This is only a preview of the July 2017 issue of Silicon Chip. You can view 44 of the 104 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 "RapidBrake - giving the guy behind extra stopping time":
Items relevant to "Deluxe Touchscreen eFuse, Part 1":
Items relevant to ""Over-the-Top" rail-to-rail op amps":
Items relevant to "The low-cost VS1053 Arduino audio playback shield":
Items relevant to "We put the VS1053 Arduino shield to work":
Items relevant to "Completing our new Graphic Equaliser":
Purchase a printed copy of this issue for $10.00. |
JULY
2017
ISSN 1030-2662
07
9 771030 266001
The BEST DIY Projects!
9
PP255003/01272
$ 95* NZ $ 12 90
INC GST
INC GST
Emergency Stopping signalling for ANY vehicle
RapidBrake
Gives the guy behind you
EXTRA time to pull up!
Understandin
g
LED DOWN
L
AND DIMMIGHTS
ERS
And why man
y don’t work
well together
!
We visit
Tasmania’s
siliconchip.com.au
...
July 2017 1
Aussie ship builders to the world!
PROJECT OF THE MONTH
Our very own specialists are developing fun and challenging
Arduino®-compatible projects for you to build every month,
with special prices exclusive to Nerd Perks Club Members.
BATTERY POWERED NIGHT LIGHT USING ARDUINO®
This project has three purposes. Firstly, it provides you with a handy standalone, motionactivated night light. Secondly, it teaches you how to build your own Arduino®-compatible
board (cool!), and thirdly, teaches you how to get the best performance from your Arduino®
when running on batteries. The standby current on this project is less than a milliamp,
which will be enough to run it for months.
Note: Some soldering required
VALUED AT $51.80
WHAT YOU WILL NEED:
ATMEGA 328P IC AND 16MHZ CRYSTAL
HIGH POWER LED MODULE
PIR MOTION DETECTION MODULE
ARDUINO COMPATIBLE LDR SENSOR
SOCKET-SOCKET JUMPER LEADS
ULTRA MINI EXPERIMENTER’S BOARD
4X AAA BATTERY HOLDER
HEADER STRIP
28 PIN IC SOCKET FOR ATMEGA 328P
PK OF 8 10KOHM RESISTORS
100NF POLYESTER CAPACITOR
ZZ-8727
XC-4468
XC-4444
XC-4446
WC-6026
HP-9556
PH-9268
HM-3212
PI-6510
RR-0596
RM-7125
$12.95
$10.95
$5.95
$5.95
$5.95
$4.95
$2.45
$0.95
$0.75
$0.55
$0.40
NERD PERKS CLUB OFFER
BUY ALL FOR
$
SEE STEP-BY-STEP INSTRUCTIONS AT
jaycar.com.au/battery-night-light
4495
SAVE OVER 10%
IMPROVE THE SOFTWARE
ISP PROGRAMMER
FOR AVR XC-4627
USB TO SERIAL
ADAPTOR MODULE
Unbrick, install or update Arduino®
compatible boards.
XC-4464
A mini-USB to
6-pin serial port
module used to
communicate
with Arduino®
boards and modules.
• 3.3V & 5VDC power switch
• Send & receive indicators
14 95
$
NERD PERKS CLUB MEMBERS RECEIVE:
10%
OFF
POWER CABLES
Finished Project.
Batteries not included.
DON'T FORGET YOUR ESSENTIALS
ECLIPSE ALKALINE
BATTERIES SB-2334
AA/AAA. Pk 12.
7
$ 95
19 95
$
MID-SIZED
BREADBOARD PB-8820
6
$ 95
Mid-sized prototyping
breadboard with 400 tie points.
EARN A POINT FOR EVERY DOLLAR SPENT
AT ANY JAYCAR COMPANY STORE• & BE
REWARDED WITH A $25 JAYCOINS GIFT
CARD ONCE YOU REACH 500 POINTS!
Conditions apply. See website for T&Cs
*
*
*Applies only to cables listed on page 5 of the July 2017 Flyer
Catalogue Sale 24 June - 23 July, 2017
REGISTER ONLINE TODAY BY VISITING:
www.jaycar.com.au/nerdperks
To order phone 1800 022 888 or visit www.jaycar.com.au
Contents
Vol.30, No.7; July 2017
SILICON
CHIP
www.siliconchip.com.au
Features & Reviews
16 We visit Incat – another Aussie success story
Imagine a 100m+ ferry plowing through waves at almost 100km/h – they’re the
craft Tasmanian shipbuilder Incat are exporting all around the world. Despite
early setbacks, Incat are now a major force in the field – by Ross Tester
24 LED lights/downlights and dimmers
LEDs are now the choice for home lighting but many people have found they
don’t work well (if at all) with their existing dimmers. We explain how and why
and how to fit a dimmer which will work properly – by Leo Simpson
The 109m wave-piercing
catamaran “Francisco”, built by
Incat in Tasmania– Page 16
57 Review: Tecsun’s new S-8800 “AM listener’s receiver”
While this new model receiver from Tecsun covers FM, shortwave and even
longwave, it’s the AM broadcast band where it really excels – by Ross Tester
60 “Over-the-Top” rail-to-rail op amps
Most op amps can’t operate even close to their supply rails. But there’s a class of
op amps which can get within a couple of millivolts – by Nicholas Vinen
72 The low-cost VS1053 Arduino audio playback shield
The VS1053 is a low-cost Arduino shield with a microSD card slot which can
decode and play back many different audio formats – by Nicholas Vinen
Constructional Projects
32 RapidBrake – giving the guy behind extra stopping time
You may recall our “QuickBrake” project (Jan 16). This one is different: it senses
rapid deceleration and flashes either your brake lights or hazard lights to alert
following drivers, giving them extra time to avoid a rear-ender! – by John Clarke
The things you
DIDN’T know about LED
lights and dimmers – Page 24
RapidBrake
gives vital
extra warning
to the driver
following – Page 32
40 Deluxe Touchscreen eFuse, Part 1
You asked for a deluxe version with higher specs, so here it is! Based on a
Micromite BackPack, this new eFuse handles higher current, higher voltages,
split supplies, 1ms triggering and so much more – by Nicholas Vinen
77 We put the VS1053 Arduino shield to work
Here’s how to turn the VS1053 (see above) into a real project for audio
playback and recording – by Bao Smith
82 Completing our new Graphic Equaliser
Here’s the fun bit: putting it all together! It’s housed in a laser-cut acrylic case it
looks great – and with up-to-the-minute circuitry it works just as well. Add one of
these to your hifi system and really hear the difference – by John Clarke
Your Favourite Columns
62 Serviceman’s Log
A blast from the past: perished belts stop a cassette deck – by Dave Thompson
87 Circuit Notebook
(1) Remote water level monitoring using LoRa and Arduino
(2) Wien Bridge Oscillator delivers high power
(3) Simple constant speed controller for permanent magnet DC motors
(4) 12V DC Cyclic Pump Timer
92 Vintage Radio
The DKE38 Deutscher Kleinempfänger– by Ian Batty
Everything Else!
2 Publisher’s Letter 103 Market Centre
4 Mailbag – Your Feedback 104 Advertising Index
siliconchip.com.au
98
Ask SILICON CHIP 104 Notes and Errata
101 SILICON CHIP Online Shop
Deluxe version
of our popular eFuse, with
touchscreen, higher power, split
supplies and much more
– Page 40
Tecsun’s new S-8800
receiver is a solid
performer on all
bands but it’s a
real whiz on AM! –
Page 57
Cheap Arduino
shield to play
(and record)
audio files from
and to an SD
card – Page 77
July 2017 1
www.facebook.com/siliconchipmagazine
SILICON
SILIC
CHIP
www.siliconchip.com.au
Publisher & Editor-in-Chief
Leo Simpson, B.Bus., FAICD
Editor
Nicholas Vinen
Technical Editor
John Clarke, B.E.(Elec.)
Technical Staff
Ross Tester
Jim Rowe, B.A., B.Sc
Bao Smith, B.Sc
Photography
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
Brendan Akhurst
Ian Batty
David Maddison B.App.Sc. (Hons 1),
PhD, Grad.Dip.Entr.Innov.
Associate Professor Graham Parslow
Dave Thompson
SILICON CHIP is published 12 times
a year by Silicon Chip Publications
Pty Ltd. ACN 003 205 490. ABN 49
003 205 490. All material is copyright ©. No part of this publication
may be reproduced without the
written consent of the publisher.
Subscription rates: $105.00 per year
in Australia. For overseas rates, see
our website or the subscriptions page
in this issue.
Editorial office:
Unit 1 (up ramp), 234 Harbord Rd,
Brookvale, NSW 2100.
Postal address: PO Box 139,
Collaroy Beach, NSW 2097.
Phone (02) 9939 3295.
E-mail: silicon<at>siliconchip.com.au
Printing and Distribution:
Derby Street, Silverwater, NSW 2148.
ISSN 1030-2662
Recommended & maximum price only.
2 Silicon Chip
Publisher’s Letter
Incat’s world-class really fast ferries
– designed and built in Tasmania
Back in April this year I was fortunate to visit Incat’s
impressive production facilities in Hobart, Tasmania, as
the guest of Gary Johnston, of Jaycar Electronics. This
was actually an extension of a trip with Gary and Dick
Smith to attend the 35th birthday celebration dinner of
the Historical Radio Society in Melbourne where Dick
Smith was the keynote speaker at the event. That was a
most enjoyable experience but the trip to Incat was a truly memorable bonus as
we were given an extensive guided tour by the founder of Incat, Bob Clifford.
While the article starting on page 16 of this issue attempts to describe the
scale of the overall production facilities and gives some dimensions of the
vessels that we saw being built, being on-site gives an entirely different impression. These vessels are huge. For a start, they are 32 metres wide; that’s
over 100 feet in good olde Imperial units. This is the same beam dimension
as ships which comply with the so-called Panamax standard, allowing them
to – just – pass through the Panama Canal!
Even standing outside these ferries really doesn’t drive home just how big
they are. To fully appreciate their size, you have to walk the length of the ship
on the various decks, particularly the one which accommodates the massive
semi-trailers and which allows them to turn around at the end of the deck
and drive back out!
That these vessels are also designed and completely manufactured in little
old Tasmania with a highly skilled and highly motivated workforce is truly
gratifying. It shows that Australian companies really can compete with the
rest of the world, in spite of our high labour costs and distance from the main
markets in Europe.
LEDs are now the overwhelming choice for domestic lighting
If you have not recently visited some newly constructed homes or apartment blocks, you may not have realised how ubiquitous LED lighting in homes
has now become. In virtually every new home, the standard lighting source is
the flush-mounting LED downlight, designed to fit into a 90mm circular cutout in plasterboard ceilings. A typical 4-bedroom home could easily have 60
or more of these downlights. The once popular 12V halogen downlights and
those horrible compact fluorescent lights have gone but so has any other form
of incandescent (halogen or otherwise) and fluorescent lighting too.
This is good from an energy perspective, because it means that the lighting
energy limits in Australian building standards are now fairly meaningless.
People can have as much lighting in their homes as they want, without worrying about energy cost, climate change or any limits placed on them by overbearing government regulations. That is not to say that everything about LED
lighting is good – some of these fittings do generate a lot of interference and
there is no indication when you buy a LED fitting that it might be a problem.
Of course, you need not be confined to downlights for domestic lighting.
There is now a LED equivalent for virtually every conceivable lamp shape and
function with the only notable exception being those lamps exposed to high
temperatures, such as those used in ovens. The only drawback with some LED
lamps is that they may not be suitable for bedrooms and in living and dining
rooms, particularly those that are cool white.
Some people may find their light too bright and harsh. In that case, they
would need to choose warm white for those rooms and even then, probably
need dimmers in each bedroom and living room. And the old faithful dimmers which worked OK with incandescent may not be suitable, as we discuss
in the article starting on page 24 of this issue.
Leo Simpson
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”.
True confessions
and the HMV Little Nipper
With regard to the Vintage Radio
article on the HMV 64-52 Little Nipper restoration in the May 2017 issue,
and my letter on the topic in the June
2017 issue, while I realise we are
dealing with restoration rather than
improvements to the original, I would
like to make the following comment
regarding the loop antenna.
After the loop antenna was wound
on a mandrel, a current was then
passed through it, of just sufficient
strength to melt the wire’s plastic covering and make it rigid to mount on
the plastic back.
With the benefit of hindsight, a better grade of plastic covering could have
been used, as the “welding” of the
cheap plastic increased self-capacity
and lowered the “Q”, thus affecting
sensitivity and selectivity.
Neville Snow,
Burwood, NSW.
Cathodes don't glow; filaments do
I am writing about the HMV 6452 Little Nipper radio featured in
the Vintage Radio pages of the May
2017 issue (www.siliconchip.com.au/
Article/10657).
I must have refurbished at least a
dozen of these. I did a double-take at
the statement: "I noticed that the cathodes were glowing all but the 6BA6
valve". Oops! Cathodes don’t normally
glow; filaments, heaters and globes
do; plates may, but only when things
are not right.
Also to be noted in that series is the
screen resistor in this set, R6. Originally that was 2 x 22kW, 1W, in parallel. Later versions used a single 10kW
resistor. As the dissipation exceeds
1W, that resistor often fails.
I actually have one of these sets. Its
only failure since refurbishing, ages
ago, was a sudden and massive "off-frequency" event. That was truly a bug in
the system. A large arachnid had perished on the top of the oscillator coil!
4 Silicon Chip
Regarding the author's comment
that powering up that 64-52 set "cold"
(ie, without inspecting it first) was a
bad idea; I have to agree.
One person that I know of decided
that as his Dad had restored the set he
was selling, it could be powered up to
demonstrate for a buyer. That resulted in the immediate and spectacular
demise of one type 80 valve. So he
then replaced the valve and powered
it back on again!
Fortunately, when the plates went
red, they shut it down and the valve
survived. However, inside the pan and
on the floor of the cabinet was an impressive powder-coating job, done by
the first unit to fry.
Marc Chick,
Wangarratta, Vic.
Editor's note: keep in mind that some
battery-operated valves use a directly
heated cathode and in this case, the
cathode would actually glow (albeit
very faintly).
Synchronous inertia for grid stability is
currently our best bet
I would like to comment on the
recent letter from Dr Kenneth Moxham
(Mailbag, February 2017), in which he
presumes to discuss alternative methods for achieving grid stability. Since
the publication of his letter, Victoria's
Hazelwood power station has been
shut down and the power crisis in
South Australia continues.
While some might believe that
this is a time to discuss alternative
generation technologies, the average
person in South Australia, faced with
the prospect of yet another blackout
at any time, quite reasonably wants
the problem fixed and preferably now.
Those of us who are professional
engineers have a clear responsibility
to discuss solutions that can be implemented immediately, not those that
might be available only far off into
the future.
Discussion should be restricted to
those means that use readily availa-
ble, off-the-shelf equipment. Furthermore, when we speak as professional
engineers, we need to indicate that we
have taken due regard of the published
literature. I mention these points because I note that Dr Moxham signed
his letter as a professional engineer.
I discussed the matter of synchronous inertia in an earlier letter (Mailbag, December, 2016). I cited a paper
by a Marcelle Gannon (2014) because
it addressed this very issue: the thenemerging stability issue on the Eastern
Australian grid.
In this paper, not only are the mechanisms that contribute to grid stability
discussed in considerable detail but
work on potential alternatives to the
use of rotational inertia is cited (Section 3.4.4).
Furthermore, Table 2 and Section
5.2 of the paper examine various alternative ways for providing both conventional synchronous inertia and its
replacement “synthetic inertia”.
The paper also provides an excellent review of work internationally,
and within Australia by the AEMO, the
AEMC, and other professional organisations. Dr Moxham might also like to
read: http://siliconchip.com.au/l/aacz
Clearly then, both the relevant professional bodies and the grid manager
have been actively discussing the
emerging stability issue and how to
tackle it for some years. This contradicts Dr Moxham's concern that “no
one seems to be talking about controlling the system in another way so the
stability is not compromised” or that
“no one seems to be thinking outside
the square”.
Dr Moxham states, categorically:
“It is wrong to suggest that the rotational inertia that comes from the kinetic energy of the spinning mass is
the source of stability under fault conditions.” Perhaps Dr Moxham meant
to include the words “only possible”
siliconchip.com.au
Mailbag: continued
LED downlight
interference problems solved
Some time ago, I wrote to you
regarding LED lights that were
installed in my kitchen interfering
with the TV reception on my Topfield
set-top box (STB) feeding a Sony rear
projection analog TV. Until now, we
just had to put up with it.
The Topfield STB gave up the
ghost and as they’re out of business, I bought a new STB, a Teac,
for $58.00 rather that get a new TV,
since a similar one to what we have
would cost approximately $1500.
As the STB was brand new and
the problem was still there, I rang
Teac's help line and one of their
“technicians” suggested some new
automated channel searches that did
not fix the problem; he said that the
STB was OK.
So I contacted a local antenna
company and their representative
knew of this problem. Using a signal strength meter, he found that the
LEDs in the kitchen have a noise/
hash output that affects TV broadcasts that are around 150-170MHz,
to which the Teac STB was tuned,
using the auto search.
He manually tuned the TV stations in the STB to UHF frequencies
between the words “the” and “source”.
As this last statement of Dr Moxham's stands, it is quite simply wrong.
Every grid systems engineer around
the world will disagree with it.
Again, Gannon's paper, Section 3,
provides a more than adequate explanation as to how a network of conventional generators, each with its inherently large rotational inertia, provides
more than sufficient synchronous inertia, hence system stability, and therefore protection to deal with transient
fault conditions.
Also importantly, in conventional
power stations, synchronous inertia
is already available, essentially “free”,
as its provision is an inherent part of
the generator design.
As a young engineer, I very quickly
learned that if I thought to criticise
any engineering work, I was required
6 Silicon Chip
above 550Mhz — problem solved!
The Teac “technician” made no such
suggestion.
These LEDs also affect FM broadcasts above 100MHz and I use an
analog TV aerial that is wired to the
antenna system within our home for
picking up FM broadcasts.
The antenna man said that as I
was using the analog antenna to
supply the FM receiver, to leave it
there, otherwise he would suggest
I remove it.
The offending LEDs came from
Kogan, and another LED installed
in the room with the TV, a Philips
one, has very little or no hash output. So I’m going to ditch the Kogan
LEDs and replace them with Philips
units, despite the TV tuning being
OK anyway.
Apparently, some LEDs have “No
RF interference" printed on the packaging but the Philips one doesn’t
have this. Anyway, looking out for
LEDs that are marked might be a
good idea in future.
The average punter wouldn’t have
a signal strength meter but if you
know the solution, you can tune to
the higher TV frequencies manually.
Ian Stewart,
Glenhaven, NSW.
to provide a costed alternative, accompanied by a complete description of
how it would work.
That is an essential requirement
of one's Engineers' Code of Conduct.
By contrast, Dr Moxham provides no
suggestion as to what actual, available technology (his “other ways”),
might replace conventional rotational
inertia.
Tantalisingly, he provides no suggestion as to how those whom he criticises might “think outside the square”.
If he had, as Ms Gannon, for example,
has done, he might well have found
that proposed alternatives are not only
untested, but are also unrealistically
expensive.
For example, presently fashionable as a “solution” is battery storage.
How many batteries? For SA's needs,
my colleague Dr Tom Quirk has done
some calculations, using real, live,
AEMO grid data. The outcome? Well,
it's rather more than the couple of AAA
cells needed in your TV remote.
To support a 100% renewables scenario just for South Australia, for example, Dr Quirk estimates a Li-ion battery requirement of some 2.1 million
tonnes. The cheaper Lead-Acid route
would require some 7.5 million tonnes
of batteries. Cost? Oh, a mere $60-90
billion. Simple really.
This calculation does not address
the necessary battery replacement inventory or the generation to charge it,
all of which adds to the cost. It also
does not discuss the very substantial
CO2 emissions cost in such as the mining and milling of the ores to obtain
the lithium or the lead, and in the battery fabrication. See http://siliconchip.
com.au/l/aacy
Dr Quirk also investigates the (quite
mad) scenario that includes battery
storage, presently on offer from the
South Australian government, at
www.onlineopinion.com.au/view.
asp?article=18948 Clearly, this battery-powered route is going nowhere.
Is there an immediate solution to
South Australia's ongoing grid stability issues and skyrocketing power
prices? As I said in my earlier letter,
the Federal Government should abolish the MRET subsidy scheme immediately.
Removal of the very lucrative MRET
subsidies would remove the price distortion in the electricity market that at
present has the absurd side-effect that
it forces out schemes such as cleanburning gas-fuelled power stations (for
example, Pelican Point).
Also necessary is that the South Australian government finds a replacement
for the now demolished Port Augusta
Power Stations, for the reasons earlier
discussed. South Australians, and in
particular residents in northern parts
of SA (such as Port Lincoln, Ceduna, Whyalla and Roxby Downs) who
have experienced power outages of as
much as a week at a time might then
see the restoration of a secure electricity supply.
The Hazelwood power station must
also be restarted. Hazelwood's closure
not only places further risks in the way
of grid stability, its lack will cause a
large jump in prices, particularly for
siliconchip.com.au
au.element14.com |
Supporting your journey at every stage
Find out what this means for you. Visit:
au.element14.com/your-development-distributor
1300 361 005
Mailbag: continued
Helping to put you in Control
DCM260B 3D electronic compass
DCM260B is a low-cost 3D
electronic compass with RS485
output. Housed in a small
IP67 enclosure, it produces
tilt compensation, using USA
patented technology of hard
magnetic and soft magnetic
calibration algorithm.
SKU: SRS-205
Price: $319.00 ea + GST
Self-Powered 5 Digit LCD Process
Indicator 0 to 10 VDC
5 Digit LCD programmable
process indicator with
internal battery and 0 to
10 VDC signal input. Suits
cutout 24 × 48 mm.
SKU: AXI-0062
Price: $109.00 ea + GST
SparkFun TeensyView
The SparkFun TeensyView
brings you an easy way to add
a small, white-on-black OLED
to your Teensy development
board.
SKU: SFC-062
Price: $20.50 ea + GST
240W Slim DIN Rail Supply
New 240 W economical slimline
single output industrial DIN
rail power supply. 24 VDC at
up to 10 A output. This series
has a working efficiency up to
88%, and has an operating
temperature between -20 to 70
under air convection.
SKU: PSM-1943
Price: $120.00 ea + GST
Modbus Temp/Humidity
Transmitter
A wall mount Temperature
and humidity transmitter with
Modbus RS485 output and LCD
display.
SKU: RHT-010
Price: $225.00 ea + GST
3 Digit Large Display
100mm high digit process
indicator can be read
50m away. It features
a 4-20mA input and is
24VDC powered.
SKU: DBI-020
Price: $449.00 ea + GST
24VAC to 12VDC Power Supply 3W
DIN rail mounting. Isolated DC
output up to 250mA. Short circuit
and overload protection.
SKU: PAS-001
Price: $69.95 ea + GST
For Wholesale prices
Contact Ocean Controls
Ph: (03) 9782 5882
oceancontrols.com.au
Prices are subjected to change without notice.
8 Silicon Chip
South Australians, dependent as they
are on Victorian power via the interconnectors, as Hazelwood's output
will have to be replaced by more expensive gas-fired generation.
Let Dr Moxham understand that
where he signs a letter as a professional
engineer, he is required to discuss the
detail of any alternative “solutions”
that he might propose, to provide the
necessary literature review, and to
provide detailed costings. To merely
mention that alternatives might exist
does not make them viable solutions.
Paul Miskelly,
Mittagong, NSW.
Virtins software activation
Further to your publication of my
letter regarding a problem with the
Virtins multi-instrument software
(page 5, June 2017), I was contacted by
David Wang of Virtins. He requested
my site code and MID and when I provided them he responded with a new
activation code which worked, so the
software is now restored to operation.
Thank you for publishing my letter
which was apparently instrumental in
clarifying the logical course of action.
Barrie Davis,
Hope Valley, SA.
Improvements can easily be made to
High Performance 6GHz+ RF Prescaler
The article on the 6GHz+ RF
Prescaler project (May 2017; www.
siliconchip.com.au/Article/10643)
contains contradictory statements.
Towards the end of the section headed "Output Stage", it says the output
impedance is 75W, the output voltage
swing is 2V peak-to-peak but only
about 300mV when terminated with
50W or 75W.
If the output impedance were actually 75W, terminating it with an equal
value would exactly halve the output
voltage. This much larger observed
change implies a much higher output
impedance.
A glance at the circuit diagram
makes it obvious that the output impedances are actually 300W.
Q1 and Q2 form a long-tailed pair
and act as a current source, presenting
a very high (ideally infinite) imped-
ance, so the output impedances are
determined solely by the resistances
between CON1 and CON2 and ground.
It is not clear that the 100W resistors
serve any useful purpose, their impedance is negligible in comparison to that
presented by Q1 and Q2.
Closer examination reveals a further
anomaly: for an ECL output-low level
of nominally 1.95V, the Q1/Q2 emitter current should be approximately
8.8mA, which is switched alternately
to the two 300W output resistors, giving output voltages of 2.7V into an
open circuit, 528mV into 75W and
378mV into 50W. The observed 2V
unloaded output is clearly very low.
The reason for this is that, with its
base at 1.95V, Q1's emitter will be at
about 2.1V and, with the given 400W
collector load, Q1 will saturate (the
same applies to Q2). When saturated,
the predicted open-circuit output voltage is 2.05V, in good agreement with
that observed. Transistors are slow to
recover from saturation so it is best
avoided in high frequency circuits.
Output terminations below 220W will
prevent saturation of Q1/Q2.
To properly match 75W (or 50W)
lines, the 300W resistors could be
replaced with 75W (51W) resistors (or
perhaps one of each), giving open circuit output of 660mV (450mV), and
330mV (225mV) into matching loads.
These levels could be increased by reducing the value of the 330W Q1/Q2
emitter resistor.
Anthony John Ellis,
Wellington, New Zealand.
Editor's note: your analysis is correct.
This part of the circuit was based on a
number of previous prescaler circuits,
none of which were criticised as being
incorrect, although they clearly were.
The assumption was obviously that
the output impedance of Q1/Q2 was
zero, so the 100W and 300W resistors
in parallel gave an output impedance of 75W. But as you point out, this
assumption was wrong because of the
high collector source impedances of
transistors Q1 & Q2.
Your suggested changes can be
made by simply substituting 0W resistors for the 100W resistors and 75W
resistors for the 300W resistors.
siliconchip.com.au
silicon-chip--order-with-confidence-strongman.pdf
1
5/31/17
2:04 PM
C
M
Y
CM
MY
CY
CMY
K
siliconchip.com.au
July 2017 9
Mailbag: continued
On page 104 of this issue we have
published Notes & Errata covering
this suggested change. Thank you for
bringing it to our attention.
Forcing children to learn robotics
may lead to frustration
The article on Industrial Robots
(May 2017) attracted my attention.
Dr Maddison has produced another
fine overview of a subject and it included quite a few details that I was
not aware of.
It reminded me that sometimes you
don't know what you don't know. I
have spent considerable time looking
for information on robotics and still
didn't know about all the robots Dr
Maddison wrote about.
During the past year, I have been
looking at scanned copies of early
magazines and books etc at archive.
org I am just amazed at how much information is available.
I am not just referring to programs
and robotics; the same applies to electronics and mechanics. The material
might be old, but quite a number of
articles etc have provided me with the
clues to solve problems.
Solar hot water heater controller
wanted
In your Publisher's letter in May,
you mentioned the possibility of a
project which would operate a pool
pump and salt water chlorinator
when solar power was available. I'm
very interested in that project as I'm
building a house in Victoria and attempting to work out the most economical way to provide hot water.
My feedback from plumbers is that
solar hot water systems are quite
hit and miss affairs in Victoria. The
people I talk to say they rarely understand why one system works and
another doesn't (same brand).
So I am looking at a heat pump
water heater which looks quite
promising, but for best performance
should run on solar generated power and not power from the network.
My thoughts on a controller are that
it should be able to:
10 Silicon Chip
For example, there are quite a few
issues of Radio Electronics available
at: https://archive.org/details/radioelectronicsmagazine
Unfortunately, it takes a lot of time
to search through the magazines.
To change the topic, I would like
to comment on the action plan of the
Queensland government to require all
students to study coding and robots.
This was confirmed with a consultation report dated 14 October 2015.
I had to study programming when I
was studying for a Mechanical Engineering degree part time and failed it
miserably twice before passing.
It was the root cause for me terminating my studies as I hated it. It
wasn't until I bought a Sharp PC1500A
pocket computer that my attitude completely changed. The computer was
programmed using BASIC and very
quickly I was able to understand how
programming worked. I have never
looked back.
Some years later, I was working in
the School of Civil Engineering and
saw a group of students in the lab who
were very angry about something.
I asked them why; they told me
•
Accurately determine the time
(GPS) for tariff knowledge and
solar prediction.
• Determine the Solar power input and be able to disconnect the
load should the Solar input drop
below the load requirement.
• Have spare sensor inputs that
determine the heat input required to ensure sufficient hot
water is available or decide that
no extra heating is required.
• Be user programmable to refine
the control characteristics.
This would mean opening the design to be more user-configurable
and making the controller user programmable. I look forward to seeing
what you can come up with.
Tony Riedle,
via email.
Comment: one of our staff members
has a heat pump solar system and
it failed just before the 5-year war-
that a new subject had been created
in which they had to learn about stepper motors plus (I assume) the electronics and programming. They absolutely hated the idea. They had chosen
the Civil Engineering degree because
they were not interested in electronics. They were interested in buildings,
roads, dams and earth works.
I have no doubt that there will be
students who will thrive in the environment set up by the Queensland
government but I also have no doubt
that there will be many more students
who will reject everything to do with
coding and robotics (and electronics).
I have a lot of sympathy for them.
I also have a lot of sympathy for those
who are lured into robotics without
being told how difficult it would be.
I saw this a lot at university. Students
were coerced into engineering without
being told about the heavy maths and
science that they would need to know
and they suffered. Hard core robotics
is far worse than any single science
because it requires knowledge covering so many different areas.
Also I am sure that the kids will be
required to learn one of the approved
ranty ran out (fortunately). We also
would be concerned about the noise
from these units as the compressor
runs. His unit was very noisy before
it failed and now, some 18 months
later, the replacement is heading in
the same direction.
If you did decide on the heat pump
option, we would be inclined to run
it from the "controlled off-peak"
output of your smart meter as the
default option but have a controller (our design) switch over to solar
power during the day.
This could work well if you use
most of your hot water in the morning – solar will bring the tank back
up to the thermostat setting.
If you have showers in the evening,
that concept won't work so well. In
that case, having a webserver which
would allow you to intervene (depending on weather or other variables) might be a useful addition.
siliconchip.com.au
siliconchip.com.au
July 2017 11
Mailbag: continued
programming languages and BASIC
will not be included. I can see a repeat
of what happened to me.
Finally, I saw the question in Ask
Silicon Chip, May 2017, on page 110
where K. S. requested some help to
control the speed of a 180V DC motor. I
needed variable speed many years ago
for some pump experiments at university and I decided to use large variacs with DC motors. When I asked a
local manufacturer for suitable motors,
he specified 180V motors with shunt
field windings.
I queried him about the voltage but
he assured me that was the correct voltage for the rectified AC. I later found
a small motor and controller for a different project and that motor was also
rated at 180V. I thought that I would
tell you about my experience because
12 Silicon Chip
there was some doubt in the Silicon
Chip reply about the motor being suitable for 230VAC operation. Note that
no capacitors were required.
George Ramsay,
Holland Park, Qld.
Comment: your remarks about 180V
motors are pertinent. Any power or
kitchen appliance with a built-in speed
control will employ a 180V motor.
However, the caution about the motor having suitable winding ratings
to work at the peak voltages from our
mains supply is still relevant.
Measuring lamp brightness
with a smartphone
Recently at work I had to make some
leads to plug into automotive cigarette
lighter. It was really time-consuming
task to get all the wire strands into the
screw terminal and make the work
profitable. Later that night, while at
home I was thinking about it. My
thought was: what if our suppliers are
supplying metric wire but components
like plugs and sockets are made with
tooling using Imperial measurements?
At home, I replaced a 23W mercuryfilled energy-saving lamp. The lamp
has same shape as a water jug element;
it was supposed to be the equivalent of
a 100W incandescent lamp. I replaced
it with a 13W LED lamp. Since then
I have been blown away by the extra
brightness of the LED lamp.
I wonder why cell phone manufacturers have not put a lux meter into
their phones so we can check out these
things more easily. In physics class,
one experiment was to get a piece
of paper and put an oil patch on it.
siliconchip.com.au
Mailbag: continued
Microbridge serial interface isn't compatible
with LCD BackPack
I really loved the Microbridge article in the May 2017
issue. I know that Silicon Chip is not the originator of this
project however I do have a bit of an issue. The pinouts for
the serial connectors are different between the Microbridge
and both the original BackPack and the BackPack V2.
The connections on the Microbridge are +3.3V, +5V, RX,
TX, GND while the BackPack uses +5V, TX, RX, GND. If I
am to use both, they would require different connectors
for the USB to TTL adaptor. I know that the Microbridge
can be plugged into the BackPack for programming, but
if the BackPack is installed into a box, like I have, then
there is not enough room to plug in a Microbridge.
Mike Flor,
Wyongah, NSW.
Comment: unfortunately, we didn't notice that difference
in pinouts. If we had, we could have modified the Microbridge circuit and PCB prior to publication, to make it
plug-in compatible with the BackPack projects. Sorry!
Solution to losing the mouse
In a recent article about the Philips 43-inch 4K monitor in
the March 2017 issue, the reviewer mentioned the difficulty
of locating the mouse cursor. Windows has the ability to
change cursor behaviour under Mouse Properties→Pointer
Options tab→Visibility. I have mine set to Pointer trails
Long. It helps heaps as soon as you start moving the mouse.
Warren Hudson,
via email.
As you move the sheet between two
lamps, you can clearly see when the
brightness is the same on each side of
the paper and thus determine which
is brighter, by the distance from the
lamps (ie, the paper will be further
from the brighter lamp).
Eric Richards,
Auckland, New Zealand.
Editor's note: there are a number of
"lux meter" apps for Android and we
would assume for iPhone too. Presumably, they use the light meter built into
most cameras, which is used to determine the aperture and shutter speed
for taking photos. We would treat
measurements made with these apps
as being approximate but they do seem
to work quite well for comparing the
brightness of various lamps.
Having said that, you have to be cautious in making comparisons between
lux measurements of different lamps
because these are spot measurements;
14 Silicon Chip
two lamps with an identical light output in lumens could give different lux
measurements depending on how focussed their beams are.
Lamps with very focussed beams
tend not to be less useful for domestic lighting (with certain exceptions,
ie, where you want spot lighting) but
do give higher maximum readings on
a lux meter.
As for your comment about fitting
wire into screw terminals, clearly
there are some metric/imperial mismatches but given the large variety of
wire thicknesses available, the main
issue is more likely to be that the
socket was intended to be used with
thinner gauge wire, either because it
isn't intended for high current use or
to save money.
An interesting book
on regenerative braking
I have been following the letters on
regenerative braking, starting with the
original request in Ask Silicon Chip on
page 99 of the January 2017 issue and
following on in the March and May
Mailbag sections.
For those with an interest in regenerative and rheostatic braking there is
a really good book about it called "The
Regenerative Braking Story" by Struan
JT Robertson and John D Markham,
published by the Scottish Tramway
and Transport Society. I purchased
it from Camden books in the UK on
the basis of the review in their catalog and it more than lived up to their
accolades.
It is currently available from Amazon at http://siliconchip.com.au/l/
aad0 It's based around trams and trolley buses. I liked it because it blended
the technical with history and has lots
of pictures and circuits.
Neil Bruce,
SC
Elphinstone, Vic.
siliconchip.com.au
Design, Develop, Manufacture with the latest Solutions!
Showcasing new innovations and technology in electronics
In the fast paced world of electronics
you need to see, test and compare
the latest equipment, products and
solutions in manufacture and systems
development.
Make New Connections
• Over 90 companies with the latest
ideas and innovations
• New product, system & component
technology releases at the show
• Australia’s largest dedicated
electronics industry event
• New technologies to improve design
and manufacturing performance
• Meet all the experts with local
supply solutions
• Attend FREE Seminars
Knowledge is Power
SMCBA CONFERENCE
The Electronics Design and
Manufacturing Conference delivers
the latest critical information
for design and assembly.
Local and International presenters
will present the latest innovations and
solutions at this year’s conference.
Details at www.smcba.com.au
In Association with
Supporting Publication
Organised by
Free Registration online!
www.electronex.com.au
Melbourne Park Function Centre 6-7 September 2017
Another Australian
manufacturing success story
Boatbuilders to the World
You may not have heard of Incat, a family-owned company in Hobart,
Tasmania, but the chances are high that you’ve seen some of their products.
They build a variety of aluminium vessels – but their big, fast, ocean-going
wave-piercing catamarans are recognised as world leaders.
T
he first thing that strikes you about Incat Tasmania
is the sheer size of the assembly plant. The address
is quite deceiving – 18 Bender Drive, Derwent Park (a
suburb of Hobart on the Derwent river) – it almost sounds
like a suburban house block! But as you travel down Bender
Drive towards the Prince of Wales Bay, north of Hobart,
you realise that Incat is no backyard operation. It’s huge!
Then again, simultaneously building several vessels up to
120m long means it’s not likely to fit into a backyard shed!
And the fact that there are five huge undercover construction buildings along with a large range of ancillary services
suggests it’s going to occupy a lot of area. And it does – have
a look at the site map/photo and you’ll see what we mean.
There’s over 70,000 square metres of production halls alone,
spread across five massive buildings.
Perhaps an introduction to this Australian success story
might be in order here. Incat Tasmania is acknowledged as
the world leader in the manufacture of high-speed wavepiercing catamarans. Not just a leader, but the leader!
Wherever you go in the world, you’re likely to spot (or
maybe travel on) an Incat Tasmania vessel – whether you’re
taking a car or lorry across the Baltic Sea or Mediterranean, traversing the Thames in a high-speed passenger ferry,
flitting between ports in Asia or South America, swapping
16 Silicon Chip
crews and equipment on off-shore oil rigs . . . or even taking a quick trip (sometimes very quick!) on Sydney Harbour.
