NEW
MODEL!
Z 6309A
144
$
112 $144
$
Z 6302G 4GB RAM
7” Touchscreen to suit Raspberry Pi®
New 8GB
version now
available!
Create all-in-one, integrated projects such as tablets, infotainment systems and
gaming consoles. Connects via DSI port on your Pi. 800x480 resolution. 10 finger
capacitive touch. Screen dimensions 192x111mm (inc. bezel).
Z 6302H 8GB RAM
10.95
$
NEW!
Red Raspberry Pi®
4 Aluminium Cases
P 1925
NEW!
P 1993
Available in dual fan
cooled or passive cooled
versions. These cases provide protection and thermal dissipation for your Pi
4. *Pi not included.
8
$ .65
39.95
$
H 8959
Dual Fan
29.95
$
H 8954
Passive
In Line Power Switch
Micro HDMI Adaptor
Switch your Pi 4 on or off. USB type C.
S 1147
Use your HDMI cables with your Pi 4.
SAVE $30
85
$
SAVE
28%
SAVE 25%
SAVE 34%
7
$ ea
Colourful Arcade
Gaming Switches
Jumbo arcade machine momentary
switches with 12V illumination and
customisable button plate.
25mmØ hole.
S 0910 Red
S 0911 Green
S 0912 Blue
S 0913 Yellow
S 0914 White
15
$
S 1148
USB Interface For
Joystick & Buttons
A handy interface board for a
joystick and up to 12 arcade
buttons. Includes pre-terminated
cables.
Heavy Duty
Arcade Joystick
17
$
Great for retro gaming projects
or for direction control in serious
projects. Adjustable plate allows
2, 4 or 8 way control. 95x59mm
mounting plate.
Z 6518
64x32 RGB
Full Colour LED Matrix Panel
These linkable panels are ideal for making highly visible scrolling signs,
information readouts, clocks and timers. Readable up to 52m away!
5mm pitch LEDs. 384x192mm.
60 LEDS
per metre.
4 for
$
Z 6393
28
SAVE 30%
16
$
SAVE 30%
SAVE 25%
12
$
Z 6392
Lightweight SG90 Servo
A great micro servo for lightweight
robotics applications. 180 degree
rotation (±90°). 3.5-6V operation.
Z 6444
High Torque MG995 Servo
MG90S Micro Metal Servo
A high speed metal geared servo with
12kg/cm torque. Weighs 55 grams. 120
degree rotation (±60°)
A high speed metal geared servo with
2kg/cm torque. Weighs 14.5 grams.
180 degree rotation (±90°).
22
$
A cut down version of our popular MegaBox which
provides a backlit 16x2 LCD for simple readouts,
plus room to customise the front panel with buttons
or IR sensor. UNO (sold separately) fits neatly
behind the screen and provides room for add-on
shields as required.
SAVE $50
85
$
5050 size
LEDs for
superior light
output!
Create
Amazing LED
Light Effects!
5m reel of
addressable RGB
5050 LED strip - this
means you can
program the colour of
every individual LED
using an Arduino/
Raspberry Pi. 60 LEDs
per m. WS2812B
chip on board. 10mm
width, adhesive
backed. 5V, 3.6A/m
(max).
Arduino Handheld
Game Kit
K 9675
SAVE 22%
X 3223A
per 5m roll.
MegaStand Acrylic
16x2 LCD UNO Kit
2048
LEDs per
panel!
SAVE 19%
SAVE 24%
40
60
$
$
Arduino Keypad Plate
Arduino Control Plate
Perfect for Arduino based access
control designs, this handy
wallplate has a atmega328p
chip and is suitable for use with
standard shields. K 9650
Perfect for Arduino based
automation projects, this handy
wallplate has a atmega328p
chip and is suitable for use with
standard shields. K 9655
Buying for business? Save with a VIP-Trade Card
Provides all the
hardware to build your
own handheld console,
then you can upload
open source games from
online communities or
have a go at coding your
own. Requires 2xAAA
batteries.
Have a go at coding
your own games!
Z 6457
SAVE $10
58
$
Sale pricing ends August 31st 2020.
Great value security deals.
499
NEW!
$
120
$
S 9901J
SAVE $100
IS PRICE!
20 SYSTEMS ONLY AT TH
S 9018
Why settle for
just HD? This
system features
2K detail and
clarity.
Affordable 5 Megapixel
CCTV Surveillance System.
NEW!
• HARD DRIVES TO SUIT: 1TB $120 (D 5514), 2TB $170 (D 5516).
Great for monitoring in remote
locations, temporary CCTV
monitoring etc. Runs off
batteries, so its quick & easy
to set up anywhere you need
to keep an eye on things.
Weatherproof case with LCD
screen. Requires 8xAA batteries
& DA0322 16GB
NEW!
SD card $14.95.
The safe & easy way to monitor
the front door. Records photos
of visitors when you’re not home.
Easy to wire up yourself with 4 core
cabling (ie: W 2341). Plus it hooks
up to two extra CCTV cameras to
monitor other parts of your home.
Supports 2 doorbells, 4 indoor
monitors & 2 CCTV cameras, plus
remote door latching capability
(when used with a door strike).
1080p video
or 20MP
still shot
resolution.
189
$
425
Cable Free
Solar Light
12
$
SAVE 13%
S 9179B
With solar powered
flashing red LED
Dummy Bullet
Camera With LED
Deter vandals and thieves from
your home or business with a
pretend CCTV camera.
NEW!
S 9395 Indoor Monitor
+ S 9396 Outdoor Camera
$
S 9178A
Dummy Dome
Camera
Deter vandals and thieves
from your home or business
with a pretend CCTV camera.
A 0326
35
$
Battery Free Door Bell
Never change batteries again! Kinetic
action of the button press powers
the signal to a wireless chime unit
inside your home. 25 ring tones.
100m range.
Instant
security
light!
Stylish motion
activated design.
Charges by day,
lights at night.
Weatherproof
design. Requires no
batteries or cabling.
145Wx96Hmm.
SAVE 25%
22
$
X 2375
SAVE 25%
15
$
S 5327
Window/Door Open Alert
Alerts you when a door or window
opens with an alarm or chime. Great
for notifying you when customers
arrive at your business. Adhesive
backed, installs in seconds! Requires
2xAAA batteries.
Joondalup Store OPENS AUGUST 3RD
2/182 WINTON RD JOONDALUP, WA. OPEN 7 DAYS.
Western Australia
Build It Yourself Electronics Centres
Sale Ends August 31st 2020
Phone: 1300 797 007 Fax: 1300 789 777
Mail Orders: mailorder<at>altronics.com.au
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Vintage Radio
Velco
Velco 1937
1937 radio
radio chassis
chassis restoration
restoration
By Ken Kranz
Back in the 1960s, I rescued this 1937 Velco radio chassis from the tip.
I’m not sure what radio it came out of; it may have been a kit radio built
into a custom cabinet. The cabinet was long gone, but I reckoned that
one day, I could get the radio working again. Fast forward to 2019, and I
finally had the chance to do just that.
This chassis clearly was for a battery-powered radio, as it lacked a
mains transformer and rectifier. I
wasn’t sure which exact set it was
from. Velco made several ‘kit’ radios
so it could have been one of those.
I searched the internet to get some
information about the manufacturer,
Velco. Arthur J. Veall Pty Ltd (247249 Swanston Street Melbourne, 302
Chapel Street Prahran) manufactured
Velco-branded products from 1931 to
1955. From 1950, Velco Sound Systems Pty Ltd was at 65 Latrobe Street,
Melbourne.
siliconchip.com.au
Velco-branded products included
radios, signal generators, “set analysers”, volt-ohm meters, valve testers,
multimeters and tape recorders. Velco
manufactured a model 365B receiver
in 1937. Its specifications were:
Valves: 1C4, 1A6, 1C4, 1K6, 1D4
Intermediate Frequency: 175kHz
Wave bands: broadcast band only
Batteries: 2V (A) and 135V (B)
Speaker: permanent magnet
Case: timber
Valve markings on my set indicate the valve lineup to be 1C4 (RF
preamp), 1C6 (converter), 1C4 (first IF
amplifier), 1B5 (demodulator & audio
preamp) and 1D4 (audio output stage).
A 1K6 dual-diode pentode had been
fitted in the place of the 1B5, with the
pentode triode-connected.
This is very similar to, but not exactly the same as what’s specified for
the 365B. The 1A6 pentagrid converter
has the same pin connections as the
1C6 and very similar specifications.
So I think that this radio is a 365B
derivative.
Circuit details
Unfortunately, I could not locate a
83
Fig.1: the Velco 1937 radio circuit was traced from the original set and then modified. One modification was adding a set
of diodes to clamp the filament supplies and protect it from any high voltages during repair.
circuit diagram, so I had to create one
by tracing out the circuit. It is shown
in Fig.1. I drew the original version
of this diagram using LTspice, so I am
also able to simulate the operation of
the radio. The component designators are unlikely to match the original schematics, as I had to number
them myself.
Excellent SPICE models are available for all the common audio valves
and many RF valves, although it’s difficult to find models for pentagrid converters. You can download the files
for my circuit diagram/model from
siliconchip.com.au/Shop/6/5573 The
download package also includes many
handy valve models that could be used
to simulate other sets.
Looking at the circuit, there’s nothing really remarkable about this set.
It does have an RF gain stage built
around valve V1. The following mixer/oscillator is a conventional configuration, as are the IF transformers and
sole IF gain stage.
The two diodes in V4 are used to
demodulate the audio signal and to
derive an AGC control voltage, which
is used to vary the bias conditions of
the first three stages (V1-V3; RF amp,
converter and IF amp). The audio output stage (V5) is a very basic Class-A
configuration.
Fixing it up
The first thing I did after I got it on
my workbench was to take a good look
at it. I found that the tuning gang had
a bent shaft, presumably due to the
cramped nature of its storage location
for the last 50 plus years.
I removed the tuning capacitor and
placed the shaft in a vice. Quite some
force was required to make it almost
straight. I feared one extra adjustment
would break the shaft, so I stopped
there and refitted to the chassis with
new rubber mounting grommets, to replace the disintegrated originals.
A number of the paper caps tested
leaky, so I replaced all of them with
Shown here is the underside of the Velco radio chassis before it was repaired, with the finished set shown adjacent for
comparison. One of the biggest changes was the replacement of all the paper capacitors with newer film capacitors.
84
Silicon Chip
Australia’s electronics magazine
siliconchip.com.au
modern types. The back-bias resistor
was open-circuit; I was able to repair
it by removing one turn of its wire and
soldering that to its terminal.
I also found some badly damaged
wires and replaced them with 600Vrated black wires with silicone insulation.
I decided to add eight silicon diodes, two sets of four in series in an
inverse parallel arrangement across
the 2V filament supply. This was to
protect the radio against me accidentally connecting too high a voltage to
this supply.
The radio was initially designed to
drive a loudspeaker fitted with an im-
pedance matching transformer. So that
I could drive a modern 8W speaker instead, I decided to fit a 100V line transformer, connecting the 0.5W tap (20kW
impedance) between the anode of V5
(the 1D4 output pentode) and the B+
rail. I then connected my test speaker
across the 8W winding.
Testing the radio
I applied 2V to the filament supply
and measured the current drawn. It settled at around 700mA, which I thought
was a reasonable figure to power
the five valve heaters. I then slowly
ramped up the B+ supply to 135V DC
and measured a flow of about 10mA.
Australia’s electronics magazine
Some satisfactory noises were coming from the loudspeaker, so I fitted a
short aerial and found that all local
radio stations could be received with
good fidelity, in spite of Pimpala (ABC
891kHz) transmitting 50kW only 3km
from my location. I aligned the dial
pointer with the actual transmitted frequencies and left it tuned to 1323kHz
for some background music.
A few days later, the radio was playing away in the background when the
sound of silence hit me. The primary
winding on one of the IF transformers
had gone open circuit.
My friend Andy (VK5AAQ) advised
me that this was common on these
85
The coils for the replacement IF transformer was wound using a sewing
machine with 0.1mm copper wire (left). The coils were placed on a wooden
dowel, which is attached to the original mounting bracket as shown above.
sets, as they only switched off the filament supply; the constant B+ voltage
combined with moisture caused electrolytic corrosion, with this being a
typical result.
Rather than look for a replacement
175kHz IF transformer, I recalled that
back in the early days of radio, many
items were self-made. Inspired by B.
B. Babani’s Coil Design and Construction Manual (1960), I decided to repair
it with a home-made replacement coil.
A replacement IF transformer
The outer diameter of the coil former
was about 10mm. A sewing machine
bobbin is about 9mm; close enough for
me. I measured the wire diameter at
0.1mm. So I ordered a reel of 0.1mm
diameter enamelled copper wire and
some clear sewing machine bobbins.
I drilled a 1mm hole in the sidewall
of the bobbin for the start of the winding, then placed it on the semi-automatic coil winder of a sewing machine.
My daughter held a nylon rod with the
spool of 0.1mm wire so it could unspool freely, and the machine ¾ filled
the bobbin in no time.
The spooling speed is fully adjustable from a crawl to frightening. In
spite of the very low strength of the
0.1mm wire, we didn’t experience
any breakages.
I measured the inductance of the
good coil on the old IF transformer at
7.4mH using a TH2821B LCR meter,
and used a Fluke multimeter to determine that the DC resistance was 76W.
As both trimmer capacitors had similar
ranges (19-110pF), I decided to build
the IF transformer using two identical
7.4mH inductors.
I tested the freshly wound coil and
found it to be over four times the required value, so we transferred about
86
Silicon Chip
half of the wire onto another bobbin.
I adjusted both coils by removing
turns until the required 7.4mH was
achieved. I found that the DC resistance and Q were very similar to those
of the original coils.
I cut the wires about 6mm from the
coil former and soldered flexible ribbon cable leads onto the coil ends. I
then covered the wire terminations in
some ten-second ultraviolet cure resin.
I then slid them onto a 6mm outer diameter wooden dowel, applied a generous amount of shellac to each end
and fitted the assembly to the original
mounting bracket. The wires were terminated as shown in the photos.
The moment of truth: I powered the
set on and turned the volume full up,
but it was very quiet. A quick adjustment of the IF trimmer capacitors gave
me lots of beautiful noise. I moved to
a blank spot on the dial and used the
trimmers to peak the noise at about ½
to ¾ compression. All the local stations came in loud and clear, including 5MU. An excellent result indeed.
Although the slideable coils would
allow adjustment of the coupling coefficient, the result was so pleasing that
I immediately coated the former with
shellac, including a small amount on
the coil. As one would expect, the set
stopped working. I did not re-tune the
IFs and simply let the set dry out for a
few days. At switch-on a few days later,
the radio was again playing 1323kHz;
most satisfactory.
I refitted the IF cover and that hardly
affecting the tuning. A quick re-tweak
and the set ran for about a week until
bench real estate required its movement back into storage.
Conclusion
All that’s left is to put the original
can back in place.
The repair of this set may offend
some restoration purists. The radio
was saved from landfill in the 1960s;
it now works and might be enjoyed
by somebody in the future. I saved all
the components I removed. It could
be reinstalled in a period cabinet by
someone with the skills and inclination to do so.
It still needs a replacement 2V dial
lamp (not shown on the circuit diagram). I might make a screw-in replacement using a white LED and resistor.
Some time in the future, I am hoping to find a diecast box that will locate over the large square hole, paint
it a similar colour, and build a power
supply into it so the set will run from
a 12V plug pack. The radio consumes
less than 3W, so I might even be able
to power it from a 1A USB port.
Velco references:
siliconchip.com.au/link/ab31
siliconchip.com.au/link/ab32
www.kevinchant.com/velco.html
SPICE references:
siliconchip.com.au/link/ab33
siliconchip.com.au/link/ab34
siliconchip.com.au/link/ab35
Plotting valve curves using LTspice:
https://youtu.be/VV3e_mNQ-dQ SC
Australia’s electronics magazine
siliconchip.com.au
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PRE-PROGRAMMED MICROS
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08/20
Colour Maximite 2
Words and MMBasic by Geoff Graham
Design and firmware by Peter Mather
Part 2
We introduced the Colour Maximite 2 last month, but now we delve into the details of
building it. As it turns out, that is quite easy because all the complex stuff is on the preassembled Waveshare CoreH743I CPU Board. The PCB that you need to populate is a
simple double-sided board with mostly through-hole passive components. You should
be able to finish it off it in an hour or two.
B
efore starting, take precautions
against static electricity which
could damage the STM32 processor.
You do not need to go overboard here,
but you should discharge yourself by
occasionally touching a grounded
point on your workbench and making sure that you do not unnecessarily handle the CPU board and its connecting pins,
The main ‘motherboard’ PCB is labelled “Colour Maximite 2: V2.1” and
measures 130 x 102mm. As shown in
the PCB overlay diagram, Fig.5, it has
cut-outs on either side to clear the
moulded posts in its plastic case, and
two small cut-outs at the front with a
‘peninsula’ in between that has three
exposed copper pads on it. This is the
“Nunchuk” connector.
Start by soldering the two 80-pin
sockets used for the plug-in CPU module. The trick here is to solder them
in such a way that the solder does not
wick up the pins, preventing the CPU
module from being properly inserted.
So use the following procedure.
Place the motherboard on a flat surface and insert both 80-pin connectors
in their correct places on the board.
Then gently push the CPU board into
these connectors. We say gently because you do not want to bend the pins
88
Silicon Chip
on the connectors or the CPU board.
Then, while holding the CPU board
in place on the motherboard, turn the
board over and solder all the connector’s pins.
Don’t use a lot of solder; only a small
amount is required for each pin. The
CPU board can then be unplugged and
placed aside while the remaining components are fitted.
Next to go in should be the audio
socket. The reason for this is that the
PCB is a little crowded around it, and
it is an SMD part, so if you leave the
audio socket to last, it will be difficult
to get your soldering iron in without
causing damage. Solder its five large
pins to the pads on the top of the board.
Next, solder the SD card socket,
which is also surface mounted. This
This is the assembled motherboard without the Waveshare CPU board plugged
in. Usually hidden by the CPU board are three capacitors, a resistor and the SD
card socket. Note that this is a prototype and the final PCB will vary slightly in
its layout (see the panel for details).
Australia’s electronics magazine
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The Colour Maximite 2 in
its case. If you remember
computers like the Tandy TRS80, Commodore 64 or Apple II
from the 80s, you will be right
at home playing with this.
The differences are that this is
about a hundred times faster,
has a much better display and
costs a fraction of the price!
Fig.5: follow this PCB ►
overlay diagram to build the
‘motherboard’. Once you’ve
fitted the connectors and
larger components, there isn’t
much to it. The remaining
components are a few small
ceramic capacitors and 46
miniature 0.25W resistors.
SMD resistors can be used
instead, if desired.
has two small posts on the underside
which click into matching holes in
the PCB to ensure perfect alignment.
With the socket in position, solder
the two tabs on the right side of the
socket (viewed from the front) and
five on the left side. Some are tiny and
can be easily missed, so count them
when you have finished (seven in total). Some are also close to the shield
of the socket. So take care not to cause
a solder bridge there.
Note that the socket must be held
firm to the PCB while soldering, as any
gap between it and the PCB will prevent
an inserted SD card from making reliable contact with the connector pins.
Finish it off by soldering the nine
pins at the rear. To do this, spread some
flux paste over the pins and load up
your fine-tipped soldering iron with a
little solder; a small bump is all that
you need. For each pin, slide the tip of
your iron over the solder pad towards
the connector so that the tip hits the
connector’s pin, and the solder should
magically flow around the pin.
If you get a solder bridge, don’t worry and carry on with the other pins. Finally, examine your soldering using a
powerful magnifier and clean up any
solder bridges using solder wick. Be
careful here, as solder wick can suck
siliconchip.com.au
up all the solder so you might have
to come back and resolder any pins
that look like they don’t have enough
solder.
The last device that is to be soldered
on the top side of the PCB is the battery holder, so you might as well do
that now. Its orientation is shown on
the PCB silkscreen, and the pads are
large, so this should be an easy job.
Through-hole parts
Next, it is worth soldering the highprofile connectors and the power
switch. They will hold the PCB off
the bench when you later place it upside down to mount the capacitors and
vertically-mounted resistors.
There is nothing complicated about
soldering these components. It is just
a case of placing them in position as
shown in Fig.5 and the PCB silkscreen
printing, and soldering their pins. After you have done this, go back with
a magnifier to check and rectify any
suspicious joints.
You can then install the optional IR
receiver and DS18B20+ temperature
sensor if you wish. These can easily
be added later, so they are not critical.
There are only five capacitors on the
motherboard. Three of these are situated under the CPU module, and they
Australia’s electronics magazine
should be mounted flat on their sides
so that they will not obstruct the CPU
module when it is plugged in.
The board is designed to accept polarised Tantalum types for the 10µF
and 1µF values, but we’ve specified
ceramics as they perform better and
are more reliable, and that is what
we’re supplying in our kits. Unlike
Tantalum capacitors, which are a type
of electrolytic capacitor, they are not
polarised, so you don’t need to worry
about their orientations.
Ten of the resistors sit flat on the
PCB, and they can be soldered next
(see the colour code table on page 97).
The pads are spaced to suit 0.5W or
0.6W resistors, but you can use smaller
0.25W resistors if you want to (that’s
what we supply in our kits).
There is an additional eleventh
resistor (4.7kW) near the back panel
which is only required if you are installing the optional DS18B20+ temperature sensor. Still, you might as
well install it now anyway, as it’s
cheap and easy and you might want to
add that sensor later (this is also supplied in our kit, even though the sensor itself isn’t).
Then there are 35 resistors used in
the R-2R ladders for the VGA analog
outputs. As mentioned last month,
August 2020 89
►
these are vertically mounted to save
space, although you can also use
3216/1206-size surface mount resistors. Make sure that they match the
silkscreen legend and will not get in
the way of the CPU board when it is
plugged in.
The USB-serial converter chip
comes in a 14-pin DIL package, and
you should use an IC socket for this,
so that you can pull the chip out if
you suspect that something is wrong.
Into this socket, you can plug the MCP2221A from Microchip or the Microbridge, as mentioned last month (our
kit comes with the latter).
Both work identically, but the MCP2221A does not need programming,
so it will be the preferred option for
some.
The Microbridge (May 2017;
siliconchip.com.au/Article/10648) is
a PIC16F1455 or PIC16F1454 microcontroller programmed with the Microbridge firmware, which you can
download for free from our website.
There are six pads beside this chip for
an optional six-pin header to allow you
to program this chip, although the ones
we supplied come pre-programmed, so
that should not be necessary if you’re
building it from a kit.
The last item to install is the vertically-mounted LED module which
indicates power and SD card activ-
ity. Using this module makes it easy
to get the correct alignment with the
matching holes in the front panel,
but you can use discrete 3mm LEDs
if you wish.
If using discrete LEDs, temporarily mount the motherboard in the
case (see below and don’t forget the
spacers). Then, fit the front panel and
bend the leads of the two LEDs to suit
the front panel holes. With the leads
in place on the motherboard and the
LEDs poking through the front panel,
you can tack-solder one lead for each
LED from the top of the motherboard
to keep it in place.
Finally, remove the motherboard
and securely solder and trim the LED’s
leads on the underside of the PCB.
Initial testing
Before you apply power, it is good
insurance to go over both sides of the
motherboard in detail with a magnifier, to confirm that all the solder joints
are good and nothing has been missed.
The current drawn by the motherboard and the STM32 processor is a
good indication of the state of both.
So, for the first test, make sure that the
CPU module is not plugged in, place
a CR1220 battery in the battery holder and do not connect anything else
(VGA, SD card etc).
Using a Type-A to Type-B USB ca-
Fig.6: the current drawn by the motherboard and STM32 processor is a good
indication of whether they are functioning correctly. You can easily measure
this by plugging in the USB power cable with the front panel switch off and
connecting a DMM set to measure milliamps across the switch terminals, as
shown here.
90
Silicon Chip
Australia’s electronics magazine
ble, plug the motherboard into a 5V
source but leave the front panel power
switch off (up). Set your multimeter to
measure direct current on the order of
200mA and place the probes across the
switch contacts as shown in Fig.6. The
reading should be 0mA.
Next, prepare the Waveshare CPU
module by removing any jumpers, set
the power switch on the top side to
“5VIN” and the BOOT CONFIG switch
to “Flash”.
Then plug the module into the
motherboard. Make sure that the orientation is correct; the USB socket on
the top of the module’s PCB should be
to the rear of the computer and the 20pin IDC connector to the front.
Again, with nothing else connected to the motherboard, plug it into
a source of 5V. Measure the current
across the power switch, which should
now be about 45mA. If the CPU module has had the Colour Maximite 2
firmware loaded (your supplier might
have done this), the current drawn will
be about 180mA.
Anything significantly different
from these numbers indicates a problem; see the fault-finding steps below.
Communicating with the
STM32 processor
The STM32 processor includes its
own firmware loader/programmer so
the Colour Maximite 2 firmware can
be easily loaded via USB using a personal computer or laptop. You do not
need any specialised hardware.
First, go to the STM32 manufacturer’s website at siliconchip.com.au/
link/ab2x and download the STM32CubeProgrammer software. This is
free software, but ST requires that you
have an ST account or provide your
name and email address. They will
then email you a link to download
the software.
Windows, Linux and macOS versions of this software are available. Install the appropriate version on your
computer and check that it runs.
Now set the BOOT CONFIG switch
to “SYSTEM” – this tells the STM32
processor to expect a firmware upload. Note that this is different from
the position of the switch used in
our initial tests above. Disconnect
all cables, including the USB Type-B
power cable.
Use a USB Type-A to Type-A cable
to connect the USB Keyboard port to
a USB port on your desktop or laptop
siliconchip.com.au
2 Select connect,
refresh if needed
1 Select USB
the screenshot (the USB port number may vary).
Click on the “Connect” button. You
should then see a series of messages
as shown in Fig.7, concluding with
the message “Data read successfully”.