As of 2017, they’ve built 88 craft, ranging from a 15m
barge and 24m harbour ferries right through to 112m wavepiercing catamarans (WPC) intended for open water. The last
one was launched in April and headed for Denmark where
it was scheduled to begin service on June 1.
Construction of hull no. 89 was started just a few weeks
ago. It is scheduled for delivery in late 2018. Designers are
currently looking at even larger vessels, up to a 130m WPC.
Incat are far more than just “shipbuilders”, however. They
design the craft from the keel up, using a specialist (but inhouse) team called “Revolution Design”. And their designs
are just that – revolutionary.
Revolution Design have naval architects, engineers and
designers, working in conjunction with the concept and
creative team to develop and refine vessel design.
Incat’s latest generation craft are capable of carrying almost 100% of the ship’s own weight – they’re the only ship
builder in the world to achieve this – making Incat craft very
popular with operators who need to maximise payloads to
gain an edge over considerable opposition.
This, coupled with fast speeds, shallow draft, fast turnaround in port, flexibility in vehicle deck layout, passensiliconchip.com.au
An aerial view of the immense Incat
production facility in Hobart. Each of
the assembly halls is named after a
pioneer of Tasmanian shipbuilding, as
seen in the key at right. (The Prince of
Wales Bay marina in the foreground
is not part of the Incat Tasmania
operation).
Wilsons
Degraves
Coverdales
Inward goods
Plate shop
By Ross Tester
McGregors
Inches
Ross
Revolution Design
Main Office
What’s in a name?
If you Google “Incat”, you’re likely to find two companies answering to that name: Incat Tasmania
(www.incat.com.au) and another (unrelated) company, Incat Crowther, based in Sydney.
Incat Tasmania (short for the “International Catamarans” group) design and build ships in Hobart;
Incat Crowther design ships but have others build them under contract (often overseas).
ger comfort, minimal crewing requirements and reliable
and economic operation further add to their appeal around
the world.
For example, many roll-on, roll-off vessels require access ramps at both the bow and stern, so large trucks/semi
trailers etc can get on and off without a lot of manoeuvring.
Incat’s 98m ro-ro vessels only have stern ramps – but their
internal design allows for a semi to turn 180° on the vehicle
deck, meaning a lot more flexibility in ports.
But we’re getting a little ahead of ourselves.
Incat Tasmania’s past
The company’s roots can be traced back to the early 1970s,
when Bob Clifford (now Robert Clifford, AO, chairman of
Incat) formed the Sullivans Cove Ferry Company (SCFC)
to build conventional steel mono-hull ferries for Hobart’s
Derwent River.
The timing was rather opportune, because on January 5th,
1975, the bulk ore carrier Lake Illawarra crashed into the
supports of the Tasman Bridge (the only link between Hobart
and its eastern suburbs), bringing down part of it. In the two
years following, SCFC ferried more than nine million passengers across the Derwent while the bridge was replaced.
After the bridge re-opened, the company now called Insiliconchip.com.au
ternational Catamarans Pty Ltd (Incat) started construction
of fast ferries, made exclusively of marine-grade aluminium
alloy. They had done extensive research and development
on the merits of aluminium construction, which is one third
the density of steel.
On the downside, aluminium fabrication – welding, in
particular – requires much more skilled craftsmen than
does conventional (steel) construction. Getting those skilled
craftsmen in the early days was a significant problem, later
overcome to a large degree by co-siting a Tasmanian TAFE
college which specialised in the craft. Now called Tasmania
Polytechnic, this continues, highly successfully, to this day.
In 1983, they built a prototype 8.7m craft called “Little
Devil” and proved the wave-piercing concept. This was followed by a full-sized (28m) wave-piercing vessel, the Spirit
of Victoria, in 1985 and “Tassie Devil” in 1986.
The R&D put into these vessels is still in evidence today,
although a huge amount of R&D has continued and will
continue into the future. And the size of the craft has significantly increased.
But (if you’ll excuse the nautical pun) it certainly hasn’t
always been plain sailing for Incat Tasmania. Following the
global financial crisis, orders dropped alarmingly, putting the
company into severe financial difficulty. It had completed
July 2017 17
The world’s fastest passenger ship, the 99m Incat No. 069
Francisco, in service between Argentina and Uruguay.
Lightly loaded, it has been measured at 58.1 knots –
considerably more than 100km/h. With a full load of
vehicles and passengers AND running at only 90% engine
capacity, it cruises at 49 knots (90km/h+).
And this is what powers it (or more correctly two of what
power it!): twin 22MW GE Energy LM2500 marine gas
turbine engines driving Wartsila LXJ 1720 SR waterjets.
This engine is just over 4m long x 1.5m diameter. Incat
believe that the Francisco is capable of even faster speeds
with less fuel on board, in calm waters.
vessels it couldn’t sell and others, being built on spec, had
no sign of likely purchasers.
In fact, Incat would have gone under if its then bankers
had their way. But with help from the Tasmanian government, a relatively small amount of restructuring and redundancies (far less than the bank demanded), coupled with
the very timely sale of two completed craft, Robert Clifford
and his team were successful in trading their way out of
difficulties, in the process becoming more structured and
better managed. And they changed banks!
propellers, not the least of which is incredible manoeuvrability. Because the jets can be angled to wherever needed,
bow thrusters are not required (the jets can push the vessel
sideways). This also allows a shallower draft than vessels
fitted with propellers and a rudder.
And then, of course, there is the rather dramatic speed
capability.
An innovative Incat ferry, the world’s first LNG/dual fuel
model, holds the record for the fastest large passenger vessel in the world – the 99m ferry Francisco, lightly loaded,
has been officially “clocked” at 58.1 knots (107.6km/h).
Of course, there are many speedboats and other craft
capable of this speed . . . but not many of them can carry
1000 passengers and 150 cars in superb comfort!
This ferry, launched in 2013 and named in honour of
Pope Francis (originally from Argentina) is now in service
on the River Plate between Argentina and Uruguay. It easily
achieves a regular running speed of 49 knots at 90% power
from its twin 22MW GE Energy LM2500 marine gas turbine engines, driving Wartsila LJX 1720 SR waterjets. For
those without a nautical “bent”, 49 knots is over 90km/h!
Speaking of those engines, as gas turbines, they’re a
lot smaller than reciprocating engines used in many other WPCs: 4.29 x 1.52m diameter. But they gulp fuel at an
Jet power – and a world record
While quite a number of craft are constructed using the
traditional propellor and rudder method (eg, the new inner Sydney Harbour ferries), the larger Incat vessels – especially those intended for offshore use – are powered by
marine water jets.These have several major advantages over
Not all of Incat’s craft are luxuriously equipped: here HSV1 “Jervis Bay” is fitted out for military use. She made over
100 trips between Darwin and Dili in the 1999 emergency.
18 Silicon Chip
Its sister ship, the HSV-2 Swift, was attacked with a missile
attack by Houthi rebels off the coast of Yemen in October 2016.
Early reports had it sunk but it was only seriously wounded!
siliconchip.com.au
In this photo of the construction of the Express 2, you
can clearly see the third hull. Normally it sits above the
waterline but in big seas, helps smooth out the pitching
action and acts as a “shock absorber”.
The 20-cylinder MAN 28/33D engine (10 per side in “V”
formation) is shown here installed in the next Incat WPC
to come off the line (the Express 3) – but the engine is too
massive to get it all in the one photo!
enormous rate – another 98m Incat vessel, built and configured for military use, is quoted to consume 180 litres
per nautical mile at just 35 knots! We’ve shown a photo of
one of the gas turbine engines opposite.
mark) via the Panama Canal was just 491 days. Express 3
entered service on June 1st.
And another world record (or three)
Other wave-piercing catamarans built by Incat use more
conventional high-speed marine diesels – still immensely
powerful, still driving waterjets.
For example the four MAN 28/33D STC 20 cylinder
4-stroke diesel engines in the 112m Express1 (2012), and
Express2 (2013) are each rated at 9000kW, while the 109m
Express 3’s engines are rated at 9100kW, the engines are
almost 4m high, 2.5m wide and 8m long and weigh over
fifty tonnes. The name deciphers as 280mm bore, 330mm
stroke, while STC stands for sequential turbo charging.
With a maximum engine speed of 1000 RPM, a bore of
280mm and a stroke of 330mm, they each consume around
1700kg of fuel per hour . . . and yet are claimed to be the
most powerful and fuel-efficient 1000 RPM diesel engines
in the world. Boat speed (loaded) is 40 knots while unloaded they can achieve 47 knots.
Incidentally, build time of the Express 3 from laying the
keel in Hobart to delivery to its owners, Molslinjen (Den-
The Blue Riband (or more correctly titled, the Hales Trophy) is the much-sought-after world record for the fastest
crossing of the Atlantic by a passenger ship. It’s not only a
test of speed, it’s a test of endurance and reliability.
The Blue Riband dates back to the 1830s, when ships
fought over the honour of being the fastest transatlantic
liner. In 1935, to encourage innovation in passenger transport and formalise the Blue Riband, Harold Hales, a British
MP, commissioned and donated a four foot high, heavily
gilded solid silver trophy.
The last big liner to win the trophy was the SS United
States on its maiden voyage in 1952, averaging 35.59 knots.
Now Incat ships hold that record – in fact, the last three
times the record has been broken were by Incat vessels,
each in turn earning the right to fly the prestigious Blue
Riband. In 1990 Incat’s Hoverspeed Great Britain (hull no.
025) broke SS United States’ 38-year-old record by three
hours and 14 minutes. The 74-metre Incat wave-piercing
vessel established the record of three days, seven hours
and 52 minutes averaging 36.97 knots.
No ship’s wheel here: the bridge of Francisco is very much
controlled by wire – the tiny joystic near the middle of the
photo is all the coxswain needs to control a 100km/h vessel.
As well as luxury ferries, Incat builds utility cats such as
the 70m Muslim Magomayev, a fast oil well tender and
crew transporter, operating in Azerbaijan.
Marine diesels, too
siliconchip.com.au
July 2017 19
The empty truck deck of the Express 1. With 4.5m
headroom, it fits 23 standard semi-trailers. A second deck
holds up to 150 cars; above that again is the luxuriously
fitted out 1000-passenger deck, complete with restaurants,
bars and both business and economy class seating.
Four DAF XF-powered semi-trailers, fully laden, sit
side-by-side on the cargo deck. Unloading to empty and
reloading, once docked, is remarkably fast – this vessel
regularly achieves a 28 minute turnaround! Only stern
ramps are needed; no reversing is required.
Eight years later, Incat’s Catalonia (hull no. 047) on a
longer route from New York to Spain raised the average
speed to 38.85 knots, at the same time becoming the first
commercial vessel to cover 1000 nautical miles (1850km)
in 24 hours.
A month later, Cat-Link V (hull no. 049) broke the 40 knot
barrier for the first time, taking the Hales Trophy with a record of 41.284 knots. Remember, that’s the average speed
right across the Atlantic Ocean!
third bow hull. This is something of a paradox on a catamaran but it is one of the elements in Incat-built ships which
results in a significant smoothing of the ride for both passengers and the ship itself.
As far as we know, this feature is unique to Incat and
was added some years ago in response to difficulties with
high speed operation heavy seas.
In effect, it acts as a “shock absorber” for oncoming seas.
The way it works is this: in normal seas, the two “outer”
hulls pierce (as their name suggests) through waves while
the centre hull sits above the waterline.
In rough seas, when the ship pitches into the waves, the
Innovation and revolution
Another of Incat’s “revolutionary” developments is the
MAN 28/33D STC HIGH SPEED MARINE DIESEL ENGINE (Cutaway view)
The majority of Incat’s high-speed wave-piercing catamarans use 20-cylinder MAN
28/33D STC engines, coupled to Wartsila LXJ 1720 SR waterjets. In most craft, four
such engines and waterjets are used.
20 Silicon Chip
Bore
280mm
Stroke
330mm
Cylinders
V20
Power output
9100kW
Output/ cylinder
455kW
Speed
1000 RPM
Mean effective pressure
26.9 bar
Mean piston speed
11 m/s
Specific fuel consumption
188g/kWh
siliconchip.com.au
Launching a 109m Cat, the Natchan Rera, from the huge
“Wilsons” assembly hall on the Derwent river. The ship is
basically complete, apart from radio and radar antennas.
As well as the new inner harbour ferries, Sydney has four
Incat jet catamarans on the Manly (outer harbour) run.
Two of these are 33m and two are 24m craft.
centre hull is immersed, preventing the craft from pitching as much as it normally would, therefore damping the
pitching action.
The result is a much smoother ride for passengers and
less stress on the ship itself.
Despite this technological advance, Incat have not rested
on their laurels, continually developing and modifying the
third hull – for example, later craft have more freeboard
and less flat surface.
for maximum payload capacity (both vehicles and passengers) and passenger comfort, coupled with minimum running costs, minimum turn-around in port – and of course
reliability and low maintenance costs.
They’re all somewhat conflicting aims, although repeat
business from operators prove that Incat have achieved
them. The internal photos shown here attest to the luxurious finish and feel.
Depending on the size, most vessels can handle up to
1000 passengers in aircraft-style seating, most offering two
classes (business, with luxury leather seating and economy).
But unlike an aircraft, passengers are free to roam about –
to visit the restaurants and bars on board, watch TV, relax
or view the passing scenery from the huge all-around windows. There’s even a children’s play area on some vessels.
“SeaFrame” construction
Incat vessels are primarily constructed as a base vessel or
SeaFrame, in line with the aviation industry’s Air Frame –
the structure of an aircraft exclusive of its fittings.
Building to SeaFrame enables lower production costs –
it’s more or less a standardised production line – and consequently lower ownership costs.
It’s then up to the purchaser as to what standard and design the craft is fitted out with – everything from layout of
decks, seating arrangements, colour schemes and even the
number of bars and restaurants on board!
Incat have the specialists to guide purchasers through
all the decisions necessary to have the craft exactly suit
their requirements.
Internals
Most of Incat’s fast ferries, particularly the larger wavepiercing models, are destined for operators who are looking
Who said a ferry trip has to be boring? This is the Neptune
Clipper, (Incat no. 076), a 35m catamaran operating on the
River Thames, London.
siliconchip.com.au
Panoramic views from the passenger deck on the Express
1, with large expanses of glass coupled with comfortable,
aircraft-style seating makes for a very pleasant ride.
July 2017 21
The latest ferry to join the Sydney Harbour fleet, Incat No.
082 “Catherine Hamlin”, a 35m conventionally propelled
cat. If you don’t recognise the bridge in the background . . .
. . . it could be because it was undergoing trials on the
Derwent River. This photo, looking over the stern of the
vessel, is in slightly more familiar surroundings.
Below them are the (usually) twin decks for vehicles, one
for up to 400+ cars, the second for up to 23 full size semi
trailers, with a 4.5m clearance. In some ferries a mezzanine
vehicle deck can be moved up and down to accommodate
differing vehicle loads.
Careful attention to design means absolute minimum
turnaround times – Express 1 and Express 2, for example,
have achieved an unheard-of-time of just 28 minutes – full
load to empty to full load. Trucks and semis can be driven forward and turn 180° to drive back out – no reversing
required!
And with a combination of advanced hull design and the
world’s leading engines and marine jets, operating costs (including maintenance) are minimised.
that the various components required were made on time
and to the highest quality.
Up to six vessels can be constructed at the one time and
they are more than likely to be different models (depending
on orders), so it is essential that the shipbuilders receive the
right components at the right time.
After the design is finalised by the Revolution Design team
and the client’s particular requirements, the plate shop sets
about cutting the high-strength marine-grade aluminium alloy from which the ship is constructed.
Specialised suppliers in Australia, France and Switzerland supply the aluminium.
In pre-fabrication, these components are welded into
larger modules (in fact, some smaller vessels are completely constructed here).
Then the focus is on the main assembly halls – it is here,
in stage one of the assembly itself, where the larger components (fuel tanks, engine rooms, jet rooms and superstructures) are also transported. Naturally, many of these require
installation/fitting at a relatively early stage of production.
Stage two of building sees the modules from pre-fabrication brought together and the “bits” start to resemble a
Incat’s “production line”
Part of the company restructure mentioned above involved
a detailed examination of Incat’s work procedures. During
construction the large ship moves through three stages of
the shed on railway bogies until it reaches the final drydock
position ready for launch. Incat set up various production
facilities around the ship-building facility itself to ensure
The BASTARD’S A GENIUS:
the authorised biography of Robert Clifford
by Alistair Mant
The story of how Robert Clifford went from
being a poor student to a global shipping entrepreneur reads more like adventure fiction
than cold hard fact. But it is all true.
The tale contains the usual quota of disaster and triumph, spiced with a fascinating
account of ingenuity and invention at work.
After all, if you go into business, you might
as well experience a financial meltdown and
a bank receivership. If you take up yachting,
you might as well win the Sydney-Hobart race
in a near photo-finish.
If you invent and then dominate a global
fast-ferry market, you might as well win the
Hales Trophy for the fastest Atlantic crossing,
not once but three times.
22 Silicon Chip
“Bob Clifford is a hero of mine. I actually sought
him out because I wanted to find out how on
earth he had learned to do what he has done ...
How did he do it? I believe he is a genius.” – Dick Smith
But behind the swashbuckling adventure
story lies a complex, affectionate and littleunderstood man of surprising sensitivity
and creativity.
He is an all-action hero consumed by
the need to conceive, shape and bring to
fruition objects of great utility and beauty.
He is a man quite unlike the standardissue ‘businessman’ and much more like
those distinguished artists and scientists
who are impelled by some inner voice to
do the work they do.
The Bastard’s a Genius
by Alistair Mant
– Allen & Unwin 9781741143
siliconchip.com.au
Vehicle (left) and pedestrian (right) access onto the Volcano
de Teno, a 96m vessel operating in the Greek Islands. For
ferry operators, minimum turnaround time is essential.
ship. Construction begins in the centre of the vessel, with
controlled, rapid growth ensuing. As the ship “grows”,
quality assurance and marine survey authorities monitor
every step.
Stage three sees engines, jets, thrusters and T foils installed and internal fitout, plumbing, wiring, hydraulics
and myriad other ship’s components and systems are fitted.
Also at this time, the ship is given her coats of paint and
decoration, in accordance with the client’s specifications.
Launching and delivery
Almost completed, it is ready for launching. Only at this
stage is it given its new owner’s name, logos etc – and once
The Tasmanian Fast Ferry Museum, on Incat’s site in
Hobart. School excursions and other groups can book to
visit this most interesting museum (phone 03 6271 1333).
launched, such things as radio and radar antennas – too
high to be installed inside the assembly hall – are fitted.
Builder’s trials and sea trials are then conducted, ironing
out any minor problems, before delivery is made. For smaller
craft, this can be as deck cargo on a much larger vessel; for
Incat’s largest models, this may be made by sailing the vessel
to the client – a perfect sea trial, if ever there was one!
The most recent (April 2017) Incat craft, the 109m Express 3, was delivered in this manner to Denmark, via the
Panama Canal on May 23 last.
Another Australian World-Beater: Liferaft Systems Australia Marine Evacuation System
One-person operation can evacuate 600 in less than 30m!
Our flying visit (literally!) to Incat Tasmania wouldn’t have been
complete without stopping in to their next-door neighbours (but independent company) Liferaft Systems Australia (LSA).
LSA have also earned a name for themselves around the world as
the inventors and manufacturers of a completely new and different
way of evacuating and rescuing those in peril from a doomed ship.
You’ve all seen the movies where the officers are shouting “women
and children first” as they clamber into liferafts or lifeboats, which
are then lowered into the water, sometimes not real successfully,
by several crew members manning the winches. You just know it’s
not going to end nicely for at least some of them . . .
LSA, a privately-owned Australia company established in 1992,
have developed a completely different method. Their Marine Evacuation System (MES) is more akin to the emergency evacuation slides
you’ve seen (at least on TV) to get people away from a downed aircraft. LSA’s system is much faster and much safer than the “old way”.
The system developed by LSA comprises an inflatable evacuation slide, which leads directly into a large capacity inflatable liferaft, which can hold 50 or 100 people in a self-righting version with
canopy or 128 people in an open, reversible version.
Both the slide and the raft are stored in a marine aluminium cradle, usually in a purpose-made “hatch” on the side of the vessel or
on deck. Each is designed for rapid installation and rapid removal
and can be actuated by one trained crew member. No power is required to operate it, there are no winches nor complicated hydraulics.
But when time is vital in evacuating passengers and crew, up to
siliconchip.com.au
600 people can be evacuated by
each MES station in less than 30
minutes. Moreover, it doesn’t
discriminate on age, physical
impairment, injuries or physical
ability. The way the slide is designed means there is no risk of
blockages while injuries (or further injuries) are virtually unknown.
The LSA MES is designed to suit (and is being used on) all types
of vessels, including conventional passenger ferries, high speed
craft, military vessels and even large private yachts – including, as
you might imagine, all vessels made by Incat.
More information: LSA (03) 6273 9277; www.lsames.com SC
July 2017 23
By
LEO SIMPSON
LED downlights
and dimmers
In the past two years there has been a quiet revolution in the domestic
lighting market. Incandescent and compact fluorescent lamps are rapidly
disappearing, being supplanted by LED lamps of all sorts. But while
LED lamps are great for low power consumption, they cannot be used
with conventional leading-edge dimmers, which are ideally suited to
incandescent lamps. This article surveys the domestic LED lamp scene
and discusses the leading-edge, trailing-edge and universal dimmers.
S
ome years ago, incandescent lamps were largely choice for domestic lighting in new dwellings. This will
banned from the Australian and New Zealand mar- be confirmed if you take a walk through any newly conkets, with a variety of incentive schemes sponsored structed home or home unit. Or have a look at any new proby governments to promote the use of more efficient com- ject home – downlights are used in just about every room.
Apart from the whims of fashion, there are two main reapact fluorescent lamps (CFLs).
sons for this trend. First, all new dwellWhile this may have been well-intentioned, CFLs ofings in Australia must meet the Building
ten failed to live up to their promise of long life and for a
Code of Australia for energy efficiency,
number of reasons, they proved to be
and in New South Wales, the BASIX ena less than satisfactory replacement
ergy standard.
for incandescent lamps in many apBoth standards set out how much
plications.
lighting, based on power consumption,
Now CFLs are rapidly being discan used per unit area of the dwelling.
placed from the market and LED
This effectively rules out the use of inlamps are taking their place. Nocandescent, 240VAC halogen and parwhere is this more apparent than in
ticularly 12V halogen lamps, because
newly constructed homes and home
they are power gobblers.
units where the overwhelming lightThe second reason is that virtually all
ing choice is flush-mounted ceiling
new homes and home units in Australia
LED downlights.
are built with a minimum ceiling height
But there is also an ever-expanding
of 2.4 metres. This means that headroom
range of direct substitutes for incanbelow hanging light fittings can be indescent lamps.
sufficient for tall people. Who likes to
In fact, apart from the occasional
be banged on the head by a low-flying
LED accent light or a rail light, or in
pendant light fitting?
situations where their use is preclud- These “Clipsal” trailing edge dimmers
Conventional light fittings also often
ed (eg, bathroom heat lamps) LED are specifically intended for use with
downlights are now the universal mains-powered LED lamps (up to 400W). have poor light distribution and apart
24 Silicon Chip
siliconchip.com.au
We made this jig to show the differences in light colour from various types of lamps (unfortunately printing processes tend to
mask the differences somewhat). On the left is a “cool white” (4000K) 15W CFL; second is a “warm white” (2500K) 15W CFL;
third is a “warm white” (2700K) 60W incandescent (shh!) while on the right is a “cool white” (labelled 2700K!) 13W LED.
from that, they are dust-catchers which can make small
rooms seem even smaller.
So flush-mounted ceiling downlights are a neat solution
and they provide a bonus in giving lots
of light for relatively little power; typically 10 to 14W. A further benefit is
that when they are off, they virtually
disappear into a white-painted ceiling.
We should also note that there are
LED equivalents to the familiar MR16
12V halogen downlights but these are
less widely used and they are generally
not as bright. The LED downlights we
are referring to require a 92mm cut-out
in the ceiling, vs 75mm for the MR16s.
consequence, they are considerably less bright.
But the high brightness of Cool White or Natural White
LEDs can be too bright and harsh for many rooms, particularly in bedrooms but also in lounge
and dining rooms where full brightness may not be required for most
of the time.
In those situations, dimmers become highly desirable. But most LED
downlights, in fact most LED lamps,
are not dimmable. Furthermore, all
LED lamps are marked on their packaging as to whether they are dimmable or non-dimmable. More usefully,
some LED downlights are labelled
If a LED lamp is dimmable, it should
as “trailing edge” dimmable. If you
clearly say so on the body. If it doesn’t
LED disadvantages
cannot find any information on the
say so, it isn’t! And then it’s only with a
So what are the drawbacks? There trailing edge dimmer.
packaging, you can assume that any
are several but the main one is that
LED lamp is not dimmable.
most LED downlights are not dimmable – and those that
The reason that most LED lamps are not dimmable is
are will not work with conventional “leading-edge” dim- that they employ a switchmode power supply which will
mers which are so effective with incandescent lighting. So work over a very wide range of AC mains voltage. Most
why dim them at all?
will work at voltages between 250VAC and around 80VAC,
The over-riding advantage of LED downlights is that with very little change in brilliance.
they are bright, particularly those that are rated Cool White
(typically 5000K) or Natural White (4000K); Warm White
SWITCH ON
(typically 2700K). Warm white LED lamps are intended to
imitate the lighting given by incandescent lamps and as a
A
S1
Ls
Rt
TRIAC
DIAC
N
LAMP
LOAD
siliconchip.com.au
G
A2
Cs
A1
Rs
Ct
Fig.1 (left) shows the circuit of
a typical “leading edge”, triacbased light dimmer.
Fig.2 (right) shows the waveform across the lamp load –
when triggered early, the lamp
is at its brightest, while it gets
progressively dimmed as the
trigger point (set by variable
resistance Rt) is later in the
half-cycle.
SWITCH ON
A
EARLY TRIGGERING: HIGHER OUTPUT
SWITCH ON
SWITCH ON
B
LATER TRIGGERING: LOWER OUTPUT
July 2017 25
S1
A
Ls
–
Cs
N
SWITCH OFF
+
SWITCH OFF
D
ZERO CROSSING
DETECTOR AND
PULSE GENERATOR
LAMP
LOAD
G
HIGH S
VOLTAGE
MOSFET
A LATER TRIGGERING: HIGHER OUTPUT
SWITCH OFF
Ls
Fig.3 (above): a “universal” dimmer can be set to leading edge or trailing edge.
A high voltage Mosfet is used to switch the load.
Fig.4 (right): the waveform across the lamp is essentially the opposite of Fig.2
– in this case it’s for a “trailing edge” dimmer which turns the power off at a
certain point in the cycle; the later it does so, the brighter the lamp.
SWITCH OFF
B EARLIER TRIGGERING: LOWER OUTPUT
If you do try them out with a conventional light dimmer,
they will not dim but will inevitably flicker uncontrollably.
Dimmable LED lamps have a slightly more complicated
switchmode power supply which allows their brilliance to
vary in proportion to the mains supply voltage, although
typically, their brilliance cannot be varied over the same
wide range as that for incandescent lamps.
Sadly, while a LED lamp may be labelled as being dimmable, they will not work if you try them with a standard
dimmer that may have been installed in your home for a
number of years. That is because it will be a Triac-based
“leading edge” dimmer.
What you need for LED lamps is a “trailing edge” or
“universal” dimmer. But even if you have a trailing edge
dimmer installed, it may not work satisfactorily with your
particular “dimmable” LED lamp.
Before we discuss why a dimmer may or may not work
with a LED lamp, let us define and describe “leading edge”
and “trailing edge” dimmers. As already noted, leading
edge dimmers are based on Triacs and the general layout
of a Triac dimmer is shown in Fig.1.
A Triac is a a four-layer bi-directional semiconductor device which is non-conducting until a small trigger pulse is
fed to its gate electrode. It then switches to a low resistance
state, allowing current to be fed to the load until the voltage across it (the Triac) drops to zero or reverses in polarity.
In more detail, as well as the Triac as the power switching element, there is an RC network (RT and CT) and a Diac
(another four-layer semiconductor device) which provides
the phase-delayed triggering pulse to the gate of the Triac
(see Fig.1).
The triggering network is effectively a pulse generator
synchronised to the mains voltage waveform. So at the start
of each half-cycle, the Triac will be off and the capacitor
connected to one side of the Diac will charge, at a rate determined by RT, to between 30 and 40V where it reaches
the “breakover” voltage of the Diac. The Diac then dumps
the capacitor’s charge into the gate of the Triac, turning it
on so it can pass current to the load.
The inductor LS, capacitor CS and resistor RS are for interference suppression and voltage “snubbing” to reduce
transient voltages when the Triac turns off at the end of
each half-cycle.
The method by which a Triac controls the power level
in an AC circuit is referred to as “phase control”. Consider
that the mains voltage is a 230VAC sinewave; the voltage
varies sinusoidally between +325V and -325V at 50Hz (or
60Hz in the Americas and some other countries).
Here’s an example of a “leading edge” dimmer triggering
an incandescent lamp very late in the 230V mains cycle.
Only a small amount of power is delivered to the lamp.
Triggered much earlier in the cycle, the lamp would be
almost as bright as it could be with a large amount of
power delivered.
26 Silicon Chip
siliconchip.com.au
Fig.5: taken from the Fairchild data sheet,
Similarly (to the earlier photo), at left is a 2.5W LED “COB” lamp (bordering on useless!); next is a “cool white” 16W LED;
a decorative “warm white” 75W incandescent and finally the same 13W “warm white” (2700K[?]) LED as before. Even
though that 2700K is on the label, we don’t believe it. The incandescent lamp to its left would be much closer to 2700K.
The power fed to the lamp load by the Triac dimmer circuit is varied by the timing of the gate trigger pulse with
respect to the sinusoidal voltage waveform. If the trigger
pulse is early in each half-cycle of the waveform, the power
level will be high and the lamp will be bright.
Conversely, if the trigger pulse is late in each half-cycle
of the waveform, the power level will be low and the lamp
will be dimmed. The corresponding circuit waveforms are
shown in Fig.2 and the scope screens below.
These Triac circuits are also referred to as “phase-controlled” dimmers (sometimes also referred to as “phasecut” dimmers). So far so good but what is the basis for the
term “leading edge”?
In fact, leading edge refers to the “leading edge” of a
pulse where the voltage rises from zero to maximum (either positive or negative).
By extension, the end of the pulse is referred to as “falling” or “trailing edge”. So the voltage waveform fed to the
lamp load by the Triac rises from zero to the instantaneous
value of the sinusoidal voltage at the time of the trigger pulse
to the gate – hence, by definition, that is a “leading edge”.
Here’s what happens when you try to use a LED lamp with
a leading-edge dimmer. It might work some of the time but
is more likely to not work.
This is an even worse example of the non-dimmable LED
being dimmed. The LED was noticeably flickering, as you
can see by this very confused waveform.
siliconchip.com.au
Trailing-edge dimmers
OK. So now let’s look at a typical trailing edge dimmer.
Instead of being based on a Triac, these are based on one
or two Mosfets or IGBTs (Insulated Gate Bipolar Transistor) depending on the particular circuit.
A typical single Mosfet trailing edge dimmer is fed by a
July 2017 27
The typical driving circuitry
of a mains-powered LED
lamp, showing both sides of
the power supply PCB.
These flush-mounting 240V AC LED
downlights from Altronics are available in 6 & 10W
dimmable and 14 & 25W non-dimmable (the 25W are very
bright!) in both cool white and natural white. Their rated
life is 25,000 hours – much better than halogen bulbs!
bridge rectifier from the 230VAC mains supply, arranged
so that the Mosfet switching element is turned on at the
beginning of each mains half-cycle and then turned off
later in the half-cycle. A general form of this circuit is
shown in Fig.3.
The waveforms for the trailing-edge circuit are shown in
Fig.4 and they are effectively the reverse of those for the
leading-edge waveforms shown in Fig.2. In this case, for
high power to be fed to the load, the Mosfet is turned on
at the start of each mains half-cycle and is turned off late.
Note the trailing-edge cut-off as the Mosfet switches off.
For low power operation, the Mosfet turns off much earlier in each half-cycle.
So why is the trailing-edge dimmer preferred for LED
lamps? There are two main reasons.
The first is that typical mains voltage-rated LED lamps
use a small switchmode current driver, comprising a bridge
rectifier feeding a capacitor, which provides a supply voltage of around 325V DC to feed the switchmode current
driver; typically using a small high voltage Mosfet.
These bridge rectifier capacitor input power supplies
draw a very high current at the switching point on each
half-cycle when feed by a leading-edge dimmer.
This can play havoc with the operation of the dimmer
as well as the LED current driver itself.
The waveform of a trailing edge dimmer and incandescent
lamp triggered very early in the 230V AC mains cycle.
There would be very little light produced by the lamp.
28 Silicon Chip
However, when the same LED lamp circuit is fed with
the more benign voltage waveform from a trailing-edge
dimmer, those nasty current pulses into the capacitor input power supply are much more subdued.
However, there is another reason why leading-edge dimmers and typical LED lamps are not compatible and this has
to do with the “holding current” specification for a Triac.
For typical Triacs, this current is around 50mA. This is
the current that needs to pass through a Triac for it to remaining a conducting state. If the current falls below the
holding value, the Triac will switch off even though the
total voltage across it and the accompanying lamp load
might still be quite high.
This is why a typical Triac dimmer has a minimum lamp
load of 40W; any lower and the lamp will tend to flicker,
regardless of the brightness setting. However, a LED lamp
may only be rated at 10 to 15W (or less) – far below the
minimum load for a Triac (leading-edge) dimmer.
Universal dimmers
Just to complicate the scene, there are “universal” dimmers which will provide a choice of leading-edge and trailing-edge operation. Hence, these can used in leading-edge
mode to control incandescent and halogen lamps, or in
The same dimmer/lamp combination triggered significantly
later (about 1/3) of each cycle. In this case, the lamp would
be glowing but not particularly brightly.
siliconchip.com.au
ing-edge dimmers and produced a series of
waveforms, shown below.
RZC
Both the leading-edge and trailing-edge
MONITOR
K
1
ZC
OC 10
Q1
dimmers were made by Deta, a low cost
MONITOR
SENSE1
G
RGATE
brand sold in Bunnings hardware stores.
2
DIM
DRV 9
C GATE E
CONTROL
GATE
The Deta 6031 trailing-edge dimmer
VR
IC1
3
8
adj
E
worked satisfactorily with the dimm-able
VDD FL5150 OC
SENSE2
G
L-E
LED downlights discussed in this article
R2
4 DIM
LOW 7
C3
Q2
POWER
but the only way to be sure is to do a bench
MODE
C1
T-E
R1
5
6
C
test set up.
VR
VS
GND
offset
Rather than comment on the waveforms
Q3
K
RSENSE2
in
detail, we’ll let the waveforms and the
C2
D1
captions
tell the story.
N
A
However, there are significant differences in performance between leading-edge,
Fig.5: taken from the Fairchild data sheet, the FL5150 dimmer which can be
trailing-edge and universal dimmers. Apart
set for leading edge or trailing edge.
from the fact that leading-edge edge dimtrailing-edge edge mode, to control dimmable LED lamps mers simply won’t work with LED lamps, they are better at
driving incandescent and halogen lamps than the trailingand dimmable compact fluorescent lamps (CFLs).
These typically use two high voltage Mosfets or IGBTs edge or universal types.
With an incandescent lamp, the maximum brightness is
controlled by a special driver such as the Fairchild FL5150
slightly higher (due to less conduction losses) and the minor the ST STEVAL-1LD005V1.
Fig.5 shows the Fairchild FL5150 in a 230VAC circuit imum brightness is considerably lower, due to the fact that
using two high voltage IGBTs; in this case set up for lead- the minimum conduction angle in each half-cycle is much
smaller than can be achieved with a trailing-edge or uniing-edge operation (selected by the DIM mode pin).
Note that regardless of whether you elect to use a trail- versal dimmer circuit (even when in leading-edge mode).
On the other hand, a trailing-edge (or universal) dimmer
ing-edge or universal dimmer with a dimmable LED lamp,
there is no guarantee that they will work happily together. does have the advantage that it gives a soft turn-on rather
Or you may get a situation where a dimmer will work than the instant snap-on effect with a Triac dimmer. A trailhappily with just a few LED lamps connected in parallel ing-edge dimmer always gives a slight delay between switchin a small room but may misbehave with a larger array of ing on and the lamp actually lighting up.
So if your Triac leading-edge dimmer had failed and you
LED downlights.
Some licensed electricians will only use a particular have yet to replace it, it is worthwhile to replace it with a
brand and model of universal dimmer because they may trailing-edge dimmer.
This will provide the advantage of soft start which may also
have found it to be reliable in the past.
However, there is nothing to stop you from bench-testing avoid the sudden failures of incandescent lamps at switcha particular light dimmer and some LED lights to see if they on, together with the accompanying failure of the dimmer
are OK, before they are installed by a licensed electrician. itself. This failure scenario is most common with lamp fittings where the lamp does not hang down but is upright.
Waveforms and performance
The installation instructions that come with some leadWe have run a series of tests with leading-edge and trail- ing-edge dimmers warn about this hazard.
A
RSENSE1
D2
Here a dimmable LED is being powered by a trailing-edge
dimmer. The waveform is not as clean as the incandescent
lamp but you’d be hard-pressed to notice the “step”.
siliconchip.com.au
A
C
And finally, a dimmable LED is being driven by the dimmer
triggered quite late in the cycle. You’ll never get 100% of
the LED’s brightness from a dimmer even at maximum.
July 2017 29
K
K
ZD1
BZV55B15
A
47 F
D7
S1M
25V
A
F
F
D1 S1M
100nF
K
A
2.2k
P1B
INT
6 x 12k
F
100k
2.2nF
D
1k
14
1M
1
560k
2
P1A
1M
8
3
150k
4
5
11
120k
12
13
Y1
F
9
K
A3
F
B1
B2
IC1
40 25 B
Y2
G
D3
S1M
A1
Q1
6
A
2
VR1
VARISTOR
10k
1k
22k
G
S
D6
1N4007
Q2
C1
C2
Y3
D STF17H62K3
100k
10
2.2nF
C3
F
J1
LINE
1
NEUTRAL
CON3
A
K
6 x 12k
2.2k
D2 S1M
K
A
10k
0
D4
S1M
F1
FUSE
K
S STF17H62K3
K
B3
Vss
7
22nF
A
Vdd
A2
22k
D5
1N4007
A
Fig.6: by contrast, this trailing edge dimmer uses two STF17N62K3 620V Mosfets and two diodes across the AC supply
and in series with the lamp load. Interestingly, no microcontroller is used, with the switching being controlled by a
CD4025BE CMOS logic gate device. It can handle lamp loads up to 300W on a 230VAC supply.