Any messages in red indicate an error.
Programming the firmware
3 Check messages
Fig.7: the STM32CubeProgrammer software is used to load the firmware into
the STM32 processor. Select USB as the communications method; if the USB
connection is not recognised, click on the small blue circle to refresh the entry.
Your screen should look like this (the USB port number may vary).
computer. This will power up the Colour Maximite 2 regardless of the position of the power switch. You should
also hear a sound from your desktop
computer as the Colour Maximite 2
connects to it.
Note that if you don’t have a Type-A
to Type-A cable, you can use a TypeA to micro Type-B cable and plug
it into the USB power on the WaveShare STM32 module. But this won’t
be accessible later when the case is
assembled, and you have to unplug
Fig.8: this is the
“Erasing and
Programming”
mode. Select the
firmware file (it will
have an extension of
.bin), tick the “Verify
programming”
checkbox and
click on the “Start
Programming”
button. Then
wait for the
“Download verified
successfully” dialog
box. The operation
will take under a
minute, and any
errors will result in
a message in red.
siliconchip.com.au
the WaveShare module to get to this
port, so it’s a good idea to get a hold
of a Type-A to Type-A cable.
Run the STM32CubeProgrammer
software on your computer. On the
top-right of the program window, select USB as the communications method (see Fig.7).
If the program does not recognise
the USB connection, click on the
small blue circle to the right of the
Port drop-down list to refresh the
entry. Your screen should look like
Now click on the download button
on the left side of the STM32CubeProgrammer window. The software will
switch to the “Erasing and Programming” mode, as illustrated in Fig.8.
Use the “Browse” button to select the
firmware file you downloaded from
our website (it has a .bin extension)
and tick the “Verify programming”
checkbox. Then click on the “Start
Programming” button.
The STM32CubeProgrammer software will program the firmware into
the flash memory on the STM32 (it
calls this “downloading”). After a
short time, a dialog box will pop up
saying “File download completed”.
Do not do anything at this point, as
the software will then start reading
back the firmware programmed into
the flash. When this has completed
successfully, another dialog box will
pop up saying “Download verified successfully”, as shown in Fig.8.
The whole operation will take under a minute, and any error messages
will be shown in red.
If all is OK, dismiss all the dialog
boxes and close the STM32CubeProgrammer software. Remove the USB
1 Select programming
3 Tick verify
2 Load
firmware
4 Start programming
5 Dismiss dialog boxes
6 Check messages
Australia’s electronics magazine
August 2020 91
Type-A to Type-A cable from the USB
Keyboard port and plug in your VGA
monitor and USB keyboard.
On the CPU board, set the BOOT
CONFIG switch back to “Flash” and
plug the Colour Maximite 2 into power
and set the power switch to on (down).
You should now see the Maximite
logo on the VGA monitor, along with
the version number of the firmware
that you have just loaded, as shown
in Fig.9.
Note that initially, some monitors
may truncate the text on the margins
or show an image that seems to shimmer or flicker. In most cases, this can
be fixed by pressing the auto setup
button on the monitor or, failing that,
using the monitor’s image setup mode
to adjust parameters such as the clock,
phase and position.
When MMBasic is first loaded, it
will prompt for the keyboard type and
the date/time. On subsequent firmware upgrades, MMBasic will preserve these settings (in addition to the
real-time clock settings) and will not
prompt for them again. All of these
can be changed later using the relevant
OPTION commands.
As a final test, the current drawn
with the STM32 running the Colour
Maximite 2 firmware should be 160220mA, depending on the current
drawn by your keyboard and SD card.
If you wish to load another version of the firmware (eg, to upgrade
it), this can be done by repeating the
steps above.
To avoid having to open the case
up to change the position of the
BOOT CONFIG switch when upgrading, MMBasic has a handy command:
“UPDATE FIRMWARE”. This reboots
the Colour Maximite 2 directly into
bootloader mode.
Case assembly
The motherboard is designed to sit
in a standard ABS plastic instrument
case available from Altronics and
Jaycar. Some suppliers will include
the front and back panels made up as
printed circuit boards, without copper
tracks and with cut-outs in the correct
places. In that case, they should just
drop straight in.
If not, you will have to manually
make the cut-outs in the blank panels supplied with the enclosure by
following the dimensions in Fig.10.
The simplest way of doing this is to
download this as a PDF file from the
Silicon Chip website and print them
with 1:1 scaling. You can use that as
the template for the cut-outs.
Fig.10 also includes the front panel
artwork. We printed this onto heavyduty adhesive-backed paper and then
covered the printed surface with adhesive clear plastic film, of the type
used to cover books. After you have
trimmed the label and made the cutouts using a sharp razor blade or hobby knife, stick it onto the front panel
for a professional result.
An additional benefit of this technique is that you can make the cut-outs
in the plastic front panel slightly larger
than necessary, and the adhesive label
will hide any rough edges.
The motherboard can be fastened to
the pillars in the enclosure using four
ordinary 8mm M3 screws (self-tappers
are not required) – see Fig.11.
You need to add 5mm spacers on
each mounting pillar to elevate the
PCB and its connectors to match the
Fig.9: when you power up the Colour Maximite 2 with a VGA monitor plugged
in, you will see a splash screen like this. It shows the version of MMBasic
installed. Check this against the latest version on the Author’s website to see
whether an upgrade is available. When MMBasic is first loaded, it will prompt
for the keyboard type and the date/time.
92
Silicon Chip
Australia’s electronics magazine
cut-outs in the front and rear panels.
You may be able to get away with two
M3 nuts instead of the 5mm spacer, but
it would be better to use the real thing.
What can I do with it?
Here are a few things that you can
try out first, just to prove that you have
a working computer. All of these commands should be typed at the command prompt (“>”). What you type is
shown in bold, and MMBasic’s output
is shown in normal text.
Try a simple calculation:
> PRINT 1/7
0.1428571429
See how much memory you have:
> MEMORY
Flash:
0K ( 0%) Program (0
lines)
516K (100%) Free
RAM:
0K ( 0%) 0 Variables
0K ( 0%) General
5471K (100%) Free
What is the current time?
> PRINT TIME$
09:04:01
Draw a circle:
> CIRCLE 400, 100, 50
Draw a line:
> LINE 0, 0, 799, 399
Fault-finding
What if it does not work? The first
step is to measure the current drawn
by the assembled device. If it is 160220mA then that indicates that the
firmware has been loaded and is running correctly.
If this is OK but you cannot see anything on your VGA monitor, that probably means that something is wrong
between the STM32 processor and
the monitor.
Try a different VGA cable, check for
bent pins on the CPU module, check
the ladder resistors and, of course,
check your soldering. If the current
drain is about 45mA then it’s likely
that the firmware has not been correctly loaded into the STM32 processor, so you should re-run those steps.
Anything other than the above indicates a serious problem.
You can test the Waveshare CPU
module by removing it from the mothsiliconchip.com.au
Fig.10: these are the
cut-outs required for the
front and back panels.
You can download
this diagram from the
Silicon Chip website,
print them with 1:1
scaling and use them as
templates for making
the cuts. The front panel
artwork can be printed
onto adhesive-backed
paper to make a label
(see text).
erboard, placing shorting jumpers on
all header pins except PA9-VBUS and
setting the power switch to USB and
the BOOT CONFIG switch to SYSTEM.
Then plug a USB cable into the micro USB connector on the top of the
Waveshare module and the other end
into your desktop computer. Both
LEDs on the module should illuminate, and it should connect to your
computer.
If the VBUS LED does not illuminate, you probably have not configured the board correctly, or USB power
is not available. If VBUS illuminates
but the PWR LED doesn’t, check the
3.3V regulator on the underside of the
module.
Then, using the steps listed above,
try loading the Colour Maximite 2 firmware onto the STM32 processor using
this USB cable and your desktop computer. The procedure is the same as described above when loading the firmware via the USB keyboard port using
the STM32CubeProgrammer software.
If this process goes without a hitch,
you can be sure that your Waveshare
CPU module is perfectly OK and your
problem must be something to do with
the motherboard.
By the way, this is an alternative
method of loading the firmware if you
siliconchip.com.au
do not want to use a USB Type-A to
Type-A cable to load the firmware via
the USB Keyboard port.
The motherboard itself is so simple
that, if you suspect a fault with it, you
can just use traditional troubleshooting steps. Check for bent pins (especially on the Waveshare CPU module),
check all component leads/pads are
soldered, check for short circuits between pads and pins etc.
A table showing the pin layout of
the Waveshare CPU module can be
found overleaf.
Calibrating the real-time
clock (RTC)
We have found that the out-of-thebox accuracy of the real-time clock in
the STM32 is rather poor. This is not
a huge problem, as usually the date/
time is only used for time-stamping
files on the SD card. But if you would
like it to be more accurate, the STM32
can be tweaked to correct for any drift.
This is done in MMBasic with the
OPTION RTC CALIBRATE command.
This command takes a number between -511 and + 512; each step corresponds to a change of about 0.0824
seconds per day.
Negative numbers will slow the
clock down while positive will speed
it up. With a bit of patience, you can
get it spot-on. The best approach is to
set the time accurately using an Internet time source, eg:
TIME$ = “hh:mm:ss”
Then, after (say) a week, check the
current clock time with the following
statement:
PRINT TIME$
Fig.11: the motherboard fastens to four of the pillars in the enclosure using
8mm-long M3 machine screws (self-tappers are not required) and 5mm spacers.
The spacers elevate the PCB and its connectors to match the cut-outs in the front
and rear panels.
Australia’s electronics magazine
August 2020 93
Simple arithmetic (number of seconds offset ÷ [0.0824 × total days
passed]) will then tell you the correction needed, and you can apply that
as follows:
OPTION RTC CALIBRATE ±nn
Just make sure to get the correction
sign right, ie, make it positive if the
clock drifted behind the actual time,
or negative if it was ahead.
Interacting with MMBasic
Communication with the Colour
Maximite 2 is via the console at the
command prompt (ie, the greater than
symbol > on the console).
On startup, MMBasic issues the
command prompt and waits for a command to be entered. It will also return
to the command prompt if your program ends or if an execution error is
encountered.
When the command prompt is displayed, you can issue commands related to the program that you are working
on (EDIT, LIST and RUN). You can set
some options (the OPTION command)
and delete, copy and rename files and
directories (FILES command).
Almost any command can be entered at the command prompt; this is
often used to test a command to see
how it works. A simple example is the
PRINT command, which you can test
by entering the following at the command prompt:
PRINT 2 + 2
Not surprisingly, MMBasic will
print out the number 4 before returning to the command prompt. This ability to test a command at the command
prompt is handy when you are learning to program in BASIC.
The CTRL-C sequence (hold down
the CTRL key then press the C key) is
called the break key or character. When
you type this on the console, it will
interrupt whatever MMBasic is doing
and immediately return control to the
command prompt. Remember this, as
it can get you out of all sorts of difficult situations.
Test Program “bounce.bas”
BOX 0, 0, 800, 600, 1, RGB(yellow), RGB(black)
x = 400
y = 300
dx = 1
dy = 1
DO
CIRCLE x, y, 30, 2, ,0, RGB(red)
x = x + dx
IF x = 31 OR x = 768 THEN dx = dx * -1
y = y + dy
IF y = 31 OR y = 568 THEN dy = dy * -1
PAUSE 2
LOOP
do with it. As you read the following,
keep the user manual handy so that
you can look up the details of the commands used.
You can use the built-in editor to
enter this program. If you have used
a text editor before, you will find its
operation familiar.
The keyboard arrow keys move your
cursor around the text while the Home
and End keys take you to the beginning
or end of the line. The delete key deletes the character at the cursor, while
backspace deletes the character before
the cursor.
You must have a properly formatted card in the SD card slot, as this
is where the editor will save your file
when you have finished entering it.
To start the editor, type EDIT “bounce.
bas” at the command prompt and
press Enter. Then type in the program
shown above.
Press the F2 key to save your program and run it. You should see a yellow boundary drawn around the edges
of the screen and a red ball bouncing
around inside it, as shown in Fig.12.
As mentioned earlier, you may need
to adjust your monitor to see all of the
yellow boundary (ie, press the auto
setup button on your monitor).
If there was an error in your program, you will get a message with the
line number and the error description.
You can then re-enter the command
EDIT (or press F4 at the command
prompt) and you will be taken back
into the editor, with the cursor positioned on the line that caused the error.
Correct the error and then save/re-run
the program by pressing F2.
Program details
This program demonstrates how
BASIC and the graphics commands
work. At the start, we draw a box
which is as big as the screen using yellow for the outline and filled
with black. The RGB() function returns a colour value so, for example,
RGB(yellow) will return the value of
the colour yellow, and that is passed
to the BOX command as the colour
to be used.
The next two lines set the variables
x and y to the initial coordinates (or
position) of the centre of the ball that
we are going to draw. By setting x =
400 and y = 300, we start by positionFig.12: if you’ve entered the
test program correctly, once
you run it, you will see a
screen like this. The ball will
bounce around the screen,
changing direction each time
it touches one of the edges.
Test program
This simple program will cause a
red ball to zoom around the screen
bouncing off the ‘walls’.
It is not particularly complex, nor is
it very useful, but it is worth exploring as it will give you a feel using the
Colour Maximite 2 and what you can
94
Silicon Chip
Australia’s electronics magazine
siliconchip.com.au
Table 1: Pin Layout of Waveshare STM32 Module
LEFT
No.
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
35
37
39
41
43
45
47
49
51
53
55
57
59
61
63
65
67
69
71
73
75
77
79
GND
PE2
PE4
PE6
PI8
PC14
PI9
PI11
PF1
PF3
PF5
PF7
PF9
PH0
RST
PC1
PC3
PA1
PH2
3.3V
3.3V
PH4
PA3
PA5
PA7
PC5
PB1
PF11
PF13
PF15
PG1
PE8
PE10
PE12
PE14
PB10
PH6
PH8
PH10
3.3V
RIGHT
5VIN
PE3
PE5
VBAT
PC13
PC15
PI10
PF0
PF2
PF4
PF6
PF8
PF10
PH1
PC0
PC2
VREF+
PA0
PA2
PH3
GND
GND
PH5
PA4
PA6
PC4
PB0
PB2
PF12
PF14
PG0
PE7
PE9
PE11
PE13
PE15
PB11
PH7
PH9
PH11
5VOUT
PI7
PI5
PDR
PE0
PB8
PB7
PB5
PB3
PG14
PG12
PG10
PD7
PD5
PD3
PD1
PC12
PC10
PA14
GND
GND
PI1
PH15
PH13
PA13
PA11
PA9
PC9
PC7
PG8
PG6
PG4
PG2
PD14
PD12
PD10
PD8
PB14
PB12
GND
GND
PI6
PI4
PE1
PB9
BOOTO
PB6
PB4
PG15
PG13
PG11
PG9
PD6
PD4
PD2
PD0
PC11
PA15
PI3
PI2
3.3V
3.3V
PI0
PH14
PA12
PA10
PA8
PC8
PC6
PG7
PG5
PG3
PD15
PD13
PD11
PD9
PB15
PB13
PH12
3.3V
No.
2
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
44
46
48
50
52
54
56
58
60
62
64
66
68
70
72
74
76
78
80
Table 1: use this pin layout as a guide if you need to troubleshoot the Waveshare CPU module, as the silkscreen ends up
upside-down relative to pin 1 and how the module is placed on the Colour Maximite 2 PCB.
ing the ball in the centre of the screen.
The coordinate system used by
MMBasic involves two axes: the x
or horizontal axis and y or the vertical axis. x = 0 and y = 0 refers to the
pixel at the top left of the screen. The
coordinates get larger as you move to
the right and down the screen. So x =
799 and y = 599 is the position of the
pixel in the bottom right corner (the
default resolution of the screen is 800
x 600 pixels).
dx and dy are the amounts by which
we move the ball in the x and y-axis
every time the program loops around
siliconchip.com.au
(d = delta). With these both set to 1, the
ball moves right and down one pixel
each time the loop is executed. When
the ball hits a wall, the polarity of these
is reversed (more on that below).
DO…LOOP
The program then enters a DO…
LOOP which causes the enclosed
code to be repeated forever (well, at
least, until something stops it!). The
first thing that we do in this loop is to
draw a circle (ie, our ball) at the coordinates given by the variables x and
y and with a radius of 30 pixels. The
Australia’s electronics magazine
outline of the ball is black and is two
pixels thick, while the centre is filled
with red.
Drawing the outline in black means
that when we move the ball and redraw it, the black outline will erase
any part of the last ball’s image that
was left behind. This works well because we only ever move the ball by
one pixel at a time.
We then either increment or decrement the value of x depending on
the value of dx, which is 1 or -1. This
results in the ball moving one pixel
either left or right on the next loop,
August 2020 95
when the ball is redrawn. The program
line after that checks to see if the ball
is about to hit the left or right boundaries and, if it is, it reverses the sign
of dx, causing the ball to travel in the
opposite direction.
The same is done for the vertical
direction (dy) and taken together,
this means that the ball will appear to
bounce off all four edges of the screen.
The purpose of the PAUSE 2 command is to slow down the program so
that you have time to see the ball move.
To see how fast the Colour Maximite 2
can really go, change this to PAUSE 0
(or remove that line entirely) and then
re-run the program. The ball will just
turn into a blur.
You will notice that while this
program is running, you will not get
the command prompt back. This is
because MMBasic is now busy executing your program and drawing
the bouncing ball. You can stop the
program whenever you want to by
Last-minute PCB changes
The motherboard illustrated in the
photographs has gone through
a few changes and so may not
exactly match the PCB overlay
diagram and final board that you
receive.
Most changes were minor layout
adjustments, but one significant
change was the provision for an
external 8MHz crystal oscillator
to replace the 8MHz crystal on the
Waveshare CPU board.
In testing, it was found that some
VGA modes (such as 800x600
pixel 16-bit colour) caused difficulty for some monitors. This was
traced to instability in the on-chip
8MHz oscillator in the Cortex-M7
CPU.
Most constructors will be unaffected and will not need to do
anything. However, if this change
is needed, it can be easily implemented by removing the 8MHz
crystal on the Waveshare CPU
board and installing the external
oscillator and a capacitor on the
motherboard.
The parts required are one SMD
100nF 50V X7R ceramic capacitor in a 3216/1206 package, and
one 5x7mm SMD 8MHz oscillator (QX7 XO 25ppm), eg, RS Cat
813-6194.
96
Silicon Chip
entering CTRL-C at the console, and
you should get the command prompt
back again.
best way to understand it is to get in
there and try it out.
Full-screen editor
The File Manager is a great way
of managing the files and directories
on the SD card. You can always use
the traditional BASIC commands at
the command prompt (COPY, CHDIR
etc) to do this, but the File Manager is
much easier.
It provides a graphical list of the
contents of the SD card and, using
the arrow and Page Up/Down keys,
you can select a file or directory and
rename it, delete it, edit it etc.
To get into the File Manager, use
the FILES command or press the
F1 key at the command prompt. On
startup, it defaults to listing the current directory.
Fig.13 shows what it looks like. Files
and directories are colour-coded, and
the status lines at the bottom will tell
you what file you have selected and
the key commands that are available to
you. You can choose a different sorting
order for files and directories by using
the CTRL-S key.
Positioning the cursor on a directory
and hitting Enter will take you into that
directory; if the directory has a name
consisting of two dots (ie, “..”), pressing Enter will take you up the directory tree by one level.
Hitting Enter while a program file
is selected will run that program, and
pressing F4 will edit it. You can even
play a WAV, FLAC or MP3 file via the
audio output by selecting it and pressing Enter.
CTRL-F will enter the search mode,
which works similarly to search in the
full-screen editor.
This will prompt you for the search
text and, as you type this in, the cursor will automatically be positioned on
the first file or directory with a matching name. You can then use the down
arrow key to search for the next occurrence, or the up arrow for the previous
occurrence.
As with the editor, the best way to
get to know the File Manager is to fire
it up and try it out.
If you are familiar with the editor
used in the original Colour Maximite
and the Micromite, this editor is similar but it has extra features. These include a much larger clipboard (capable of holding many lines), the ability
to edit very long lines (the screen will
scroll sideways) and a much-enhanced
search function.
Entering the above program should
have given you a feel for how the editor
works and, as we said, its operation is
reasonably intuitive. The colour-coded
text makes it easier to understand the
program (commands are in cyan, comments in yellow, constants in green
and so on). The status bar at the bottom of the screen shows the name of
the file being edited, and the location
of the cursor within it.
Below this, there is a summary of
the common key commands.
Two important functions of the editor need further explanation: search
mode and mark mode.
CTRL-F enters search mode. This
will prompt you for the search text,
and as you type this, the editor will
automatically position the cursor at
the first match found. You can then
use the down arrow key to search for
the next occurrence, or the up arrow
for the previous occurrence.
In this mode, the Enter key leaves
the cursor where it is and returns to
normal editing mode, while CTRL-V
will replace the searched text with
whatever is in the clipboard (see below). Escape (Esc) aborts the search.
CTRL-S enters mark mode. In this
mode, you can use the arrow keys,
Home or End to mark (or select) text
and copy it to the clipboard. It will be
highlighted on the screen as you move
the cursor around. Then CTRL-C will
copy the selection to the clipboard
while CTRL-X will copy and delete
(cut) the selection.
Delete (Del) will simply delete the
selection without changing the clipboard, and Escape (Esc) will return
to the normal editing mode without
changing anything.
You can use the editor to edit any
text file, not just programs – all you
need to do is specify the full file name,
including the file’s extension (eg, EDIT
“myfile.txt”). As we said before, the
Australia’s electronics magazine
File Manager
The serial console
Usually, a VGA monitor and USB
keyboard are used as the console
for MMBasic. But as mentioned last
month, you can connect to a desktop
or laptop computer via the serial console and use its keyboard and screen to
siliconchip.com.au
Resistor Colour Codes
do the same job. This is handy if your
Colour Maximite 2 does not have an
attached monitor and keyboard; it also
makes it easier to transfer programs
and data between the two.
To access the serial console, connect
the Colour Maximite 2 to your personal
computer via the USB Type-B connector on the rear panel (this also provides
power). When you do this, the Colour
Maximite 2 will appear as a USB virtual serial port, which acts much like
a standard serial port.
Windows 10 includes the required
device driver. For Linux, Mac and earlier Windows versions, you can get a
driver and instructions from Microchip at siliconchip.com.au/link/ab2y
You will need a terminal emulator
program on your desktop computer.
This acts like an old-fashioned computer terminal; it will display text received via the serial link, and any key
presses will be sent back.
For Windows users, Tera Term is a
good choice. You can download it from
http://tera-term.en.lo4d.com/
For Mac users, a terminal emulator
is built into macOS (Terminal); refer
to the Colour Maximite 2 User Manual for instructions (siliconchip.com.
au/link/ab2z). For Linux users, there
are a few options like PuTTY (https://
www.putty.org/).
The terminal emulator and the serial port that it is using should be set
to the Colour Maximite 2 standard
o
o
o
o
o
o
o
o
o
No.
6
1
2
19
13
3
1
1
Value
10kΩ
4.7kΩ
1kΩ
240Ω
120Ω
75Ω
10Ω
2.2Ω
4-Band Code (1%)
brown black orange brown
yellow violet red brown
brown black red brown
red yellow brown brown
brown red brown brown
violet green black brown
brown black black brown
red red gold brown
of 115,200 baud, eight data bits and
one stop bit.
When you have the serial port and
terminal emulator set up, reset the Colour Maximite 2 and you should see the
MMBasic banner and prompt on the
terminal emulator.
Loading a program from a PC
If you have prepared a program on
your computer, you can transfer it to
the Colour Maximite 2 via the serial
console using either the AUTOSAVE
or XMODEM commands.
The AUTOSAVE command looks
like this:
AUTOSAVE “filename”
After this, you can simply copy the
program to your desktop computer’s
clipboard and paste it into the terminal emulator (eg, Tera Term). From the
Colour Maximite 2’s perspective, this
is the same as if a high-speed typist
types in the program. After the pro-
5-Band Code (1%)
brown black black red brown
yellow violet black brown brown
brown black black brown brown
red yellow black black brown
brown red black black brown
violet green black gold brown
brown black black gold brown
red red black silver brown
gram has transferred, press the F1 key
and MMBasic will save the program
to the SD card and return to the command prompt.
The XMODEM command is a
bit more complicated and uses the
XModem protocol to transfer a BASIC
program file, including an integrity
check which will detect most transfer
errors. The Colour Maximite 2 User
Manual goes into the details of how
to do this – it is reasonably straightforward.
MMEdit
Another convenient method of creating your programs and sending it to
the Colour Maximite 2 is to use MMEdit, written by Jim Hiley from northern
Tasmania.
It can be installed on a Windows
computer and it allows you to edit
your program on the PC then, with a
single button click, transfer it to the
Colour Maximite 2 for testing.
MMEdit is easy to use with colourcoded text, mouse-based cut and paste
and many more useful features such
as bookmarks and automatic indenting. Because the program runs on
your PC, you can save and load your
programs to and from the computer’s
hard disk.
MMEdit can be downloaded from
Jim’s website at www.c-com.com.au/
MMedit.htm It is free, although he
would appreciate a small donation.
Conclusion
Fig.13: one of the new features of the Colour Maximite 2 is the File Manager,
shown here. Use the arrow keys and Enter to navigate the files and directories
on the SD card. Other keyboard commands available are shown at the bottom of
the screen.
siliconchip.com.au
Australia’s electronics magazine
So there you have it. The Colour
Maximite 2 is a powerful but inexpensive computer that is fun to use.
Now would be a good time to download our tutorial “Introduction to Programming with the Colour Maximite
2” (siliconchip.com.au/link/ab30)
and start working your way through
it. Enjoy!