But if you like the ability of a leading-edge dimmer to give
very low brightness setting with incandescent lamps, or if
you need to drive a bigger lamp load, then stick with those.
Typically, trailing-edge dimmers are limited to a maximum
of around 300-400W.
On the other hand, if you want to provide for the day
when you eventually change to LED lighting as incandescent lamps become too costly or hard to obtain, go for the
trailing-edge dimmer.
Having discussed cool white and warm white LED lamps,
we should note that there is at least one interesting variant: a
downlight which can vary its colour temperature from cool
white to warm white in response to varying input voltage.
Made by Opal Lighting (www.opallighting.com.au),
they employ a special COB (chip on board) LED assembly
from Sharp Corporation, called the Tiger Zenigata tuneable
white COB. This COB has alternating LED stripes with cool
and warm phosphor coating that ranges from 3000k down
to 2000K, which most closely replicates the colour range
of an incandescent lamp when dimmed by a leading-edge
(Triac) dimmer.
Indeed, it must be used with a leading-edge dimmer or a
universal dimmer that is set to leading-edge mode. We have
a couple of pictures at the start of this article (page 24) to
demonstrate its range.
We should also mention that colour sequenced LED pool
The all-in-one, mains-operated Phillips SmartBright LED
batten photographed with the end cap removed (not an
easy job!) There is no separate LED tube in this fixture;
you can see the row of SMD LEDs disappearing into the
distance. The bottom of the fixture is polycarbonate, the
top (semi-circular) section is an integral diffuser.
This LED downlight is the popular 12W/220-240V AC cool
white model and, as is marked, is trailing-edge dimmable.
Light output is an impressive 900 lumens. They are designed
to replacee the MR-16 12V halogen downlights used in
millions of homes and offices – but no 12V transformer is
needed. They also need a larger (92mm) ceiling cutout.
Variable colour LED lights
30 Silicon Chip
siliconchip.com.au
for use in standard 36W T8 fluorescent battens. (See www.
siliconchip.com.au/Article/277).
These are now available much more cheaply but you can
now also purchase LED battens such as the Philips SmartBright LED Batten (see https://reductionrevolution.com.au/
products/philips-smartbright-led-batten).
These do not have a separate LED tube but use a 1.2mlong PCB with a row of SMD white LEDs under a white diffuser. A switchmode mains power supply is incorporated in
the polycarbonate housing of the batten which will operate
down to about 80VAC with very little change in brightness.
They are rated cool white (4000K), consume 21W and
are not dimmable.
At left is a 15W 240V decorative
“candle” MES globe, with its 4W
warm white LED globe
equivalent alongside.
Below, the same two lamps are
fitted in the one “wall sconce”.
Their brightness and colour are
not all that different.
Conclusion
lights are available which can typically provide a choice of
three colours, white, blue and green, cycled each time the
lamp is turned on.
LED fluorescent battens
In the September 2010 issue, we featured an article on
then relatively new (and expensive) LED fluorescent tubes
As this article shows, there is now an enormous range of
LED lamps to replace virtually every incandescent and fluorescent lamp used in homes and offices.
About the only lamp application where a LED replacement could not be used is in conventional electric ovens,
microwave ovens and lamps incorporated into kitchen exhaust hoods.
It also may not be advisable to replace the incandescent
lamp used in combination bathroom exhaust fan/heat lamps
as the housing can become quite hot.
One final point: you may have noticed that we refer to
both LED lamps and incandescent lamps as “240V” in this
feature when the mains supply in Australia is (nominally)
230V AC. The reason is that most lamps are labelled 240V
AC, (some are labelled “250V AC”). Indeed, many LED lamps
are labelled “220-240” or even “220-250” V AC.
SC
The SILICON CHIP
Inductance - Reactance
- Capacitance - Frequency
READY RECKONER
For ANYONE in
ELECTRONICS:
HU
420x59G4Em
on heavy
photo pa
m
per
You’ll find this wall chart as handy as
your multimeter – and just as ESSENTIAL!
Whether you’re a raw beginner or a PhD rocket scientist . . . if you’re
building, repairing, checking or designing electronics circuits, this is what
you’ve been waiting for! Why try to remember formulas when this chart
will give you the answers you seek in seconds . . . easily!
Read the feature in Jan16 SILICON CHIP (you can view it online) to see
just how much simpler it will make your life!
All you do is follow the lines for the known values . . . and read the
unknown value off the intersecting axis. It really is that easy – and quick
(much quicker than reaching for your calculator!
Printed on heavy (200gsm) photo paper
Mailed flat (rolled in tube) or folded
Limited quantity available
Mailed Folded:
Mailed Rolled: ORDER NOW AT
$10.00
$20.00
inc P&P & GST
www.siliconchip.com.au/shop
siliconchip.com.au
inc P&P & GST
JJuly
uly 2017 31
2017 31
Give the guy behind you more time to pull up!
by John Clarke
RapidBrake
EMERGENCY STOP signalling for virtually any vehicle
Every time you need to brake heavily to avoid an obstruction there
is a risk that a following vehicle will crash into you. But you can
significantly reduce the risk of that happening with the RapidBrake.
Normal brake lights won’t necessarily give other drivers sufficient
warning but this easy-to-build unit will flash your hazard lights during
heavy braking to give following drivers a more dramatic warning.
Y
ou may have noticed that some lights indicate to others that you are grab other drivers’ attention in the way
modern vehicles, when braking braking but they don’t indicate how that RapidBrake will.
Around 23% of all vehicle collisions
heavily, will flash their brake hard you are braking – so they won’t
are nose-to-tail collisions.
or hazard lights at a fast rate.
These collisions are more
It’s called “vehicle emerlikely to happen during
gency stop signalling” and
rapid braking where the
serves as a visual warning
• Detects hard braking and warns other drivers by flashing the
driver of the vehicle befor following vehicles where
brake or hazard lamps
hind is too close and/or
they may need to quickly
• Complies with Australian Design Rules 13/00 and 31/02
unaware of how hard the
slow down to avoid running
vehicle standards
vehicle is braking.
into the car in front.
• Adjustable deceleration thresholds
Flashing the brake or
Does your car have emer• Test points and diagnostic output provided for calibration
hazard lamps clearly exgency stop signalling? Prob• Onboard/off-board LED to indicate when the unit is triggered
presses the sense of urably not. But you can add it
• Uses a 3-axis accelerometer
gency to the applied brakwith the RapidBrake and re• Compensation for up-hill and down-hill road conditions
ing and may snap the
duce the risk of a nose-to-tail
• Can be mounted in two different orientations
driver behind out of their
collision.
• Suitable for cars and trucks but not motorcycles
trance and get them to apRemember, your brake
Features
32 Silicon Chip
siliconchip.com.au
ply their brakes
with the same
vigour.
RapidBrake
details
RapidBrake
is presented as
a PCB module
that is housed in a
small plastic case.
The PCB includes
an accelerometer
module, processing circuitry and
relays for connecting to the hazard or
brake lamps.
RapidBrake is intended to be installed
under the dashboard, with connecting wires made to the ignition
switch and chassis for power and to
the brake switch or hazard lamps.
Under normal braking, the brake
lights will light normally and the hazard lights will not flash unless intentionally switched on using the normally dash-mounted switch.
RapidBrake only starts to rapidly
flash the brake lights or the hazard
lights when it detects heavy braking.
Whether RapidBrake flashes the
brake lights or the hazard lights is your
choice and is determined by how you
wire it into the vehicle.
Australian Design Rules
RapidBrake follows the Australian
Design Rules (ADR) for vehicle emergency stop signalling. These standards
set the flash rate and how the rapid
braking rate is detected.
The permissible flashing rate is defined by “Vehicle Standard (Australian Design Rule 13/00 – Installation of
Lighting and Light Signalling Devices
on other than L-Group Vehicles) 2005”.
The RapidBrake
can be mounted in a 129 x 68 x 43mm Jiffy
box – no holes are required except for a cable gland at the end
and, if desired, a single “operate” LED mounted on the lid (this LED can also be
externally mounted). Power is supplied via the vehicle’s switched “ignition” line.
Section 6.23.7.1. of ADR 13/00 states
that “all the lamps of the emergency
stop signal shall flash in phase at a
frequency of 4.0±1.0Hz.” However,
section 6.23.7.1.1. states that “if any
of the lamps of the emergency stop
signal to the rear of the vehicle are
filament types, the frequency shall be
4.0+0.0/-1.0Hz.”
RapidBrake uses a 3.85Hz flash rate
and that’s just under the 4Hz maximum for filament lamps. We chose
this frequency to suit both LED and
filament lamps.
There are options for how rapid
braking is detected. “ADR 31/02 –
Brake Systems for Passenger Cars”.
Section 5.2.23.1. states that “emergency stop signalling shall be activated by
the application of the service braking
system at a deceleration of or above
6m/s2 and de-activated at the latest
when the deceleration has fallen below 2.5m/s2.”
Alternatively, section 5.2.23.2. of
ADR 13/00 says “the emergency stop
signalling may also be activated when
brakes are applied at a speed above
50km/h and the anti-lock braking system (ABS) is fully cycling. It shall be
deactivated when the ABS is no longer
fully cycling.”
We opted not to use this alternative
method as it would preclude RapidBrake from being used in a vehicle
that does not have ABS. This method
also requires access to digital signals
that may not be available in an older
vehicle.
Accelerometer
RapidBrake activates signalling
based on detecting deceleration rates
as detailed in the first option, by using a 3-axis accelerometer.
This means that RapidBrake can be
used in any vehicle.
An accelerometer will measure
the acceleration and deceleration of
the vehicle together with the force of
gravity.
You can read more details about
QuickBrake
We published a related project, the Quickbrake, in January
2016. This detects if you rapidly lift your foot from the accelerator pedal and activates the brake lights well before you have
time to place your foot on the brake. Quickbrake can typically
provide an extra half-second of brake lights indication for the
driver of the vehicle following you to take appropriate action.
See: www.siliconchip.com.au/Article/9772
You could incorporate both QuickBrake and RapidBrake into
the same vehicle for maximum safety. Alternatively, you can just
use RapidBrake on its own if QuickBrake is not suitable for your
vehicle or you prefer not to have Quickbrake.
siliconchip.com.au
July 2017 33
+3V
VS
ADXL335
OUTPUT
AMPLIFIER
3-AXIS
SENSOR
AC
AMPLIFIERS
C DC
DEMOD
OUTPUT
AMPLIFIER
OUTPUT
AMPLIFIER
COM
~32k
XOUT
CX
~32k
YOUT
CY
~32k
Z OUT
CZ
ST
© SC 2017
Fig.1: the internals of the ADXL335 accelerometer IC. The outputs of the three
MEMS capacitive linear accelerometers are amplified and demodulated, to
remove the capacitor switching frequency. The resulting DC is then further
amplified and fed to the output pins via nominal 32kΩ internal impedances, so
that external capacitors can be used to determine the bandwidth.
this in the panel opposite titled “Accelerometers”.
The accelerometer we are using is a
3-axis module designed for use with
Arduino (but not limited to such). It is
available from Jaycar with catalog code
XC4478. The module incorporates a
3V regulator and an Analog Devices
ADXL335 3-axis accelerometer IC.
100nF output capacitors (CX, CY and
CZ) filter the separate analog outputs
for the X, Y and Z axes.
Fig.1 shows the block diagram of
the ADXL335 accelerometer IC. The
accelerometer outputs indicate the
separate components of deceleration
or acceleration along the X, Y and Z
axes. The readings are a result of gravity and acceleration due to changes
in velocity.
We only use two outputs from the
accelerometer module for the RapidBrake; the Z output and either the X
or Y-axis output. You get to choose
which output (X or Y) is used and
that depends upon the orientation of
the RapidBrake unit when installed
in your vehicle. The Z-axis is always
used and is oriented in the up/down
direction, sensing gravity and vertical
acceleration.
The X or Y-axis output is selected
to be the one that’s oriented fore and
aft inside the vehicle. Fig.2 shows
the orientation of the accelerometer
within a vehicle with either the X or
Y outputs.
The following description assumes
Z
VE
W H IC
H E LE
N OR
Y
AX IEN T
A
IS
IS T IO
US N
ED
Y
VEHICLE ORIENTATION
WHEN X AXIS IS USED
–X
X
Fig.2: how the X, Y and Z axes
correspond to the Jaycar XC4478
accelerometer module. The Z-axis
is the one perpendicular to the
PCB itself. The X-axis is the is
aligned with the pin header, while
the Y-axis is at right angles to the
other two.
–Y
© SC 2017
34 Silicon Chip
–Z
the X output is used but it works basically the same way if the Y output
is used.
The accelerometer X-axis is arranged to be parallel with the floor of
the vehicle. On a flat road, this axis is
horizontal and the accelerometer’s X
output sits at a half supply voltage, indicating no acceleration/force.
With the XC4478 module oriented
inside the vehicle as shown, the output increases above this half supply
with deceleration (slowing down) and
decreases below the half supply rail
under acceleration (increasing speed).
Detecting the deceleration rate
Detecting deceleration seems like
it should be should be simple: just
measure the X output voltage that is
produced when braking and at a deceleration of 6m/s2, activate the emergency stop signalling.
Then when deceleration has fallen
below 2.5m/s2, stop the emergency
stop signalling.
That would be valid if the vehicle
is travelling along a horizontal road,
but with undulating terrain, it is not
quite as easy.
When the vehicle starts to go up or
down a hill at a constant speed, the X
output changes (even with no acceleration or deceleration). That is because
the X-axis is no longer horizontal and
so there is a gravity component incorporated into the X-axis reading.
The X output will increase when
pointed down hill and decrease when
pointed up hill. That will a major effect
on the X output voltage level when the
vehicle is accelerating or decelerating
up hill or down hill.
The amount that the X output changes with angle is quite significant. If the
vehicle is facing down a 37.71° hill,
the 6m/s2 threshold will be reached
without any braking.
That would be an impossibly steep
hill; for example, Sydney’s steepest
hill, Attunga Street in Double Bay, has
a slope of 14°.
But it does indicate the magnitude
of the problem; coasting down Attunga Street would still give an X output
equivalent to a deceleration of 2.5m/s2.
So in that case, it would only require an extra 3.5m/s2 of braking deceleration will start the emergency
stop signalling.
Even if the vehicle comes to a halt
on that hill, the lower 2.5m/s2 threshold will not be reached and the emersiliconchip.com.au
Accelerometers
An accelerometer is a device that measures static and
dynamic acceleration forces. Static forces are generally
due to gravity while dynamic forces are due to movement.
The term “accelerometer” is arguably a misnomer since it need not be accelerating or even
moving to make a non-zero measurement.
An accelerometer actually measures force
but is calibrated in such a way that its own
mass is eliminated from the reading,
hence the measurements are in units of
acceleration (m/s2).
This is termed “proper acceleration”
and is defined as the “acceleration relative
to a free-fall, or inertial, observer who is momentarily at rest relative to the object being
measured”; see https://en.wikipedia.org/wiki/
Proper_acceleration
Consider that standing on the ground, you experience
the downward force of gravity but you are not actually
accelerating because the ground is pushing up on you
with the exact same force, cancelling it out. But an accelerometer will still measure this gravitational force.
Accelerometer output is normally calibrated to show
acceleration forces in “g” units where 1g is the gravitational force experienced by an object near the Earth’s
surface and equates to 9.81m/s2.
Accelerometer readings can be from one of several
sources. One is due to the change in speed along a straight
line. So an accelerometer can, for example, measure a vehicle’s acceleration as it moves off from a standing start.
It can also measure deceleration of a vehicle under braking. Note that we use the word deceleration although this
is just acceleration in the opposite direction.
An object moving at a constant speed but changing direction also experiences a sideways cornering force and
an accelerometer can measure this too. The third measurement from an accelerometer is that due to gravity, as
described above.
Accelerometer measurement is along one axis only so if
there is acceleration at right angles to the axis, then there
will be no measurement. Many accelerometers include
gency stop signalling will not cease.
These would both result in the violation of ADR 31/02.
The way around this problem is to
also utilise the reading from the Z-axis.
On a horizontal roadway, the Z-axis
output will be reading the full effect
due to gravity. As the angle moves off
from horizontal, the Z output reading
reduces in value.
This reduction follows a cosine
curve where the output is at its maximum (measuring the full acceleration
due to gravity) for a 0° slope and the
output is zero (ie, at half supply) for
a 90° slope.
The output is reduced by 3% for a
siliconchip.com.au
three separate measuring elements, so that acceleration
in any direction can be measured. A 3-axis accelerometer has X, Y and Z axis outputs. The actual
acceleration vector can be determined
by making a vector sum of the acceleration measurements along
each individual axis.
So if, for example, the acceleration is along the X axis, then
only the X output will show a change
in reading. The Y and Z outputs will
read zero.
But an acceleration within the Z-plane
could give a reading on both the X and Y
outputs.
For the RapidBrake, we use an accelerometer
module available from Jaycar with catalog code
XC4478. This incorporates an ADXL335 3-axis
accelerometer IC. This is a MEMS (Micro-Electro-Mechanical Systems) device. It contains very small electromechanical components to make up the accelerometer sensors.
A MEMS accelerometer can be imagined as a small
mass attached to a spring. Added circuitry detects movement of the mass that either compresses or expands the
spring, depending on the force of acceleration. The electromechanical components comprise a polysilicon sensor
suspended on polysilicon springs for each of the three
X, Y and Z planes.
When the accelerometer sensor moves, the change in
the mass position alters sensor capacitance and so provides a measurement of acceleration. For a more detailed
description see www.instrumentationtoday.com/memsaccelerometer/2011/08/
We also described the operation of an accelerometer in
our August 2011 article on the Digital Spirit Level project; see www.siliconchip.com.au/Article/1122
Fig.2 (opposite) shows the three axis orientations for
the XC4478 module containing the ADXL335 accelerometer IC. Acceleration in the positive axis direction or
deceleration in the negative axis direction produces an
increasing output for that axis.
14° slope, ie, (1 – cos(14°)) x 100.
Similarly, for the X output, the increase or decrease with slope follows
a sine curve.
The change in output is zero for a
0° slope and sees an increase of 24%
for a 14° slope, ie, sin(14°) x 100. It is
measuring the full acceleration due
to gravity for a 90° slope (also known
as a “cliff”).
Although the change in the Z output
for normal road slopes is small, by amplifying the Z output and doing some
calculations, we can use the Z output
to compensate for changes in the X
output that are due to slope.
So effectively, we can compute a
compensated X output value that does
not change with slope over a range of
slope angles.
This compensation does not affect
the readings caused due to the vehicle’s own acceleration or deceleration. That’s because the acceleration
and deceleration occurs along the Xaxis only.
The Z-axis is perpendicular to the
acceleration and deceleration along
the X-axis and so it is not affected.
We store the “quiescent” accelerometer X and Y output values, from when
the accelerometer is in a horizontal position, in the microcontroller’s
non-volatile memory (EEPROM).
July 2017 35
These values are set during calibration. Whether the vehicle is going up
or down hill is determined by comparing the X reading with the stored
horizontal quiescent X value. If the X
reading is greater in value compared to
the quiescent, then the vehicle is facing down hill. If the X reading is less
than the quiescent then the vehicle is
facing uphill.
The Z reading due to gravity will always be less than the quiescent horizontal Z value if the unit is not perfectly level. Since we know whether
the vehicle is going up or down hill,
the compensated reading is produced
by reducing the X axis reading if the
vehicle is going downhill or increasing it when going uphill.
The amount of compensation applied is non-linear, in accordance with
the fact that the Z output changes following a cosine curve and the X output following a sine curve with respect to the slope angle. In practice, a
lookup table in the software is used to
calculate the required compensation
amount, with an adjustment included for compensation gain. The result
is an acceleration/deceleration value
which does not change depending on
slope angle.
Gain compensation is determined
by the calibration procedure. This is
required to account for the fact that
the X output voltage at 1g may not be
exactly the same as the Z output voltage at 1g. This is due to manufacturer tolerances in the accelerometer as
well as differences in gain in the op
amp circuits.
It is the compensated value that’s
compared against the upper and lower
deceleration thresholds for braking, to
determine whether or not to activate
the emergency flashers. By the way,
the fact that the X output will be using a wider part of its output range due
to the effect of gravity on the readings
does not affect accuracy.
Linearity of the sensor is within
0.3% from 0 to 3g (3 x 9.81m/s2 or
29.4m/s2) which more than covers the
range the sensor will experience during driving.
Note that we don’t use the Y output
to compensate for any changes in the
Z-axis gravity reading output due to
road camber.
That’s because the accelerometer in
the Y axis cannot distinguish between
gravitational changes due to a slope
and acceleration caused by corner36 Silicon Chip
47
+5V
100 F
10 F
100 F
X OR Y
SELECT
JP1
+5V
IC1: LMC6482AIN
X
X
XC4478
ACCELEROMETER Y
MODULE
5
Y
Z
1 F
0V
IC1b
6
+5V
10k
X OR Y
OFFSET
GND
TP+5V
OUT
VR1
10k
7
TP2
VR2
10k
LP2950
IN
8
43k
TP1
Z
OFFSET
2
IC1a
3
2N7000
1
4
10 F
D G S
TP3
LED
VR3
UPPER 1k
K
A
TP
GND
1N4004
A
SC
20 1 7
THRESHOLD
ADJUST
2
(6m/s )
K
RAPIDBRAKE
VR4
LOWER 10k
THRESHOLD
ADJUST
2
(2.5m/s )
100nF
100nF
TP4
(EMERGENCY STOP SIGNALLING)
ing. While there is very little change
in readings due to camber (because
camber is rarely more than a few degrees), the cornering acceleration can
be much higher.
So using the Y output for compensation of readings could result in severe errors.
Circuit details
The full circuit for the RapidBrake is
shown in Fig.3. The circuit comprises
the accelerometer module, dual operational amplifier (IC1), microcontroller
(IC2) plus a regulator, relays and associated components.
The XC4478 accelerometer module
is powered from a 5V supply via a series 47Ω resistor and decoupled using
a 10µF capacitor, forming a low-pass
filter which rejects supply noise. The
module contains its own 3.3V lowdropout regulator.
The Z output is filtered using a 10µF
capacitor that effectively gives the output a one-second response to variations in acceleration, in combination
with the 32kΩ resistance built into
each of the accelerometer IC’s outputs.
Amplifier IC1a provides gain for the
module’s Z-axis output signal, with
VR1 allowing its DC offset voltage to
be adjusted. Gain is typically around
9 times and is dependent upon the
43kΩ feedback resistor and the setting of VR1.
JP1 is used to select which of the X or
Y output is fed to the microcontroller
from the accelerometer module. The
selected output is output is filtered
using a 1µF capacitor that effectively
gives a 100ms response to variations
in acceleration.
Amplifier IC1b provides gain for this
signal with VR2 setting the DC offset
and adjusting the gain all at once. Gain
is typically around 3 times and is dependent upon the 10kΩ resistor value
and the VR2 setting.
The acceleration signals are monitored at the analog inputs AN2 and
AN3 of microcontroller IC2. IC2’s
firmware uses its internal analog-todigital converter (ADC) to convert
siliconchip.com.au
REG1
LP2950ACZ-5.0
+5V
OUT
IN
D3 1N4004
V+
K
CON4
A
+12V
IGN
K
GND
100nF
47
ZD1
100 F
16V
1W
A
100 F
100nF
0V
10k
3
2
1
Vdd
RA5/MCLR
RB4
RA4
RB3
AN3/RA3
RA1
10
LED1
AN2/RA2
470
6
COM
K
NC
D1
1N4004
RA0
RB5
RB1
AN6/RB6
K
RELAY 1
A
TP5
D
47
16
IC2
RA7
PIC16F88
PIC1 6F8 8
15
–I/P
OSC2
12
NO
A
MONITOR
RB0/PWM
13
K
9
18
CON1
CON5
G
S
RELAY 2a
CON2
47
17
NO
COM
11
7
JP2 QUIESCENT
SET
JP3
NC
K
D2
1N4004
A
NC
UP/DOWN
AN5/RB7
RB2
Q1
2N7000
RLY2
4
A
RLY1
14
8
D
CALIBRATE
Vss
5
G
S
COM
NO
Q2
CON3
2N7000 RELAY 2b
Fig.3: complete circuit for the RapidBrake. Two of the analog outputs of the
accelerometer module are fed to dual op amp IC1a and IC1b which amplifies
them and those amplified signals are then fed to two analog inputs of
microcontroller IC2. Trimpots VR3 and VR4 feed two other analog inputs,
to set the upper and lower deceleration trigger thresholds respectively. If
triggered, output pins RA0, RA1 and RA7 combine to flash LED1, switch on
RLY1 and switch RLY2 on and off at just under 4Hz.
the voltages at these inputs to digital
values.
After compensating the X or Y signal at the AN3 input using the Z signal
at the AN2 input, the resulting value
is compared against the settings from
VR3 and VR4.
VR4 sets the upper 6m/s2 threshold
for braking, while VR4 sets the 2.5m/s2
lower braking threshold.
VR3’s wiper connects to the AN6
analog input of IC2, while VR4’s wiper
connects to the AN5 input. The voltages at these inputs are converted to
digital values in a similar way as for
the AN2 and AN3 inputs.
Note that VR4 connects between the
wiper of VR3 and the 0V supply rail.
This means the wiper of VR4 can only
range between 0V and up to the wiper
voltage set by VR3.
This is done so it is impossible to
have the lower threshold set by VR4
any higher in voltage than the upper
threshold set by VR3.
During emergency stop signalling
(after the upper threshold is reached),
siliconchip.com.au
the RA1 output is switched low (toward 0V) and high (toward 5V) at
3.85Hz to flash LED1 which is blue.
Note that an off-board LED can be
used instead, connected via CON5. If
an external red or yellow LED is used,
Where do you
get those
HARD-TO-GET
PARTS?
Many of the components used in
SILICON CHIP projects are cutting-edge
technology and not worth your normal
parts suppliers either sourcing or
stocking in relatively low quantities.
Where we can, the SILICON CHIP
PartShop stocks those hard-to-get
parts, along with PC boards,
programmed micros, panels and the
other bits and pieces to enable you to
complete your SILICON CHIP project.
SILICON CHIP
PARTSHOP
www.siliconchip.com.au/shop
it will shunt LED1’s current and so the
external LED will light but LED1 will
not, because a red or yellow LED has a
lower forward voltage than a blue type.
Or alternatively, simply omit LED1
and use whatever colour of external
LED you want.
Output RA0 is driven identically
to RA1, to drive the gate of Mosfet Q2
which switches RLY2 on and off at
The RapidBrake circuitry (including the accelerometer) is all mounted
on a single PCB measuring 106 x 58.5mm (shown here about life size). All
connections are made via the terminal blocks on the right side.
Complete constructional details and setup will be presented next month.
July 2017 37
3.85Hz. At the same time, output RA7
goes high while RA0 and RA1 are being pulsed. RA7 drives Mosfet Q1 to
switch on RLY1.
RLY1 is therefore latched for the entire duration of the emergency stop signalling period; it does not switch on
and off at 3.85Hz.
So why have two relays?
Relay RLY1 is used when the hazard lights are used for emergency stop
signalling.
It’s used to disconnect the normal
control signals from the indicator
lamps, so that they do not interfere
with the RapidBrake’s use of those
same lamps. While RLY1 disconnects those lamps from the vehicle,
RLY2 then switches them on and off
at 3.85Hz.
Alternatively, if the brake lights are
being flashed, RLY1 is not used and
RLY2 flashes the brake lights at 3.85Hz;
they will have already been switched
by the brake pedal switch.
When deceleration drops below the
lower threshold, output RA1 goes high
to switch off LED1 and outputs output
RA0 & RA7 go low to switch off the
two relays. Diodes D1 and D2 quench
the voltage spike that occurs when the
relay coils are switched off.
Calibration circuitry
Parts list – RapidBrake
1
1
1
1
1
3
2
1
1
2
1
2
4
4
4
7
double-sided PCB coded 05105171, 106 x 58.5mm
UB3 plastic utility Jiffy box, 129 x 68 x 43mm (Jaycar HB-6023, Altronics H0153)
3-axis accelerometer module (Jaycar XC-4478)
12V SPDT 10A relay (Jaycar SY-4050, Altronics S4197) (RLY1)
12V DPDT 5A relay (Jaycar SY-4052, Altronics S4270A) (RLY2)
3-way screw terminals with 5.08mm spacing (CON1-CON3)
2-way screw terminals with 5.08mm spacing (CON4,CON5)
18-pin DIL IC socket
8-pin DIL IC socket (optional)
cable glands for 6mm diameter wiring
snappable 10-way pin header (JP1-JP3)
2-pin shorting plugs
6.3mm long M3 tapped Nylon spacers
M3 x 6mm machine screws
M3 x 5mm machine screws
PC stakes (TP1-TP5,GND & +5V)
Semiconductors
1 LMC6482AIN dual CMOS op amp (IC1; Jaycar ZL3482)
1 PIC16F88-I/P microcontroller programmed with 0510517A.hex (IC2)
1 LP2950ACZ-5.0 5V low drop out regulator (REG1; Jaycar ZV1645)
2 2N7000 NPN Mosfets (Q1,Q2; Jaycar ZT2400)
3 1N4004 1A diodes (D1-D3)
1 16V 1W zener diode (ZD1)
1 3mm blue LED (LED1)
Capacitors
4 100µF 16V PC electrolytic
2 10µF 16V PC electrolytic
1 1µF 16V PC electrolytic
3 100nF MKT polyester
1 100nF ceramic
There are several jumper links to
provide for calibration. JP2, for example, is used to set the quiescent voltage
reading at AN2 and AN3, with the accelerometer module on a level surface.
This provides the reference voltages
against which the software calculates
change in voltage from the Z output
and the X or Y output for angles off
horizontal.
We’ll look at calibration in more
detail once we have finished the construction details next month.
REG1 is protected against transients
(a vehicle supply is never “clean”!)
using a 47Ω resistor from the V+ supply, a 100µF bypass capacitor and zener diode ZD1 that clamps its input
voltage at 16V.
Power supply
Next month
Power for the RapidBrake comes
via the vehicle’s ignition switch and
passes through diode D3 to provide the
supply for the relay coils (V+). REG1
is used to provide a stable 5V rail for
op amp IC1 and microcontroller IC2.
This is important to maintain accelerometer accuracy since the output
voltages of dual op amp IC1 are supply
dependent, since VR1 and VR2 connect across the 5V supply. The ADC
in IC2 also uses the 5V rail as a reference voltage.
If you’re interested in building the
RapidBrake, you can order the PCB
from the SILICON CHIP online shop (catalog code SC4321) and start gathering
38 Silicon Chip
Resistors (0.25W, 1%, through-hole)
1 43kΩ
2 10kΩ 1 470Ω 4 47Ω
3 10kΩ top adjust multi-turn trimpots (VR1,VR2,VR4)
1 1kΩ top adjust multi-turn trimpots (VR3)
the parts, as laid out in the parts list
in this issue.
The programmed PIC is also available from the SILICON CHIP online shop
(catalog code SC4322); all other components should be readily available
from your normal suppliers.
Next month we’ll go through the
process of assembling the PCB, calibrating it, putting it in the case, mounting it in the vehicle, wiring it up and
SC
testing it.
Resistor Colour Codes
No.
1
2
1
4
Value
43kΩ
10kΩ
470Ω
47Ω
4-Band Code (1%)
yellow orange orange brown
brown black orange brown
yellow purple brown brown
yellow purple black brown
5-Band Code (1%)
yellow orange black red brown
brown black black red brown
yellow purple black black brown
yellow purple black gold brown
siliconchip.com.au
Higher power, loads more features . . .
Deluxe, higher
spec eFuse
Part one:
by Nicholas Vinen
No sooner had the eFuse article (April 2017) hit the streets than readers
were asking, “Great – but what about (fill in the gaps!)?” So we decided to
produce a deluxe version of the eFuse which filled in just about every gap
we could think of: higher voltage, higher current, single-ended or bipolar,
a touch-screen interface, selectable time constants, a real-time voltage,
current and tripping display. It’s based on the tried-and-tested Micromite
LCD BackPack.
T
his deluxe eFuse/DC circuit
breaker acts like one or two DC
fuses, except that these fuses
can be “magically” restored once they
“blow”, at the touch of the screen,
potentially saving you a lot of money
and hassles.
If you decide you need a different
fuse value or blow speed, you can simply change it on the fly.
And unlike a normal fuse, this one
shows you how close to blowing it is
at any given time.
It’s especially valuable when you
are building or repairing equipment
since you can set the fuse
“blow” (trip) current low initially, switch on and see
what happens.
If it doesn’t blow then
you can wind up the trip
current and increase the
load and/or activate more
features in the device you’re
testing, progressively checking each function.
If something goes wrong, the
eFuse will very quickly cut the
power off and you can then figure out what the problem is, without letting any of the smoke out.
As we mentioned earlier, we
published a simple eFuse DC circuit breaker project in our April 2017
40 Silicon Chip
issue. That one was a small and lowcost device that was quite easy to build.
However, it had limited voltage
(16V) and current (10A) capability and
you had to change one or two fixed resistor values to adjust the trip current.
It also had no display of any sort,
apart from LEDs indicating the presence of power and whether the fuse
had “blown” or not.
This new and much fancier eFuse is
more complex, larger and more expensive but it provides a lot of extra
features to make up for that.
Just look at the many features and
specifications listed in the adjacent
panel, starting with the higher maximum voltage (32V), much higher current capability (25A+), split supply capability, easy trip current setting via
touch-screen and the real-time display
of voltage, current and simulated fuse
temperature to save you the hassle of
hooking up a bunch of multimeters so
you know just what’s going on.
Basically, it’s a comprehensive DC
load and supply protection and
monitoring solution which
can be used in a lab environment or as a semi-permanent
or permanent part of a piece
of equipment.
Despite all its features,
all the components are
through-hole types and fit
on a modestly sized (132
x 85mm) PCB which itself fits into a low-cost
UB1 jiffy box.
One bonus feature
that you don’t get with
regular fuses is that if
you are using it with a
The prototype
split supply, for examPCB for our Deluxe
Touchscreen eFuse (there may be ple, when testing an auminor differences between this and the dio amplifier (albeit with
final PCB to be described next month). a maximum supply voltsiliconchip.com.au
Features and Specifications
DC circuit breaker
positive supply breaker only, positive and negative supply breaker with independent trip,
positive and negative supply breaker with simultaneous trip
Working voltage range:
12-32V or ±12-32V
Normal trip current:
selectable from 0.1A to 30A in 0.1A steps
Instantaneous trip current:
>68A for >1ms
Continuous current handling:
25A; automatic switch-off at elevated temperature
Series resistance:
approximately 16 milliohms per channel
Voltage loss:
<0.25V at 10A; <0.5V at 20A; <0.75V at 30A
Quiescent current:
~50mA (operating, with screen off)
Quiescent dissipation:
~0.5-2W depending on supply voltage and LCD backlight brightness
Extra dissipation:
~2.5W per channel at 10A; ~7W per channel at 20A; ~10W per channel at 25A
Trip response time (selectable): fast (~10ms for 2x overload),
normal (~100ms for 2x overload)
or slow (~1s for 2x overload)
Read-outs (with screen on):
positive and negative input voltage, positive and negative current flow, breaker trip bar
graphs (indicates how close to tripping each channel is), breaker state for each channel
Extra features:
soft start, touchscreen configuration, non-volatile settings, start-up on/off/last state, complete
input and output protection with one-way current flow, brief transient protection, overheating
protection, binding posts for supply and load connections, adjustable screen brightness,
screen auto-off, built-in diagnostics with under-voltage lockout, safety protection fuses
Function:
Operating modes:
age of ±32V), you can program it so
that if either rail draws too much current, they will both be switched off simultaneously.
This will often prevent one fault
from cascading into several, in the
case where the DC fuse in one rail
blows but the other does not.
We can’t guarantee it but this eFuse
may react fast enough to sudden high
current draw to prevent the destruction of output transistors; it’s well
known that conventional fuses are
not fast enough (the output transistors “blow to protect the fuses” [!]).
Our eFuse can react in well under
1ms when set to its most sensitive
mode, so it might just save you some
expensive transistors...
The input and output connections
are made via high-current binding
posts and you can use banana plugs
for currents up to about 10A and bare
wires for higher currents.
We’ve made an effort to minimise its
additional power supply current drain
and internal dissipation, although it
will (unavoidably) get a little warm
if operated for long periods near its
maximum rated current.
Touchscreen control
The Micromite is part of the reason
why we’re able to provide so many
siliconchip.com.au
features with a modestly complex circuit. Many of the additional features
have been provided with software,
rather than additional circuitry. And
the touchscreen makes it easy to set
up and use.
General operating principle
Refer to the simplified circuit/block
diagram, shown in Fig.1.
The fundamental tasks required
for an electronic fuse/DC circuit
breaker are to monitor the current
flowing between the input and output terminal(s) and to be able to stop
the current flow if it exceeds the programmed limit for long enough (with
a progressive overload response more
or less approximating that of a real
fuse or circuit breaker).
To achieve this, the two main
parts of the circuit are N-channel
“SenseFET” Mosfets Q1 and Q3 and
the Micromite LCD BackPack (equivalent) circuitry.
The Mosfets have a dual role: they
allow us to efficiently monitor the
current flow and also to interrupt
that current flow should it become
excessive.
We explained SenseFETs in some
detail in the April 2017 eFuse article,
as this type of device was contained
within the ICs used in that project.
But this is the first time we’re using
discrete SenseFETs, so they deserve a
brief explanation.
Essentially, a SenseFET is two Mosfets, one large and one small, connected in parallel in a single package.
Because their construction is similar, current flowing through the device is split proportionally between
the two.
Fig.2 shows the basic arrangement.
At left (Fig.2a) it shows how current
flow is measured with a traditional
Mosfet. The value of resistor “R” normally needs to be very low, say 1mΩ,
in order to avoid very high dissipation.