For updates to MMBasic and more,
go to the Author’s website at http://
geoffg.net/maximite.html
SC
August 2020 97
Vintage Workbench
The
The Tektronix
Tektronix Type
Type 130
130 LC
LC Meter
Meter –– Part
Part 33
Calibration
Calibration
By Alan Hampel, B. Eng. (Electronics, Honours)
In the last two articles, Alan Hampel described how the T-130 LC meter
works and how he cleaned up the dirty and faulty unit that he got from
eBay. In this last part of the series, he describes how he got it correctly
calibrated and working again.
Servicing the controls
Checking with a multimeter, I found
that the resistance of each contact in
the RANGE SELECTOR switch varied
with each engagement from around
5-15W. That isn’t very good, but the
contacts looked OK to the eye, with
no excessive wear.
I applied contact cleaner/lubricant
sparingly (just achieving a wet appearance), and rotated the switch through
the whole range numerous times.
Checking again with the multimeter,
all contacts showed no perceptible resistance. Then I applied some grease
to the clicker mechanism.
I applied some contact cleaner/lubricant to the shafts of the COARSE
ZERO and FINE ZERO variable capacitors. Everybody who is an electronics
enthusiast or technician soon learns
that pots need lubricant because of
the racket dry pots make in audio gear.
Variable capacitors need lubricant too.
But the effect of dry capacitors is more
subtle: a certain amount of oscillator
frequency instability.
Checking components
I checked all 50 resistors for correct
resistance and visual integrity. That
was possible without unsoldering
anything for all but 10, because unpowered valves are open circuits (normally). I checked the remaining 10 by
powering up and checking for correct
voltage division, and checking current
by shorting each in the chain with a
milliamp range of my multimeter.
This revealed three things:
1) Resistor R96 was 20% high. R96
(470W) and R95 (33kW) back-bias the
Restoring the manual
When I restore a vintage electronic item, I like to have an immaculate manual to go with it. When I bought this T-130, the eBay seller threw in an original
printed instruction manual. Unfortunately, it was for a different serial number,
and was in very poor condition, with numerous stains and pages missing.
I downloaded a manual from the Boat Anchor website (http://bama.edebris.
com/manuals/), but it too had missing pages, and the scan quality was poor.
I decided to re-create the manual in the Tektronix style by re-typing it and
re-taking the photos from the same angles as Tektronix did. I also scanned
the drawings and cleaned them up with Microsoft Paint and Media Impression (a software package that came with my PC and does much the same
job as Photoshop).
I have a Tektronix/US-style symbol library in my CAD system, so I re-drew
the circuit diagram in Tektronix style. The Tektronix original had several errors, which I corrected. I also drew component layout diagrams, though Tektronix never included them in their manual.
All this work on the manual was a good investment. It made me thoroughly
familiar with the circuit, how it works, and what clever tricks the designer Cliff
Moulton used to get excellent performance. That knowledge was invaluable
for fault-finding and calibration.
98
Silicon Chip
Australia’s electronics magazine
charge and discharge diodes, balancing out contact potential. This would
cause too much meter back-bias.
2) Resistor R405 (1.5W) was twice
its correct value, which would starve
the variable oscillator valve of heater
current.
3) Valve V60 (a 6BE6) had about
50kW leakage between the first grid
and the cathode.
I checked electrolytic capacitor
C401 (2 x 15µF) by measuring the ripple voltage on it. It was still good; I
measured 7V versus the 8V stated in
the manual. I saw no corrosion; this
is sometimes seen when electrolytics
leak electrolyte.
I checked electrolytic C402 (6.25µF)
by measuring the ripple voltage on it.
It too was still good.
Surprisingly, electrolytics C99 (5µF)
and C100 (25µF), factory originals,
were installed backwards! Not surprisingly, they each had only about
10% of their rated capacitance and
were very leaky.
As the ripple on the 150V rail was
exactly as stated in the manual, that indicated that polyester capacitor C403
(22nF) was still good. The only other polyester capacitors are the range
capacitors, which are Sprague Black
Beauty polyester. I checked them insitu for leakage (even though leakage
is unlikely) – all had no measurable
leakage.
All other capacitors are professional ceramic types that are known to almost never fail.
Methodical checking
I replaced the temporary and weak
6X4, and the 6U8 in the V30 socket,
with the new 6X4 and one of the 6U8s
siliconchip.com.au
The right side interior of the T-130 chassis neatly houses all the valves, transformers and a few other parts. The large
transformer marked “T-130 PA1” at bottom right (T400) is used to power the valve plates and heaters, T30 at upper right
is part of the fixed oscillator (V30), while T1 is marked at lower left and and is part of the variable oscillator (V4).
the seller sent me, following Rule 10
(from “14 rules of restoration” from
the last article):
Every single time you replace a component, do a comprehensive set of
checks to verify both that the fault due
to that component has been cleared,
and that no new symptoms have appeared.
siliconchip.com.au
I replaced faulty heater dropping resistor R405, again following Rule 10.
As it’s a wire-wound component, if it’s
high, it’s most likely about to go open.
I couldn’t find a source of resistors
identical to the original, but I installed
a Welwyn part that at least looks like a
type available in the 1960s. Changing
it made the instrument zero slightly
Australia’s electronics magazine
more stable, but still too far off to allow the 3pF range to be used.
Now that I could deem the power
supply good, I went through the rest of
the instrument, stage by stage, checking waveforms. This revealed that:
● The 6U8 variable oscillator
valve (V4) had low emission. I replaced
it with another of the 6U8s the seller
August 2020 99
The interior left side of the chassis houses nearly all the capacitors, resistors and other components mounted on ceramic
strips and connected via point-to-point wiring. Note the two replacement silver-coloured electrolytics (C99 & C100) at the
top right corner; Tektronix factory-installed the originals in backwards!
sent me. That stopped over-deflection
on the 3pF range. The instrument zero
became a bit more stable, but now had
a small backwards deflection.
● Since the 6BE6 mixer (V60) had
extremely high grid-cathode leakage, it
could well be about to fail completely.
I replaced it with a NOS valve from
eBay. This improved things – instead
of the meter dropping back past about
80pF, it didn’t start to drop back until
about 200pF.
100
Silicon Chip
The low-pass filter is pretty crude,
and its output falls somewhat as frequency increases. The low-emission
valve from the old radio had offset the
input to the Schmitt trigger, so that
triggering up and down ceased past a
certain point.
● Checking waveforms around
the Schmitt trigger confirmed that it
couldn’t follow the filter output past
about 10.9kHz (200pF indicated). With
resistor checks already done, presumAustralia’s electronics magazine
ably, the problem was valve V70 (another 6U8). On plugging in a replacement, the T-130 now followed a variable capacitor up to 250pF.
This was far from perfect, but as all
other components have been checked,
I assumed that I could correct it with
50kW symmetry trimpot R68, which
adjusts the bias on the Schmitt input
to centre the signal between the trigger
levels. That turned out to be correct.
● I then replaced defective elecsiliconchip.com.au
T-130 applications
The obvious applications of the T-130
are checking small capacitors and inductors before soldering them into circuit and – via the probe lead – checking suspect parts in-circuit.
The guard voltage output removes
the need to isolate parts before checking them; a facility that most modern
capacitance and inductance meters
do not have.
Something that almost all design
engineers of valve circuits had to
grapple with is the Miller effect, which
affects amplifier frequency response
and may make negative feedback circuits unstable, requiring compensation (see the panel in part one). The
T-130 makes the measurement of
Miller effect capacitance easy.
First, the static (or stray) capacitance at a grid can be measured by
the T-130 and probe lead with no HT
on the circuit under test. Then the HT
can be switched on, and there will be
an increase in the measured capaci-
tance – this increase is due to the
Miller effect.
The T-130 can be used to identify
short lengths of coax (<< 1/4 wavelength of 140 kHz, ie, << 500m) without knowing the actual length. Just
measure the capacitance with the far
end open, and the inductance with
the far end shorted. Then, Z ≈ √L ÷ C.
For example, let’s say the inductance measured on the T-130 is 0.60µH
and the capacitance is 104pF. Then
Z is approximately 76W. If the sheath
diameter is 10.3mm, the coax must
be RG11/U.
The T-130 with the Dielectric Test
Adapter can help with evaluating the
effect plastics and other insulators
have on RF circuits, provided a flat
sample of at least 55mm diameter is
available. It can, by measuring relative permittivity (dielectric constant),
assist in identifying plastics.
There was another use for the
T-130. The space charge increases
the apparent grid-cathode capacitance of a valve – the denser the
space charge, the greater the capacitance (this capacitance can appear to be negative at RF under certain conditions!). It’s useful to know
this variation when designing stable
oscillators.
A valve produces both white noise
and flicker noise due to the random
emission of electrons from the cathode. Fortunately, both are reduced
by the space charge. The denser the
space charge, the lower the noise.
This suggests an inverse correlation
between noise level and grid-cathode
capacitance, and indeed there is.
In a noise-critical application, it may
be desirable to predict the noise in a
tube operated in conditions different
to the that given as typical in data
sheets. One can measure the noise
in a prototype circuit directly, but it can
be quicker and easier to measure the
capacitance.
trolytics C99 and C100 with new tantalum units, following Rule 10. No
symptoms were cleared, and no new
symptoms appeared. C99 and C100 are
too small to provide any meter damping. They were only installed from serial number 6040 onwards. Presumably, the Schmitt trigger sometimes
oscillated due to the transients in the
meter circuit wiring getting back to the
Schmitt input.
● Schmitt triggers can oscillate if
the valve gm is very low. Sure enough,
checking it (V70, 6U8 again) showed
that was the case. I replaced it with
a NOS valve (following Rule 10 of
course). The wild pointer swings no
longer occurred when rotating a tuning capacitor under test.
● V45 (another 6U8) had low
emission in the triode, which works
as the discharge diode in the meter
circuit. This caused the backwards
and somewhat unstable deflection of
the meter, as its contact potential was
too weak to balance out the back-bias
from resistors R95 and R96.
● The output of the cathode follower was low, with a lot of hum.
Changing the 6BH6 (V110) fixed it.
movement plastic case was broken on
the left-hand side. A previous owner
had patched it up, but there was still
a gap. That was unacceptable, as it
would let dust in, eventually ruining
the movement. The scale markings had
faded as well.
Damaged meter movement
While not the original, the meter looks very close to some of the later models,
which can be viewed at http://w140.com/tekwiki/wiki/130
As mentioned earlier, the meter
siliconchip.com.au
Australia’s electronics magazine
Fortunately, I had another 4.5-inch
meter that fitted the mounting holes
and had the same full-scale deflection
current. It even looks like the meter
Tek fitted to later T-130s. It did not, of
course, have the same scales.
I photographed the scales in the bro-
August 2020 101
Restoring the S-30 Delta Standards Box
Users of the T-130 could send it back
to the Tektronix factory for adjustment
and calibration, but this would have
been inconvenient, to say the least.
Tektronix sold the S-30 Delta Standards Box as an accessory. The S-30
plugs into the UNKNOWN connector
and enables you to check the T-130
accuracy. The S-30 contains preset
capacitors for each range, an inductor, and a choice of 1MW and 100kW
resistors.
Only one inductor is needed because if all the capacitance ranges
read correctly, and any one inductance range reads correctly, the other inductance ranges must be right.
The resistors allow you to check the
resistance compensation of the variable oscillator.
The capacitors and the inductor in
the S-30 were adjusted in the factory
to within 1%. Combined with the T-130
basic accuracy and repeatability of
±1%, using the S-30 to calibrate the
T-130 then gives you a T-130 with an
accuracy of ±2%.
Typical of reputable American
companies, only ±3% accuracy was
claimed in Tektronix marketing – a
“safety” margin of an additional 1%.
I purchased an S-30 from another
eBay seller. It arrived with the outside marred by wear and tear and
some gum from ownership stickers
was present.
I removed the single control knob,
FRONT
BACK
C2
1.5-5.1
C4
1.5-5.1
-3µµF
C6
2.3-14.2
+3µµF
C7
3-12
C8
22
C10
82
C9
4.5-25
C12
285
C11
4.5-25
0µµF
+10µµF
+30µµF
+100µµF
+300µµF
1 MEG
100K
SHORT CIRCUIT
R2
1M
300µH
R1
100K
TYPE S-30
DELTA STANDARD
the anodised front panel and the case,
and gave them all a wash in the sink
with dishwashing liquid. This easily removed the grime and the sticker gum,
but made the wear and tear more obvious. I decided not to do anything
about the wear and tear.
What was more of a concern was
that the inner chassis had rotated
within the case, so that a connection
could not be made. Further disassembly revealed that the inner chassis was secured only by the switch
L15
220-330µH
boss and nut – there was nothing to
stop rotation when the switch knob
was turned.
Using a generous amount of Blu
Tack to contain chips and prevent
them spreading within the inner chassis, I carefully drilled a location hole
and installed a nut and bolt to prevent
rotation – something Tektronix should
have done.
The Blu Tack left a grease mark,
so I used a cotton bud and isopropyl
alcohol to get rid of it.
This is one
of the ‘old’
style S-30s,
the ‘new’
style ones are
slightly taller
with a visible
logo and
smaller print
(http://w140.
com/tekwiki/
wiki/S-30).