Even a 5mΩ resistor would dissipate nearly 5W with 30A flowing
through it, and yet the full-scale sense
voltage would be just 150mV. That’s
far from an ideal situation and a lot
of power to waste.
However, in reality, a high-power
Mosfet is actually multiple, smaller
Mosfets in parallel. Fig.2b shows how
two would be paralleled but it’s many
more than that. This works because
they are all on the same die and all
virtually identical, so current is shared
between them.
The SenseFET takes this one step
further, as shown in Fig.2c; the majority of smaller Mosfets are paralleled
to provide one main Mosfet which
July 2017 41
CON1
Q1
Q5
VH
+IN
S
+OUT
KS
27k
3k
Q7
D
IS
G
+5V +3.3V V+H
V+H
GATE
DRIVE
LEVEL
SHIFTER
VH
22
GND
HIGH
SIDE
POWER
SUPPLY
IC2b
1M
V–H
GND
1M
IC2a
+3.3V
2.2M
2.2M
3k
Q6
27k
Q3
VL S
–IN
Q8
D
KS
IS
G
+3.3V
GATE
DRIVE
LEVEL
SHIFTER
+5V
SC
22
20 1 7
–OUT
V+L
IC3b
PIC32
MICROMITE
+5V
LCD
TOUCH
SCREEN
V+L
VL
LOW
SIDE
POWER
SUPPLY
1M
1M
IC3a
2.2M
2.2M
V–L
carries virtually all the current. A few
are split off from the rest and resistor
R can be inserted in series with their
source terminal.
Since a small fraction of the load
current flows through this resistor, it
can have a much higher value, giving
a higher and more practical voltage
reading while dissipating much less
power, because most of the load current bypasses it entirely.
As long as the Mosfets share current
in fixed proportions, this scheme provides accurate current measurement
with far fewer drawbacks compared to
the scheme shown in Fig.2(a).
In the case of the BUK7909 devices used here, the current split ratio is
very close to 1:999, so in other words,
current through the small Mosfet is
1/1000th that of the total current flow.
This means that 99.9% of the current
does not pass through this resistor,
minimising voltage and power losses.
The BUK7909 is supplied in a TO220 package with five pins. A typical
Mosfet has three pins: gate, drain and
source. The BUK7909 has one gate
(shared by both internal Mosfets),
42 Silicon Chip
V–L
Fig.1: the key devices in
the Touchscreen eFuse
circuit are the SenseFETs
Q1 and Q3.
drain (shared), two connections to the
large Mosfet source (“source” [S] and
“Kelvin source” [KS]) and the small
Mosfet source (“Isense” [IS]), as depicted in Fig.1.
The Kelvin source connection is
provided so that we can accurately
measure the voltage at the larger Mosfet’s source even when a high current
is flowing through its lead which will
cause a voltage drop due to its inherent resistance.
Now, while we showed the bottom
end of the source resistor connecting
to the main Mosfet’s source in Fig.2(c),
for maximum accuracy, the two Mosfet
source terminals must be kept at the
same voltage, despite the sense resistor in series with the small Mosfet.
Op amp maximises accuracy
An increase in the voltage at IS compared to S/KS would mean that the
two parallel Mosfets would have different gate-source voltages and thus
the current split would not necessarily be 1:199.
To solve this, as shown in Fig.1, op
amp IC2b monitors the voltage at KS
and drives the bottom end of the sense
resistor to maintain identical voltages
at KS and IS.
However, this is not easy to arrange.
The op amp’s negative supply rail must
be far enough below the source voltage to allow it to produce the required
voltage across the sense resistor. This
actually is more of a problem for IC3b/
Q3 since Q3’s source terminal is at the
fully negative supply voltage when it
is in conduction.
Also, the sense op amps must be
able to handle the maximum current
that can flow through the 22Ω resistor.
Even at 1/1000th of the full current,
that’s still up to 68mA for a 68A total
peak current.
We achieve this by using an emitter-follower transistor buffer at the op
amp output (not shown in Fig.1). The
op amp automatically cancels out the
added base-emitter voltage because of
the negative feedback.
The op amp negative voltage supply must also be capable of delivering
68mA. If the op amp or supply can’t
deliver 68mA, that could potentially
result in an under-reading of the actual current flow and the fuse may not
trip on an overload; that would be bad!
Because the current through the
sense resistor does not flow to the
output of the device, this effectively means a 0.1% increase in current
drawn from the supply compared to
that which is supplied to the load
(in addition to the device’s quiescent
current).
The output of op amp IC2b is a voltage which is initially the same as the
source voltage of Q1 when there is no
current flow (ie, VH minus the voltage
drop across Q1) and the voltage drops
as current flow increases.
So that the microcontroller (which
runs off a 3.3V rail) can sense this voltage, the other half of the dual op amp,
IC2a, is used as a differential amplifier.
It has a gain of 2.2 times, as determined by the ratio of 2.2MΩ and 1MΩ
resistors and its output is the difference between the voltage at the KS
terminal of Q1 and the output of IC2b,
multiplied by 2.2.
So its output is 0V for no current
flow, rising to around 3.3V for a current flow of 68A (68A ÷ 1000 x 22Ω x
2.2 = 3.29V). This is fed to the onboard
Micromite microcontroller.
This micro also monitors the voltage
at VH, via a 27kΩ/3kΩ resistive divider, which divides the input voltage by
siliconchip.com.au
LOAD
CURRENT
D
LOAD
CURRENT
SENSING
MOSFET
D
G
G
S
R
SC
LOAD
CURRENT
MAIN
MOSFET
D
SENSING
MOSFET
MAIN
MOSFET
G
MIRROR
R
SOURCE
20 1 7
MIRROR
SOURCE
Fig.2: (a) shows how current flow through a normal
CURRENT
Mosfet can be sensed with a series resistor.
(b) shows how a small and large Mosfet can be paralleled
within a single device, with the load current split between them, with a ratio
dependent on the size of the two Mosfets. (c) expands this concept to include
a resistor in series with the smaller “sensing” Mosfet, allowing us to monitor
the overall current while keeping power and voltage losses low.
a factor of ten. This is used primarily
for display purposes.
It also monitors the V+H rail (not
shown in Fig.1) and will refuse to operate unless it’s high enough to allow
Q1 to be switched on properly.
The micro controls Q1 via level shifter circuitry, shown here as a
“black box”. This pulls the gate of Q1
up to V+H when it is to be switched
on, which is around 10V above VH.
The gate voltage drops to around 15V
below VH to switch Q1 off. Its default
condition is off.
The circuitry to monitor the current through Q3 essentially mirrors
that to monitor Q1, with a few minor
differences.
Firstly, Q3’s source goes to the input side, rather than the output side,
as it controls current flow in the opposite direction. Op amp IC3 runs off
supply rails of +5V and V-L (around
6V below VL), compared to the V+H
and GND supply for IC2.
The gate drive level shifter for Q3
drives it high to V+L (around 10V
above VL) and low, to VL.
Choice of op amps
IC2 and IC3 are LT1490A dual
“Over-The-Top” op amps from Linear Technology. These were chosen for
very specific characteristics which few
op amps possess and that are required
in this circuit.
We have a detailed review of these
devices (and the very similar LT1638)
on page 60 of this issue.
They have rail-to-rail input and
output voltage ranges, with the output able to produce voltages just a
few millivolts above the negative rail.
This is important since IC2a needs
to be able to produce an output very
siliconchip.com.au
close to 0V when there is no current
flowing through Q1 and its negative
supply rail is GND.
To use an op amp without this capability would require a more complex
power supply, to produce a -1V rail
for IC2’s negative supply (or something like that).
Very few rail-to-rail op amps will operate at up to 44V but these op amps
will. That makes them ideal for levelshifting and differential amplifier circuits which need to handle relatively
high input voltages, like this one.
Also, the quiescent currents of IC2
and IC3 are very low at about 0.1mA,
so they minimally load the V+H and
V-L supply rails, both of which are provided by charge pumps which have a
relatively high output impedance and
thus their voltages could drop under
significant load.
IC3a’s positive supply is the 5V
rail because if we used the 3.3V rail,
it wouldn’t be able to produce output
voltages above about 3V; the LT1490
isn’t as good at swinging to the high
supply as it is to the low supply rail.
To keep its total supply voltage below the 44V limit, that means V-L can’t
go below -39V with the maximum VL
voltage of -32V (or -33V to be safe).
This has been achieved by making
the charge pump that generates the
V-L rail purposefully “lossy” (as will
be explained below) so that its typical unloaded voltage with VL=-33V
is pretty much exactly -39V.
Zero voltage “diodes”
We haven’t mentioned the “diodes”
labelled Q5, Q6, Q7 and Q8 yet. These
are “ideal diodes” in the sense that
they have virtually no voltage across
them when they are in forward con-
duction.
As you may have guessed (since
they’re labelled “Q”), while they are
shown as diodes, they are actually
Mosfets which are made to act like
diodes.
So why are these Mosfets/diodes
included?
Firstly, with a single SenseFET to
control the current flow between each
input/output pair, we can only block
current in one direction.
So without additional protection, if
you accidentally mixed up the input
and output terminals, the circuit could
not be broken and so the eFuse and/or
load could be damaged.
These four “diodes” prevent current
flow in this case. They also protect the
unit against accidentally reversed supply polarity, especially for the input
terminals. They will be explained in
more detail later.
Control and power supply
As you may have gathered, our circuit has two negative supply generators since we need to monitor two
SenseFETs with different source voltages (for positive and negative supply
situations).
It also has a boosted positive supply generator for the upper SenseFET,
to generate a sufficiently high voltage (above the positive input supply)
to bring its gate high enough for full
conduction.
The high-side power supply contains three linear regulators and one
charge pump. The linear regulators
generate a +5V rail for the touchscreen and a +3.3V rail for the microcontroller.
These rails are also used for other
purposes. The third linear regulator
derives a V-H rail 10V below VH. This
is then inverted by the charge pump, to
produce a V+H voltage about 6V above
VH, used primarily for Q1’s gate drive.
The low-side power supply contains
one linear regulator and one charge
pump. The linear regulator is used
to derive V+L, about 10V above VL,
which is primarily used for Q3’s gate
drive. This is inverted by the charge
pump to derive V-L, above 10V below VL, used for op amp IC3’s negative supply.
Two simple level-shifting transistor circuits allow the microcontroller
to bring the Mosfet gate voltages high
to switch on the SenseFETs for normal operation.
July 2017 43
Fig.3: the complete circuit diagram. You can relate the shaded boxes to various elements in Fig.1;
see the labels within. The “ideal diode” sections behave similarly to diodes but with almost zero forward
voltage (about 5mV/A). The red and mauve power supply sections generate the voltages required to run op
amps IC2 and IC3 and also to drive the gates of Q1 and Q3 to the correct voltages to switch them on fully.
44 Silicon Chip
siliconchip.com.au
siliconchip.com.au
July 2017 45
These circuits are biased so that the
Mosfet gates are pulled low by default,
so that no current flows until the microcontroller is ready and supervising
the current flow.
If the micro then resets for any reason (eg, a supply voltage drop-out or
software error), the current flow is interrupted and the load is switched off.
Circuit description
The full circuit of the Touchscreen
eFuse is shown in Fig.3. You should
be able to see the similarity between
its upper-left quadrant and the simplified circuit/block diagram of Fig.1.
The internal structure of the four
“ideal diode” sections is now visible,
each within a blue shaded box.
Q5 and Q7 are P-channel Mosfets
while Q6 and Q8 are N-channel Mosfets, to suit their low-side and highside situations respectively.
The control circuitry for each of
those four Mosfets is identical, except
it is mirrored for the N-channel Mosfets compared to P-channel Mosfets,
ie, NPN driver transistors rather than
PNP and so on.
The Mosfet types have been chosen
to have similar characteristics, critically, a breakdown voltage of at least
30V, a continuous current rating of
more than 50A and an on-resistance no
more than about 5mΩ, to keep losses
low, even at high currents.
Looking at the circuitry around
Q5, PNP transistors Q9 and Q10 are
arranged so that they are constantly
“comparing” the voltage across Q5’s
channel. Diodes D9 and D10 protect
Q9 and Q10 from reverse breakdown
of their base-emitter junctions in case
of reversed supply polarity.
Since the current through these
small-signal diodes is similar, their forward voltage will be similar and hence
a difference in voltage between Q5’s
drain and source terminals appears
as a difference in voltage between the
emitters of Q9 and Q10.
Q9 has its base and collector joined,
effectively making it a diode, which
is forward-biased by current flowing
through its 10kΩ collector resistor.
As Q9 and Q10 are the same transistor types, so if Q5’s source voltage is
lower than its drain voltage, Q10’s
base-emitter voltage is too low for it
to switch on fully and the 22kΩ collector resistor pulls the gate of Q5 to
ground, switching it on.
Current can therefore flow from the
46 Silicon Chip
+IN terminal of CON1 to Q1 (ie, “VH”),
as long as the +IN voltage is above
VH, ie, current is flowing from left to
right. Zener diode ZD3 prevents Q5’s
gate from being more than 15V lower
than its source terminal; a much higher gate-source voltage than that could
break down Q5’s gate insulation and
ultimately, damage it.
Should the voltage at Q5’s source
rise above that of its drain, the baseemitter voltage of Q10 becomes higher
than that of Q9 and hence Q10 switches on, bringing Q5’s gate high and thus
cutting it off. This prevents current
flow from right to left through Q5.
While this is a linear circuit and thus
could theoretically drive Q5 into partial conduction, which could result in
very high dissipation, in practice this
will not happen.
That’s because, in partial conduction, the voltage across Q5 becomes
very high and the higher the voltage
differential, the more Q5’s gate is driven either up to its source voltage or
down towards 0V, switching it either
fully off or fully on. So essentially, this
circuit is stable only in one state or the
other, not in between.
Q5’s intrinsic diode is orientated in
the normal direction of current flow.
If the supply polarity is reversed, Q5’s
gate remains discharged and so current
can not flow. We won’t describe the
other three “ideal diode” blocks since
they all operate identically.
Current sensing details
The two current sense circuit blocks,
shaded in green, operate as shown in
Fig.1, however, there are a number of
circuit details which were hidden in
that simplified diagram.
Firstly, there is the current buffering
arrangement at the output of IC2b (Q2)
and IC3b (Q4). These emitter-followers ensure that the op amps can sink
at least 100mA. The op amp negative
feedback automatically compensates
for the ~0.7V drop across each baseemitter junction.
The collector of each transistor is
connected to V-H and V-L in turn.
Since op amp IC2b’s negative rail is at
0V, well below VH and IC3b’s negative
rail is V-L, 10V below VL, in both cases
the bottom end of the 22Ω sense resistor can be driven well below the respective source voltage, so that IS=KS
during normal operation.
Diodes D7 and D8 prevent the baseemitter junctions of Q2 and Q4 respec-
tively from becoming reverse biased
when Q1/Q3 are switched off. The
10pF capacitors between the output
and inverting input of each op amp
prevent oscillation due to the capacitance and phase shift of the added
emitter-followers.
The differential amplifiers/level
shifters based around IC2a and IC3a
are quite simple and almost identical. In both cases, a resistive divider
is connected between KS and ground,
and the junction of the two resistors
is connected to the non-inverting input, pin 3. There is a similar divider
between the negative end of the 22Ω
sense resistors, the pin 2 inverting input and the pin 1 output.
These two pairs of resistors have the
same division factor of 0.3125 times
(1M ÷ [1M + 2.2M]). Trimpots VR1 and
VR2 are included in the middle of one
divider so that you can trim them to
give exactly the same division ratio, so
that the output of IC2a/IC3a is at 0V
when there is no voltage across the 22Ω
resistors (ie, no current flow through
Q1/Q3). This provides a high common
mode rejection ratio (CMRR), preventing changes in the supply voltage from
affecting the current measurements.
Consider how IC2a operates. The
voltage at pin 3 is 0.3125 times KS
(which is the same as VOH, the highside output voltage). If there is no current flowing, with no voltage across the
22Ω resistor and KS=IS, the top of the
1MΩ resistor connected to pin 2 is at
the same potential as KS.
Therefore, to have the same voltage at pin 2 as pin 3, the bottom end
of that divider needs to be at GND potential, just like the identical divider
connected to pin 3. This will be when
the pin 1 output is at 0V.
Hence, negative feedback determines that pin 1 is at 0V when no
current is flowing. When current does
flow, the voltage across the 22Ω resistor causes the voltage at pin 2 to drop.
But the voltage at pin 3 has not
changed, so output pin 1’s voltage
must rise in order to keep the voltage
at pin 2 and pin 3 the same. Hence, the
output voltage increases as the current
flow increases. The 2.2MΩ feedback
resistor’s ratio with the 1MΩ resistor
means that the overall gain is 2.2 times.
The outputs of IC2a and IC3a are
fed to analog inputs AN4 and AN5 of
microcontroller IC1 via 4.7kΩ resistors, which limit the current flow in
case these pins are over-driven. Since
siliconchip.com.au
IC1 has a 3.3V supply, this is the
maximum voltage which can be read
at those inputs. Given the 2.2 times
gain, that equates to a maximum voltage across the 22Ω resistors of 1.5V
(3.3V ÷ 2.2) .
That equates to a current flow of
68mA (1.5V ÷ 22Ω) and given the
1000:1 current sense ratio, a maximum
sense current of 68A.
Anything higher than this will simply read as 68A, hence we have set the
instantaneous (~1ms) trip current to
this level since the actual current flow
could be higher and the safety protection fuses (F1 and F2) could blow if
this is not interrupted, along with possibly Q1 and Q3 being damaged.
Gate drive
NPN transistor Q17 is biased on by
default, by a 100kΩ resistor from its
base to the 3.3V rail. This pulls Q1’s
gate down to 0V, keeping it off, although it is clamped to about 16V below VOH to protect Q1.
When Q1 is off, VOH tends towards
0V as no current can flow through it,
so ZD1/ZD2 will not normally conduct for very long. The current through
them is normally limited to about
10mA (3.3V ÷ 100kΩ x 300 – typical
beta for Q17) .
When microcontroller IC1 wants to
switch Q1 on, it pulls its RA2 output
low, switching off Q17 and allowing
the 100kΩ resistor to V+H to pull Q1’s
gate above VH/VOH. The relatively
high 100kΩ value combines the Q1’s
gate capacitance of around 10nF to
provide a “soft start” time of about
1ms (100kΩ x 10nF).
This prevents very high current
surges into capacitive loads, although
switch-on current flow could still be
enough to trip the eFuse, depending
on how it’s configured (just like a normal fuse or circuit breaker).
The gate drive for Q3 is a little different. PNP transistor Q21 is normally
switched on due to the 100kΩ pulldown resistor at its base. It, in turn,
supplies current to the base of NPN
transistor Q18 which has its emitter
tied to VL, normally below 0V. This
pulls Q3’s gate down to VL, which is
its source voltage, hence keeping it off.
To switch on Q3, microcontroller
IC1 brings its RA3 output high, forcing Q21 to switch off and in turn, Q18
loses its base current. This allows
Q3’s gate to be pulled up to V+L via
the 100kΩ resistor, again giving a softsiliconchip.com.au
start time of around 1ms. No gate protection is needed since V+L is never
more than 15V above VL.
Voltage monitoring
The VH and VL input supplies are
monitored by IC1 primarily so that
they can be displayed for the user.
However, they are also used to provide the under-voltage lockout function, where IC1 will refuse to switch
on Q1 and Q3 if the relevant supplies
are not high enough to guarantee correct operation. Normal operation starts
with a supply voltage of at least 11V
and will continue as long as the supplies do not drop below 10V.
VH is divided by a factor of ten using 27kΩ and 3kΩ resistors and applied to analog input AN0 of IC1 (pin
2). Thus, it can read up to 33V. The
3.3V supply is used as a reference; the
MCP1700 regulator has a typical error
of ±0.4% at 25°C, so calibration is not
critical although the software does allow you to calibrate the readings for
high accuracy.
V+H is also monitored, in a similar
manner, although the divider resistors
are 390kΩ and 30kΩ.
The higher values are to reduce the
loading on the V+H rail as it has limited current delivery and the division
ratio has been increased to one-fourteenth, since the V+H rail can range
up to about 42V (not coincidentally,
just below the maximum recommended supply voltage for the LT1490 op
amps of 44V).
The arrangements for monitoring
the VL and V-L rails, at analog inputs
AN9 (pin 26) and AN11 (pin 24) are basically the same, except the “far end”
of the divider goes to +3.3V rather than
ground; this is to keep the voltages at
these pins between 0V and 3.3V. The
software subtracts 3.3V from the readings at the same time as compensating
for the divider values, to get true voltage readings.
Monitoring V-L and V+H has three
purposes. One, it provides a debugging
feature; if the power supply is not built
properly, IC1 will detect this and display a message on the screen.
Two, it protects the unit against
damage in case either or both boosted rails drop below the minimum required for correct operation, in which
case the outputs will automatically
be tripped and a message displayed.
This should not normally happen and
could indicate a faulty component or
that the power supply voltage dropped
too much under load.
Finally, it allows the microcontroller to fairly accurately model the dissipation in Mosfets Q1, Q3 and Q5Q8 during operation and track their
assumed temperatures. The unit will
then shut down the outputs if any is
at risk of serious overheating.
While the unit can be configured
with a trip current of up to 35A, we’ve
quoted a continuous current handling
rating of 25A since both Q1 and Q3
will be dissipating 4.7W (25A x 25A
x 7.5mΩ) at 25A. That’s fairly substantial, despite them having flag heatsinks, especially in a plastic jiffy box
and especially if high currents are being drawn from both outputs.
With a sustained current of say 30A,
the unit may not trip normally but the
Mosfets could still get very hot. So the
unit will trip to prevent overheating
and damage and will display a message
on the screen indicating this.
Power supply details
The high-side power supply, responsible for generating the +3.3V,
+5V, V+H and V-H rails, is shown in
the red shaded box.
Schottky diode D1 is used even
though there is an “ideal rectifier” between +IN and the VH rail so that brief
drops in the incoming supply voltage, due to high load current (eg, at
initial switch-on of a capacitive load)
to not cause the supply rails to drop
too quickly.
The 1Ω resistor and 33V zener diode ZD7 combine to filter out very
brief spikes which may occur, for example, due to back-EMF from a motor load, protecting linear regulators
REG2 and REG3.
REG2 is an LM337 negative adjustable linear regulator. The 680Ω and
100Ω feedback resistors set its output
voltage very close to 10V below VH.
In this case, its “input voltage” is
ground and its “ground” voltage is
VH. This produces the V-H rail. REG2
is in a TO-220 package which uses the
PCB as a heatsink, since it may need
to (briefly) supply up to 100mA with
a 22V input-output differential which
works out to a dissipation of 2.2W.
555 timer IC4 is connected between
VH (after D1) and V-H, ie, the output
of REG2. So with a +IN voltage of say
+24V, its VCC pin will be at around
+23V while its GND pin will be at
around +13.7V (ie, 10V below VCC).
July 2017 47
Since its output (pin 3) is connected
via a resistor to the threshold and trigger inputs (pins 6 and 2 respectively),
it will oscillate with a 50% output duty
cycle; each time the output switches high, this will charge the 220pF
capacitor between pins 1 and 2 until
pin 6 reaches 2/3 its supply voltage.
The output will then switch low and
discharge that same capacitor until it
reaches 1/3 the supply voltage, then
the output will switch high again and
the process will repeat.
The time constant of the 22kΩ resistor and 220pF capacitor sets the oscillation frequency to around 100kHz.
Each time output pin 3 goes low,
the 1µF capacitor charges to around
9.7V, via schottky diode D2 from VCC.
When output pin 3 goes high, the anode of schottky diode D3 is raised to
around 9.7V above VCC and so D3 is
forward-biased and the 1µF capacitor between VCC and V+H charges.
The result is that V+H tends towards
around 9.4V above VCC, ie, around
9V above VH.
The remainder of the high-side supply is quite simple, with 5V linear
regulator REG3 producing the +5V
rail for the LCD touchscreen and op
amp IC3 and this is also fed to REG1
to produce the +3.3V rail for microcontroller IC1.
Because the combined total of these
currents can exceed 100mA and because the input to REG3 can be up
to about 32V, giving a differential of
27V and a dissipation in excess of
3W, REG3 uses the PCB as a heatsink.
The software automatically limits
LCD brightness with a high supply
voltage to ensure REG3 doesn’t overheat and “drop its bundle” (go into
thermal limiting, likely shutting down
the whole device).
The low-side power supply more
or less mirrors the high-side supply,
although without the 5V and 3.3V
regulators. It is shown shaded in
mauve.
Diode D4 is a cheaper 1N4004
standard diode rather than a schottky diode (like D1) since the critical
V+L supply which is used to drive
the gate of Mosfet Q3 does not rely
on the charge pump and so it has a
lower effective dropout voltage. Thus
the extra forward voltage of D4 is not
a major issue.
V+L is derived in a similar manner
to V-H, only using an LM317 positive
regulator rather than an LM337 neg48 Silicon Chip
ative regulator. V+L sits about 9.3V
above VL. This is then fed to another
555 timer, IC5, which inverts this voltage in a similar manner as described
above for IC4. The result is V-L, which
is around 6V below VL.
As we mentioned earlier, this is a
purposefully lower supply voltage
than V+H in order to keep IC3a within
its maximum supply rating of 44V (ie,
V-L can not exceed -39V).
This is achieved by using 1N4148
standard signal diodes in the charge
pump, rather than 1N5819 schottky diodes, each adding about 0.5V further
voltage drop, plus red LED1 in series
with D5 for an additional voltage drop
of around 1.8V.
The full load current of IC5 must
pass through LED1, which equates to
just over 30mA with a load current
through Q3 of 30A.
As a result, we specify a current
rating for LED1 of 50mA, which is
available in a 3mm package from Jaycar. This is pretty safe, since a sustained Q3 current of 50A will pretty
quickly trip the output off, also protecting LED1.
Microcontroller and touchscreen
The arrangement of IC1, REG1 and
the LCD touchscreen is copied directly from the Micromite LCD BackPack,
a standalone project which was published in the February 2017 issue.
While we could have designed this
unit to use the BackPack as a plug-in
module, we decided that integrating
the circuit onto the main PCB would
save cost.
The same kit of parts can be used
to build this section of the board, minus the BackPack PCB and laser-cut
lid (since the box used in this project
is bigger).
There isn’t much to the BackPack;
besides the power supply, there’s just
PIC32 microcontroller IC1, its 10kΩ
MCLR-bar pull-up resistor that prevents spurious resets, the bypass
capacitors and required core filter
capacitor between pin 20 of IC1 and
ground, a 4-pin serial interface connector (CON3) and the 14-pin female
header for the LCD touchscreen to plug
into (CON4).
IC1 communicates with the LCD
using two SPI interfaces, one to send
commands and data to the LCD and
one to interface with the onboard
touch sensor IC.
They share three wires: pin 25, the
SPI clock, pin 3, the SPI OUT data
line (which goes to the data inputs of
the LCD controller and touch controller) and pin 14, the SPI IN data line
(which goes to the data outputs of the
two controller ICs).
The touch SPI interface is selected
when IC1 drives pin 17, T_CS-bar low
while the LCD SPI interface is selected
when IC1 drives pin 4, CS-bar low. Pin
5 will reset the LCD controller when
brought high and is kept low for normal operation.
Pin 22 (D/C) is used to indicate to the
LCD whether bits being sent represent
data or a command. Pin 15 (T_IRQ) is
used by the touch controller to send
a signal to IC1 when the touchscreen
is being used.
There are really only two differences
between this circuitry and the Micromite LCD BackPack. Firstly, we have
omitted the in-circuit serial programming (ICSP) header to save space.
This means you need to plug a preprogrammed Micromite chip into the
board but it can still be configured
and programmed through the CON3
serial interface.
The other change is that we have replaced the manual backlight control,
which used a trimpot as a rheostat,
with transistors Q19 and Q20. A PWM
signal from output pin 18 of IC1 is used
to control the backlight brightness.
When pin 18 is driven high, it switches on NPN transistor Q20 which sinks
current from the base of PNP transistor Q19, applying 5V to the backlight
anode pin, pin 8 on CON4.
Q20’s base is driven with approximately 26µA ([3.3V – 0.7V] ÷ 100kΩ).
Given a typical beta of around 230 at
that current level, it will sinks around
6mA from Q19’s base, which is more
than enough to drive it into saturation,
given the typical 100-200mA drawn by
the LCD backlight LED array.
Pin 18 is not a dedicated Micromite
PWM output; we use a CFUNCTION
in the software to provide an emulated PWM function at around 1kHz, to
prevent backlight flicker without using
too many of IC1’s CPU cycles.
Next month
Next month we will show the final
PCB design, the fully assembled unit,
go over some of the details of the software, go through the PCB assembly,
case preparation and final assembly
procedures and explain how to use
the unit.
SC
siliconchip.com.au
SMART
POWER
SOLUTIONS
PROGRAM YOUR
ARDUINO® BOARD OVER WI-FI
YUN WI-FI SHIELD XC-4388
Allows you to easily program and operate your
Arduino project over Wi-Fi and allow it to access
the Internet. The on-board Linux computer is
based on the Open WRT firmware, giving you
access to a multitude of built in functions
and downloadable software packages.
Connect a 3G dongle to provide
connectivity for your Arduino on-thego, and use it as the basis for your
next IoT project.
• Wi-Fi, Ethernet, USB
and Serial interfaces
• Web configuration interface
• 77 x 54 x 26mm
Due out early July
7995
$
$
79 95
PERFECT FOR
ARDUINO® NOOBIES XC-3900
Looking to get into Arduino® but don’t quite know
where to start? We have specially selected the components
in this kit to allow an easy entry into the world of Arduino®.
The all-in-one kit is supplied with a UNO Arduino compatible
board, breadboard and an extensive range of components to make
hundreds of projects. Includes user manual to get you started.
Visit jaycar.com.au/arduino-learning to find out more.
See pages 2 & 3 for more
NEW RANGE OF SMPS
We have been selling Mean Well power supplies for over 17 years now, and found them to be of a very high quality. Here are just
some of their new range of SMPS that have just landed, ideal for home projects to industrial applications. Backed by a 3 year warranty.
MINI ENCLOSED
MINI ENCAPSULATED
DIMMABLE LED POWER SUPPLIES
• 5G anti-vibration capability
• High operating temperature up to 70°C
• 300VAC input surge
• Suitable for critical applications
SINGLE OUTPUT:
• 62.5(L) x 51(W) x 28(H)mm
5V 15W 3A
MP-3295 $19.95
12V 15W 1.3A MP-3296 $19.95
12V 25W 2.1A MP-3297 $24.95
24V 25W 1.1A MP-3298 $24.95
DUAL OUTPUT:
5V/24V 65W 6A/3A 129(L) x 98(W) x 38(H)mm
MP-3299 $49.95
5V/24V 125W 4.6A/4.6A 199(L) x 98(W) x 38(H)mm
MP-3300 $79.95
Compact and extremely low
(<0.1W) no load power
consumption.
• 91(L) x 39.5(W) x 28.5(H)mm
5V 30W 6A
MP-3301
12V 30W 2.5A MP-3302
Constant current dimmable LED drivers to control 12V or
24V LED panel lighting, downlights, decorative lighting,
and many other applications. IP67 ingress protection for
outdoor applications. 1.8m lead. 5yr warranty.
• 90~305VAC input, built-in active PFC function
• Built-in 3-in-1 dimming function
(1~10VDC, PWM signal or resistance)
12V 40W 3.34A MP-3374 $79.95
12V 60W 5A
MP-3376 $89.95
24V 40W 1.67A MP-3375 $79.95
24V 60W 2.5A MP-3377 $89.95
See website for full specifications
FROM
$
19 95
$
39 95
ea
$
FROM
79 95
12V 450A LI-PO JUMP STARTER
AND POWERBANK MB-3757
$
29 95
CAR BATTERY
DISCHARGE PROTECTOR MB-3676
Warns you when battery power is running
low & disconnects when power gets too low.
• Max Power Output: 8A
• 12V cigarette lighter connection
• 95(L) x 35(W) x 155(H)mm
$
39 95
9.6A 4 PORT BACKSEAT USB
CAR CHARGER MP-3690
Simultaneous 4-port USB charging: two USB
up-front, and two more charging ports for the back seats.
1.8m cable connects the backseat unit with the cigarette
lighter front unit. Rated at 2.4A each port. 12/24V.
Will crank an engine up to a
5L petrol, or 3L diesel.
• 300A continuous, 450A peak
• LED Torch
• 2 x USB port <at> 5V 2A/1A
• 11,100mAh capacity
• 66(W) x 142(D) x 30(H)mm
ALSO AVAILABLE:
12V 700A JUMP STARTER
& POWERBANK MB-3758 $279
179
$
SEE PAGE 8 FOR WHAT'S NEW!
TAREN POINT HAS MOVED: 160 TAREN POINT RD, CARINGBAH NSW 2229
Catalogue Sale 24 June - 23 July, 2017
To order phone 1800 022 888 or visit www.jaycar.com.au
LONG RANGE DATA COMMUNICATIONS
Introducing LoRa™, a powerful new technology enabling secure wireless data
communications over long distances (even several kilometres!!) without the need of a mobile
GSM network. LoRa™ can be used in many outdoor or indoor applications, such as building
automation, weather monitoring, irrigation systems control, smart metering, smart cities, and
much more. LoRa™ has a low power consumption and AES128 security encryption.
ARDUINO® COMPATIBLE
RGB LED STRIP MODULE XC-4380
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. 54mm x 10mm x 3.5mm
• 5V supply
• 256 brightness levels
• 500mA per module max
9
$ 95
Learn much more at www.lora-alliance.org
LONG RANGE LoRa™ SHIELD
XC-4392
The Arduino® Compatible Long Range LoRa™ shield
turns your Arduino® into a LoRa™ node capable of
transmitting and receiving data over long distances.
The perfect solution to your remote sensor and
control projects.
• Compatible with 3.3V or 5V I/O Arduino Board.
• LoRa™ frequency Band: 915MHz
• Low power consumption
• Includes external Antenna
(via I-Pex connector)
Radio transmitting devices must be used in
accordance with Australian Communications &
Media Authority guidelines www.acma.gov.au
Due out early July
RELAY BOARDS
$
The easiest way to use
your project to switch real world
devices. Can switch up to 10A
per channel.
• Status LEDs show
channel status
• Screw terminals for
easy connection to
relay contact
1 WAY 5VDC XC-4419 $5.45
4 WAY 12VDC XC-4440 $12.95
8 WAY 12VDC XC-4418 $19.95
69 95
XC-4419
XC-4440
FROM
5
$ 45
MAKE WITH PCDUINO & LINKER ACCESSORIES
PCDUINO V3.0
WITH WI-FI XC-4350
$
• Built in Wi-Fi capability
• Supported digital
audio via I2C
• 121(L) x 65(W)
x 15(H)mm
89 95
VOLTAGE
CONVERTER
MODULE XC-4362
$
29 95
Marries 5V Arduino®
shields with the 3.3V
pcDuino to stop damage
caused by connecting
a 5V shield to pcDuino.
70(L) x 50(W) x 4(D)mm
PCDUINO 5MP
CAMERA XC-4364
BLACK
ENCLOSURE XC-4354
$
House your pcDuino
in this enclosure for a
safe and presentable
appearance.
• Suits XC-4350
19 95
SATA CABLE
XC-4366
Connects your pcDuino
V3.0 to a hard drive
or SSD.
• 150mm long
(approx.)
Connects directly to
pcDuino V3.0, and
captures an active array
of video and images up to
2592 x 1944 resolution.
$
19 95
7" LCD TOUCH
SCREEN MONITOR
4
$ 95
XC-4356
• 1024 x 600 resolution
• LVDS screen with driver board
• 167(L) x 107(W) x 10(D)mm
10% OFF THESE LINKER MODULES & SHIELDS
FOR NERD PERKS CLUB MEMBERS
The Linker range
LINKER JUMPER LEADS
Connects Linker kit sensors/modules and
is based around a
Linker kit base shield. 2.54mm headers for easy
series of Arduino®
compatible modules, and tidy connection. 4 pins, 2.54mm spaced.
• Sold individually
shields and cables.
200MM XC-4558
The Base Shield
500MM XC-4559
$ 95
attaches to your
4 ea
1000MM XC-4560
pcDuino, Uno, Mega
or Leonardo boards, LINKER BASE SHIELD XC-4557
and allows any of the This is the base shield of Linker kit, it
Linker modules to be allows a connection between ®all Linker
sensors/modules and Arduino /pcDuino.
plugged in.
• Connections: 1 x SPI, 2 x IIC, 1 x UART
• 69(W) x 59(H) x 18(D)mm
SEE MORE AT
www.jaycar.com.au/linker
Page 50
$
24 95
FROM
$
89 95
XC-4568
XC-4574
4
$ 95
XC-4569
LINKER MOMENTARY PUSH BUTTON SWITCH
DOUBLE BUTTON MODULE
TILT MODULE
BUZZER MODULE
LIGHT SENSOR
TEMPERATURE MODULE
ROTARY POTENTIOMETER MODULE
LED BAR
TOUCH SENSOR
4-DIGIT 7-SEGMENT MODULE
Follow us at facebook.com/jaycarelectronics
XC-4571 $4.95
XC-4573 $4.95
XC-4575 $4.95
XC-4580 $5.95
XC-4574 $6.95
XC-4576 $6.95
XC-4578 $6.95
XC-4568 $9.95
XC-4572 $10.95
XC-4569 $11.95
Catalogue Sale 24 June - 23 July, 2017
ARDUINO® PROJECT OF THE MONTH
LONG DISTANCE REMOTE RELAY
We were very excited to test just how far we could get a signal using
new LoRa technology. With one test, we were able to get a signal
to travel about 200m, including through the corrugated iron of the
warehouse and the concrete office building. We then set about building
a practical project to make best use of the technology, which our
readers could easily adapt to their own application. We came
up with this easy to build Remote Relay. It has four
buttons at one end and four relays at the
other end, so you can operate up to
4 devices remotely across a very
long distance. It also has LEDs
next to the buttons, so unlike
other remote relay systems,
there is feedback that the
relays are operating as
commanded. Brilliant!
KIT VALUED
AT $244
XC-4410
XC-4392
XC-4482
XC-4440
Finished project.