102
Silicon Chip
Australia’s electronics magazine
siliconchip.com.au
The capacitance and inductance trimmers are mounted on the sides of the S-30 chassis. They are meant to be adjusted as
required with the aid of an RLC bridge, and can be accessed by removing the blue case.
ken meter and converted them into a
CAD file. I then jury-rigged a Rotring
technical pen in a desktop NC milling machine and used that to inscribe
new scales, complete with Tektronix logo, to fit the replacement meter
movement.
Adjustment and calibration
T-130 owners could buy an S-30
Standards Box for calibration (see panel). This contained various adjustable
capacitors that could be checked on a
standard audio RLC bridge (see diagram at left). It also contained an adjustable inductor. Since this inductor
was designed for 140kHz, it could not
be checked on a standard RLC bridge.
The T-130 manual describes an “Inductance Standardizer” which contains a 1% tolerance 4310pF capacitor. This resonates when connected in
series with a correctly adjusted S-30
inductor at 140kHz. The T-130 is used
as a 140kHz null resonance indicator.
Tek didn’t sell the Inductance Standardizer – they expected S-30 owners
to build it themselves.
I bought an S-30 from another eBay
seller, and I made an Inductance
Standardizer with paralleled 1nF and
3.3nF 1% capacitors.
However, calibration with a frequency counter is easier and more ac-
curate. All you need is a Production
Test Fixture, a 300pF 1% capacitor, a
100pF capacitor (accuracy unimportant) and two 0.5W carbon resistors,
100kW & 1MW. The resistors must be
identical types.
The Production Test Fixture (shown
overleaf) ensures the stray capacitance
in connecting the capacitor and resistors is always the same. The T-130 can
easily resolve 0.05pF, so physical precision in connection is vital.
Carefully zero the meter with the
mechanical adjustment. Turn on the
T-130 and leave it for one hour to warm
up and stabilise. Connect a frequency counter to the output of the fixed
oscillator buffer at R49 (1.5MW) and
adjust T30 for a reading of precisely
140,000Hz.
Then, with the COARSE ZERO adjusted for half-scale deflection on the
3pF range, adjust resistance compensation trimmer C7 until the deflection is the same for both the 100kW
and 1MW resistors. The manual says
adjustment should be made last, but
since it has a significant effect on the
adjustment of T1, it’s better to do it
now.
Next, connect a scope to the Schmitt
trigger output on R74 (15kW). Select
the 300pF range and insert the 300pF
capacitor. Adjust R68 (symmetry) for
the best waveform symmetry.
Now connect a frequency counter to
R74 (or leave the scope connected, if it
has an inbuilt frequency counter). Adjust the COARSE and FINE ZERO controls for a dead beat on the 3pF range
with nothing in the Production Test
Fixture. Re-insert the 300pF capacitor
and adjust T1 for precisely 15,477Hz.
Repeatedly adjust COARSE ZERO,
FINE ZERO and T1 until you get dead
beat and 15,477Hz without further adjustments. Then, with the 300pF capacitor still inserted, adjust R78 for exactly full-scale deflection of the meter.
At this point, the total tuning capacitance without the 300pF capacitor is
1136pF, T1 is 1136µH, and both the
300pF and 300µH ranges are correct.
The Schmitt trigger output for all ranges is correct and the range trimpots R97
through R100 can then be adjusted.
Insert the 100pF capacitor and adjust the COARSE and FINE ZERO controls to get precisely 5781Hz. Then adjust the 100pF range trimpot R97 for
C1 3.3nF 1% RS 168-3336
S1
TO 130
C2 1.0nF 1% RS 168-3346
L1
330µH
RS 104-8416
TO S-30
R1
7.5
RS 386-143
The circuit diagram for the Inductance Standardizer is shown above, with the
INDUCTANCE
STANDARDIZER
interior shown slightly below actual size (64mm long diecast box).
Inductance Standardizers were meant
to be constructed from the circuit
provided in the manual and as made
obvious from the labelling, this wasn’t
made by Tektronix.
siliconchip.com.au
Australia’s electronics magazine
August 2020 103
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An excerpt form the Tektronix catalog from 1975 showing the T-130 and a photo of the Production Test Fixture, right at
the end of its production life. A replica of the Production Test Fixture, made from stainless steel and a standard UHF-to-N
adapter, was shown in the first article of this series in the June issue on page 39.
104
Silicon Chip
Australia’s electronics magazine
siliconchip.com.au
exactly full-scale deflection.
When I made this adjustment, I
found that R97 was hopelessly noisy.
Applying lubricant didn’t fix it. I could
not locate an identical pot, so I moved
the wire on one end of the track to the
other end – that solved the problem.
Next, remove the 100pF capacitor
and adjust the remaining trimpots for
full-scale deflection on the remaining ranges with the correct frequencies. Use the COARSE ZERO and
FINE ZERO controls to get the listed
frequencies: 1812Hz to adjust R98
(for 30pF range), 612Hz to adjust R99
(10pF) and 184Hz to adjust R100 (3pF).
Finally, remove the Production Test
Fixture, set COARSE ZERO to about
5° back from maximum and set FINE
ZERO to its midpoint. Adjust zero
span trimmer C2 for a dead beat on the
3pF range. Seal all adjustments with
tamper-proof seal or red nail varnish.
Performance after restoration
The T-130 is very good. There is no
perceptible drift in zero over the specified supply voltage range of 210-250V
AC. The drift of the zero setting in the
initial warm-up is less than 0.15pF
indicated. After that, no drift in zero
or full-scale deflection is perceptible
on any range except the 3pF and 3µH
ranges, which in any case remain within 5% and 1% when the FINE ZERO is
Fun with screws!
I re-assembled the instrument using
new screws because the old ones
were all corroded and unsightly.
Typical for an American company,
Tektronix used Unified Coarse (UNC)
6-32, 8-32 and 4-40 threaded screws
to hold their instruments together.
They used a mixture of CSK (countersunk), FH (flat head), PH (pan head)
and TH (truss head – a wide version
of pan head) screws. They used Keps
nuts; these are the sort that have a star
lock washer pre-attached to the nut.
I found I had run out of some of the
screws needed. There are three specialist fastener shops in Perth. I rang
the first one and asked:
“Do you have in stock screws UNC8-32 x 1/2 THS plated or stainless?”
“Err, do you want wood screws?”
“No, I’m asking for UNC-8-32 x 1/2
screws.”
“Err, um, but what sort do you want,
do they have a pointy end?”
“Forget it, mate. You don’t understand UNC screw terminology – that
tells me you don’t sell UNC.”
I rang the second firm. The chap
clearly knew his screws, and had them
in stock. But his minimum sale quantity was 200 of each item. Cripes, I’ll
never use that many in the rest of my
life, and all the sizes I need would cost
me more than the instrument is worth.
I rang the third firm. That chap also
understood the terminology, but he
didn’t stock them. He told me to ring
firm number 2.
I fired up eBay and bought 20 of
each size from a Chinese seller. They
arrived within a week, post free, costing me about $4 for each size. And
local shops wonder why they are losing sales...
adjusted just before making a reading.
Tek claimed that the oscillators will
not pull in together above 1Hz separation (0.016pF indicated). Mine certainly betters that specification.
a 25pF capacitor and got a stable reading. Clearly, with all the faults the
T-130 had, it could not measure anything. Did he lie? Not necessarily.
He probably connected the 25pF capacitor, selected the 100pF range and
switched the T-130 on. The 1N2630
probably didn’t short the heaters until he shipped it to me. Because of the
incorrect rectifier not being properly
grasped by the socket, there was no
HT, therefore no back-bias to oppose
contact potential in the charge and
discharge valves.
One of them had weak emission,
and it just so happened that the weak
emission produces about 25% meter
deflection. So it might have appeared
that the instrument was working, at
least in that one specific test case! SC
Did the eBay seller lie?
The seller claimed he tested it with
►
siliconchip.com.au
Australia’s electronics magazine
The T-130 LC Meter with the
Inductance Standardizer and S-30
Delta Standards Box connected
together.
August 2020 105
ASK SILICON CHIP
Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line
and we’ll answer your question. Send your email to silicon<at>siliconchip.com.au
How to program
the PIC16F1459
I read with interest the article on
the Infrared Remote Control Assistant project in your July 2020 issue
(siliconchip.com.au/Article/14505).
I note at the beginning of the article
that PIC16F88 is not to be used in any
new designs.
I have MPLAB v8.20, which is
pretty old now. I was interested to
see if I would be able to program a
PIC16F1459, as used in that project,
but it is not listed in my version.
I also have a PICkit 3 which has
served me well, and was wondering what version of MPLAB you
use and whether the PICkit 3 would
work to program these devices. The
PIC16F1459 datasheet does not show
PGD or PGC pins on the device. A bit
of web searching revealed that ICSPDAT is equivalent to PGD and ICSPCLK to PGC. Is that correct? (G. C.,
Toormina, NSW)
• MPLAB version 8.92 can be used
to program the PIC16F1459, and you
should be able to use the PICkit 3 as
we’ve programmed those chips with
one without issue. However, it’s easiest to just switch over to MPLAB X entirely; it is a free download (although
the free versions of the compilers are
somewhat limited).
Yes, ICSPDAT has the same programming function as PGD and PGED.
Likewise, ICSPCLK is the same as PGC
or PGEC.
er (January-March 2017; siliconchip.
com.au/Series/308).
I have them hooked up to a pair
of JBL 4312 control monitors. This
is a truly superb stereo system, and
you would have to pay a (very) large
amount of money to acquire similar
performance commercially. The USB
codec in the DAC works flawlessly;
however, you must have a computer with a USB port that recognises
the codec to be able to use it. It’s OK
for me but useless for the rest of the
family.
I see that the Maximite can read several music formats and send the digital
data to the DAC in the STM32 chip.
Now if the Maximite could send this
data out the USB port to the codec in
the CLASSiC DAC, or alternatively,
output S/PDIF, we would have the necessary tools to create our own music
player on the Maximite (with powerful graphics to enhance it).
The 128GB SD card would allow
around 300 full albums to be stored in
FLAC format – surely enough for most
music fans. (G. B., Strathalbyn, SA)
• Geoff Graham responds: that’s an
interesting idea, but we don’t want to
add this feature to the CMM2.
The main reason is that the CMM2
is designed as a fun BASIC computer
and this would force it into a different,
possibly conflicting, path. Also, the
sole USB port is used for the keyboard
and with that connected to a DAC, you
would then have no way of controlling
the CMM2 as a standalone computer.
A suggestion for the
Colour Maximite 2
Which type of infrared
receiver to use
The Colour Maximite 2 described
in last month’s issue is a fabulous project. Well done to all concerned in its
creation.
I would like to suggest a possible
enhancement or additional project
which I think the Maximite would
be able to handle. Like many of your
readers, I built the CLASSiC DAC
(February-May 2013; siliconchip.com.
au/Series/63) plus the SC200 amplifi106
Silicon Chip
In your March 2020 article on the
Programmable Thermal Regulator
(siliconchip.com.au/Series/342), the
infrared receiver IRX1 doesn’t appear
in the parts list. Is Jaycar Cat ZD1952
suitable? (B. W., Inner Park, Qld)
• Yes, Jaycar Cat ZD1952 is suitable.
We have also recommended Altronics Z1611A as an alternative in previous projects. Practically speaking,
most 3-pin infrared receiver/decoders
Australia’s electronics magazine
can be used. Ideally, its bandpass filter (usually 36kHz, 38kHz or 40kHz)
should be matched to your remote,
but in practice, it isn’t critical, and a
38kHz receiver will generally work
with any remote.
Measuring very low
distortion and noise
I want to measure the specifications of the Ultra-LD Mk.4 amplifier that I have built (August-October
2015; siliconchip.com.au/Series/289).
I mainly want to measure the signal-tonoise ratio (SNR) and total harmonic
distortion plus noise (THD+N). You
published photos of my amp in the
Mailbag sections of the June 2016 and
March 2018 issues.
To measure the THD+N, I first
looked at the Quant Asylum QA400
audio analyser you reviewed in the
March 2015 issue (siliconchip.com.
au/Article/8388), and for which you
published a Balanced Input Attenuator in May 2015 (siliconchip.com.au/
Article/8560). However, this model
has been discontinued by the manufacturer. Its replacement, the QA401,
costs two and a half times as much!
There are a couple of reviews available on the internet (siliconchip.com.
au/link/ab42 and siliconchip.com.
au/link/ab43), and they measure the
THD+N at -99dB (0.0011%). According to the graph on page 37 in the
August 2015 issue, the THD+N of the
Ultra-LD Mk.4 amplifier is better than
-106dB (0.0005%). So that won’t be
suitable.
I also looked at second-hand instruments like the Audio Precision analysers or the Rohde & Schwarz UPL units,
but they trade at no less than a couple
thousands of dollars used on eBay.
Regarding the SNR, my understanding is that I need to measure the output at full power (though it could be
done at lower power, say 20W only)
against the noise measured with no input signal. Since the rated power into
8W is 135W, that means 32.86V RMS
across its output at full power before
siliconchip.com.au
distortion if I am not mistaken. That
translates into 30.33dBV.