USB cables not supplied
SP-0601
NERD PERKS CLUB OFFER
169
$
SAVE $75
SEE OTHER PROJECTS AT www.jaycar.com.au/arduino
BREADBOARD LAYOUT
PROTOTYPING BOARDS
ZD-0250
WC-6028
WHAT YOU WILL NEED:
2 X UNO MAIN BOARD
2 X LORA SHIELD
1 X FOUR CHANNEL RELAY MODULE
1 X PROTOTYPING SHIELD
4 X TACTILE PUSHBUTTON SWITCH
1 X PACK OF 470 OHM RESISTORS
4 X RED/GREEN BICOLOUR LEDS
1 X PLUG-SOCKET JUMPER LEAD SET
BUY ALL FOR
SEE STEP-BY-STEP INSTRUCTIONS AT
www.jaycar.com.au/lora-remote
RR-0564
XC-4410
XC-4392
XC-4440
XC-4482
SP-0601
RR-0564
ZD-0250
WC-6028
$29.95
$69.95
$12.95
$15.95
$0.95
$0.55
$1.25
$5.95
FROM
4
$ 95
A fantastic way to transfer your concept
breadboard design to PCB without having
to go to the trouble of designing and making
a PCB. Includes five holes on each side per
row and power rails running the length of the
board. Two sizes to choose from.
SMALL
• 25 rows, 400 holes
• 73mm x 47mm x 1.4mm
HP-9570 $4.95
LARGE
• 59 rows, 862 holes
• 155mm x 58mm x 1.4mm
HP-9572 $9.95
HP-9572
8
HP-9570
DELUXE
MODULES
PACKAGE XC-4288
$
0.25W CARBON
FILM RESISTORS RR-1680
ATMEGA 328P IC
WITH 16MHZ CRYSTAL ZZ-8727
Includes five of virtually each value from
1 Ohm to 10 Meg. Sixty different values.
• 300 pieces
Build your very own customised Arduino®
compatible projects. Comes with the
Arduino® Uno bootloader pre-installed and
16MHz crystal oscillator.
To order phone 1800 022 888 or visit www.jaycar.com.au
$
Includes commonly used sensors and
modules for duinotech and Arduino®:
joystick, magnetic, temperature, IR, LED and
more. 37 different sensors and modules.
12 95
$ 95
NERD PERKS CLUB OFFER
13 50
$
99
RRP $129
SAVE $30
NS-3010
15 95ea
$
BREADBOARD JUMPER KIT
DURATECH SOLDER
PB-8850
Kit includes 70 stripped pieces of single
core sturdy wire.
• 5 pieces each of 14 different lengths
• Supplied in a plastic box for easy storage
60% Tin / 40% Lead. Resin cored.
0.71MM NS-3005
1.00MM NS-3010
See terms & conditions on page 8.
Page 51
WORKBENCH
ESSENTIALS
There has been an obvious resurgence in people getting back to the workbench and
reviving skills involving manual dexterity. As you will see across the following pages,
Jaycar has all the DIY tools you'll need to equip your workbench so you can create
projects from the power of your brain and your hands.
4
149
$
4. DESKTOP LED MAGNIFYING LAMP
QM-3544 WAS $64.95
• 60 LEDS provide ample illumination,
perfectly even light
• 3x and 12x magnifying lenses
• 350(H) x 180(Dia)mm
2. STAINLESS STEEL CUTTER
& PLIERS SET TH-1812
• Set of five 115mm cutters and pliers
• Soft ergonomic grips
5. STORAGE CASE HB-6388 WAS $39.95
• For small instruments or test equipment
• Purge valves
• ABS construction
• 210 x 135 x 90
3. CAT III AUTORANGING DMM WITH
TEMPERATURE QM-1323
• Compact, lightweight with
rugged moulded case
• AC/DC 10A
• Data hold, capacitance, temperature
• Relative measurement
• 600V, 4000 count
• 137(H) x 65(W) x 35(D)mm
6. 70W ESD SAFE ANTI-STATIC SOLDERING
STATION WITH LED DISPLAY
TS-1440 WAS $299
• Precision, Japanese manufactured with
temperature stability and anti-static
• 230-240VAC supply voltage
• 65W capacity heater
• 200 - 480°C temperature range
• 0.5mm tip supplied
TECH TIP
DISTANCE TO SPOT RATIO EXPLAINED:
Safely measure temperature in hard to reach places, hot or
hazardous areas. Backlit LCD. Built-In Laser pointer.
$
SAVE $7
$
NOW
54 95
SAVE $10
6
3
NOW
$
49 95
$
29 95
249
SAVE $50
2
3
$ 95
Distance to spot ratio is the ratio of the distance of the thermometer to the
object being measured, and the diameter of the temperature measurement
area. The larger the ratio number the better the resolution.
NON-CONTACT THERMOMETERS
32 95
5
1
1. 80W SLIMLINE LAB POWER SUPPLY
MP-3842
• Includes banana to alligator clamp leads.
• Constant current and voltage options
• 0-16V/5A, 0-27V/3A, 0-36V/2.2A
• 53(W) x 300(D) x 138(H)mm
$
NOW
5 WAY
CRIMPING TOOL
8
$ 95
TH-1828
Cuts and strips wire.
Also cut bolts with diameter M2.6,
M3.0, M3.5, M4.0 & M5.0.
5M INSULATION TAPE - 6PK
NM-2806
• One roll each of green, black,
yellow, white, blue and red
• 19mm wide
• Each 5m in length
18
$
95
5 PIECE TORX
SCREWDRIVER
SET TD-2070
Swivel head for
easy use.
• 20mm blade length
• Torx sizes: T6, T7,
T8, T9 & T10
12 95
$
19 95
$
$
NOW
49 95
NOW
119
$
NOW
199
$
SAVE $20
SAVE $50
8:1 SPOT
12:1 SPOT
30:1 SPOT
QM-7215 WAS $59.95
• 3 Digit
• 8:1 Distance to spot ratio
• Temp range: -30 to +260°C
• Auto data hold
• Carry case included
QM-7221 WAS $139
• 3.5 Digit
• 12:1 Distance to spot ratio
• Temp range: -50 to +650°C
• Holster included
QM-7226 WAS $249
• 4.5 Digit
• 30:1 Distance to spot ratio
• Temp range: -50 to 1000°C
• Carry case included
Page 52
Follow us at facebook.com/jaycarelectronics
SAVE $10
32 PIECE
PRECISION
DRIVER SET TD-2106
• Slotted, Phillips, Pozidriv,
Torx and Hex pieces
• With extendable shaft
HEATSHRINK PACK WH-5524
Contains 160 lengths of different sizes in a
handy storage case.
Catalogue Sale 24 June - 23 July, 2017
POWER FOR THE WORKBENCH
Our range of highly efficient and reliable benchtop power
supplies are specially selected to suit your unique testing
and servicing applications. They use proven technology
and are designed to give long service life in workshop
situations. Features include low noise, low ripple and
protection against overload and short circuit. Available in
fixed or variable voltages. The most cost effective solution
for your laboratory use, electronic and communications
equipment maintenance.
NOW
199
$
SAVE $40
FREE LED MAGNIFIER
FOR NERD PERKS CARD HOLDERS*
Valid with purchase of
MP-3098, MP-3802 or MP-3087.
*
TH-1989
VALUED AT $44.95
VARIABLE LABORATORY
AUTOTRANSFOMER (VARIAC)
MP-3080 WAS $239
Encased in heavy-duty steel housing, this unit enables
the AC input to a mains powered appliance to be easily
varied between 0 to full line voltage (or greater). A must
for testing mains performance.
• 500 VA (fused) rated power handling
• 0~260 VAC <at> 50Hz output voltage
• 165(D) x 120(W) x 160(H)mm
199
$
49
95
$
MP-3098
MP-3802
MP-3087
MP-3802
MP-3087
Features
Fixed output voltage. Short circuit
protection.
Compact size, high current and
variable output.
Dual output. Operated
independently. Digital voltage and
current meters.
Output Volatge
13.8VDC
0-16VDC
2 x 0-32VDC
Output Current
20A
30A, 25A continuous
0-3A (x2)
Display
N/A
Analogue Meter (backlit)
LCD (backlit)
Size (W) x (D) x (H)
170 x 160 x 85mm
148 x 162 x 62mm
260 x 400 x 185mm
DESKTOP POWER SUPPLIES
Highly reliable desktop style single-output green
adapters complying with the latest efficiency regulation
(Energy efficiency level).
• No load power consumption <0.075W
• 90-264VAC input
• 60W/120W
• 12/24/48V
60W 12V 5A MP-3252 $49.95
60W 24V 2.5A MP-3254 $49.95
60W 48V 1.25A MP-3256 $49.95
120W 12V 8.5A MP-3258 $99.95
20VA TOROIDAL
TRANSFORMER
High efficiency, small size, &
low electrically induced noise.
Easy single bolt mounting.
• Outer/Inner 74mm / 21 x 30mm.
9V+9V 1.11A SERIES 2.22A PARALLEL
MT-2082 $29.95
12V+12V 0.833A SERIES 1.66A PARALLEL
MT-2084 $24.95
15V+15V 0.666A SERIES 1.333A PARALLEL
MT-2086 $24.95
399
$
MP-3098
50VA 240VAC TO 115VAC
STEPDOWN TRANSFORMER MF-1091
Includes overheat protection. When
overheating , the thermal fuse will open,
then close after unit cools down,
restoring operation. Two pin US
socket on unit for 110V appliance
and cord plug for 240V power.
Not for use in wet areas.
• This is not dielectrically
isolated
• 50W
199
$
$
IEC LEADS
FROM
24
FROM
$
• 1.8m
• Earthed
• SAA approved
STRAIGHT IEC FEMALE TO 240V PLUG
PS-4106 $8.95
RIGHT ANGLE IEC FEMALE TO 240V PLUG PS-4107 $9.95
95
MULTI-TAPPED
TRANSFORMERS
15-30V, 30VA, 1A
MM-2008
6-14V, 30VA, 2A
MM-2004
18 95ea
$
AC MAINS CABLE
240V Power Flex fig.8 wire.
TWO CORE 7.5A WB-1560
$1.25/m or $99/100m roll
THREE CORE 10A WB-1562
$2.85/m or $229/100m roll
Conditions apply. See website for T&Cs
PS-4106
4 /m
$ 15
1/m
PVC insulation. 250V wiring.
7.5A 24 X 0.2mm. WH-3040 - WH-3042
$0.55/m or $42/100m roll
10A 32 X 0.2 mm. WH-3050 - WH-3052
$0.80/m or $72/100m roll
*
8
$ 25
HEAVY DUTY POWER CABLES
EARN A POINT FOR EVERY DOLLAR SPENT
AT ANY JAYCAR COMPANY STORE• & BE
REWARDED WITH A $25 JAYCOINS GIFT
CARD ONCE YOU REACH 500 POINTS!
FROM
$ 95
FROM
FROM
55/m¢
See website for specification.
4995
HIGH CURRENT
POWER CABLES
PVC insulation.
56A 8 gauge OFC.
RED
WH-3060
BLACK WH-3062
NERD PERKS CLUB MEMBERS RECEIVE:
10%
OFF
POWER CABLES
*
REGISTER ONLINE TODAY BY VISITING:
www.jaycar.com.au/nerdperks
To order phone 1800 022 888 or visit www.jaycar.com.au
*Applies only to cables listed above
See terms & conditions on page 8.
Page 53
POWER MANAGEMENT
CONTROL IT
These clever devices allow you to operate mains appliances using your Smartphone
across Wi-Fi, and can also turn on and off appliances in hard to reach places. Applications
include turning on lights to trick would-be burglars into thinking someone was home, or
routinely turning on a cooler or heater. Choose between hardwired or plug-in models.
Common features:
• Freely available app for Android and Apple devices
• Scheduled timer (Routine operations)
• Countdown timer (Turns off after pre-set time period)
REMOTE CONTROLLED
MAINS OUTLET CONTROLLER
MS-6122
Turn any standard mains outlet on/off via
remote! Great for hard-to-reach power points.
30m range. Remote control up to 4 outlets.
• Mains outlet: 97(L) x 55(W) x 60(D)mm
1 OUTLET PACK
MS-6148 $19.95
3 OUTLET PACK
MS-6147 $39.95
See website for full details.
PLUG-IN:
PLUG-IN WITHOUT POWER METER 240VAC 10A 2400W.
MS-6122 $59.95
PLUG-IN WITH POWER METER 240VAC 10A 2400W.
MS-6124 $64.95
HARD WIRED:
MS-6126
95
$
WI-FI WIRELESS SWITCH MODULE WITH APP
240VAC 7.5A 1800W. 1 year warranty. MS-6126
NSW CUSTOMERS: Unfortunately, these products are not available for sale in NSW.
49
$
FROM
59 95
FROM
19 95
$
TEST & MONITOR
SINGLE RCD (SAFETY
SWITCH) OUTLET MS-4013
POWER POINT AND
EARTH LEAKAGE TESTER QP-2004
This RCD (residual current
device) unit is designed to cut
power within a second in the
event of a fault condition, thereby
preventing electrocution.
• Test function
• Reset button
• 10A 240V rated
Assess the safety of installed main sockets
and earth voltages, and identify dangerous
electrical installations.
• Rated current: 30mA +/-5%
• Rated voltage: 230VAC <at> 50Hz
• Buzzer and three LEDs
assist to quickly
identifies issues
• IP65 rated enclosure
$
2795
MAINS POWER METER
MS-6115
Shows how much an appliance is
costing to run and tracks the total
power being used.
• 10A max rating
NOT AVAILABLE IN NSW
$
34 95
2195
$
REDUCE YOUR POWER BILL WITH LED LIGHTING
BRIGHT 12V LED STRIPLIGHTS WITH SWITCH
Encased in an attractive aluminium alloy, this pre-assembled LED
strip features a generous beam angle with evenly distributed
light. 12VDC powered.
280 LUMEN 313mm long.
ST-3930 $24.95
520 LUMEN 513mm long.
ST-3932 $34.95
$
FROM
24 95
240V IP65 180 LED LIGHT FIXTURE
ST-3945 WAS $99.95
Ideal replacement for traditional flourescent lights. Energy
efficient and produces 2600 lumens. Weatherproof and dustproof.
IP65 rated suitable for indoor and outdoor use. Comes with
mounting bracket and a 1.8m length of lead with mains plug.
• 2600 lumen
• 30W power
• 675(L) x 135(W) x 93(D)mm
50% OFF DIMMER FOR NERD PERKS CARD HOLDERS*
Valid with purchase of ST-3930 or ST-3932
*
ST-3938 VALUED AT $14.95
ULTRA BRIGHT IP67 WATERPROOF
LED FLEXIBLE STRIP ZD-0579
Fully encapsulated, waterproof, perfect for
any outdoor application. Daisy chain strips
together for longer length. Ultra bright, 960
lumens. 12VDC.
$
39 95
LOW COST 5M FLEXIBLE
ADHESIVE LED STRIP LIGHTS
$
69 95
ea
Can be cut to size and back
with adhesive tape. Two colour
temperatures available. 12VDC. 950
Lumens/metre.
COOL WHITE ZD-0575
WARM WHITE ZD-0577
NOW
79 95
SAVE $20
MR11 LED REPLACEMENT LIGHT
G4 LED REPLACEMENT LIGHT
High brightness MR11 LED globes commonly
used for lighting caravan and marine
interiors, desk lamps, and also used in retail
shop ventilated display cabinets.
• 12VAC/DC, 2.2W
• 230 lumens
COOL WHITE
ZD-0650
WARM WHITE
ZD-0652
An easy replacement for a G4 2-pin type
halogen globe that uses significantly
less power. Great for benchtop lighting,
reading lamps, and a whole host of other
applications.
• 12VAC/DC, 2.2W
• 230 lumens
COOL WHITE
ZD-0655
WARM WHITE
ZD-0657
14 95ea
$
Page 54
$
Follow us at facebook.com/jaycarelectronics
13 95ea
$
Catalogue Sale 24 June - 23 July, 2017
TECH TIP
LOWER YOUR ENERGY COST THIS WINTER
The sun still shines bright through the short winter days, so you can still capitalise on free energy using
solar. While the outside temperatures fall, if you're using electric heaters or air conditioning to keep your
home warm, solar power can drastically reduce your energy bills. The best part is, you'll then be able to
utilise the solar for summer-cooling when the mercury rises again too! Getting setup with solar is easy read more online, or ask our friendly staff at your local store. They're knowledgeable and ready to help you.
FOR MORE DETAILS ABOUT LOW COST ENERGY VISIT:
www.jaycar.com.au/save_with_solar
STEP 1: SELECT YOUR SOLAR PANEL
12V SEMI FLEXIBLE
SOLAR PANELS
12VDC. Ideal for
mounting to curved or
other irregular surfaces
such as an RV
roof or boat.
15W ZM-9149 $99.95
30W ZM-9151 $169
80W ZM-9153 $269
$
FROM
99
12V MONOCRYSTALLINE SOLAR PANELS
SOLAR POWER METER QM-1582
Smaller, thinner, higher in efficiency and more affordable
than our previous models, designed to withstand harsh
environmental conditions.
• Aluminium frame
• Junction box included
5W ZM-9053 $24.95
10W ZM-9054 $37.95
20W ZM-9055 $59.95
40W ZM-9056 $99.95
80W ZM-9057 $179
120W ZM-9058 $249
150W ZM-9059 $299
Find the optimum location for solar panels to
get the best performance. Expressed as W/
m2 or BTU/ft2.
• Includes carry case
• Range: 0-1999W/m2 (634BTU/ft2)
ZM-9153
95
$
FROM
129
$
24 95
STEP 2: CONTROL
STEP 3: STORE
STEP 4: CONVERT
12V 8A WATER RESISTANT PWM
SOLAR CHARGE CONTROLLER
12V AGM
DEEP CYCLE BATTERIES
12VDC TO 230VAC
PURE SINE WAVE INVERTERS
MP-3720 WAS $64.95
Suits wet-cell and sealed lead-acid batteries.
Pulse width modulation (PWM) for optimal 3-stage
charging. Over current, over voltage, short circuit, over
temperature and reverse polarity protections.
• 97(L) x 46(W) x 26(H)mm
Store large amounts of energy. Superior
deep cycling performance for many
different recreational and industrial
applications such as camping, boats,
motorhomes etc.
75AH 20KG WEIGHT SB-1680 $249
100AH 28KG WEIGHT SB-1682 $299
Designed to power large devices suitable for
remote power applications.
• Over & under voltage protection
• USB port
200W MI-5726 WAS $199 NOW $169 SAVE $30
400W MI-5728 WAS $249 NOW $219 SAVE $30
Visit website for full specifications.
$
NOW
54 95
SAVE $10
SOLAR CHARGE CONTROLLERS
WITH LCD DISPLAY MP-3129
Protect your valuable
solar installation and
maximise battery service
life with our photovoltaic
(PV) charge controller.
12V 20A MP-3129 $179
12V 30A MP-3722 $219
FROM
FROM
179
$
3.2V LIFEPO4 RECHARGEABLE BATTERIES
Lithium iron phosphate (LiFePO4) is a more chemically
stable type of lithium rechargeable cell and becoming
increasingly popular, due to increased safety and
longer cycle life over traditional Li-ion cells.
FROM
1195
$
SB-2305
$
169
$
FROM
249
SAVE $30
Power 12V devices from your
car cigarette lighter socket.
1.8m long.
• LED power indicator
• Supplied with 8 DC plugs
9
$ 95
3.7V LI-ION
RECHARGEABLE BATTERIES
15A CIGARETTE SOCKET
TO 8MM EYE TERMINAL
Choose between nipple or solder tabs to make into
battery packs for replacement or new projects.
PT-4451
Power your 12VDC cigarette
lighter plug devices from
a range of 12VDC
sources.
• 15A max.
SB-2301
FROM
10 95
$
To order phone 1800 022 888 or visit www.jaycar.com.au
CIGARETTE LIGHTER
2 WAY SPLITTER
CIGARETTE LIGHTER
ADAPTOR CABLE PP-1996
12 95
$
WITH 2 USB PORTS
PP-2136
Power 2 12V accessories
and 2 x USB devices at the
same time. 12/24VDC.
• Under-dash or panel
mounting
15 95
$
3 WAY CIGARETTE
LIGHTER SOCKET
WITH USB &
VOLTMETER PP-2120
Power up to 7 devices! 3 x cigarette lighter
sockets, 2 x high-current 2.4A USB charging
sockets, and 2 x standard 1A USB charging
sockets. 12/24VDC.
See terms & conditions on page 8.
$
29 95
Page 55
WHAT'S NEW?
PCB MOUNT PLUGS & SOCKETS
A new range of PC mount connectors to
suit the latest USB & HDMI technologies.
USB:
TYPE-A 3.0 MALE
PP-0923
TYPE-A 3.0 FEMALE
PS-0924
PP-0925
TYPE-A MICRO 3.0 MALE PP-0925
TYPE-A MICRO 3.0 FEMALE PS-0926
TYPE-B 3.0 FEMALE
PS-0928
TYPE-C 2.0/3.0/3.1 MALE
PP-0929
TYPE-C 3.1 FEMALE
PS-0930
HDMI:
TYPE-A MALE
PP-0941
TYPE-A FEMALE
PS-0942
MICRO FEMALE
PS-0946
PP-0941
MINI PLUG
PP-0943
MINI FEMALE
PS-0944
3 ea
DETACHABLE WALL
PLATE DOUBLE
ADAPTOR WITH 2 USB
PP-0929
PORTS MS-4009
Can be easily fixed
to an existing
power outlet
without opening
and rewiring.
2 x USB ports 5V,
3.1A (total).
• 230-240VAC,
• 10A (Max.), 2400W
$ 95
JAYCAR
JINDALEE
601 SEVENTEEN MILE ROCKS RD,
SEVENTEEN MILE ROCKS, QLD
PH (07) 3715 6377
JAYCAR
ALEXANDRIA
366-370 BOTANY RD,
BEACONSFIELD, 2015 NSW
PH: 02 9699 4699
39 95
14 95
SOLDERING
TOOL KIT TH-1851
Heatsink clip, Phillips screwdriver, springloaded tweezers and 3 double-ended tools
for poking, scraping, leg-bending and
flux-removal.
AUSTRALIAN CAPITAL TERRITORY
HEAD OFFICE
320 Victoria Road, Rydalmere NSW 2116
Ph:
(02) 8832 3100
Fax:
(02) 8832 3169
ONLINE ORDERS
Website: www.jaycar.com.au
Email:
techstore<at>jaycar.com.au
FREE CALL ORDERS: 1800 022 888
$
$
PP-0944
OPENING SOON!
3000A TRUE RMS AC
FLEXIBLE CLAMP METER
Belconnen
Fyshwick
Ph (02) 6253 5700
Ph (02) 6239 1801
Tuggeranong
Ph (02) 6293 3270
NEW SOUTH WALES
Albury
Alexandria
Ph (02) 6021 6788
Ph (02) 9699 4699
Bankstown
Blacktown
Bondi Junction
Brookvale
Campbelltown
Castle Hill
Coffs Harbour
Croydon
Dubbo
Erina
Gore Hill
Hornsby
Hurstville
Maitland
Mona Vale
Newcastle
Penrith
Port Macquarie
Rydalmere
Shellharbour
Smithfield
Sydney City
Taren Point
Tuggerah
Tweed Heads
Wagga Wagga
Warners Bay
Warwick Farm
Ph (02) 9709 2822
Ph (02) 9672 8400
Ph (02) 9369 3899
Ph (02) 9905 4130
Ph (02) 4625 0775
Ph (02) 9634 4470
Ph (02) 6651 5238
Ph (02) 9799 0402
Ph (02) 6881 8778
Ph (02) 4367 8190
Ph (02) 9439 4799
Ph (02) 9476 6221
Ph (02) 9580 1844
Ph (02) 4934 4911
Ph (02) 9979 1711
Ph (02) 4968 4722
Ph (02) 4721 8337
Ph (02) 6581 4476
Ph (02) 8832 3120
Ph (02) 4256 5106
Ph (02) 9604 7411
Ph (02) 9267 1614
Ph (02) 9531 7033
Ph (02) 4353 5016
Ph (07) 5524 6566
Ph (02) 6931 9333
Ph (02) 4954 8100
Ph (02) 9821 3100
Wollongong
QM-1568
Features a flexible "clamp"
loop that unclips on one side.
features min/max and data hold
& backlit LCD. CATIII 1000V and
CATIV 600V rated.
• Massive 3000A current
• Autoranging
• 2 x AAA batteries included
• 105(W) x 270(H) x 28(D)mm
(When closed)
2 USB OUTLET 3.1A
CHARGER WITH MAINS
POWER OUTLET
MS-4007
Provides up to 3.1A charging.
2 x USB ports. Single mains
socket.
• 230-240VAC, 50Hz
• 10A Max, 2400W
Ph (02) 4225 0969
QUEENSLAND
Aspley
Browns Plains
Burleigh Heads
Caboolture
Cairns
Caloundra
Capalaba
Ipswich
Jindalee NEW
Labrador
Mackay
Maroochydore
Mermaid Beach
Nth Rockhampton
Redcliffe
Strathpine
Townsville
Underwood
Woolloongabba
Ph (07) 3863 0099
Ph (07) 3800 0877
Ph (07) 5576 5700
Ph (07) 5432 3152
Ph (07) 4041 6747
Ph (07) 5491 1000
Ph (07) 3245 2014
Ph (07) 3282 5800
Ph (07) 3715 6377
Ph (07) 5537 4295
Ph (07) 4953 0611
Ph (07) 5479 3511
Ph (07) 5526 6722
Ph (07) 4922 0880
Ph (07) 3554 0084
Ph (07) 3889 6910
Ph (07) 4772 5022
Ph (07) 3841 4888
Ph (07) 3393 0777
VICTORIA
Altona
Brighton
Cheltenham
Coburg
Ferntree Gully
Frankston
Geelong
Hallam
Kew East
Melbourne City
Melton
Mornington
119
$
Ph (03) 9399 1027
Ph (03) 9530 5800
Ph (03) 9585 5011
Ph (03) 9384 1811
Ph (03) 9758 5500
Ph (03) 9781 4100
Ph (03) 5221 5800
Ph (03) 9796 4577
Ph (03) 9859 6188
Ph (03) 9663 2030
Ph (03) 8716 1433
Ph (03) 5976 1311
Ringwood
Roxburgh Park
Shepparton
Springvale
Sunshine
Thomastown
Werribee
18 95
$
Ph (03) 9870 9053
Ph (03) 8339 2042
Ph (03) 5822 4037
Ph (03) 9547 1022
Ph (03) 9310 8066
Ph (03) 9465 3333
Ph (03) 9741 8951
SOUTH AUSTRALIA
Adelaide
Clovelly Park
Elizabeth
Gepps Cross
Modbury
Reynella
Ph (08) 8221 5191
Ph (08) 8276 6901
Ph (08) 8255 6999
Ph (08) 8262 3200
Ph (08) 8265 7611
Ph (08) 8387 3847
WESTERN AUSTRALIA
Belmont
Bunbury
Joondalup
Maddington
Mandurah
Midland
Northbridge
O’Connor
Osborne Park
Rockingham
Ph (08) 9477 3527
Ph (08) 9721 2868
Ph (08) 9301 0916
Ph (08) 9493 4300
Ph (08) 9586 3827
Ph (08) 9250 8200
Ph (08) 9328 8252
Ph (08) 9337 2136
Ph (08) 9444 9250
Ph (08) 9592 8000
TASMANIA
Hobart
Kingston
Launceston
Ph (03) 6272 9955
Ph (03) 6240 1525
Ph (03) 6334 3833
NORTHERN TERRITORY
Darwin
Ph (08) 8948 4043
TERMS AND CONDITIONS: REWARDS / NERD PERKS CARD HOLDERS FREE GIFT, % SAVING DEALS, DOUBLE POINTS & MEMBERS OFFERS requires ACTIVE Jaycar Rewards / Nerd Perks Card membership at time of purchase. Refer to website for Rewards/Nerd
Perks Card T&Cs. PAGE 3: Nerd Perks Card holders receive the Special price of $169 for the Lora Remote Relay Project, applies to XC-4410, XC-43920, XC-4440, XC-4482, SP-0601, RR-0564, ZD-0250 & WC-6028 when purchased as bundle. Nerd Perks Card holders
receive double points with the purchase of HP-9570, HP-9572, RR-1680, NS-3005, NS-3010, ZZ-8727 & PB-8850. PAGE 4: Nerd Perks Card holders receive double points with the purchase of NM-2806, TD-2106, TH-1828, TD-2070 & WH-5524. PAGE 5: FREE TH-1989 LED
Magnifier valid with purchase of MP-3098, MP-3802 or MP-3087. PAGE 6: 50% OFF DIMMER ST-3938 for Nerd Perks Card Holders valid with purchase of ST-3930 or ST-3932.
Arrival dates of new products in this flyer were confirmed at the time of print but delays sometimes occur. Please ring your local store to check stock details. Occasionally there are discontinued items advertised on
a special / lower price in this promotional flyer that has limited to nil stock in certain stores, including Jaycar Authorised Stockist. These stores may not have stock of these items and can not order or transfer stock.
Savings off Original RRP. Prices and special offers are valid from Catalogue Sale 24 June - 23 July, 2017.
A new, high performance
DSP BCL radio receiver . . .
aimed squarely at AM listeners!
The Tecsun S-8800
Although it is a multiband receiver, covering shortwave (with SSB), long
wave and FM (way down to 64MHz), it’s the long-neglected AM radio
listener that this new release from Tecsun Radios Australia is obviously
aimed at.
W
hen we say long-neglected,
it’s true: manufacturers seem
to have gone out of their way
to improve reception for FM listeners
and even provided many more “bells
and whistles” for short wave and even
long wave enthusiasts. But to a large
degree, AM reception has been much
siliconchip.com.au
the same for many years.
And that’s a pity, because despite
what you might think, AM radio hasn’t
lost much (if any) of its popularity and
many listeners, particularly in “the
By Ross Tester
bush” have been crying out for a decent AM radio.
They might just have one with the
Tecsun S-8800.
It’s not a cheap set – with a recommended retail price of $349, you’d expect pretty good performance. Early
tests in fringe AM listening areas (eg,
July 2017 57
anywhere any distance from a transmitter!) suggest that the S-8800 is right
up there, even exceeding many higherpriced sets in its ability to not only resolve distant stations but to maintain
them at an enjoyable level.
OK, what does it offer?
The first thing you’ll notice when
you unpack the box is the infrared
remote control. What’s that? A radio
with a remote control?
Unusual – but it’s a bit of luxury
for the user. All functions can be controlled via this remote so you don’t
have to get up from your favourite
armchair to, for example, increase the
volume! It will also allow you to turn
the receiver on and off, change bands,
scan (either memories or the band) and
even let you enter frequencies directly
via the keypad.
Another major departure from most
receivers is the inclusion of rechargeable lithium-ion batteries, as distinct
from the AA, C or even D cells most
use. So you won’t be forever buying
new batteries – the two 18650 cells are
Tecsun’s own brand and are rated at
2000mAh, so should give you long listening! It draws around 75mA turned
on (depending on volume, of course)
or about 80uA when turned off.
Recharging is achieved by plugging
in to any “USB” source (eg, a computer
or a USB power supply [not included])
via a mini-D USB socket on the rear.
The adaptor cable is included.
You can also run the radio from a
5V/300mA external DC adaptor – but
be warned, most “switchmode” plug-
SPECIFICATIONS
FREQUENCY RANGES
FM:
87-108 / 87.5-108 / 76-108 / 64-108MHz (Tuning Step 0.01MHz / 0.1MHz)
SW:
1711- 29999 kHz (Tuning Step: 1kHz / 5kHz)
MW: 522 -1620 kHz (with 1kHz / 9kHz tuning step)
520 -1710 kHz (with 1kHz / 10kHz tuning step)
LW:
100 - 519kHz (Tuning Step: 1kHz / 9kHz)
SENSITIVITY
FM (S / N = 30dB): <3μV
MW (S / N = 26dB): <3mV / m
LW (S / N = 26dB): <5mV / m
SW (S / N = 26dB): <20μV
SSB (S / N = 10dB): <3μV
SELECTIVITY (Factory default of AM IF bandwidth is Narrow Band)
FM:
>35 dB (± 200kHz)
MW/LW:
>40 dB (± 9kHz)
SW:
>40 dB (± 5kHz)
S/N RATIO
FM:
MW/LW:
SW:
IFs
SSB, AM
FM:
>5dB
>40dB
>45dB
1st IF: 55.845MHz
10.7MHz
FM STEREO CROSSTALK:
>35 dB
OUTPUT POWER (distortion 10%):
450mW
pack adaptors will introduce an intolerable amount of noise. If you can find
one, choose a linear (ie transformer)
supply – or simply charge the batteries regularly.
Incidentally, the infrared remote
control uses standard “AAA” batteries, not some high-priced button cells.
We’ll gloss over the longwave (LW)
The display on the S-8800 doesn’t show much . . . but it shows enough!
58 Silicon Chip
2nd IF: 10.7 kHz
section of the receiver because there’s
not a great deal to listen to down there
(unless you’re into aircraft beacons. . .).
Longwave is used a lot more overseas, particularly Europe, and because
of the characteristics of this band, you
might be able to tune into some of
those stations from time to time.
The shortwave (SW) and FM bands
are much more interesting to Australian listeners, with a range of interesting stations on the shortwave bands
including amateur operators (you’ll
find them around 1.8, 3.5, 7, 10, 14,
18, 21, 24 and 28MHz), older 27MHz
CB radio (which often isn’t worth listening to!) along with emergency, business and commercial users.
Finding them can be a bit of a “hit
and miss” affair but once found, you
do have the luxury of being able to
store up to 650 stations in memory.
The shortwave section covers just
above the broadcast band (1.711MHz)
through to almost 30MHz (actually
29.999MHz and with its single sideband plus AM reception, along with
fine tuning, you’ll be pulling in stations that you didn’t know existed!
FM is quite different to what you
might expect. As well as the FM broadsiliconchip.com.au
Rear and side views show there aren’t a huge number of controls – most of the work is done by the receiver itself. On
the back you have connectors for antennas and a mini-USB charging socket, while the side has switches for internal and
external antennas, DX and local reception plus stereo (on FM) headphone socket and line outs.
cast band (88-108MHz) you can also
tune in as low as 64MHz. In this 6488MHz “slot” there’s quite a lot of twoway radio used by all sorts of businesses and organisations.
Both the FM and SW bands can be
significantly enhanced by the connection of an external antenna; provision
is made for this on the back panel via
a BNC socket.
AM reception
As we noted at the start of this review, AM (amplitude modulation) is
where the Tecsun really shines. There
are two major features required of a
good AM receiver – excellent sensistivity and excellent selectivity. The
first mainly refers to the radio’s ability to pick up very weak stations. Selectivity refers to the radio’s ability to
differentiate those weak signals from
those (perhaps stronger) on adjacent
channels.
Another important characteristic
is frequency stability – it’s one thing
tuning in that elusive, faint station –
the last thing you want is the receiver
“drifting” so you lose it.
Overlaying all this is the fact that the
Tecsun offers Digital Signal Processing
on the HF band so you virtually have
the power of a computer to help you
enjoy listening.
In deep fringe areas, far outside the
“normal” range of AM radio stations,
the P-8800 consistently outperforms
other receivers, even those costing
siliconchip.com.au
considerably more.
One feature which long-distance (or
“DX”) listeners will enjoy is the AM
bandwidth switching. When an AM
signal is noisy, being able to adjust the
bandwidth from 6kHz down to 3kHz,
or even 2.3kHz, can mean the difference between annoying noise and an
intelligible signal. Reduced bandwidth does have a cost, of course, and
that is reduced fidelity. But if there’s a
choice between receiving a station or
not, it doesn’t really matter!
You also have the choice of channel
spacing. Here in Australia, AM stations are 9kHz apart, so that is where
you’d normally have the switch set.
But if you’re listening to some overseas DX, you might want to change to
10kHz spacing. This has another benefit: you’ll extend the normal range of
520-1620kHz up to 520-1710kHz. You
can step through the dial in 1kHz steps,
if you wish.
Like the FM and SW bands, the AM
band can be rather siginificantly enhanced by connection of an external
antenna (again, connections on the
back). The difference is that the AM
external antenna input is high impedance, so a “long wire” antenna is ideal.
While (theoretically) an AM antenna
should reflect the frequency you want
to listen to, there’s an old bushie rule
of thumb: as high and as long as you
can make it!
If you do get into trouble with too
much signal (maybe from a local radio
station), there is a local/DX switch to
attenuate it.
While we’re talking about sound
quality, the Tecsun S-8800 offers 2W
of audio output, driving a relatively
large – for a radio – speaker (40mm).
You won’t suffer for lack of volume –
and there are bass and treble controls
to tailor the sound the way you want
it. And remember, all these functions
are available on the remote control.
One thing we haven’t mentioned is
its size. It’s no hand-held, at 192(W)
x 113(H) x 33mm (D), and weighs just
over half a kilogram without batteries. And we almost forgot – the Tecsun also sports a clock with various
alarm functions on its large, easy-toread LCD display.
So there it is: a great performer on
LW (for what it’s worth), SW and an
extended FM band. But an outstanding
performer on AM with a range of user
controls and functions to make listening a pleasure, rather than a chore.
If you live in, or go “bush” and want
a radio that will let you keep listening where other radios have given up,
or if you’re a city resident who wants
to give DX listening a go, try the Tecsun S-8800.
Where from:
Tecsun Radios Australia
Unit 24, 9 Powells Road,
Brookvale, NSW 2100
www.tecsunradios.com.au
SC
July 2017 59
“Over-The-Top”
rail-to-rail op amps
by Nicholas Vinen
In our Deluxe Touchscreen eFuse project this month, we’re using two
“Over-The-Top” rail-to-rail op amps which provide functions available
in few other op amps. Made by Linear Technology (now part of Analog
Devices), they are very useful in instrumentation applications.
O
p amps are one of the most
common types of IC. We est-imate that there are close to 10,000
different types available; if you discard
those which are related (single/dual/
quad versions, for example) there are
still more than 1000 distinct designs.
So it’s unusual to have design criteria so strict that you are only left with
one or two suitable types.
The combination of attributes which
make these “Over-The-Top” op amps
useful in the eFuse would also make
them valuable in other instrumentation roles.
The particular op amps have the following type codes: LT1490A/LT1491A
and LT1638/LT1639, representing dual
and quad versions respectively. The major difference between the two pairs is
the trade-off between bandwidth, noise
and power consumption.
One of their unusual features is the
fact that both the differential and common mode input range is 44V, regardless of the op amp’s supply voltage. So
you could use these op amps to measure
the voltage across a shunt that is supplying the high side of a motor running
off 36V DC, even if your op amps are
only running off a 3V supply.
That’s why they’re called “Over-The-
they do have much more flexibility than
a difference amplifier, providing traditional op amp functions, along with a
much higher input impedance for more
accurate measurements.
Other notable features
Top” and it’s a feature normally reserved for what is called a “difference
amplifier” (as distinct from an operational amplifier). Difference amplifiers
are similar to instrumentation amplifiers but they lack input buffering, having
an internal precision divider between
each input and an internal instrumental
amplifier. One example is the INA117
from Texas Instruments.
So difference amplifiers are capable
of handling very high input voltages and
tend to have very good common mode
rejection ratios (CMRR), in order to allow them to accurately measure small
differences between those input voltages. However, they are quite restricted in their applications, as they often
have fixed gain and the higher the allowable input voltage, the higher the
gain tends to be.
While the LT1490/1490/1638/1639
can’t handle particularly high voltages,
While the Over-The-Top feature is
interesting, that isn’t actually why we
chose these devices for the eFuse.
The main reason is their combination
of a very wide operating supply voltage
range, from 2V to 44V (!) along with railto-rail inputs and outputs, with an output which can swing close to each rail
(maximum 10mV) and a low typical input offset voltage of ±110µV (maximum
±800µV from -40°C to +85°C).
Two of the biggest drawbacks of traditional rail-to-rail op amps are their
limited supply voltage range (usually
2.7-16V; the LMC6482 we often use
has a rating of 3-15.5V) and the fact
that the output voltage will only swing
close to either supply rail, but not actually reach it.
While it’s impossible for an op amp
output to actually reach either of its supply rails, the op amps described here
can get very close, typically to within
about 3mV of the negative rail when
lightly loaded, as you can see from
Specifications (typical figures)
LT1490A/LT1491A
LT1638/LT1639
Supply voltage range (Vs) ........................
Quiescent current .....................................
Gain bandwidth product ...........................
Slew rate ...................................................
Input offset voltage....................................
Input bias current .....................................
Input noise voltage ...................................
Large signal voltage gain...........................
Output swing, no load...............................
Output swing <at> 5mA.................................
Output short circuit current.......................
PSRR ........................................................
CMRR <at> 1kHz ..........................................
2.4-44V
40µA/amplifier
200kHz
60mV/µs
150µV (250µV for LT1491A)
1nA
50nV/√(Hz)
1500V/mV <at> Vs=3-5V, 250V/mV <at> Vs=30V
3mV to Vs-12mV
250mV to Vs-600mV
+15, -30mA (Vs=3V), +25, -30mA (Vs=5V)
98dB
92dB
2.4-44V
170µA/amplifier
1.2MHz
380mV/µs
250µV (350µV for LT1639)
20nA
20nV/√(Hz)
1500V/mV <at> Vs=3-5V, 500V/mV <at> Vs=30V
3mV to Vs-20mV
250mV to Vs-600mV
+15, -25mA (Vs=3V), +20, -25mV (Vs=5V)
100dB
103dB
60 Silicon Chip
siliconchip.com.au
Fig.1. By comparison, the LMC6482’s
output saturation voltage is similar
when sinking 100µA+ but only drops
down to around 10mA when sinking
just 1µA.
While the LM358 isn’t a rail-to-rail
op amp, it is designed for operation
from single supplies and was one of
the earliest designs to have an output
swing that came close to the negative
rail. It’s still in common use but it too
struggles to deliver an output voltage
below 10mV.
CHARGER
VOLTAGE
RS
0.2Ω
RA
2k
IBATT
RA´
2k
Q1
2N3904
+
1/4 LT1491A
–
–
1/4 LT1491A
LOGIC
+
RB
2k
Q2
2N3904
+
RB´
2k
LOGIC HIGH (5V) = CHARGING
LOGIC LOW (0V) = DISCHARGING
1/4 LT1491A
–
LOAD
+
+
RG
10k
VBATT = 12V
S1
10k
VOUT
1/4 LT1491A
–
90.9k
1490A TA01
Power supply, bandwidth and
noise
VOUT
V
IBATT =
= OUT AMPS
(RS)(RG/RA)(GAIN) GAIN
S1 = OPEN, GAIN = 1
RA = RB
S1 = CLOSED, GAIN = 10 VS = 5V, 0V
Fig.2: an example circuit from the LT1490 data sheet which takes advantage
of the “over-the-top” capability of these op amps.
The LT1490/1491 have a low power consumption figure of just 40µA/
amplifier and 170µA/amplifier for the
LT1638/1639. The trade-off in achieving this is in the bandwidth and noise
figures. The LT1490/1491 have a gain
bandwidth (GBW) product of just
200kHz while the LT1638/1639 have
a GBW of 1.075MHz. Noise figures are
50nV/√(Hz) for the LT1490/1491 and
20nV/√(Hz) for the LT1638/1639.
But for instrumentation purposes
like our eFuse, those figures are more
than adequate. A bandwidth of say
50kHz (ie, with an effective gain of
four) still results in a 0.1% settling
time of around 20µs. So if you are feeding the op amp output to an analog-todigital converter (ADC) in a microcontroller, unless you’re sampling above
50kHz, it could be an advantage as it
will act as a low-pass filter to reduce
aliasing in the ADC.
Another unusual feature of the op
amps described here is that they will
tolerate a reverse supply condition (ie,
V+ below V-) with less than 1nA of
current flow for reverse voltages up to
18V. So they could be used in batterypowered applications and powered directly off the battery without concern
for damage if it were to be accidentally
reversed. No damage will occur with
input voltages down to -2V.
And they will tolerate up to 18V on
all input and output pins in the absence
of supply voltage, allowing them to be
“shut down” by switching V+ off using a transistor. They will also tolerate
driving a capacitive load of up to 200pF,
with no extra compensation, or up to
10nF (LT1490/1) or 1nF (LT1638/9)
with an added Zobel network at the
output.
High open-loop gain (1.5 million
times) and CMRR (98dB), along with
phase reversal protection, makes these
op amps suitable for precision DC work.
They also have a reasonably strong out-
Output Low Saturation Voltage vs Load Current
1000
put drive, of ±25mA, rising to ±40mA
at higher supply voltages. For AC/audio
applications, total harmonic distortion
(THD+N) is quite low at around 0.002%,
limited mainly by noise.
Conclusion
These op amps are excellent general purpose devices and come about
as close to an “ideal op amp” as we’ve
seen. They have little change in performance over a wide range of supply
voltages and their high maximum supply voltage makes them very useful in
circuits with multiple supply rails.
It also means that they will be useful
in a variety of situations, whether you’re
building a circuit which runs off a single Li-ion cell, a 12V power supply or
with substantially higher voltage rails.
We expect we will use this family
of op amps in more projects in future.
They are available from Digi-Key (DK)
and element14 (e14), with catalog codes
as follows:
LT1490ACN (dual, 200kHz, DIP) –
DK LT1490ACN8#PBF-ND; e14 9560530
LT1490ACS (dual, 200kHz, SOIC) –
Fig.1: a plot of the typical
output voltage of four
different op amps when
fully to the negative rail
versus load current. The
LT1490/1638 op amps go
lower than most other
high-voltage-capable railto-rail op amps. Note that
to take advantage of this,
the op amp output must
be very lightly loaded.
siliconchip.com.au
Output Saturation Voltage (mV)
TA=25°C
DK LT1490ACS8#PBF-ND; e14 1663433
VS=5V
LT1491ACN (quad, 200kHz, DIP) –
100
DK LT1491ACN#PBF-ND; e14 9560556
LT1491ACS (quad, 200kHz, SOIC) –
DK LT1491ACS#PBF-ND; e14 1330667
LT1638CN (dual, 1.2MHz, DIP) –
LT1490
10
DK LT1638CN8#PBF-ND
LT1638
LT1638CS (dual, 1.2MHz, SOIC) –
LMC6482
DK LT1638CS8#PBF-ND; e14 1663461
LM358
LT1639CN (quad, 1.2MHz, DIP) –
DK LT1639CN#PBF-ND
1
0.1µ
1µ
10µ
100µ
1m
Sinking Load Current (A)
10m
100m
LT1639CS (quad, 1.2MHz, SOIC) –
DK LT1639CS8#PBF-ND; e14 1330682
SC
July 2017 61
SERVICEMAN'S LOG
Perished belts stop a cassette deck
Thirty years ago, virtually everyone had
one or more cassette players or decks and
cassettes were the favoured music source
when you were on the move. But few are
used now, so much so that I thought a recent
request to fix a dual cassete deck was a joke.
A few weeks ago, another April
Fool’s day slipped past almost unnoticed, as is typical for me. In fact, I
don’t really get into the spirit of Halloween, Valentine’s Day and other
similar "celebrations".
I suppose I’m being cynical but
to me they seem to be just another
opportunity for marketing people to
exploit an occasion for commercial
gain.
When I was growing up, nobody I
knew ever gave Halloween a second
thought, other than perhaps to acknowledge it as an ancient, vaguely
religious date on the theological calendar, celebrated overseas, mainly by
Americans.
Yet in recent years, the creeping
Americanisation of our society has
resulted in costumed "Trick or Treaters" going from house to house begging for lollies while in the weeks before, retail chain stores hawked cheap,
Halloween-themed merchandise hoping to cash in.
Kids probably have no idea what it
even means. Give it a few years and
we’ll probably be celebrating Thanksgiving…
I can recall two rather excellent
technology-related April Fool’s gags
that at the time made quite an impact.
The first was in the mid-nineties when
PlayStation gaming was new and all
the rage; one of the biggest games at
the time was called Tomb Raider. I was
one of many who bought the game and
it was worth every penny.
It was also ground-breaking in
graphics, in-game physics and for introducing Lara Croft, the main character.
62 Silicon Chip
This stirred up a lot of controversy
in the increasingly politically-correct
landscape of the times. On the one
hand, it was commendable to have
a female heroine, instead of some
muscle-packed, wise-cracking, cigarchomping meathead like Duke Nukem
and his mates.
Yet on the other, she was created
with some rather unrealisticallyproportioned, um, attributes, raising
the hackles of feminists everywhere.
Despite the backlash, the game sold
millions of copies and the franchise
went on to rake in gazillions of dollars for everyone involved.
At the height of this fervour, one of
the bigger technology magazines of
the day published an article revealing a supposed "Easter egg" that players could activate within the game by
tapping their PlayStation controller
buttons in a certain sequence, in time
with a Spice Girls hit song of the day.
If they got it right, players could
complete the rest of the game with Lara
Croft naked! Nowadays, this might
seem a little lame but back then, it was
huge news as rumours had followed
the game since it was released about
a supposed "nude patch" built in by
the developers.
However, players soon discovered
that no matter how hard they tried,
I couldn’t get the hack to work. Er, I
mean, they couldn’t get it to work.
I’ll bet a lot of controllers were worn
out trying, but it was all an elaborate
April Fool’s joke on the part of the
magazine and it certainly fooled a
lot of people.
In a similar vein, around the late
nineties, a technology web-site pub-
Dave Thompson*
Items Covered This Month
•
Panasonic RX-FT570 dual
cassette deck repair
•
•
Currawong amplifier repair
Sometimes a drill repair isn't
always best
*Dave Thompson runs PC Anytime
in Christchurch, NZ.
Website: www.pcanytime.co.nz
Email: dave<at>pcanytime.co.nz
lished a story on how to defeat the
hard-wired frequency lock on a particular model of the latest Intel processor, thus allowing it to be overclocked.
The back story to this is quite interesting; the then-new Celeron and
Pentium range of processors from Intel sold like hot-cakes because previous versions of these CPUs had been
an overclocker's dream, with some users running the Celeron versions hundreds of megahertz faster than they
were designed and rated for, just by
upping the frequency multiplier on
their motherboards.
Until this was discovered, overclocking any CPU usually resulted in
an extremely unstable system and in
most cases just wasn’t worth the effort.
However, experimenters soon discovered the Celeron processor, as long as
it was kept cool, could be thrashed
mercilessly and would remain stable
and very usable at ridiculous speeds.
These supposedly lower-end processors cost far less than the Pentium
equivalent, yet over-clocked Celerons
were out-performing their pricier Pentium cousins, something Intel hadn’t
considered and certainly didn’t approve of, and were soon designing
ways to stop people doing it once
and for all.
To prevent buyers getting more for
less, the following generation of Intel
processors featured a bus lock that
prevented users over-clocking them
by the usual means. This meant that
you couldn’t increase the clock fresiliconchip.com.au
quency and run the chip faster – well,
you could, but the processor wouldn’t
take any notice and would simply chug
along at its rated speed.
That is, until a respected technology-related website published a ‘howto’ on how to defeat this locking system. Apparently, owners could physically disable the lock by drilling a tiny
hole into their chip at a very precise
location, the process of which was
clearly detailed in the article.
And of course, many overclockers
raced out to their workshops and got
their electric drill and proceeded to
drill this hole in their CPU, failing to
notice the publication date of the story;
April 1st. It was all an April Fool’s gag
and one the publishers considered so
obviously fake and so patently ridiculous that nobody in their right mind
would actually go ahead and do it.
Sadly, they underestimated their audience and had to quickly upload a retraction and apology in the hope that
it would stop the wholesale slaughter
of thousands of Celeron processors.
It was an excellent prank; unless you
were fooled by it!
I mention all this because on April
1st last, I got a call from a guy asking me if I sold cassette tape players
or more specifically, a portable cassette player with two tape decks so he
could do tape-to-tape dubs. This caller
siliconchip.com.au
happened to sound very much like a
friend of mine who is well known for
his prank phone calls, such as calling
and claiming to be from Inland Revenue, or the police etc.
He’s gotten me a few times over the
years and given this current caller’s
slightly odd vocal syntax was very
similar to my friend’s, I congratulated
him on his inventiveness but informed
him I’d busted him this time.
Embarrassingly, it was a real customer with a real request and I had
to eat a big piece of humble pie and
apologised profusely. Once I’d explained my April Fool’s supposition,
we had a bit of a laugh and got down
to business.
He explained that he was a choirmaster and his method of teaching the
choir-members' separate vocal parts
was to record his part onto a cassette
tape using his trusty portable Panasonic RX-FT570 tape recorder. He’d then
make several copies using the twin
tape decks and pass the tapes out to
other members to be learned.
Hmmm, I still wasn’t sure this
wasn’t my prankster friend, riding
out the gag for as long as he could.
The caller further explained he’d used
this system for the last 20 years and it
July 2017 63
Serr v ice
Se
ceman’s
man’s Log – continued
had worked perfectly until the previous day, when he had gone to record
something and discovered the tape no
longer turned in the drive.
He remarked that he could still hear
the motors whirring away inside the
unit, but the tape was no longer moving in either deck. He suspected it was
time to throw it into the skip and buy
another one, hence his calling around
the different companies in the phone
book.
By the sounds of it, he was not having much success. By now I was convinced this was a serious request and
being relatively up-to-date with all
this modern digital recording stuff,
I politely suggested that perhaps he
would consider modernising? Instead
of tapes, people these days were using
digital voice recorders, and this might
be the answer.
He responded with a very resounding: “No!” He told me he was "oldschool", didn’t own a computer and
had no interest nor idea how any of
this new-fangled stuff worked. I had
to be honest and tell him that I imagined the only suitable cassette players
around now would be second-hand
from the auction sites, as I knew of
nobody selling them new.
Thinking the best way forward
might be to repair his old one, I asked
him a few more questions about what
his recorder was doing when he
pushed the play button or tried rewinding and so on. He repeated that
when he pushed any of the buttons,
he heard noises from within but the
tape didn’t roll.
He’d tried several tapes so it wasn’t
a jammed cassette and the radio and
speaker side of things still worked as
normal. I told him that it sounded to
me like a belt, capstan, tension wheel
or something similar had come adrift
in the transport mechanism, but given
the thing was almost half as old as I
am, it wasn’t all that surprising.
He was under the impression that
because the recorder had seen so much
use over the years, it was likely time
for a new one anyway. However, being a Panasonic, I knew it would have
good hardware in it and suggested it
wouldn’t hurt for me to at least take
a look at it before he junked it, as it
might be repairable.
He confessed he hadn’t even thought
64 Silicon Chip
about that option and became quite
animated knowing that I might be able
to fix it. I warned that he shouldn’t get
too excited until I had a look and arranged for him to bring it around to the
workshop the following day.
When he arrived, he was a lot older
than I’d pictured by his voice, which
explained why he was not overly interested in adopting more modern
technology. I did mention briefly the
possibilities of digital recorders and
pointed out there were cassette to
digital converters available these days
but he was convinced it would be too
complicated.
I happened to have a digital voice
recorder I’d constructed a few years
before and dragged that out to show
him. And while he seemed quite impressed by it, he made the comment
that as all his colleagues were much
like him with regards to modern technology and would likely have trouble
getting to grips with using something
like this; perhaps it would be best to
stick with their tried-and-true method.
And that was fine by me; it worked
for them well in the past so now all I had
to do was try and get this thing working. I assured him I would try my best.
Anyone who has had a tape deck
of any description apart before will
tell you that they are complicated devices. The concept is simple enough:
a motor drives a rotating shaft which
turns a spool (the capstan) inside the
cassette, causing the audio tape to be
dragged past the record or playback
head at a certain speed.
The magnetic information on the
tape is read by the head and passed
on to the pre and main amplification
system, whether it is an internal amp
as in this portable device or an external amp as in a home stereo system.
However, the mechanism to do this
is anything but simple. A typical cassette player usually contains a transport mechanism module and this can
be unbolted and replaced as a whole
if required, or sometimes individual
parts can be replaced if they wear out.
In this particular unit, there are two
such modules, sitting side-by-side and
each individually operated by its own
set of buttons but driven by the same
motor and belts arrangement. The core
of any such system comprises the various rubber drive belts that turn the
different spools, gears, capstans and
wheels.
siliconchip.com.au
This view of the Panasonic's RX-FT570 dual-cassette transport mechanism
shows some of the belts. All of the belts had perished or cracked.
Considering these tape systems were
designed in the days before computers,
they really are a feat of engineering and
design. Each of the two systems consist of dozens, if not hundreds, of tiny
springs, levers, cogs, bearings, gears
and pulleys, all designed to move the
tape at a constant speed over the playback and record heads.
If the speed was to change, the resulting distortion, including wow and
flutter, would be immediately noticeable, so it is vital that the tape speed
remains absolutely constant, and at
the exact speed required.
It wouldn’t be so bad if the tapes to
be played were recorded only on this
machine, as then it wouldn’t matter
what speed the tape travelled at, as long
as it was the same for record and playback, but pre-recorded tapes could also
be played and so the playback speed
must match a standard recording speed.
When belts start to stretch and slip, the
speed changes and problems arise.
In the old days, one would simply go down to the local supplier and
grab a replacement belt; you’d tell the
bloke behind the counter what player you had and he would go and pick
out the required belts and you’d be
on your way.
Of course, those days are long gone;
one, you’d be hard-pressed to find anyone selling one belt, let alone a range,
and two, shop-keepers with that kind
of product knowledge died with the
corner grocer.
Opening the player was simplicity
itself; none of these silly, so-called security screws, just plain old Philipshead PKs. Six held the case together,
with one cleverly hidden under the
siliconchip.com.au
folding handle to reinforce the top
section and once removed, the case
split apart.
Demonstrating the class and quality
of this era of manufacturing were the
plugs and sockets connecting speakers, antenna and battery compartment;
once the plugs were separated, the
front of the case came away completely,
revealing the two transport mechanisms in all their glory.
I could see straight away that one
of the belts was lying askew and after
removing a couple of retaining screws
and turning the entire tape-playing
section over, I could see another, smaller belt also off its tracks.
I was actually happy to see this, even
though I knew it unlikely I had the correct-sized belts in my bits-boxes, as it
meant that replacing them would likely get this thing up and running again.
It could just as well have been any one
of the multitudes of tiny coil springs,
leaf-springs, actuators, trunnions,
levers, mechanical sensors or other
impossible-to-replace parts that had
worn out, fallen off or failed instead.
A closer inspection revealed that
all of the belts were in a pretty sorry
state, with minute cracking and perishing obvious under the magnifying
glass, so I decided to replace them all.
As is becoming the norm these days,
I hit AliExpress and there was a belt
kit containing 30-odd different-sized
belts, all for a couple of bucks shipped
to my door. I promptly ordered the kit.
The only worry was disassembling
the motor and transport assembly
enough to get the old belts out and the
new ones in, and this is where lots of
photos and parts location awareness
pays off as every screw is specific to
its location and purpose, and mixing
them up can result in no or limited
movement.
It’s always tricky when there is a
week or more between pulling something apart and reassembly, so those
photos and even a screw map can really help. Once the kit arrived, the
belts were changed and the player reassembled as per my references and
the customer happy as Larry. Job done.
Blaming an old lady for an
amplifier mishap
P. C., of Woodcroft, SA, blamed his
80-year old Mum for his inadvertent
ham-fistedness when testing an amplifier. This is unchivalrous to say
the least but it does emphasise how
you need to concentrate when making
high voltage measurements in a piece
of electronic equipment.
In this case it was the Silicon Chip
Currawong 20W/channel valve amplifier that I had enjoyed assembling. I
had been umming and ahhing for the
past six months or so as to whether to
build the Currawong amplifier. It interested me from the moment it was
published back in 2014.
After all, I had only finished the
20W Class-A amplifier and two sets
of Senator speakers towards the end
of 2016. But the idea kept nagging at
me so I proceeded to order the PCB,
front and rear panels as well as the top
Perspex cover. After all, you only live
once and if I didn’t do it now I probably never would.
After a while the parts started to
arrive and as they did I spent an enjoyable time in the shed workshop assembling the PCB. The transformer was the
last to arrive and while waiting for it,
July 2017 65
Serr v ice
Se
ceman’s
man’s Log – continued
time was spent building, sanding and
painting the plinth. Then it was time
to begin the final assembly.
It all went together quite quickly
and the initial testing went very well
although I was a little concerned that
the HT at the cathode was measuring
375VDC whereas the value on the circuit is 310VDC. I had almost 14VAC
on the 12.6V heater supply for the
12AX7s also.
I then wondered what my mains
supply voltage was… good grief – nearly 256VAC! So much for Australia’s
official mains voltage being 230VAC.
We have recently had an underground
mains cable upgrade and a new transformer fitted across the road.
Apart from that, all the test procedures went to plan. The power LED
started out red and after about 20 seconds went green and I had HT; time to
plug in the valves. I chose the EH6L6
matched quads and the EH 12AX7s as
they seemed a good compromise between performance and price. I fitted
10W, 5W resistors across the speaker
terminals as dummy loads.
It was now time for my final voltage checks. I was concentrating hard
on not shorting anything and keeping
in mind the high voltages present. I
had the negative meter probe on the
metal valve base and the other poised
over the cathode of D1 ready to lightly
66 Silicon Chip
touch it when, out the blue came “Yoo
Hoo, Peter” in a loud, shrill voice that
could only be my Mother.
It scared the living daylights out of
me! Almost simultaneously, there was
a loud thwack sound and I now had
two very black and violently blown
fuses, F1 and F2.
This could not be good. There was
just an eerie silence followed by the
request to join my Mum and wife for
coffee and cake. Talk about bad timing!
I thought about it, decided it might be
time for a break and complied. I held
my tongue and did not mention the
chaos Mum had caused but just enjoyed the coffee.
After about an hour I came back
to the workshop for a post mortem. I
worked out that as I jumped when she
called out to me, I managed to short
the cathode of D1 to the load end of F1,
effectively shorting the 470µF, 400V
capacitor. No wonder there was quite
a loud thwack.
From here I though it might be a
good idea to test it in two steps; the
HT section first followed by the LT/
control section. My first move here
was to check D1 & D2 – both OK. At
this point I removed the plug from
CON8, leaving CON7 in place, fitted
a new 1A slow-blow fuse and gingerly
switched on.
I was greeted by the four blue LEDs
near the output transformers, glowing
brightly. The HT measured 275VDC
once more. No more problems
here, so it was onto the
LT/control section.
After the LEDs faded
down to nothing, I removed the plug from
CON7 and refitted the
plug to CON8. Doing this
meant I could work the
rest of the circuit without fear of getting zapped
from the HT supply.
Before applying power I did a quick probe
around with my ohmmeter, looking for obvious
shorts – I found nothing
so I turned it off, fitted a
new 3A slow blow F2,
switched it on again and
that blew the fuse again.
Oh, Bother! It was time
to have a closer look at
the circuit diagram of the LT power
supply.
I then noticed CON9 which does
not seem to be used or fitted on the
PCB. It does have plated-through
pads on top of the board which could
be handy for me to apply 12V DC
from a current regulated bench power
supply.
I removed the CON8 plug for total
isolation, applied 12V DC to pin 1
of CON9 (+) and the negative to the
metal frame of an octal valve base, set
the maximum current at 800mA and
switched on.
The current shot up to this maximum
and I noticed that the headphone relays
were switching in and out before the
current limit kicked in. Weird!
At this point, I also got the very faint
whiff of burning smell. Putting two
and two together, I suspected transistor Q9 and this felt quite hot to the
touch. I de-soldered it and tests revealed it had gone faulty, measuring
about 15W leg to leg.
I soldered a new one in its place
and retested in the same configuration. This time everything went OK.
The power LED would come on red
and turn to green after 20 seconds and
I had the correct supply on pins 1 &
7 of the 4093B IC. I then reconnected
the plug into CON8, fitted a new 3A
fuse and switched on to be greeted
by… nothingness!
My previous tests had proven there
was nothing wrong with REG1 or any
other component; which left only the
W04 rectifier. Reluctantly, I de-soldered BR1 and tests showed it to have
failed open-circuit, which is a blessing
because if it had failed short-circuit
who knows how much more damage
might have been done?
I did not have another in my parts
store but at this point it was only about
mid-afternoon on a Saturday so my
local would still be open. It took only
half an hour to get there and back and
fitting took a few minutes at most.
After I refitted everything I switched
it on and everything went smoothly
from there.
I set the amplifier up on the kitchen
table feeding an old set of surround
sound speakers that I use for this sort of
thing, connected my venerable Marantz
CD74 CD player and was greeted by
sweet and clear valve-amplified music.
The total parts count of this mishap only came to one transistor and a
small bridge rectifier plus four fuses,
siliconchip.com.au
so it was not a big issue and the time
from when I heard those first startling
words “Yoo Hoo, Peter” to the time it
was all up and running again was only
a matter of a couple of hours.
It should never have happened in
the first place but I kept the workshop door open that day because it
was warm and I needed the airflow
in the shed. Mum doesn't know anything about it!
In summary, it certainly was an interesting build. I chose to upgrade the
carbon resistors to metal film in the
hope it might help value drift in the
longer term as in the old days carbon
resistors used to drift high. There was
quite a wait on the two 470µF, 400V
capacitors, as well as the transformer.
The valves I ordered from a company called Evatco and they arrived
next day. I was rather shocked at the
prices of some valves. It would have
been easy to spend up to $550-600
on the valves alone. This makes me
a bit annoyed when, as a teenager in
the mid-1970s, I had collected a huge
shipping trunk full of the things and a
shed load of old radio and TV chassis
that I used to muck about with.
Then my father decided it was his
shed after all and he wanted it back;
he made me load it all into a trailer
and carted it to the local tip. We did
not really get on that well after that.
When a repair isn't the best option
A. F., of Kingscliff, NSW got a reward recently for looking at a damaged
electric drill and he didn’t do any repair work at all.
When I read Dave Thompson’s Story
about a brand new nail gun that failed
after a short period of use, it reminded
me of a brand new electric drill that
I purchased a short while ago which
failed. It eventually resulted in me receiving the most unexpected and highly rewarding gift, and I did not even
have to do any repair work!
This saga started when a young family member named Ron asked if he
could borrow my electric drill, to install some shelves in the garage of his
new home. I was reluctant to lend him
this old tool, as I had used it a lot during my renovations to my first home,
when I was struggling to pay off my
loan and also afford the renovation
costs and tools.
I explained to Ron that my drill had
to be used gently, due to its age. When
I used it, if the body of the drill became
siliconchip.com.au
warm, I knew that it was time to go for
a coffee break.
The drill was an old two-speed model with a two-stage trigger. When the
trigger was first pulled, the circuit routed the power to the brushed armature
through a single power diode, which
resulted in a half-wave DC being applied to the armature, resulting in a
slower RPM at the chuck of the drill.
Pulling the trigger all the way resulted in the diode being shorted out and
full wave 230VAC being applied to the
armature and field coil, and a higher
RPM; simple but effective.
Ron disappeared with my drill, and
it was several days later that he showed
up, with an unhappy look on his face,
like a puppy that knows it has been
naughty. He explained that my drill
had stopped working.
One sniff at the ventilation slots of
the drill and I knew from the pungent
smell of burnt varnish that he had
cooked the windings on my old drill.
Ron quickly explained that he would
replace my drill with a new one, if I
would use my knowledge of power
tools to buy myself a new suitable drill,
and buy a second one for him.
I went off to Bunnings Warehouse,
and found an Ozito brand domestic
quality drill on special for less than
$50. I bought two drills and gave one
to Ron, along with his receipt. The next
time I saw Ron, he explained that the
drill that I bought him had failed and
that he had bought a different one,
with more power.
I didn’t query Ron as to what kind
of work he was doing, as I had now
learnt that he was a “Bull in a China
Shop” kind of worker who was not
able to take a break when his tools
become hot.
I asked Ron if he had taken his
drill back for replacement, as it had a
12-month warranty. Ron said that he
had thrown his receipt away along
with the packaging. He offered me his
non-working Ozito, in case I wanted
to remove some parts from it before it
went into the recycle bin.
I was curious as to what had gone
wrong with Ron’s brand new drill,
as there was no burnt varnish smell
coming from it. I carefully opened
the drill casing, and could immediately see that the “Forward / Reverse”
double-pole double-throw switch had
deformed for some reason and the
contacts were no longer touching, to
make the circuit.
I was going to try to repair or replace
the switch when I remembered that the
unit was still under warranty. I had
worked in quality control many years
ago and I knew that the manufacturers liked to receive their failed products back, so that they could examine
them, to find out why they had failed
in actual customer service.
So I carefully reassembled the drill
and took it to Bunnings, along with
the receipt for my drill, and asked if it
could be replaced under the Ozito warranty. I was told that the drill would
have to be sent back to the manufacturer for examination, before a decision could be made.
Several weeks later I received a
phone call, asking me to call in to Bunnings, to discuss my drill. I was told
that Ozito would replace my drill but
would also offer me a no-charge upgrade to their industrial quality drill,
as they thought I would benefit from
the additional power in their heavy
duty machine. I was as happy as a motorist who is let off a speeding fine, to
be offered a better unit for free.
Some weeks later when I went to
visit Ron, I found out that we were
not allowed into the backyard, due
to his construction works. He had
been building a deck on the back of
his house and was busy drilling halfinch holes through four-inch hardwood posts. No wonder the poor little domestic duty drills had been unable to cope!
I was tempted to let Ozito know why
their drill had been unable to make the
grade but having gained a “You Beaut”
machine for free, I thought I had betSC
ter keep quiet!
Servicing Stories Wanted
Do you have any good servicing stories that you would like to share in The Serviceman
column? If so, why not send those stories in to us?
We pay for all contributions published but please note that your material must
be original. Send your contribution by email to: editor<at>siliconchip.com.au
Please be sure to include your full name and address details.
July 2017 67
Sale ends July 31st 2017.
www.altronics.com.au
1300 797 007
Build It Yourself Electronics Centre®
Mid Year Sale!
NEW!
S 9437
225
$
FREE BONUS!
Raspberry Pi®
Starter Platform Kit
S 9439 GPS module for
Google Map integration.
Valued at $44.95
A handy starter kit for educators or Pi
newbies. Includes a Raspberry Pi board,
red acrylic base, 5V 3A power supply,
GPIO breakout & breadboard.
K 9620
Raspberry Pi®
VESA Mount
NEW!
Cut, Polish, Grind,
Sand & Carve!
74.95
$
Micron® 172pc Rotary Tool Kit
T 2120
This workbench essential is just the shot for electronics projects,
crafts, hobbies and odd jobs around the house! Powerful 130W
motor (this is a real power tool!) with variable speed between 8000
and 33000 RPM. Included is a massive accessory kit of grinding
wheels, drills, cutters, sanding discs, polishing pads and more! And
it all stows safely away in a hard plastic carry case.
SAVE
24%
55
$
1080p Dashcam Recorder
This high spec recorder captures every minute
you’re driving in full 1080p HD, plus motion detect
and parking monitor modes allow footage recording even when you’re not driving!
Features: • 2.7” LCD screen • Selectable white
balance, exposure, dynamic range, resolution,
audio recording. • Optional second 720p camera
(S 9438 $54.95).
119
$
M 8194
SAVE $30
Includes jumper leads,
charger & case!
13.95
$
USB Car Jumpstarter
& 2-in-1 Floodlight
NEW!
A versatile acrylic bracket
for mounting the R-Pi behind
monitors - with or without a
bracket! VESA 75 & 100mm
compatible. Includes cable
ties & holes to secure leads.
Case sold separately, H 8957
$11.75.
ProtoHAT for
Raspberry Pi®
12
$
NEW!
Z 6307
Arduino Expansion
Shield for R-Pi
Mash the two worlds of
Arduino and Raspberry Pi
together using this handy
expansion shield with onboard
atmega32u4 and
$48
X-bee slot.
Tests 13 types of leads for continuity. A real time saver!
Tests: 6.35mm, DIN (3/5/7/8 pin), RCA, XLR (3/5
pin), Speakon (4P/8P), RJ45, USB & banana. Requires
9V battery (S 4970B $3.95). Cables not included.
T 2282
15.95
$
NEW!
Pi sold separately.
‘Roadies’
Cable Tester
This nifty 12 in 1
pocket sized saviour
helps you fix lifes
little problems
then folds up to
the size of a pack of
gum! Includes belt
pouch.
H 8190
A HAT board with soldermasked 0.1” holes and
stackable header so you dont
lose access to the GPIO pins.
Slots included for display &
camera cables.
Q 2022
The Pocket Hero
is here!
125
$
A must have for winter driving! Starts cars
from dead flat. • 300 cranking amps • Fits in
your glovebox • High power LED flood light
• Narrow beam torch • USB phone charging
• Suits 12V vehicles only.
Build It Yourself Electronics Centres
» Virginia QLD: 1870 Sandgate Rd » Springvale VIC: 891 Princes Hwy » Auburn NSW: 15 Short St
» Perth WA: 174 Roe St » Balcatta WA: 7/58 Erindale Rd » Cannington WA: 5/1326 Albany Hwy
Z 6550
40
$
Arduino Nano
Breakout Board
Plug in an Arduino nano
and quickly connect cables
to all the atmega328 pins
via screw terminals. Nano
to suit $29.95 (Z 6372).
Size: 53 x 32mm.
NEW!
Z 6263
Follow <at>AltronicsAU
www.facebook.com/Altronics
8
$ .50
Iroda®
Butane
Powered Heat Gun
A high output butane
powered hot air gun with two
nozzle attachments ideal for
heatshrinking, bending and
forming of plastics, paint and
solvent removal, auto body and
interior repair, general heating
and drying. • One-click ignition
• 550°C output • Integrated
protective collar and bench
stand. • Refillable 160g bottle
offers 3 hour run time.
NEW
LINE!
69.95
$
NEW
LINE!
T 2163
SAVE $24
Get started in electronics
with this handy 20pc kit.
T 2498
Upgrade your old clunker iron!
A jam packed starter kit including soldering iron,
multimeter, solder sucker, wire stripper, cutters, pliers
and more! Ideal for beginners & enthusiasts.
119
$
Amazingly compact handheld
10Mhz oscilloscope!
Everything you need to
disassemble and repair
most smartphones and
tablets. See web for full
contents list.
Stock up the
workbench with
this value pack
of quality double
scrubbed butane.
Doesn’t clog your
tools like the
cheap stuff!
28
SAVE 12%
Don’t let the size fool you, this oscilloscope
packs alot of features into a tiny handheld
device. It lets you take an oscilloscope
into the field with total ease. A must
have for the serious enthusiast of
technician on the go! Up to 8
hour operating time from 4 x AAA
batteries (S 4904 lithium $4.95 2pk).
$32.50
Top seller!
4 for
$
26
$
T 2164
145
$
Velleman® HPS140MK2
Smartphone/Tablet
Repair Tool Kit
Iroda Butane
4 Pack
T 2418A
This excellent multi purpose 80W soldering iron is ideal
for service technicians, schools, engineers, R&D, production work etc. Japanese long life ceramic element. 200°480°C. 0.8mm tip. 2 year warranty.
NEW!
Q 0205
315
$
T 2451
54.95
$
A tool box
essential!
T 2247A
Digital Vernier Calipers With Fractions
$47.95
Precision measuring with ease! 150mm length, suitable
for measuring internal, external and depth dimensions.
0.01mm, 0.0005” and 1/128th” display.
$
38
T 4021
ESD Safe Workbench Matting
An workbench essential! 1m x 0.5m with anti-static wrist strap.
Designed for
electronics use
Fine Tune Your
Sound System
Laser Tape
Measure
T 1552A
$39.95
30
$
T 2749
NEW!
Built to last a lifetime, this
sturdy crimper is a must have
for any tool box. Securely
crimps yellow, blue & red lugs.
9
$ .95
T 3014
All Metal Ratcher
Kwik Crimper Tool
$58
Connect Wire
Without Soldering!
Wire glue is a handy repair
compound that bonds copper
conductors together without the
need for soldering. 9ml.
44
$
Tungsten 5” Side Cutters
Super quality. Ideal for cutting
solid core steel, copper & piano
wire. HRC72º hardened jaws.
This SPL meter
measures up to 130dB
(1.4dB accuracy). Used
widely in the audio
industry for ensuring
legal sound levels.
Includes 9V battery.
Great for trades
& consultants.
Accurate to
2mm up to 30m.
Requires 2 x AAA
(S 4904 $4.95
4pk)
NEW!