With an SNR rated at -124dB (unweighted at full power), I should measure -91dBV noise with no signal.
So I built the High Resolution Audio Millivoltmeter (October 2019;
siliconchip.com.au/Article/12018)
along with its companion Precision
Audio Signal Amplifier. After running my amp for more than an hour, I
measured -75dBV at the output of each
amplifier module.
I remembered that the output had to
be tuned to be below 0.5mV by adjusting VR2 on the board. I took this opportunity to re-calibrate the quiescent current of my two modules, but could not
get a better output noise figure. With a
50W load on the Audio Millivoltmeter,
it shows -89dBV, which should be just
at the edge of the precision I need for
this measurement.
It seems very challenging to adjust
the output of the amplifier closer to
0mV just with VR2. Is my methodology correct?
Finally, in the June 2020 issue, you
mention you would publish a USB
SuperCodec. Would it allow measurements precise enough for audio
gears like the Ultra-LD Mk.4? Keep
up the great work, and thank you. (O.
A., Singapore).
• It is difficult to find test equipment
that can measure the performance of
the Ultra-LD Mk.4 amplifier for less
than a few thousand dollars. That design, and some others we have published, are approaching the limit of
practical distortion measurement,
being down in the low single digits
part-per-million range (approaching
-120dB).
Your approach to measuring its SNR
is valid, but as the input of the Digital
Audio Millivoltmeter is AC-coupled,
any output DC offset from the amplifier should not affect its reading.
Have you terminated the Ultra-LD
Mk.4 input when making the measurement? You can use a 100W resistor,
although simply shorting the input to
ground is usually OK.
If you leave the input open, you
will get more noise due to the higher-than-usual input impedance. The
signal source impedance usually is
100W or less when it’s connected to a
device like a CD player, so you want
to maintain that situation when testing the no-signal condition.
The USB SuperCodec (starting on
siliconchip.com.au
page 24 in this issue) is probably the
closest you will get to the performance
of an Audio Precision or similar device
for under $1000. We haven’t added up
its parts cost, but we’re guessing it’s in
the range of ‘a few hundred’ dollars.
It certainly can measure very low
distortion numbers. It isn’t as good
as our Audio Precision System 2 at
measuring THD+N or SNR. But there
are ways around that. With appropriate software, some resistive dividers
and some careful measurements, you
could get accurate THD+N and SNR
readings for the Ultra-LD Mk.4 using
the SuperCodec.
The main trick is to measure the
distortion and noise separately, then
combine the readings. You can use the
bare SuperCodec to measure the noise
floor with no signal, then measure the
full-scale amplitude and THD using a
divider feeding into the SuperCodec.
Some RMS calculations should then
give you the correct THD+N figure.
If you still can’t get close to the
-106dB/0.0005% THD+N figure that
we quoted, it’s possible that your power supply is injecting noise into your
amplifier outputs. Check the grounding carefully.
Problem uploading
DAB radio BASIC code
I’ve built your DAB+/FM/AM Radio (January-March 2019; siliconchip.
com.au/Series/330), and it’s powering
up OK, but I’m having a lot of trouble
trying to load the BASIC code into the
Explore 100. For the life of me, I cannot
get the ‘crunched’ file to load properly.
I have the same problem as a previous constructor (July 2019, pages 106107 in Ask Silicon Chip); after the upload, it shows 64727 bytes saved and
not 66104 bytes as expected.
I have downloaded the file from
your website several times, used both
Stuffit Expander and 7Zip, at different
stages, to decompress the file and Tera
Term to upload the resultant crunched
file to the Explore 100, but to no avail.
I have tried to use MMEdit to load the
uncrunched version and crunch it during load, but I don’t know how to load
it into the Explore 100.
Any tips would be greatly appreciated. (A. V., Ferntree Gully, Vic)
• We haven’t been able to recreate
this problem, but we think it may be
a glitch with the XMODEM protocol
that is used with TeraTerm. During the
Australia’s electronics magazine
development of this project, we used
MMEdit to upload the BASIC program,
so it should work using that method.
It appears to use a different protocol.
With MMEdit, you need to select
CONNECT → NEW to set up a serial
port, then the port will appear in the
CONNECT menu and must be selected.
After this, auto-crunch on load
can be selected from the ADVANCED
menu. Load the BASIC program and
run it by using the button at top right
that looks like a running man.
MMEdit behaves differently to many
other programs, so it can be a bit tricky
to use. You can download the manual from www.users.on.net/~tassyjim/
stuff/MMedit.pdf
We have another possible solution
for you, which would allow you to continue using TeraTerm. We have split
the BASIC file into a library CFUNCTION and the main BASIC code.
Using TeraTerma and XMODEM RECEIVE, send the CFUNCTION.BAS file
to the Explore 100, then issue the command LIBRARY SAVE. This moves the
CFUNCTION out of the BASIC program space. Then send the “DAB FM
AM Radio Firmware2.bas” file via XMODEM RECEIVE. It is crunched and
smaller than 64727 bytes. Assuming
that this transfer works, try running
the program.
More queries on
uploading BASIC code
I assembled the DAB+/FM/AM Radio project using a pre-programmed
Explore 100 and a pre-loaded radio
board, then uploaded and ran the radio BASIC program using MMedit and
a USB-serial interface.
It seems that something has gone
wrong; while I get messages in the
MMChat console that indicate the radio board is working (“booting radio…
booted” etc), the BASIC code halts
with the error “Invalid font number
#14”. This makes me think that the BASIC code has not uploaded correctly.
The display initially presents the
four main buttons which do not respond to pressing; however, by touching different areas on the screen, most
of the main screen finally appears. The
radio does not activate in any of the
three modes, of which AM is the first
highlighted. Where to from here? (B.
F., Mount Eliza, Vic)
• While most people who have built
the DAB+/FM/AM Radio got it up and
August 2020 107
running, we’ve had about three people
including yourself write in to say that
the BASIC code will not run correctly.
In the other cases, we’ve determined
that this was because the upload was
truncated (the number of bytes uploaded was smaller than the size of
the BASIC code).
The problem is that we have never been able to reproduce this on our
own Explore 100; using MMEdit (as
you have done), the upload is always
successful. We haven’t been able to
identify the common factor with people who have had this problem.
So our recommendation is for you to
get a PIC programmer (even the Snap
programmer is sufficient) and load
our supplied HEX file directly into the
flash memory of the PIC. That way, you
don’t have to upload the BASIC code
as it is already loaded in the HEX file.
No response from
Explore 100 chip
I am building your DAB+/FM/AM
Radio which incorporates the Explore
100 module (September-October 2016;
siliconchip.com.au/Series/304).
Firstly, I have built two Explore
100s, but I can’t get either of them to
work. I have gone through the faultfinding procedure in the articles and
all appears OK. The current drain is
110mA. I’m using TeraTerm V4.88 Terminal Emulator and a serial converter.
Hitting enter on the PC doesn’t give
me the Micromite command prompt.
Looking at the Tx pin with a CRO,
when the Reset button is pressed,
I see a DC change but nothing else.
The chips are supposed to be preprogrammed. On the emulator, I see
a flashing block prompt which stops
flashing when I press Reset. What can
be wrong?
Also, when I plug in the assembled
radio board and power the whole thing
up, the current draw changes very
little. I ran an infrared thermometer
over the radio board to check for hot
spots. There were none, just the opposite. Not even the radio chip, IC1
was heating up; I thought it should be
getting warm, seeing there is so much
crammed into it.
I checked to see if the crystal oscillator was working and it wasn’t; there
was nothing across the 12pF capacitors, yet there was on the Explore 100
board – about 2V peak-to-peak.
I can measure 1.8V and 3.3V in vari108
Silicon Chip
ous places around radio chip IC1. So
it looks like there is a fault in the radio section. But most of those components came pre-soldered to the board,
so why isn’t it working? (T. V., Burpengary, Qld)
• Try pressing Ctrl-C in TeraTerm to
get the MMBasic prompt; this will also
interrupt any running commands. You
should see any typed text echoed back
in any case.
Have you set the terminal baud rate
to 38,400? The terminal will not work
if the baud rate is not configured correctly. Have you tried connecting to
the Explore 100 using the native USB
serial port? This will at least narrow
down whether the processor is ‘alive’.
We suspect that the DC change you
are seeing on reset is being detected
as a ‘break’ condition by the Terminal,
which might be why the flashing stops.
It’s normal for the radio chip, IC1,
to be drawing no power and for its
crystal oscillator to be shut down until it is commanded to start up by the
Explore 100. Clearly, that is not happening as you have not been able to
load the BASIC firmware yet, given
that you are having trouble accessing
its console.
Even if the Explore 100 is programmed, if the radio chip is not operating, most likely the fault will be
in the connections between the two
boards, rather than a problem with
the radio chip itself. The radio board
will do very little without the Explore
100 driving it.
First, make sure that the Explore
100 is working and MMBasic is responding. Then ensure that the radio
software is loaded and running on the
Explore 100. If you purchased it from
us, the radio firmware was pre-loaded
on the flash chip. So as long as the interface (the dual-row headers) between
the two boards is good, you can then
expect radio chip IC1 to start drawing
current and doing something.
Getting CSV data from
Arduino Seismograph
Hello, I built your Arduino-based
3-axis Seismograph (April 2018;
siliconchip.com.au/Article/11030). I
have never worked with this chip (the
MPU6050) before, nor WAV files. I’ve
been able to get basic X, Y & Z information out of the chip, and your project
works as it was intended to.
I’d like to modify your project to
Australia’s electronics magazine
write this data to a CSV file on the SD
card, along with the date and time from
the real-time clock. I can then visualise
it in all axes using the R programming
language, which is more useful for me.
The code for your April 2018 sketch
is impressive (and works fine on a
Nano, by the way) but it’s way over
my head. Can you help? I need to be
able to match the data within a few
seconds to the microphone I’m using
on another platform. I just need to get
the data as numbers and write it into
a CSV file. (M. M., via email)
• The Seismograph delivers CSVcompatible data to the serial port, although this may not include timestamps.
To change the format of the data
saved to the card, you will need to
change the file.write() command in the
main loop. Instead of writing WAV audio data, this can be replaced by something like the data that is printed to the
Serial port a few lines later.
The dosync() and openfile() functions will also need to be changed.
The name of the file created should
be changed from having a .wav extension to .csv, and the line that prints the
header should instead print an appropriate CSV header.
The sync function will probably
work if it is changed to do nothing; all
it does is to update the WAV headers
with the number of data bytes (which
is not necessary for CSV files).
The CSV format requires significantly more data to be written than WAV
(this is one of the reasons we chose
WAV), so you may find the Arduino
struggles to keep up. If so, lower the
sampling rate.
Sync signal from Vintage
TV RF Modulator
I’ve constructed the Analog AV
Modulator for Vintage TV Sets
(March 2018; siliconchip.com.au/
Article/11007), and it’s working perfectly. It is a most useful device for
helping me maintain my several 1956
Astor SJ receivers. It does indeed provide a true 1950s TV signal; a perfect
solution.
I’d like to take an output from the
modulator to provide a composite
sync signal to a TV waveform monitor.
The required signal should have only
sync/blanking pulses, not luminance
or chrominance signals. Looking at the
circuit on page 84, it appears that pin 1
siliconchip.com.au
(the B1 input) of IC3 is being fed with
the composite sync pulses I’m seeking,
but I’m not entirely certain.
I’m hoping either yourself or the article’s author, Ian Robertson, can assist me with advice on the following:
Is there a point in the circuit at which
all sync pulses (excluding luma and
chroma signals) are aggregated?
If so, what form would you suggest
for a buffered take-off circuit with a
75W output impedance for connecting to an external device? (G. D., Bunyip, Vic.)
• Ian Robertson replies: pin 1 of IC2
(the LM1881 sync separator), labelled
CSout, delivers composite sync at TTL
levels. It is not connected in the current design.
Unfortunately, this output is not
capable of driving a back-terminated
load directly. You would need to add
an emitter-follower, using a general-purpose NPN transistor such as a
BC547. The collector of this transistor goes to +5V (Pin 8 of IC2), and the
base goes to pin 1.
To get approximately 1V into a
75W load you need a voltage divider
of two 150W resistors, connected in
series from the emitter of the BC547
to ground. The composite sync output comes from the junction of the
two resistors. There will be a small
DC offset, but that shouldn’t worry
a monitor.
Class-D amplifier is
refusing to start
One of my boys for the HSC has built
the CLASSiC-D amplifier in mono
form (November-December 2012;
siliconchip.com.au/Series/17), powering it from the Ultra-LD Mk.3 power
supply. We have a 40-0-40V toroidal
transformer with 3.31A available.
When I power up an amp, I always put
a current limiting incandescent bulb
(65R) in series with the mains supply
as a safety limiter.
This drops the supply to around
100V (measured) and the amplifier
powers up and functions perfectly
with a good audio output.