89
$
.95
$179
129
$
T 2252
$50 OFF
Q 1264A
LIGHT UP YOUR WORKSPACE!
Get a crisp
clear view!
This stylish white desk
lamp provides up to
1000 lumens of crisp
‘daylight’ for your work
space. Adjustable
brightness via touch
sensitive buttons.
X 4220B
Features a mini flood
light, top mount
spot torch & SOS
beacon. Requires
3xAAA batteries
(S 4904 2pk).
Magnetic base.
39
$
X 0199A
NEW!
24.95
$
Super Bright Head Torch
$49.95
NEW!
19.95
$
X 0223
Dual Lamp
LED Pen
Torch
The
Amazing
BlockliteTM
3 in 1 LED
Work Light
Great for work or play this high
brightness 1 Watt LED torch features 7
light modes. Requires 3 x AAA (S 4904
$4.95 4pk)
With flood and
spot beam. Fitted
with magnetic
clip - great for
the glovebox.
Requires 3xAAA
batteries (S 4904
long life lithium
$4.95 2pk).
A piercing
bright LED
torch that’s
amazingly
small and runs
from standard
9V battery
(included).
X 0218
7
$ .95
30hr run
time!
Shop online 24/7 <at> www.altronics.com.au
9
$ .95
X 0220
1300 797 007
DEALS TO GET YOUR AV SYSTEM UP AND RUNNING!
349
Same sound quality as
the big brand names for
a fraction of the price!
$
pr
SAVE $50
A 2698A
Get Digital Radio: More channels, more choice!
C 0870
SAVE $100
269
$
This digital DAB+ radio tuner with Bluetooth® audio streaming provides instant
access to local digital FM stations & the music on your phone! 20 station presets.
S/PDIF & RCA outputs. Includes remote.
$109
SAVE $24
Opus One® 2x30W
Wi-Fi Wireless Ceiling Speakers
These stunning high performance kevlar cone speakers offer wireless music
streaming by connecting to your home wireless router. Playback can be via stored
music, podcasts, Spotify or other music streaming services. Plus you can install
multiple pairs to create an app controlled multi-zone audio system. Apple Airplay
allowing easy audio streaming directly from a huge array of iOS and Mac appstore
applications. Sold with active and passive speaker.
D 5584
Wi-Fi audio streaming for any amp!
This brilliant music streamer simply plugs into your
existing amplifier’s RCA/3.5mm input and pairs
with your smartphone or tablet for instant high
quality audio streaming. Can be networked into
a multi-zone system which can be controlled by
multiple devices.
Why Wi-Fi? Wi-Fi speakers typically offer better range and audio quality than Bluetooth, plus they
can be networked into a full multi-zone system which can be controlled by one or a few devices.
Stream live TV over
your wi-fi to your tablet!
70
$
79
Control your AV gear up to 200m away!
Use your remote control up to 200m away (line of sight)
from your equipment. Perfect for controlling your AV system
from the patio or entertaining area. Includes plugpacks, IR
emitter & receiver. Size 45W x 44D x 32Hmm.
64.95
99
$
$
D 2358
Handy Desktop
Monitor Mounts
Single or dual models with
springloaded gas strut
arms and USB ports in the
base for easy peripheral
connection. Suits monitors
up to 30”, VESA 75 &
100mm. Easy desk clamp
installation. Max 9kg.
A 3089
USB C HDMI & Ethernet Hub
Splits USB C port into USB 3.0, HDMI
and ethernet connection. 4K output
resolution. Easy in-line connection.
5 Way HDMI Signal Switcher
A handy switcher for connecting up
to 5 HDMI sources to a 4k/2k or
HD display. Includes plugpack.
$139
125
$
A 3216A
A 3124
NEW!
Long Distance HDMI Sender
As used by hundreds of commercial
AV installs! Send 1080p from a HDMI
source up to 50m over Cat5e/6 UTP.
Includes TX, RX & plugpacks.
69
$
A 3834
4K Upscaler & Audio Extractor
Scale 1080p to 4K/2K res. Plus optical
audio output. Includes plugpack.
99
209
$
$
H 8230 Single
H 8232 Dual
S 9359
NEW!
165
$
PB7311 30m
NEW!
99
$
SAVE $20
145
$119
$
PB7309 20m
Run HDMI over
longer lengths!
$89.95
$30 OFF
Transmit stereo audio & composite
video without cables from room to room.
30m range. IR sender built in. Includes
transmitter, receiver & plugpacks.
49.95
SAVE 24%
$40 OFF
5.8GHz Wireless AV Sender
$
Mini HDMI Repeater
Extends HDMI leads up to 25m. Inline
connection. Supports 4K <at> 60Hz.
SAVE $94
A 2796
SAVE $20
NEW!
$119
135
$
Also great for the kitchen.
Provides access to up to 14,000
global internet radio stations
streaming over your home wi-fi.
Alarm clock with snooze and
weather display. 95x115x115mm.
$
Phone for illustration purposes.
D 2804
A world of radio
at your bedside!
A 0920
$99
Watch live TV on your iPad, iPhone &
Android – without using any data.
Totally portable device with built in
rechargeable battery. Great for watching
TV anywhere you go or sending TV signals
to other devices in your home. No
internet connection required - creates it’s
own wi-fi hotspot.
$59 OFF
85
$
Magnetic ‘edge to edge’ grille.
Latest technology leads fitted
with booster unit to allow for
longer cable runs. Plugs and
booster fit down standard
25mm electrical conduit.
A 1109
Instant Bluetooth®
streaming for any amp!
$49.95
40
$
Pairs with your phone to stream your favourite
tunes to your existing audio system. Includes
3.5mm lead. Buy P 6020 1.5m lead ($6) to
hook up to RCA input on most amps. USB 5V
1A charging output.
30W 2-Way Wall Speakers
Ideal for the games room, patio or
alfresco area! Wall mount bracket
makes installation a breeze.
Aluminium grills. 130x105x170mm.
1.8kg. Sold in pairs.
$169
C 0900 White
C 0901 Black
Shop online 24/7 <at> www.altronics.com.au
129
$
SAVE $40
1300 797 007
Rare Earth Magnets!
After massive customer demand we’ve found
a source of quality rare earth magnets.
T 1464 has 4.5mm countersunk hole.
NEW!
SAVE $30
Record
CD quality
sound directly
to an SD card!
99
$
139
K 9350
Control access by the
touch of a finger.
$
SAVE $40
(SC Nov’ 2015) The Fingerprint Access Controller stores and recognises up to 20 prints and
provides quick access for authorised people.
An indoor control-panel allows easy setup of the
system, while the fingerprint reader is mounted
in the supplied wall-plate.
K 9350
Touchscreen Audio Recorder Kit
(SC June 2014) Offers hours of recording and playback time
from an internal USB rechargeable Li-Ion battery. A stereo line
input and mono mic input are provided via 3.5mm jacks, plus
an internal microphone for instant handheld recordings. 3.5mm
audio output & 3.5mm headphone output also provided. All adjustments and recording options are made via the backlit colour
touchscreen. Ideal for podcasting, educators and more!
Model
Type
RRP
T 1464
25x5mm Countersunk
$10.95
$9.95
$7.95
T 1465
25 x 5mm Solid
T 1466
10 x 3mm 4 pack
Tinker Part Pack
A huge assortment of parts for
experimenting and building.
Includes diodes, LEDs,
switches, resistors, caps,
strip board, a motor & more.
Normal RRP value $55!
30
NEW!
$
K 9640
Acrylic Sheets
$41.95
New coloured 3mm acrylic
sheets to feed to your
laser cutter. Make your
own enclosures and more!
199x199mm.
35
$
$89.95
K 6130
69
Remote Switch
Mains Timer Kit
K 4344
$
(SC November ‘14) Schedule your appliances
to turn on and off with this handy kit, helps to
save power and add convenience to almost any
appliance. Includes a RF remote mains switch.
Reduce the chance of being
‘rear ended’ with the Quick Brake kit.
The Quick Brake detects fast pedal movements between
accelerator and brake and switches on the brake lights before
your foot reaches the brake pedal.
T 1090 0.5mm
T 1100 0.8mm
T 1110 1.0mm
T 1122 1.6mm
LATEST SILICON CHIP KITS
Strip Vero Board
for prototyping.
Easiest way to
build up quick
circuit prototypes
or DIY add
on boards.
160x100mm.
NEW!
K 5350
SAVE $20
13.50
$
NEW!
44.95
$
$29
Any 2 for
H 0712
25
$
$115
95
$24.75
5 for
Quality Resin Core Solder
Premium grade for leaded soldering.
200gm reels. 60% tin, 40% lead.
Easy to build!
$
K 2610
■ H 0725 Clear.
■ H 0726 Red Transparent
■ H 0727 Blue Transparent
■ H 0730 White
■ H 0731 Black
■ H 0732 Yellow
20
$
Add a spring reverb to your favourite guitar amp.
8 Digit Frequency Meter Kit
A compact high resolution meter capable of reading
up to 55MHz (even more with an external prescaler!) Ideal for technicians, general servicing and
lab use. Can be USB powered.
(SC April ‘17) This two spring tank type reverb unit provides
reverberation effects for your guitar or other instrument.
Adds complexity and depth to your sound to impress the
punters. Easy to build and integrate into other projects
thanks to its 9-15VAC or 12-15VDC power requirement.
NEW!
K 1134
NEW!
39
$
.95
NEW!
39.95
$
NEW!
K 1137
Temperature Alarm Kit
Combat zika and other mosquito borne viruses with this
cheap and easy to build inaudible tone generator. Lures male
mozzies to their doom!
A simple temperature alarm for use
with aquariums, home brew, heating
& cooling systems etc. -33°C to
125°C range. Under and over
indicators with 90dB piezo alert.
B 0091
Build a mozzie lure trap
Sale Ends July 31st 2017
Phone: 1300 797 007 Fax: 1300 789 777
Mail Orders: mailorder<at>altronics.com.au
44.95
$
K 6075
14
$
26
.95 $
.95
P 1018A 350pc
eFuse Resettable Breaker Kit
P 1014A 140pc
(SC April ‘17) Ideal resettable fuse for
fixing equipment or automotive wiring.
Adjustable trip current between 0.3 to
10A. 9-15V DC.
Prototyping Wire Packs
Handy packs of pre cut and
trimmed solid core wire for
breadboarding your next design!
$42.50
33
$
P 1012A 1660 Hole
$47.95
38
$
P 1015A 2309 Hole
Breadboards for big designs!
Huge breadboards with aluminium bases for
those designs that are beyond the scope of
your average breadboard!
Find your nearest reseller at:
www.altronics.com.au/resellers
Please Note: Resellers have to pay the cost
of freight and insurance and therefore the
range of stocked products & prices charged
by individual resellers may vary from our
catalogue.
© Altronics 2017. E&OE. Prices stated herein are only valid until date shown or until stocks run out. Prices include GST and exclude
freight and insurance. See latest catalogue for freight rates.
An Arduino stereo
audio playback
and recording shield
The VS1053 MP3 shield is a low-cost
Arduino shield with a microSD card
slot which can decode and play back
many different audio formats. It includes a
headphone output, a tiny on-board electret
microphone and a microphone input, with the possibility of recording
audio to the Ogg Vorbis compressed file format. It's very flexible and
quite easy to get up and running.
by Nicholas Vinen
T
his month, we're publishing a
project; found on page 77, which
combines a standard Arduino board
with a VS1053b-based audio playback and recording board plus an LCD
and keypad, to make a programmable
music and audio playing and recording device.
At its heart is the shield with the
VS1053 IC, microSD card connector
and a handful of other components.
Most of the audio playback and
recording work, including encoding
and decoding, is done by the very
flexible VS1053 IC from VLSI Solutions, a Finnish "fabless" IC manufacturer.
VLSI stands for "Very Large Scale
Integrated circuit" and refers to the
fact that their products tend to be ICs
which contain hundreds of thousands,
if not millions, of transistors.
As shown in the block diagram
of the VS1053 IC (Fig.1), the chip
includes many large and complex
blocks including: a Digital Signal
Processor (DSP; a microprocessor
designed to excel at signal processing tasks); read-only and random-access memory (ROM/RAM); a stereo
ADC and DAC (including volume
control); a stereo headphone amplifier (down to 30W); a microphone
72 Silicon Chip
amplifier; a phase-locked loop (PLL;
labelled "clock multiplier") and digital interface circuitry, including two
serial buses.
All these functions are combined
to provide a complete signal path
from the microphone and line inputs
to produce compressed digital data,
and then take compressed digital data,
decode it and drive headphones or a
small pair of speakers with the resulting analog audio.
One of the keys to the power of the
VS1053 is the fact that it comes preprogrammed to decode multiple different popular audio formats such as
MP3, AAC, WMA and MP4.
It's based around a fully programmable signal processor and so, by
uploading additional code, you can
add numerous other useful functions
such as the ability to encode and
decode the free and open source "Ogg
Vorbis" audio codec and even FLAC
(Free Lossless Audio Coding).
Happily, VLSI Solutions even supply pre-written code "plugins" and
provide example code to upload
them to the VS1053 for these additional tasks.
The only disadvantage is the need
for additional memory in your host
microcontroller (ie, the device driv-
ing the VS1053) to have these plugins
ready to go as needed.
In terms of performance, the VS1053
quotes a signal-to-noise ratio at full
volume of 94dB and a total harmonic
distortion plus noise figure of 0.07%.
So it isn't quite a hifi device but then
again, since it will normally be playing back digitally compressed files like
MP3, you're unlikely to be able to get
full CD quality out of it anyway.
It's quite a power-efficient device,
using just 140mW during playback, including driving a pair of 30W earbuds
to a reasonable volume level, and just
36mW when idle with no load.
The VS1053 comes in a 48-pin
LQFP or Low-profile Quad Flat Pack.
This is a surface-mount package but
if you don't like soldering these, the
good news is that the shield comes
with all components already mounted
and it barely costs any more than the
IC itself.
The "Geeetech" shield
The original VS1053 Arduino shield
was designed and sold by Sparkfun in
the USA. If you're into Arduino you
will have heard of them as they are
one of the biggest sources of shields
and accessories.
You may have also noticed that
siliconchip.com.au
Fig.1: block diagram of the VS1053 IC. All decoding and encoding is
handled internally by the VSDSP and then streamed to either the stereo
DAC (decoding), or the SO register SCI_HDAT0 (encoding). The chip also
contains a TTL RS-232 (UART) serial debugging interface which is not
wired up by the shield.
anything they produce which becomes
popular tends to lead to much cheaper,
Chinese-sourced "knock-offs" which
are either very similar to, or in some
cases, direct copies of the originals.
While the Sparkfun VS1053 shield
is better designed, it doesn’t come with
any microphone inputs. So the knockoff version provides the easiest way to
get this features.
Sparkfun have produced shields
based on newer ICs which can do
more, but given the low cost of this one
and its ready availability, we thought
we'd have a go and see if we could
build something useful around it.
If you've been paying attention
to the burgeoning Chinese electronic module industry, as documented
in our "El Cheapo Asian Electronic
Modules" series of articles, you won't
be surprised to hear that the company behind this shield, Geeetech, is
based in Shenzhen, China, near Hong
Kong.
Nor will you be surprised to hear
that their range of products includes
parts for 3D printers, Arduino type development boards and shields, UAV
components (ie, drones) and all sorts
of breakout and sensor boards.
Anyway, turning our attention back
to this particular shield, we've traced
siliconchip.com.au
out its circuit (which as far as we can
tell, is not available anywhere else)
and it is shown in Fig.2. While, as we
said, it's pretty much based on the sample circuit, there are a number of odd
design decisions here, some of which
violate best practices and deserve an
explanation.
Firstly, you will note that IC1 runs
off 3.3V and 2.5V supply rails but a
number of its I/O pins, including inputs, are connected directly to Arduino pins which will be driven to +5V or
thereabouts when taken high. There's
no mention of any 5V-tolerant inputs
in the VS1053 data sheet and it gives
an "absolute maximum" rating of 3.6V
on all pins.
Clearly, many of these shields are
in use and apparently without major
problems (including our prototype).
Measurements on our prototype
suggest that what actually happens
when you're using the shield is that
input protection clamp diodes conduct, pumping up the 3.3V supply rail
to around 4.1-4.2V because of current
flowing from the Arduino outputs. Apparently, the VS1053 chip is able to
survive this, despite an absolute maximum supply rating of 3.6V.
This is not a design practice we
would recommend. At the very least,
some series resistors to limit the current would be a good idea. In fact, on
the Sparkfun VS1053 shield board,
a 74HC4050 CMOS hex level shifter
IC is used to reduce the swing on the
MOSI, CS, DCS, SCK and reset lines
from the Arduino to VS1053 in order
to protect the latter. So the designers
of that board must have had the same
misgivings that we do.
Similarly, the microSD connector
is wired up to Arduino pins D9, D11,
D12 and D13 directly. Each pin has a
4.7kW pull-up to 3.3V and thus would
allow the use of open-collector outputs
on the micro.
But the ATmega8 chip used in most
Arduino boards doesn't have direct
support for open collector outputs
and the 4.7kW resistors would severely limit the signalling speed on these
lines anyway.
So again, it seems that the designers are relying on the microSD card to
be 5V tolerant, or its internal clamp
diodes to avoid damage. It seems to
work, but we wouldn't have designed
it this way.
As mentioned above, the MOSI
and SCK lines which are shared
between the SD card and VS1053 IC
are level-shifted by the 74HC4050 IC
in the Sparkfun shield. The remaining
spare channel on that IC is also used to
reduce the swing on the CS line for the
microSD card down to 3.3V.
One possible solution to the lack
of level-shifting would be to use an
Arduino host board which runs off
3.3V, although these are not very common.
Turning back to the shield, the
next odd thing you will notice if you
peruse the VS1053 data sheet is that it
specifies another "absolute maximum"
rating, this time for the processor core
supply voltage (CVDD) of 1.85V. And
yet the Geeetech shield uses a 2.5V
linear regulator to provide this rail!
We don't know if it's because
Geeetech found a skip bin full of 2.5V
regulators, or if they found that the
chip performed better with a 40%
higher core supply voltage than recommended.
It's even possible (though unlikely)
that the VS1053 chip on the shield
is itself a knock-off which needs a
higher supply voltage. Regardless, the
shield works fine but it certainly is a
bit weird.
One nice feature of this shield is that
it incorporates an on-board electret
July 2017 73
microphone (with interface circuitry
exactly as suggested in the VS1053
data sheet) along with a 3.5mm linein jack socket, fed to two separate inputs on the main IC.
Note though that only the tip connector of the jack socket (labelled
"MIC") is wired up, so you can only
record in mono.
At the playback end, the outputs
are fed directly to another 3.5mm jack
socket, this time in stereo. But the
sleeve of this connector is not wired
to ground, rather, it goes to the "GBUF"
output of IC1 which provides a buffered reference voltage, at the same
level as the quiescent voltages for the
LEFT and RIGHT output pins.
This is fine for driving headphones
or earphones directly, or even small
passive speakers (although they will
have to share the negative connection).
However, you may run into trouble
if you are connecting the output to an
amplifier, if that amplifier's ground is
Earthed and so is your Arduino board
(through any connection between a
ground and Earth). This will effectively
short the GBUF voltage out.
In that case, you will need to connect DC-blocking capacitors in series
with the left and right signals. Such
capacitors are a feature of the Sparkfun shield, but not this one.
The good news though is that provided the input impedance of your amplifier is high, they don't need to have
an especially high value. 1µF plastic
film (MKT/MKP) capacitors should
do just fine.
The VS1053 derives timing, both
for its CPU and sampling clocks, from
a 12.288MHz crystal. This is stepped
up internally by a PLL to provide the
CPU clock of around 54MHz.
There are two LEDs on the shield.
One is red and is connected across the
output of the 3.3V regulator, indicat-
ing the presence of power, while one
is green and is connected between the
CS line and ground, indicating activity. Both have a 1kW series currentlimiting resistor.
The DREQ output of IC1 is connected to Arduino pin D2. This is used to
signal the Arduino to feed more audio
data or to indicate when the VS1053
is ready for commands. The Arduino
is normally configured to generate an
interrupt when this goes high.
You may have noticed that the
VS1053 IC has several GPI/O pins
which can be set up by the user for
various purposes.
Most of them are not connected to
anything on this shield, or simply have
100kW pull-down resistors connected.
GPIO0 doubles as the "SPIBOOT" line
and needs a 100kW pull-down so that
it will boot off its internal memory
rather than trying to load its boot data
over an SPI bus.
Fig.2: circuit diagram for the Geeetech VS1053 shield. Many of the voltage levels in this circuit run at questionable levels,
such as the +2.5V line delivered to CVDD (40% higher than the maximum 1.85V).
74 Silicon Chip
siliconchip.com.au
Similarly, GPIO1 needs a pull-down
as it will activate "real-time MIDI
mode" if held high when the chip
emerges from reset. We're not sure why
GPIO4 has a pull-down resistor as it
doesn't seem necessary.
Finally, the shield provides a reset
button which parallels the Arduino's,
in case the one on the main board is
inaccessible with the shield plugged
in.
Driving it from an Arduino
The Arduino can read or write data
on the microSD card using the MISO/
MOSI/SCK 3-wire SPI bus on pins
D11-D13 while it's driving the SD_CS
line on pin 9 low.
The X_CS and X_DCS lines on
pins D6 and D7 are left high during
this time, so only the microSD card is
being addressed.
The VS1053 itself has two SPI serial
buses, one for control (SCI) and one
siliconchip.com.au
for audio data (SDI); the SCI control
interface is selected by bringing pin
D6 low, while the SDI data interface is
selected by bringing pin D7 low. The
VS1053 also has a TTL RS-232 (UART)
serial debugging interface, however,
that is not connected to anything on
this shield.
The X_RESET line on pin D8 has
a 100kW pull-down resistor and this
holds the VS1053 in reset until the
Arduino is ready to control it.
D8 must be brought high before
sending any commands or data to the
VS1053 chip. The only additional line
required to control the VS1053 from
an Arduino is the DREQ line on pin
D2, mentioned earlier.
We're using the freely available
SFEMP3 library to drive the VS1053
from an Arduino Uno-compatible
module, along with the venerable
SdFat library to read audio files off the
microSD card. The SFEMP3 library
code (which also comes with SDFat)
can be downloaded from:
www.billporter.info/2012/01/
28/sparkfun-mp3-shield-arduinolibrary/
Note that while the SD card and
VS1053 IC share the same SPI bus,
unfortunately, it hasn't been arranged
so that data can be streamed directly
from the SD card to the VS1053.
That's because data from the SD
card appears on the MISO (masterin, slave-out) line as the SD card is
the slave in this case, but data fed
to the VS1053 must go on the MOSI
(master-out, slave-in) line for the
same reason.
This means that the Arduino must
actively read data off the SD card and
then write it back over the same bus
to the VS1053. That doubles the effective bandwidth required.
Still, while playing back a 128kbit
audio file (fairly typical), that only
occupies about 10% of the Arduino's
time, leaving plenty of time for other
tasks.
Unfortunately, while the VS1053
and the Geeetech shield both support
recording, the SFEMP3 library does
not. However, all the code and information required to enable recording
are available from the VLSI website
at: www.vlsi.fi/en/support/software/
vs10xxplugins.html
Thankfully, while their website is
a bit difficult to navigate, their documentation is comprehensive.
If you want to get started with this
shield, we suggest you read the project
article in this issue which takes you
through building a fully functional audio player based on this shield.
Your other option is to download
the SFEMP3 library and its example
sketch and load that into your Arduino module.
Some of the functions available in
the SFEMP3 library include:
• setVolume(vol) – sets the playback
volume, either for both channels,
or for each individually; a value
of 40 is used for 100%
• setBassFrequency(Hz)/setBassAmplitude(dB) – allows you to
apply bass boost or cut
• setTrebleFrequency(Hz)/setTrebleAmplitude(dB) – allows
you to apply treble boost or cut
• playMP3(filename, time) – play
the MP3 (or other file) with the
given name starting from the given time
July 2017 75
•
•
•
•
•
•
•
•
stopTrack() – stops playback
isPlaying() – returns true if a file
is currently being played or is
paused
skip() – go forwards or back by up
to 32.5s each time
skipto() – jump to a point in the
file, limited to the first 65.5s
currentPosition() – returns a value indicating how many milliseconds of audio have been played
from the current file
pauseMusic()/resumeMusic() –
self-explanatory
setVUMeter(on) – enables or disables VU metering
getVULevel() – indicates the current VU level, in dB, for both
channels
Plugins enable other features
In addition to the plugin enabling
Vorbis encoding, there are a number
of others available, which fix bugs
and add extra capabilities. One plugin
which is highly recommended is the
"VS1053b patch w/FLAC decoder",
available from:
www.vlsi.fi/en/support/software/vs10xxpatches.html
This fixes a number of bugs, along
with adding the ability to decode losslessly compressed FLAC files.
Other plugins can add functionality
which include:
• a multi-band equaliser
• a sine/DTMF waveform generator
• a PCM audio mixer which allows
the microcontroller to feed audio
A top view look at the shield (larger than life size) gives us a better
overview of all the components used in it. You can see the on-board electret
microphone, the microphone input and speaker output populate the righthand side of the board (from top to bottom).
•
•
to the chip which is digitally
mixed with audio from the file
being decoded
a mic/line input mixer which allows input monitoring during
playback, including mono downmix capability
a pitch shifter plugin which allows changing the pitch of the audio without changing temporarily
•
a plugin which makes rewinding/
fast-forwarding WMA files easier
• a package of "loudness" enhancing filters
These are in addition to built-in
features of the VS1053b which we
haven't mentioned yet, including zerocrossing detection for smooth volume
changes, quiet power-on and power-off
and a 64-voice MIDI synthesiser. SC
Radio, Television & Hobbies: the COMPLETE archive on DVD
YES!
A
MORE THAN URY
NT
CE
R
TE
AR
QU
ONICS
OF ELECTR
HISTORY!
This remarkable collection of PDFs covers every issue of R & H, as it was known from the beginning (April
1939 – price sixpence!) right through to the final edition of R, TV & H in March 1965, before it disappeared
forever with the change of name to EA.
For the first time ever, complete and in one handy DVD, every article and every issue is covered.
If you’re an old timer (or even young timer!) into vintage radio, it doesn’t get much more vintage than this.
If you’re a student of history, this archive gives an extraordinary insight into the amazing breakthroughs made
in radio and electronics technology following the war years. And speaking of the war years, R & H had some
of the best propaganda imaginable!
Even if you’re just an electronics dabbler, there’s something here to interest you.
Please note: this archive is in PDF format on DVD for PC. Your computer will need a DVD-ROM
or DVD-recorder (not a CD!) and Acrobat Reader 6 or above (free download) to enable you to
view this archive. This DVD is NOT playable through a standard A/V-type DVD player.
Exclusive to:
SILICON
CHIP
76 Silicon Chip
ONLY
62
$
00
+$10.00 P&P
Order now from www.siliconchip.com.au/Shop/3 or call
(02) 9939 3295 and quote your credit card number.
siliconchip.com.au
MP3...WAV...MIDI...FLAC...OGG... and many more
Music Player
by Bao Smith
Got some music stored on your SD Card? Here’s an Arduino-based player
that handles most common formats. It’s cheap, easy-to-build and it will
even record as well. Build it . . . and be amazed!
T
his project uses an Arduino “MP3
shield” described in greater detail
on page 72 of this issue. This delivers
audio to a 3.5mm stereo jack which can
be plugged directly into earphones/
headphones or to an audio amplifier
to power larger speakers. For recording, it has an on-board electret microphone along with a mono 3.5mm jack
socket, which allows an external microphone to be used.
All the audio decoding/encoding and playback/recording functions are handled by the VS1053 IC
on this shield. For more information
on that IC, see the separate article on
the shield.
As well as playing back the compressed formats listed in the introduction, this IC is also capable of playing
back General MIDI files and also uncompressed WAV files. It's an impressive chip, with quite a few extra feasiliconchip.com.au
tures that we aren’t using in this project, such as digital tone controls. And
of course, you can modify the software
to take advantage of those features if
you want to.
While this device is capable of playing back a number of formats, most
constructors would use it to play back
either MP3 or AAC files, which are the
de-facto standard formats for digitally
compressed audio.
Pretty much any music player
should play back these formats. Until recently, MP3 was patented and so
required licensed software for decoding. But that patent (held by the German firm Fraunhofer IIS) expired on
the 23rd of April this year, so it is now
an open format.
Because it was patented, the similar open-source Ogg Vorbis standard
was established. And more recently,
AAC was developed, aimed mainly at
providing either higher audio quality
than MP3 at the same file size, or (in
the case of AAC+) reasonable quality
with a much smaller file size (bit rate).
We’ve chosen to use the VS1053based Arduino shield because it is
low cost, can play back all these file
types and has a decent on-board DAC
which is able to power nominally 30W
loads such as many headphones and
earphones; the minimum nominal
load impedance it can handle is 16W.
Construction
Building this project is quite simple,
with most of the connections made either by plugging a shield directly into
the Arduino board or by connecting an
external module to that same board using one of 12 short jumper wires. These
are fitted with a male DuPont connector at one end and a female at the other.
The first step is to slot the MP3
July 2017 77
Fig.1: wiring diagram for the Arduino Music
Player project. The MP3 player shield should
just slot in one-to-one with the Arduino Uno.
The LCD screen with serial I2C can either go into
Analog pins 4 & 5, or the SCL & SDA pins on the
Uno as they are wired in parallel. You might find
that your keypad has a slightly different layout,
so it’s best to check with an ohmmeter what pin
combinations correspond to which key.
shield into the Arduino Uno (or equivalent), with the power connections
matching up and the SD card slot on
top of the USB connector. While you
can upload the software at this point
and start experimenting, with control
via the USB serial monitor in the Arduino IDE, we will describe the remaining assembly steps first.
The next job is to get the serial LCD
screen running. We used a 16x4 screen
but it will also work with a 20x4 alphanumeric display, however, you will
need to modify one line in the software and the whole screen will not be
utilised by default. The software could
78 Silicon Chip
also be modified to work with a smaller
16x2 screen, if you wish.
Refer to Jim Rowe's El Cheapo Modules series article titled “part 5: LCD
modules with I2C” in the March 2017
issue for details on how these I2C LCD
modules work.
If you haven’t already fitted the I2C
module to the LCD, generally it’s just
soldered on the back, with a 1:1 correspondence between its pins and those
on the main LCD board.
We used a slightly unusual LCD
module that we have on hand with
a 20-pin connector, with pins 19 &
20 used for the back-light anode and
cathode connections, compared to a
more typical display which has these
connections on pins 15 and 16. So you
may notice on the photos that we soldered wire links between pins 15 and
19, and 16 and 20 to make the backlight work.
Once you have the I2C module soldered to the LCD, the four I2C/power
supply wires are easily connected to
the MP3 shield (already connected to
the Arduino board below), as shown
in Fig.1. The I2C module normally has
male pin headers while the Arduino
shield has female sockets on top, hence
we have specified male/female jumper
leads to make these connections.
Note that our software assumes the
I2C module uses an address of 0x3F;
some I2C modules use a different address (eg, if it uses a PCF8574T [0x27]
rather than the PCF8574AT). So we
suggest you check the supplied documentation and if necessary, change
the LCD address in the software before
uploading it.
The final set of connections to be
made are between the 4x4 keypad and
MP3 shield as shown in Fig.1. We’re
using a standard switch matrix type of
keypad which is commonly available.
If your keypad doesn’t have any pin
siliconchip.com.au
headers but rather has a series of pads
with holes on its PCB, you will need to
solder a male pin header onto it before
proceeding (straight or right angle).
The 4x4 keypad uses eight connections, four for the rows and four
for the columns. After deducting the
pins used by the “MP3 shield” and
LCD, we’re left with ten free pins on
the Arduino module and only a few of
these are digital pins. Luckily, analog
pins can also be configured as digital
I/Os, so wire up the keypad as shown
in Fig.1.
Note that your keypad may use different row and column connections
to ours but you can easily check this
by setting a DMM in continuity mode,
connecting it across each pair of pins
and pressing each key on the keypad.
You should quickly be able to determine which pins connect to the rows
and columns.
Note that after plugging in the keypad, the only pin remaining to connect
anything else to your board is digital
pin D1. If you do need to add other
devices, consider using I2C devices
which can be simply wired up in parallel with the LCD as long as they do
not use the same I2C address.
Software operation
We won’t go into much detail regarding how the software works here; you
can download and examine the code if
you want to see how it works, or make
any changes.
However, it can be helpful to know
how audio data is piped to the VS1053.
The VS1053 has a 2048-byte buffer
which can receive up to 32 bytes of
data at a time. The data is sent via an
SPI serial bus when the DREQ pin is
high (this pin also indicates the chip
is ready to receive a command over
the SCI interface).
Data can be sent either most-significant byte first (SM_SDIORD [0x9]
set to 0) or least-significant byte first
(SM_SDIORD set to 1) format; the
SM_MODE register address is 0x4800
and this is configured over the SCI interface.
The software requires four libraries to function, with one of them requiring minor changes to the code.
The libraries required are SdFat,
SFEMP3Shield (https://github.com/
madsci1016/Sparkfun-MP3-PlayerShield-Arduino-Library), LiquidCrystalI2C (https://github.com/fdebrabander/Arduino-LiquidCrystal-I2Clibrary) and Keypad (http://playground.
arduino.cc/Code/Keypad#Download).
It's important to mention that the
version of SdFat we are using will
only open files that use the old DOS
8.3 file naming convention (8 characters for name, 3 for extension). Files
with names that do not match this format will not display properly and may
cause other problems. The reason for
this restriction is to save on memory.
The software could be modified to
support long file names but given that
the basic Arduino module only has
32KB of flash and 2KB of RAM, and
our software pretty much fills this, you
would need a more powerful Arduino
board to use the modified software (eg,
one with an ATmega2560 chip rather
than ATmega328).
The software is capable of uploading various patches or “plugins” to
the VS1053b chip. These can fix bugs
in its firmware or add extra capabilities. They are stored in “little-endian”
binary format on the microSD card,
with a file extension of “.053”.
These files can be created from .plg
plugin files downloaded from VLSI's
website (www.vlsi.fi/en/support/software/vs10xxpatches.html), using a
conversion tool that comes with the
SFEMP3Player library called "vs_plg_
to_bin.pl".
Note that you might have trouble
running the above Perl script if your
version of Perl is lower than 5.10.0. As
on line 59, a parameter for the pack()
function makes use of the “<” modifier to force the data to be stored in
little-endian format. You remove this
modifier if you know your CPU architecture will only deal with data in
little-endian format, or alternatively,
you can set SM_SDIORD to 0 when
sending the plugin data.
The reason for converting them is to
save storage space and speed up loading them into the VS1053b IC; even
when converted to binary form, they
can be quite large. The SFEMP3 library
supplies some plugin files along with
the software, already having been converted to this format. Their uses are
described below.
Installing the software
The Arduino Music Player is easy to build, consisting of just four modules
which plug together; either directly or via jumper leads.
siliconchip.com.au
If you don’t already have the Arduino integrated development environment (IDE) on your PC, download
it and install it now. It’s available for
free, from www.arduino.cc/en/Main/
Software We used version 1.6.12; SdFat requires version 1.6 or higher of the
Arduino IDE to function, but it would
be possible to convert it to function on
earlier versions.
Make sure all four libraries mentioned above have been installed or
you will not be able to compile the
July 2017 79
software. Minor changes were made
to the SFEMP3Shield software to expose some internal functions required
by our sketch.
This modified version of the library
will be included in the download
package on the Silicon Chip website,
along with the actual sketch itself.
Once you have the library ZIP files, you
can install them in the Arduino IDE
via the Sketch→Include Library→Add
.ZIP Library menu option.
You will also need the two VS1053b
plugin/patch files named "patches.053" and "oggenc.053", also included in that download package. When
the sketch runs, it looks for these files
in the root directory of the microSD
card, loads them into its memory and
then uploads them to the VS1053b IC.
The first patch file is an update to
the chip’s firmware that fixes some
bugs and also adds extra capabilities.
Some of the bug fixes are required to
play certain audio files that would otherwise return errors.
The second is the code which allows
the chip to record in Ogg Vorbis format.
Without these files, the unit will not
function properly. Once you’ve placed
these files on the microSD card, along
with whatever audio files you want to
play back, plug it into the socket on
the shield.
Note that the SD card should be
formatted with either FAT16 or FAT32
file systems to work with the SdFat
library.
Having ensured the libraries are
installed, open up the sketch (called
“VS1053_example.ino”) in the Arduino IDE and plug the Arduino into your
PC using an appropriate USB cable.
We assume you know how to select
the appropriate USB serial port in the
Arduino IDE; if you’re unsure, we’ve
described this procedure before, for
example, in the Arduino-based Digital LC Meter article, published in the
June 2017 issue (on pages 35 and 36).
You can now use the Sketch→Upload
menu item to load the software into the
Arduino.
Using the module
When the software has been loaded
and the module is up and running, you
should notice that the display has lit
up and menu should be shown. This
menu can be navigated using the keypad with the keys labelled 2/8 corresponding to up/down, 4/6 to left/right,
5 being “enter” (selecting the menu
80 Silicon Chip
Parts List
1 Arduino Uno or equivalent with ATmega328 chip (Jaycar Cat XC4410)
1 Geeetech Arduino MP3 Player Shield (Silicon Chip online shop Cat
SC4315)
1 20x4 or 16x4 LCD screen with I2C backpack module (Silicon Chip
online shop Cat SC4203)
1 4x4 matrix keypad (other sizes will also work with software changes)
1 8-pin header, 2.54mm pitch, straight or right angle (to suit keypad)
12 male-female DuPont jumper leads (Jaycar Cat WC6028)
1 USB Type-A to Type-B “printer” cable (to suit Arduino module)
1 microSD card formatted in FAT16/32, capacity to suit application
1 7-12V DC plugpack with 2.1mm inner diameter plug (optional, for
standalone use)
entry that the cursor is currently on)
and * functions as a general “back”
key in all menus.
The menu items that are available on
the main menu, by default, are:
0. plays all music files available on
the SD card. Pressing 4/6 will go to
the previous/next song, “A” will
restart the song from the beginning, 5 will pause/unpause, 1/3
will decrease/increase playback
speed and 7/9 will increase/decrease playback volume.