The problem occurs when the current-limiting light bulb is taken out
and full current is supplied. Then the
amp does not progress out of red LED
protect mode and into run blue mode. I
measured the voltage out of the power
supply board, and it had risen to ±60V,
giving a head of 120V.
siliconchip.com.au
As the setup is a single amplifier
module in mono format, the load is
perhaps not as demanding as anticipated. I guess the current-limiting feature may be holding the amplifier in
protect mode. At 120V, some of the
caps and perhaps other parts will be
nearing their tolerances as well.
The student rather quickly suggested that we could hard-wire the light
bulb into the amplifier and a special
pulsating blue light could accompany
his doof doof music! Ten points for initiative. Can we modify the amplifier
in some way as an alternative? (D. K.,
Warriewood, NSW)
• The problem is most probably the
overvoltage protection that shuts
down the amplifier at around ±60V
(120V total). That’s via zener diode
ZD5 and transistor Q5.
The solution would be to lower the
voltage of the amplifier supply. For the
toroidal transformer, you can wind on
two extra windings with a few turns
that reduce the output of each of the
two secondary windings.
The windings need to be wound in
the opposite direction to the original
and then connected in series with the
secondary using a similar or larger
gauge wire.
Before connecting again to the amplifier power supply, check that each
secondary winding voltage has reduced to around 38VAC. If the voltage
is more than the original, the added
winding needs to be reversed.
To find out how many turns are
required, wind on say 10 turns and
measure the voltage. That will give an
estimate of how many volts per turn
by dividing the measured voltage by
10. You will need to wind on enough
turns for a reduction of about 2V AC
on each secondary.
Another alternative (that is not ideal) is to change the over-voltage threshold to be higher. To do this, add a diode (1N4004) in series with the zener
(anode to anode). Add another diode
in series if this is insufficient.
sible to replace with TLC549? Or can
you suggest another alternative part?
(V. V., via email)
• Yes, the TLC549 is a suitable substitute in this design.
Identifying unknown
SMD ICs
I’m trying to fix a broken Bosch 30V
500mA battery charger for a cordless
vacuum cleaner. I have no circuit diagram, and many of the parts are hard
to identify. The feedback circuit on the
low voltage side uses a 6-pin surfacemount IC marked OD=28X, instead of
a TL431. Can anyone help me to identify this part?
I am also trying to find some information on a 6-pin surface mount IC
marked TV6PE. It seems to be a protective device. Based on how it is wired,
I believe it to be a comparator with a
built-in voltage reference. (R. S., Fig
Tree Pocket, Qld)
• Identifying SMD ICs from their
markings can be frustrating. There are
websites to help do this, but many ICs
often share the same code (usually two
or three letters), and it is usually hard
to read the code. Sometimes there’s
more than one sequence of letters, and
you don’t know which one to search
by. The best website we’ve found for
doing this is https://alltransistors.com/
smd-search.php
We think the first device you
mention may be included in this
list: alltransistors.com/smd-search.
php?search=0D Note that we are
searching for 0D and not OD, as SMD
codes usually do not start with the letter O because they would be almost indistinguishable from a zero. There are
a few six-pin devices on that list, so
if you check their pinouts, hopefully
you’ll find one that matches.
The TV6PE device is a tricky one.
TV6 does come up with a few possible matches in six-pin packages, but
Alternative to TLC548
ADC chip
I would like to build your Charger
for Deep Cycle 12V Batteries (November & December 2004; siliconchip.
com.au/Series/102). But one part is
very difficult to buy anywhere, the
TLC548 analog-to-digital converter
(it has been discontinued). Is it posAustralia’s electronics magazine
August 2020 109
none are comparators. You may have
to search a vendor like Digi-key or
Mouser that has a parametric search
for components of your estimated type
in that package, then check each data
sheet until you find one with a matching pinout.
X2 capacitor failure
is too common
I have repaired several small appliances which use a mains-rated capacitor to drop the voltage down to a low
level for the circuit. These include
a wireless doorbell, night light, LED
globes etc.
The mains-rated series capacitor
slowly degrades, and the voltage supplied to the circuit is reduced until it
stops working. Most would simply be
discarded when they stop working and
end up in landfill simply because of
the failure of one component. Would
an X1 capacitor be longer lasting than
the recommended X2 type?
X2 capacitors are designed to fail
short circuit, which would destroy
the device before the circuit breaker
tripped. Would it be better to use a Y2
capacitor (designed to fail open-circuit)
in these devices? (J. B., Mirani, Qld)
• X2 capacitors are not designed to
fail short-circuit. They are allowed
to fail short-circuit, but in practice,
as you’ve noticed, they tend to lose
capacitance if abused and eventually
just go open-circuit.
X1 capacitors might be slightly more
reliable given their higher voltage rating. But a good-quality X2 capacitor
would probably be just as effective.
It’s true that the X2 series capacitors
supplied in mains-powered devices
fail too often. Our experience is that
if you replace them with a good quality X2 capacitor, they usually last a
long time.
The X2 capacitor typically has a series resistor for inrush current limiting that would likely fuse in the case
where the capacitor does go short circuit (or the PCB track would).
What are low-K
ceramic capacitors
I am restoring my Playmaster 101
valve amplifier, as described in Radio
& Hobbies, August 1962. I built the amplifier back in 1966. All has gone well,
but I’m confused about the feedback
capacitors coupling the output trans110
Silicon Chip
former secondary back to the cathode
of the first valve.
They are 220pF plastic or ceramic
types and have been specified as being “not High K”. Originally I used
polyester; I have searched the web for
“low K capacitor” and come up blank.
What type of capacitor would you recommend? (P. C., Balgal Beach, Qld)
• Low-K (C0G, NP0 or similar) ceramic capacitors are close-tolerance, highstability ceramic capacitors for use in
tuned circuits where low losses, high
linearity or excellent temperature stability are required. High-K capacitors
tend to have poor tolerances and high
voltage and temperature coefficients,
and are generally used for supply bypassing where the precise value is
not critical.
Modern capacitors can be classified according to the characteristics
and properties of their insulating dielectric. Low-loss, high-stability capacitors include mica, low-K ceramic,
polystyrene and polypropylene. Medium-loss, medium-stability capacitors
include paper, polyester, and mediumK ceramics like X7R, X6S and X5R.
For the 220pF low-K capacitors, you
could safely use NP0/C0G ceramic,
mica, polystyrene or polypropylene.
Sourcing ultrasonic
piezo speakers
I recently came across an article
featured in an old copy of Electronics
Australia, November 1985, on page 40:
“Pest Off” by Colin Dawson. I decided that I want to build it to try to reduce the number of rodents and pests
around our property.
The components are readily available from Jaycar, including a Piezo
Tweeter, Cat CT1930 (RSN1005). But
this does not meet the required frequency that the Pest Off delivers, 2364kHz.
As no part number is provided in
the article, I am hoping you can tell
me whether or not this piezo tweeter
would work in this project with a few
modifications. Or can you suggest another I can use? (K. W., Hamilton, NZ)
• The RSN1005 is the equivalent to
the KSN1005 originally specified. So
the Jaycar part is suitable. The output
frequency from these piezo speakers
does extend beyond 20kHz. Manufacturers do not tend to show the response
above 20kHz, because this is the upper-most range of human hearing.
Australia’s electronics magazine
Some mains adaptors
may not meet standards
I bought a QNAP NAS (networkattached storage device) recently,
and it came with a Delta DPS-65VB
12V/65W power adaptor. The NAS
crashed when there was a very brief
mains glitch that caused no malfunction of anything else of mine.
That got me checking things, and it
seems that the problem was caused by
the 8ms sag time and 750ms recovery
time of the power adaptor when under
load. Not good, given our occasionally flaky mains on the Central Coast!
There was no bad weather at the time.
Anyway, the power adaptor is sealed
and has a 3-pin IEC connector which
suggests to me that it is Class I. But
when I checked between the Earth
pin and the 0V/sleeve connection on
the 12V output plug, I determined that
there are two diodes in inverse parallel and a 100nF capacitor in parallel
between them.
I know that sort of configuration
used to appear years ago in various
types of equipment, but is it actually
legal? (J. R., Woy Woy, NSW)
• We have never seen diodes between
mains Earth and the 0V output of a
DC supply. Such a device is probably not safe, as the diodes could fail
open-circuit under a fault condition,
possibly leaving the output at mains
potential.
We have seen many switchmode
supplies with a floating DC output but
a three-pin plug with a mains Earth
connection. This is odd as they have
plastic cases, but cannot qualify as
Class II or ‘double insulated’ as that
class has the requirement of no Earth
connection. (However, there are valid reasons to use an Earth connection
with such an insulated device, such
as RFI/EMI suppression.)
Possibly, those supplies have an internal Earthed metal chassis and therefore may qualify as Class I, despite
being in a plastic case and having a
floating output.
This type of supply is commonly
sold in Australian retail outlets, eg,
with new laptop or notebook computers. One would therefore assume
that they meet Australian/New Zealand standards; however, we are not
100% sure. If you are concerned that
the device might not meet standards, it
would be best to contact the Electrical
continued on page 112
siliconchip.com.au
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WARNING!
SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such
projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring
should be carried out according to the instructions in the articles.
When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains
AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high
voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages
should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine.
Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the
infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any
liability for projects which are used in such a way as to infringe relevant government regulations and by-laws.
Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the
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siliconchip.com.au
Australia’s electronics magazine
August 2020 111
Coming up in Silicon Chip
5G Networks
Dr David Maddison describes the benefits and challenges of this new fifthgeneration mobile communications technology. Based on how it’s being described,
it’s as if 5G will be the best thing since sliced bread. But will it? Read our article
and decide for yourself.
High Power Ultrasonic Cleaner
Advertising Index
Altronics...............................75-82
Ampec Technologies................. 23
Dave Thompson...................... 111
Digi-Key Electronics.................... 3
Our new Ultrasonic Cleaner can deliver around 40W into a cleaning bath, ideal for
cleaning larger parts in about four litres of water or solvent. It has an adjustable
power level from 10-100%, a timer from 20 seconds to 90 minutes, over-current
protection and runs from 12V, either from a battery or mains adaptor.
OBD2 & Forscan – advanced automotive diagnostics
Emona Instruments................. IBC
Hare & Forbes....................... OBC
Jaycar............................ IFC,53-60
You’ve probably seen the dirty cheap (in some cases, less than $10) Bluetooth
car diagnostic dongles online. You may even have one or two. But dongles ain’t
dongles; for just a bit more money, you can get one that can do more than just
give you ‘trouble codes’. With the right (low-cost) gear, you can interrogate the
dozens of electronic modules in modern vehicles and even reprogram them!
Keith Rippon Kit Assembly...... 111
Satellite navigation – in space? And on the Moon?
Microchip Technology.................. 5
Yes, it is possible (if tricky) to pick up navigation signals well above the orbits of the
satellite constellations and even as far away as the Moon. NASA even has plans
to launch navigation and communication satellites in orbit around the Moon too!
Ocean Controls........................... 9
The History of Aussie GPOs
Silicon Chip Binders............... 104
We use them every day but did you ever wonder where our power point design
came from? Why is it different from the American, European and UK plugs? Why
do some countries use similar sockets but in different orientations? This article
describes all of that, as well as the history of Australian mains voltages and
frequencies, why our sockets always have switches, and more besides.
Note: these features are planned or are in preparation and should appear
within the next few issues of Silicon Chip.
The September 2020 issue is due on sale in newsagents by Thursday, August
27th. Expect postal delivery of subscription copies in Australia between August
25th and September 11th.
LD Electronics......................... 111
LEDsales................................. 111
RayMing PCB & Assembly.......... 4
Silicon Chip Job....................... 37
Silicon Chip Shop.................... 87
The Loudspeaker Kit.com........... 7
Tronixlabs................................ 111
Vintage Radio Repairs............ 111
Wagner Electronics................... 50
Notes & Errata
DIY Reflow Oven, April & May 2020: on page 32 of the April issue, in the parts list, the male/female chassis-mount IEC power
connector is described as a 15A type, but a 10A type is needed. The catalog code given (Altronics P8330A) is correct, ie, it is
the 10A type.
Equipment Safety System team at
www.eess.gov.au/about/contact-us/
Hazards of old mains
wiring
I am wondering if anyone has ever
done a study of the decomposition of
original latex coatings on ‘ancient’ wiring and the rotting of fabric bindings
etc. (S. B., Bundamba, Qld)
• See the Publisher’s Letter in the
112
Silicon Chip
November 1995 issue (“Have you had
your house wiring checked?”) and August 2008 (“Electrical wiring in older
houses can be dangerous”). As Leo said
in his 2008 column, “… if your home
is 50 years old or more, the wiring is
almost certain to be unsafe or in need
of upgrading.”
It’s amazing that fabric- and rubbercoated mains wires still are working,
in some cases over 100 years after they
were installed. But they’re bound to
Australia’s electronics magazine
fail sooner or later, and possibly start
a fire, so even if there are no apparent problems, it’s still best to replace
it all with modern vinyl-insulated
mains wiring.
Circuit breakers should be upgraded at the same time, to RCD versions.
The new wiring and breakers should
also allow you to upgrade each circuit to deliver more total current and
power, reducing or eliminating nuisance tripping.
SC
siliconchip.com.au
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