During playback, it will display
the file name, current time and a
VU meter signal level for the left
and right channel. Playback can
be stopped by pressing the “*” key
and it will stop automatically after
the last file has been played.
Note that there is a limit of 50
files due to memory constraints
(2 bytes are required per file).
The software could be modified
to remove this limitation but then
it would not be possible to step
backwards, to the previous file;
you could only skip forwards
through the list.
1. lets you select a file to play.
2. record to an .ogg file named recordXX.ogg, where XX starts at 00
and is incremented per recording.
3. toggles between mono and stereo output
4. resets the VS1053 chip to its default settings
5. produces a test sinewave from
the outputs
6. turns on/off the differential output mode
7. put the VS1053 IC in low-power
sleep mode
8. exit sleep mode
Recording uses the on-board electret
microphone. If you want to use the line
input instead, you need to add a line
at the top of the sketch which reads
“#define USE_LINEIN" without quotation marks. The audio is recorded
in Ogg Vorbis format at approximately
128kb/s and saved as an “.ogg” file.
In addition to the keypad/LCD interface described above, the software
can be controlled from your PC using
the serial monitor.
You simply read the menu options
that are displayed on the serial monitor and choose one by pressing the
associated key on your keyboard. This
interface has additional options which
can be used for debugging.
Making simple changes to the
code
Experienced programmers should
have no problems changing the software to suit their needs but even relative beginners can make some changes,
as described below.
A constant called MAX_INDEX defines how many files the software can
handle on the microSD card. Changing this will also affect how much
SRAM is used. If you increase it too
much, there won’t be enough free
memory for the software stack and it
will no longer work properly. Each
additional entry will take another 2
bytes of SRAM.
The definitions LINE1, LINE2,
LINE3 and LINE4 are the addresses of
each line of the display on your LCD
module. The module we used has the
first line at address 0 hex, the second
line at 40 hex, the third line at 14 hex
and the fourth line at 54 hex.
This is pretty standard and most
displays should use the same addresses, but if yours is only displaying the
first line correctly, you may need to
change these.
siliconchip.com.au
Silicon Chip
Binders
REAL
VALUE
AT
$16.95
*
PLUS P
&
P
Here you can see the initial display when the unit is first powered up after
loading the software, showing part of the main menu. The underline indicates
which menu item will be selected when you press enter (5 on the keypad).
Our I2C LCD uses the PCF8574AT
IC and so the software is set up from
an I2C address of 3F hex. If your LCD
interface has a PCF8574T, change the
line which reads:
LiquidCrystal_I2C lcd(0x3F,
LCD_COLS, LCD_ROWS);
to:
LiquidCrystal_I2C lcd(0x27,
LCD_COLS, LCD_ROWS);
Regarding the changes made in the
SFEMP3 library for this project, they
can be summarised as the following:
1) playTrack(uint8_t) was changed
to playTrack(uint16_t) to allow more
than 255 files on the same card (using the naming scheme trackX.mp3,
where X is a number between 0-999).
2) isFnMusic(char *) was changed to
also check for Ogg Vorbis files.
3) the following functions in the
SFEMP3 class were changed from “private” to “public” to allow the sketch
more control over the VS1053b IC:
void getTrackInfo(uint8_t, char*,
uint8_t); // Gets MP3 ID3
metadata (force appends a
null-byte)
static void
Mp3WriteRegister(uint8_t,
uint16_t); // Write 16-bits to a
given register
static uint16_t Mp3ReadRegister
(uint8_t); // read from a given
register
siliconchip.com.au
uint8_t VSLoadUserCode(char*);
// Load a .53 format plugin
Additional uses
As noted earlier, the SFEMP3Player
library has treble and bass controls,
however, our software does not use
these functions.
If readers want to work on the software, this would be one area to start.
Another improvement that could be
made is to take advantage of the library’s functions for reading header
information (eg, ID3 tags), and display
it on the LCD during playback.
The chip itself is surprisingly powerful, handling all the decoding/encoding itself in real time. It can also be
used as a graphic equaliser and MIDI
synthesiser.
VLSI also offer software to use the
chip as a FIR (finite infinite response)
filter, in combination with the free
GNU Octave software. This can be
found under VSIDE DSP Library:
www.vlsi.fi/en/support/software/
vs10xxapplications.html
Using it is outside the scope of this
article, though.
The VS1503 manufacturer's website
can be found at www.vlsi.fi/en There
you can find other example programs
(not for Arduino) along with a list of
patch files (www.vlsi.fi/en/support/
software/vs10xxpatches.html) and bonus functionality that can be loaded
SC
into the chip.
Are your copies of SILICON
CHIP getting damaged
or dog-eared just lying
around in a cupboard or
on a shelf? Can you quickly find a particular issue
that you need to refer to?
Keep your copies
safe, secure and
always available with
these handy binders
These binders will protect your
copies of SILICON CHIP. They
feature heavy-board covers,
hold 12 issues & will look great
on your bookshelf.
H 80mm internal width
H SILICON CHIP logo printed
in gold-coloured lettering on
spine & cover
Silicon Chip Publications
PO Box 139
Collaroy Beach 2097
Order online from www.
siliconchip.com.au/Shop/4
or call (02) 9939 3295 and
quote your credit card number. *See website for overseas prices.
July 2017 81
High performance 10-Octave
STEREO GRAPHIC
Part II
EQUALISER
By
JOHN CLARKE
F
Last month
we described the circuit
and performance of our new
10-octave Stereo Graphic Equaliser.
Now we conclude with assembly details of the PCB
and the acrylic case with its very smart-looking front
panel, which is actually a black screen-printed PCB
– with slots for the sliders but no tracks!
or such a large circuit, the double-sided PCB for this project is
surprisingly compact at only 198
x 76mm. It is coded 01105171.
It is very compact because we have
mounted the 10 ganged slider pots on
one side and all the active circuitry,
with 12 (or 13) LM833 low-noise dual
op amps, on the other side.
Virtually all of the resistors are surface-mount types but fortunately you
can read their printed values (with a
magnifying glass).
All of the capacitors, apart from 12
(or 13) 100nF surface-mount ceramic
bypass caps, are through-hole types,
82 Silicon Chip
so while some components are quite
small, they are also quite straightforward to solder in place.
And the benefit of soldering the surface-mount components is that you
don’t have to clip off their pigtails after soldering.
The PCB front panel shown in the
prototype above is a little smaller than
the acrylic case but we have since
modified it so that the outside dimensions of the front panel and case are
the same – it looks neater.
Mind you, the acrylic case is not
needed if the equaliser is to be mounted into existing equipment or into a
half rack width 2U case – but you will
still need some form of front panel.
Choice of supplies
We have provided two component
overlays for the PCB, one for the ACpowered version and the other for the
DC-powered version. The main difference is that the DC version omits
the components for the low voltage
AC power supply but adds the circuit
components associated with IC13, as
depicted on page 24 of last month’s
issue (June 2017).
To assemble the PCB, you will
need a fine-tipped soldering iron bit,
siliconchip.com.au
0.71mm-diameter solder, a good light
and a magnifying glass or spectacles
to be able to solder the surface-mount
components in place.
Begin by mounting the surfacemount ICs. As already noted, IC13 is
only installed if you intend to use a
DC supply.
Each IC is firstly oriented correctly
and note that the chamfered side is the
1k
100pF
100k
2.7k
L
LK2
R
1k
100k
2.7k
CON2
= 2 F
470
RIGHT
680pF
C 2017
01105171
17150110
10 OCTAVE GRAPHIC EQUALISER
100nF
91k 680
100nF
100k 680
100nF
100nF
1 F
110k 680
33nF
220nF
680 91k
100nF
68nF
390nF
IC2
820nF
680 100k
220nF
820nF
R
0V
~
CON5
~
~
47k
–
~
IN
470 F
+
OUT
10 F
REG2 7915 REG1 7815
(78XX)
W04
BR1
10 F
680nF
+
V–
siliconchip.com.au
SLIDER
SHIELD
220nF
L
680 110k
100nF
680nF
=1.5 F
IC1
=1.5 F
31.25Hz
SINGLE SUPPLY LINK
62.5Hz
100nF
68nF
100nF
IC3
125Hz
1 F
680 82k
15nF
82k 680
IC4
250Hz
390nF
33nF
10nF
47nF
100k 680
IC5
500Hz
680 100k
220nF
100nF
680 82k
15nF
22nF
4.7nF
82k 680
IC6
1kHz
100nF
10nF
100nF
680 91k
47nF
6.8nF
10nF
2.2nF
91k 680
IC7
2kHz
4.7nF
1nF
100nF
680 110k
22nF
110k 680
IC8
4kHz
2.2nF
100nF
680 82k
10nF
3.3nF
82k 680
IC9
8kHz
1nF
680pF
100nF
680 62k
6.8nF
LEFT
62k 680
IC10
16kHz
3.3nF
1nF
CON1
L IN
2.7k
1 F
L OUT
100pF
10
100nF
1 F
IC11
100pF
10
+
+/–
SUPPLY
LINKS
LK1
470
100pF
1M
= 2 F
2.7k
1nF
CON3
R IN
100pF
1 F 470nF L1
R OUT
CON4
(and for IC13 if used). Then the surface-mount resistors can be soldered
in place including that for LED1 and
those resistors used for the DC version, if that is the version being built.
We said that the surface-mount resistors have the values printed on them
but some “interpretation” is required.
A 3 or 4-digit code is used, with the
last digit being the number of zeros.
10
100nF
1 F
IC12
100pF
10
1M
470nF L2
IC1-13
LM833
pin 1-4 side of the IC. Place the IC in
position over the PCB pads and solder
one corner pin. Check its alignment
and remelt the solder if the IC needs
adjustment. When the IC is aligned
correctly, solder the remaining seven
pins. Make sure that there no solder
dags bridging any of the adjacent pins.
Then align and solder the 100nF
supply bypass capacitors for IC1-IC12
Fig.7 (left): use
this component
overlay (and
the matching
photo at right) if
you want to use
an AC supply.
It contains the
bridge rectifier,
smoothing
capacitors and
most importantly
the positive
and negative
15V regulators.
Note also the
supply links (top
left) – both are
in place. In the
photo these are
shown as header
sets but as these
would normally
be set once and
forgotten, wire
links (from
component lead
offcuts) would be
the way to go.
July 2017 83
16kHz
8kHz
VR8
1kHz
250Hz
500Hz
2kHz
01105171
VR7
VR6
VR5
125Hz
VR4
62.5Hz
VR3
31.25Hz
VR2
LED1
VR1
84 Silicon Chip
When mounting the RCA sockets,
the white ones are for the left channels and the red are for the right channels. The 3-way screw terminal CON5
is mounted with the opening to the
edge of the PCB.
Take care when mounting the bridge
rectifier, making sure that its pin labelling matches the screen printing on the
PCB. REG1 (and REG2 if used) can be
installed next, seated as far down onto
4kHz
VR10
Then install the MKT polyester
capacitors. Note that the 820nF and
680nF capacitors for the 32Hz gyrator are connected in parallel to make
up a value of 1.5µF. Alternatively, you
could use 1µF and 470nF capacitors
instead, if the 680nF and 820nF values prove difficult to obtain.
The electrolytic capacitors are
mounted next, taking care to orient
each one with the correct polarity.
VR9
So the 680Ω resistors will be labelled
6800, ie, 680 with no extra zeros. The
100kΩ resistors will be 100, with three
zeroes, ie, it is labelled as 1003.
Once all the surface-mount components have been installed, the throughhole components can be mounted.
Start with the resistors and then fit
the two ferrite beads, using a resistor
lead offcut to feed through each bead
before soldering them in place.
Fig.8: the top
side of the PCB
contains only
the 10 slider
pots and the
power LED;
everything
else is on the
underside.
Again, the
matching (same
size) photo at
right will assist
you in PCB
assembly. The
square hold in
the board is to
accommodate
the power
switch, itself
attached to the
front panel.
siliconchip.com.au
Fig.9: use this
alternative PCB overlay
if you are using a DC
supply. Only the two
end sections of the
PCB are shown – the
centre of the PCB is
identical. Note the
absence of links for
LK1 and LK2 but the
link over three pads at
the bottom (this would
be easiest achieved on
the underside of the
board).
the PCB as they will go.
For the DC supply version, you can
use a 15V regulator (7815) if the DC
source is between 18V and 25V (maximum). If the supply is less than 18V, a
12V regulator (7812) can be used provided the DC input is 15V or more.
Below this 15V, you can dispense
with the regulator and connect a wire
link between the IN and OUT terminals; the two outer pads for the component).
Naturally, this will mean the supply
is unregulated.
Headers LK1 & LK2 or LK3 can be
installed next. LK1 & LK2 are for the
AC version and LK3 for the DC version. Install the jumper links on LK1 &
LK2 for the AC powered version and a
jumper link on LK3 for the DC version.
That should complete all the components installation, apart from the 10
sliders and LED1, which are mounted
on the other side.
So it is most important that you carefully check that you have installed and
soldered all the parts correctly before
moving the to the next stage (with the
sliders).
In particular, double check parts
placement for the capacitors that
mount directly opposite the sliders.
Once the sliders are installed, you will
not have access to the soldered connections for any of these capacitors.
Before mounting the sliders on the
front of the PCB, make sure that all
siliconchip.com.au
of the capacitor leads that were soldered on this side of the PCB have
been trimmed back.
This must be done so that the sliders can be fully seated onto the PCB.
Note that the sliders only fit with
one orientation. So if they don’t seem
to fit, try the alternative 180° orientation.
LED1 also needs to mount with the
correct orientation (longer lead is the
anode) and with the top of the lens
12mm above the PCB.
Initial testing
Power can now be applied to the
equaliser circuit to test for voltage at
the op amps. For the single 16VAC supply, connect the supply leads between
an AC input (one of the outer terminals
of CON5) and the centre 0V terminal.
If your supply is from an existing
piece of equipment with a 30V centre tapped transformer, connect the
two AC voltages to each of the outer
terminals of CON5 and the centre tap
to the centre 0V terminal. The transformer must be capable of supplying
the extra current drawn by the equaliser circuit (55mA typical, so allow
for, say, 100mA).
Power up the circuit and the LED
should light. Now measure the DC
voltage between pin 4 and pin 8 of
one of the op amps. This should be
close to 30V if you are using the AC
supply and 15V (or less depending on
whether you have a 12V regulator or
if it is bridged out).
For the DC supply version, check
that voltage between pin 4 of any IC to
pins 3 and pins 5 shows half the supply voltage. In other words, this voltage should be +7.5V or thereabouts if
you have a 15V supply between pin
4 and pin 8.
The low cost and ease of assembly of our new Graphic Equaliser is due in no
small part to the laser-cut “case”, shown here with the power switch and DC
supply socket fitted.
July 2017 85
M3 x 25mm
tapped spacer
M3 x 6.3mm
tapped spacer
*
*
Equaliser
PCB
Slider Pot
Front
panel
(PCB)
*
Laser-cut
black acrylic
case pieces
(ends not
shown)
M3 x
15mm
screw
The PCB is in position, with the slider-pot shafts poking through the front panel
and the board held in place with threaded spacers. The diagram at right (Fig.10)
shows how the PCB and case components fit together
Case installation
Fig.10 shows the assembly of the
Acrylic case.
Note that we show the mains transformer in the circuit for the centretapped 30V supply but a transformer
will not fit in the acrylic case.
In addition, the power switch used
in the case is not intended for switching mains voltages which could otherwise induce hum into the graphic
equaliser circuitry. The power switch
is only intended for low voltage
switching.
For the DC supply, the polarity
needs to be correct and this depends
on the wiring to the plug that connects
to the socket. There will be no power
supplied to the circuit if polarity is
incorrect.
You need to have the positive connected to the outer terminal of CON5,
so swap the two leads to the DC socket
if the voltage is reversed. The wiring
to the switch and socket are covered
in heatshrink tubing.
The case is assembled as shown
with the front panel PCB attached
to the front of the case using M3 x
15mm screws secured with tapped M3
spacers 6.3mm long. These are placed
at the four corner mounting positions
on the PCB.
A washer is placed under each
spacer first to increase clearance.
The two mounting holes in the middle of the PCB, top and bottom are se86 Silicon Chip
cured to the front of the case with M3
x 10mm screws and M3 nuts.
The main equaliser PCB then is
placed over the screws protruding
through the 6.3mm long spacers and
with the slider adjustment shafts protruding through slots in the front panel
and front PCB.
The PCB is secured using the M3 x
25mm spacers. The rear panel of the
case is secured to these spacers using
M3 washer
*
*
M3 x
10mm
screw
*
M3 x 10mm screws after the top and
side pieces of the case are attached
in place.
The holes in the rear of the case for
the RCA sockets are made with large
enough clearance, so that RCA plugs
can pass through hole and onto the
sockets.
So connect up your new equaliser
for a new listening experience.
SC
Enjoy!
And finally, the case components are slotted together ready for the PCB/front
panel assembly to be slipped into place and screws fitted to the four threaded
spacers to complete assembly.
siliconchip.com.au
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.
Remote water level monitoring using LoRa and Arduino
In the Circuit Notebook pages of
the January 2017 issue, my circuit
on a LoRa remote repeater was published. The transmitter unit used
included an HC-SR04 ultrasonic
distance sensor which was notionally for measuring water levels,
however, it wasn't fully utilised in
that project.
Since then, the design has been
extended to monitor the water levels
in a number of different discharge
ponds, in order to ensure that none
of them overflows and results in pollution of the surrounding area.
Therefore this project is suitable
for monitoring the water level of
a swimming pool, rainwater tank
or other body of water, as long as
you can mount the unit in such
a way that the distance from the
ultrasonic rangefinder to the sur-
siliconchip.com.au
face of the water varies as the water
level changes.
Like the previously mentioned
project, this one also uses a LoRa
long-range 433MHz digital radio
module, giving it an operating
range of several kilometres, as long
as you have line-of-sight between
the transmitter and receiver, and
use modules with decent antennas. I used an E32-TTL-500 module which comes with a suitable
whip antenna.
The circuit is based around an
ATmega328P processor (IC1) programmed using the Arduino IDE but
by default it's just a bare chip without a crystal oscillator. So the chip
is programmed with a bootloader
that allows it to run off its internal
oscillator.
This micro constantly measures
the water level using the ultrasonic rangefinder connected to pins 16
and 17. It also has a Neo-7M based
GPS module, which sends data over
a serial interface between pins PB0
and PB1 (14 and 15) of the micro.
Both the distance (ie, water level)
and position are then transmitted via
the digital radio, connected to the
PD2-PD6 pins of the micro (pins 4,
5, 6, 11 & 12 respectively).
The GPS latitude and longitude
information is included, so that
when multiple water level monitor
transmitters are used, it's easy to determine where the data is coming
from. Their location and water level could even be plotted on a map.
The circuit is powered from a 6V,
5.5Ah sealed lead-acid battery via
an LM2940CT-5.0 regulator, which
continued next page
July 2017 87
provides 5V to the HC-SR04 module and then on to a 7833 regulator
which derives the 3.3V supply for
IC1, the GPS receiver and the LoRa
transmitter. Not shown on the circuit is the 10W solar panel which
keeps the battery charged.
A receiver circuit is not shown
since all you need is another E32TTL-500 module wired up to a
USB/serial adaptor, with that adaptor supplying the 3.3V to run the
radio transceiver module and with
the TXD/RXD pins wired up to the
USB/serial adaptor's RXD and TXD
pins respectively.
You can then open the USB serial
port in a terminal emulator to begin
receiving the data packets sent periodically from the transmitter unit(s).
All the transmitters use the same (default) channel/frequency.
A sample of the received data
looks like this:
32.088690, 74.648170, 12:22:20,
8.0, Loc-2
32.088690, 74.648178, 12:22:41,
8.0, Loc-2
32.088720, 74.648178, 12:23:02,
194.0, Loc-1
32.088751, 74.648132, 12:23:23,
193.0, Loc-1
The first two numbers are the latitude and longitude, followed by the
time, distance reading and transmitter ID.
The major power draw in the
transmitter unit is the GPS receiver.
The Arduino code has been written
to minimise power consumption in
the ATmega328P chip.
As a result, overall current drain
on the battery is around 90mA,
giving a battery life of around 55
hours. So as long as the solar panel
gets good insolation for a few hours
every two days or so, it should be
able to operate continuously.
The Arduino sketch uses the builtin SoftwareSerial library plus three
add-on libraries: TinyGPS, LowPower and NewPing.
These are all included in the
download on the Silcon Chip website, named “LoRa_low_power_level_sender_software.zip”, which also
includes the sketch itself. Install the
ZIP libraries in the Arduino IDE
before compiling the sketch and
uploading it to the Arduino.
Remember to install the 8MHz
bootloader on the Arduino before
uploading the sketch, so that it will
work without a crystal. Details on
how to do so are at the following
URL: www.arduino.cc/en/Tutorial/
ArduinoToBreadboard
Bera Somnath,
Vindhyanagar, India. ($50)
Wien Bridge Oscillator delivers high power
This Wien bridge oscillator is capable of delivering a low-distortion
sinewave with a voltage swing of
more than 30V peak-to-peak (more
than 10V RMS) and in excess of
500mA of output current, to drive
transformers, long cables, devices with 600W input impedance,
lamps, LEDs or other low-impedance
loads. It can be built using either an
OPA551 or OPA552 op amp. The
key specifications of both are summarised in Table 1.
The oscillation frequency is fixed
and determined by the two 16kW
resistors and two 10nF capacitors.
These set the frequency close to
1kHz. If these values are changed,
both resistors or both capacitors
should be changed by the same
amount and the resulting frequency
is roughly 1 ÷ (2π × R × C). So the
frequency can be doubled by halving
either the resistances (to say, 8.2kW)
or capacitances (to say, 4.7nF).
The output amplitude is adjusted by trimpot VR1 which varies the
feedback divider ratio, in combination with the incandescent lamp,
which also provides amplitude stability (critical in a Wien Bridge oscillator design). It does this by acting as a more or less fixed resistance
across an oscillation cycle (ie, over
a 1ms period) but its resistance varies over the longer term.
Basically, if the amplitude of the
oscillator output increases, current
through the lamp also increases and
so it heats up. This increases its resistance, reducing the closed loop
gain of the oscillator circuit, thus
reducing the output amplitude. As
such, it provides long-term negative
feedback for the output amplitude,
ensuring it remains stable at the level set by VR1.
Transistors Q1 and Q2 are configured as complementary emitterfollowers, to boost the output current from IC1 (which is limited to
an output current of up to 200mA,
for a short period) to 500mA. Q1 and
Q2 should be attached to heatsinks
to keep them cool.
Q1 and Q2 have no quiescent current and thus the circuit relies on the
Table 1 – key performance parameters of the OPA551 and OPA552
Parameter
Test Conditions
OPA551
OPA552
Maximum supply voltage
60V (±30V)
60V (±30V)
Gain Bandwidth product
3MHz
12MHz
1
5
±15V/µs
±24V/µs
Minimum gain for stability
Slew Rate
Settling time to 0.1%
CL = 100pF, step = 10V
1.3µs
2.2µs
Settling time to 0.01%
CL = 100pF, step = 10V
2µs
3µs
Rload >= 3kW
0.0005% (gain=3)
0.0005% (gain=5)
THD+N, 1kHz, 15V RMS
88 Silicon Chip
siliconchip.com.au
high slew rate of IC1 to minimise
zero-crossing distortion artefacts,
along with the direct drive which
occurs around the zero crossing from
the output of IC1 via the 47W resistor.
Diodes D1 and D2 protect the oscillator against inductive spikes if
the circuit is used to drive a transformer or other inductive load, by
clipping the output voltage to the
supply rails. LED1 and LED2 are
connected in inverse parallel, between the output and ground with
a 1kW current limiting resistor, so
they light up when the output amplitude is above about 4V peak-topeak (~1.4V RMS).
The output is available at CON2,
with or without a 600W series resistor (ie, to drive a 600W impedance),
plus three other outputs which have
10%, 1% and 0.1% of the set amplitude. Note that these additional
outputs have a much higher source
impedance, so are only suitable for
connection to high input impedance
devices such as audio amplifiers.
The power supply produces regulated ±21V DC supply rails for IC1,
Q1 and Q2 from a 20-25VAC output transformer, or centre tapped
40-50VAC transformer, connected
to CON1. The AC voltage from the
transformer is rectified by bridge
rectifier BR1 and filtered by a pair
of 1000µF capacitors.
The resulting supply rails of
approximately 26-36V DC are then
regulated down to around ±21V by
LM317 (positive, REG1) and LM337
(negative, REG2) adjustable regulators.
Each regulator has two 1N4004 diodes for protection, one across it to
protect it against input short circuits
and one between the output and
ground to prevent the output being
pulled negative if a single winding
transformer is used to power the circuit. LED3 and LED4 indicate presence of the supply rails.
The resistors which set the output voltage of REG1 and REG2 can
be changed to provide supply rails
anywhere between ±12-30V DC, depending on the voltage of the power supply transformer and the required maximum oscillator output
amplitude.
Petre Petrov,
Sofia, Bulgaria. ($50)
siliconchip.com.au
July 2017 89
Simple constant speed controller for permanent magnet DC motors
This circuit was designed to
replace the motor/driver module on
a Sonab C500 stereo cassette deck.
The first attempt involved a standard motor speed control IC but this
circuit was found to be better.
In a permanent magnet DC motor,
in a steady state, the voltage across
the motor terminals equals the backEMF plus the voltage due to the current through the armature resistance.
Motor speed is directly proportional
to back-EMF in this type of motor, so
it can be used to regulate the speed
very accurately.
If the armature resistance is
known and the motor current is
measured, the voltage across the
armature can be calculated and
subtracted from the motor voltage to
obtain the back-EMF voltage.
If the motor is then placed in the
feedback loop of an op amp, the
motor voltage can be adjusted to
keep the back-EMF voltage constant,
which is what this circuit does.
The motor current passes through
a 2.2W shunt resistor and the voltage across this is low-pass filtered to
remove switching artefacts and then
fed to the non-inverting input pin 5
of op amp IC1b.
The gain of this op amp stage is
set by the ratio of the 27kW feedback
resistor and the resistance of VR2, so
the gain can be set anywhere from
about 1.5 times (1 + 27kW ÷ 50kW),
up to 10 times or more.
Op amp IC1a controls the motor
voltage via Darlington transistor Q1,
connected as an emitter-follower. So
the motor positive terminal voltage
will be approximately 1.4V below
that of IC1a’s output pin 1.
IC1a’s non-inverting input, pin 3,
is connected to the wiper of speed
control pot VR1, wired across 6.9V
reference voltage VREF1. Thus, turning VR1 clockwise increases the motor voltage and speed.
Because the bottom end of VREF1
is connected to output pin 7 of
IC1b, which is amplifying the voltage across the 2.2W shunt, a voltage
proportional to the shunt voltage is
added to the speed control voltage
at pin 3 of IC1a. Therefore, as motor current increases, the voltage at
output pin 7 rises and so does the
90 Silicon Chip
voltage at pin 3, and thus the motor
positive terminal voltage.
Now, let’s say the armature resistance of this particular motor is 8W.
Thus, with a current of 250mA, the
voltage across the armature resistance is 8W × 0.25A = 2V and so the
voltage measured across the motor
will be 2V more than the back-EMF
voltage.
If we adjust VR2 so that with a motor current of 250mA, output pin 7
of IC1b is 2V (ie, the gain of IC1b is
set to 2V ÷ [0.25A × 2.2W] = 3.64),
this means that this error voltage
will have been completely subtracted from the motor voltage and thus
VR1 will be controlling the backEMF voltage itself.
If the motor speed drops, the feedback voltage to pin 2 of IC1a will
drop and so it will automatically
increase its output voltage to compensate.
Similarly, if the motor speed
increases, the back-EMF and thus
feedback voltage will increase and the
motor voltage will be reduced. So assuming VR2 is set correctly, a steady
motor speed will be maintained.
Ideally, you would measure the
armature resistance and then adjust
VR2 for the correct gain, keeping in
mind the 2.2W shunt resistor value
but in practice, you can simply use
a trial-and-error approach.
This involves adjusting VR2 while
placing some load on the motor (eg,
holding your finger against its shaft,
assuming that’s safe) and checking to
see how well it regulates the speed,
then iteratively tweaking the position of VR2 to get the best result.
The two 100kW feedback resistors
between the motor positive terminal,
pin 2 of IC1a and pin 7 of IC1b has no
effect on the feedback system, since
the bottom end of the divider is also
connected to the bottom end of VR1.
However, it does allow VR1 to
provide a wide range of motor speed
adjustments despite the fact that the
voltage across VREF1 is only about
half that of the 12V supply.
Note that depending on the size of
your motor, you may need to change
Q1 to a higher-current Darlington
and/or attach it to a heatsink.
The power rating of the 2.2W shunt
resistor should be sufficient to handle your maximum motor current;
the suggested 0.5W rating is only
sufficient for a motor that draws up
to 475mA.
Mauri Lampi,
Glenroy, Vic. ($50)
siliconchip.com.au
12V DC Cyclic Pump Timer
I have a bush shack with a 12V
solar power system and a 12V pressure pump on the rainwater tank.
When the Cyclic Pump Timer was
published in the September 2016
issue, it seemed ideal for my system, to protect against burst pipes,
except that it was designed to control a 230VAC pump (see http://
siliconchip.com.au/l/aacx)
This modification adapts the circuit to control a DC pump and omits
the entire 230VAC section. My pump
draws about 4A which then rises
briefly to about 10A as the pressure
builds just before it shuts off. So I
came up with a new pump current
sensing circuit based on a GY-471
module containing a MAX471 highside current sense amplifier.
This module has an open-collector logic output labelled “SIGN”
which goes low when current flows
from its RS- pin to RS+. I added a
BC557 transistor (Q1) to invert this
signal so it can then be fed to pin 7
of IC1 in the original circuit, which
indicates to the micro that the pump
is operating (the original circuit fed
the rectified output of a current sense
transformer to this pin).
The GY-471 costs just a few dollars
but it has a maximum current limit of
3A through the chip’s internal shunt.
As there is no need to measure the
current accurately, I simply paralleled its shunt with a 300mm length
of 1mm2 cross-section (1.2mm diameter) copper wire. This reduces the
current through the internal shunt
by a factor of ten.
Since the 230VAC-to-12V DC
module has been removed from the
circuit, the pump's 12V DC supply
can be used to power the unit directly. The complete circuit on standby
only draws 3.6mA and it functions
identically to the original version.
(Note: the GY-471 module is now
available from the Silicon Chip online shop, as well as the PCB.)
Richard Blyton,
Kambah, ACT. ($50)
Circuit Ideas Wanted
Got an interesting original circuit that you have cleverly devised? We need it and will pay good money to feature it in the
Circuit Notebook pages. We can pay you by electronic funds transfer, cheque (what are they?) or direct to your PayPal
account. Or you can use the funds to purchase anything from the SILICON CHIP on-line shop, including PCBs and components, back issues, subscriptions or whatever. Email your circuit and descriptive text to editor<at>siliconchip.com.au
siliconchip.com.au
July 2017 91
Vintage Radio
By Ian Batty
DKE38 Deutscher
Kleinempfänger
Germany's Third Reich produced
at least two significant products to
appeal to the common people. The
first was the Volkswagen or “People's
Car” and the second was the Volksempfänger or “People's Radio”. This
was followed by the smaller, more
economical German Small Radio, the
DKE38 Deutscher Kleinempfänger
which was a 2-valve regenerative set
and was manufactured by a number
of German firms.
Germany, battered like most of Europe by four years of war ending in
1918, had endured barely a decade of
political turmoil when the Great Depression hit the Western world.
The 1930s saw opposing political
parties struggle for supremacy from
which the National Socialist Party
emerged. Leaving the next twenty
tragic years to the historians, how
was such a takeover of a modern nation possible?
Warning High Voltages!
Note that the circuit has no power transformer so it is potentially
lethal to the touch since the
circuit can be at the full 230VAC
mains voltage. If you are working
on it, you must use a 230:230VAC
isolation transformer.
92 Silicon Chip
Apart from major political rallies,
radio was an important tool in this
process. Then, as now, stations could
be set up at moderate cost and could,
with enough power, reach every
receiver of an entire country.
With government control of licensing, radio is an ideal medium for
spreading ideas and opinions, for good
or ill. Joseph Goebbels seems to have
recognised this potential early on.
So as part of national reconstruction, ordinary people were offered
two important pieces of technology
we take for granted today: a car and
a radio. And the People’s Radio was
always intended to serve political
ends, at least as much as simply benefiting the population.
Both the VE301 Deutscher Volksempfänger and the DKE38 Deutscher
Kleinempfänger were designed by
engineer Otto Griessing, at the request
of Propaganda Minister, Joseph Goebbels. The larger VE301 was a 3-valve
regenerative circuit with a pentode
demodulator followed by an output
pentode and a full-wave rectifier for
the mains power supply.
Cheap as it was, the VE301 cost
around two weeks’ average wages, so
an even cheaper design became attractive and the DKE38 filled the bill at half
the price. With a triode-tetrode (in the
one envelope) doing all the “signal”
work and a rectifier, the Kleinempfänger is even simpler than a set I built as
a lad back in the late 1950s.
So let’s check out the D(eutsche)
K(lein) E(mpfänger) 38, which appeared in 1938. I’ve two main reasons
for this investigation: how good can a
radio be with just two active stages,
and how can a minimal regenerative
set compare with a minimal superheterodyne radio, such as the Astor DLP
siliconchip.com.au
I reviewed in the October 2016 issue?
The VE301 and DKE38 both cover
the standard broadcast (Medium
Wave) band and 145~400kHz of the
Long Wave band. Both bands had been
used for broadcasting since around
1920, principally for local and national broadcasts.
Some debate continues to this day
over the design. Was it just a cheapand-cheerful mate to the Volkswagen
“beetle”? Perhaps the VE301 was deliberately designed to prevent owners
from tuning in to politically-undesirable shortwave broadcasters such as
the British Broadcasting Corporation.
Regeneration
Early valve amplifiers had been
bedevilled by “howling” which was
oscillation due to anode-grid feedback.
Generally regarded as a curse, the effect was investigated by a young engineer, Edwin Armstrong. He seems to
have reasoned that controlled feedback could greatly increase a receiver's gain.
By 1912, Armstrong had developed his regenerative technology to
the point where he was able to pick
up messages between San Francisco
and Honolulu. Remarkably, Armstrong
was in New York; well away from the
intended transmission path. He also
detected transatlantic signals from
Ireland, a feat achieved only with difficulty by Marconi’s much larger and
more complex TRF receivers.
The circuit of the Kleinempfänger DKE38 is unusual for a number of reasons: it
is transformerless and therefore the chassis is live; the fuse can be in the Active
or Neutral line; the loudspeaker is a moving-iron type with no transformer
coupling and the bias for both valves is unconventional. The circuit also has no
volume control; this is provided by varying the aerial coupling.
DKE circuit description
Active functions are handled by the
VCL11 triode-tetrode. It has an 8-pin
base most commonly seen on German
metal valves. It uses a 50mA heater
and while this seems very low for any
heater current, the heater voltage of
90V gives an actual consumption of
around 4.5W for both sections.
Note that the heaters of the rectifier
diode and the triode-tetrode are both
in series with a tapped 2.2kW wire
resistor, R7, which enables the heater
current to be correctly set to suit the
incoming supply voltage.
The triode is a high-mu type, while
the tetrode manages a creditable 4200
microsiemens, considering its low
heater power. Note the cathodes of both
valve sections are connected to pin 3.
The incoming signal is tuned by L2
(in parallel with L3 on the MW setting)
and variable reaction capacitor C2 and
then fed to the grid of the triode via
siliconchip.com.au
July 2017 93
This shaft (left knob) varies the coupling
between the primary and secondary
aerial coils to provide the volume control.
100pF capacitor C4. C4 allows grid leak
bias to develop across 1MW resistor R1;
if C4 was not present, the antenna coils
would prevent grid leak bias.
The amplified signal appears at the
anode and is fed back via adjustable
capacitor to C3 to L4 which then couples back to L2 & L3 and of course, then
feeds back via C4 to the triode grid.
This means that the grid signal is increased. If you’re thinking this would
make a good oscillator, you’re right. It’s
got the potential to set up the “howling” oscillation described above. But
if we carefully control the amount of
positive feedback, it’s possible to lift
the stage gain from around 40 times to
well over 100.
There’s a mechanically-variable
coupling control for volume acting
on the aerial coil’s primary. The above
photo shows the tuned/reaction windings on the top side of the phenolic
chassis, with the “swinging” primary
winding and its control mechanism
below.
Band-changing occurs when the
tuning dial passes the midpoint of
its rotation. LW operation uses a single secondary winding. For MW, S1
puts the second winding in parallel
to reduce the total circuit inductance,
just as resistors in parallel give a total
lower value.
The dial is calibrated with 0-100
markings; red for LW, plain for MW.
Given that tuning accuracy is affected
by the regeneration setting, showing
tuning frequency or station markings
would not have been practical.
As well as an amplifier, the circuit
is a leaky grid demodulator, ie, a di94 Silicon Chip
This close-up shot shows an example of a typical movingiron loudspeaker. Note that the driving coil is driven directly
from the plate of the tetrode without an output transformer.
ode of sorts. “Grid leak” resistor R1 is
commonly 1MW or greater. This allows
the grid to drift weakly negative. The
valve will now rectify any incoming
signal; positive-going signal peaks will
push it to maximum anode current,
negative-going peaks towards cutoff.
The net effect is much greater
amplification of the negative signal
peaks. The amplified signal is developed across the 200kW resistor R2,
with filter capacitor C5 partially filtering the RF component in the process of
demodulating the audio, which is then
fed to the grid of the output tetrode via
capacitor C6 and resistor R4.
The output stage's grid bias is developed across R6, a factory adjustment which sets the output stage’s
anode current. It’s a classic back bias
arrangement and not, as described in
one online article, designed to reduce
HT supply hum. The bias is fed to the
grid via resistor R5.
Some confusion exists regarding
coupling components R3, C7, R4 and
C6. Taking C6 first, it’s the usual coupling capacitor from the driver to output, in this case from the triode’s anode to the tetrode’s grid.
R4 would usually be a stopper resistor, placed so that it damps parasitic
oscillations in the tetrode. But here,
it appears in combination with 30pF
capacitor C7.
Ineffective at audio frequencies, C7
provides negative feedback at aboveaudio frequencies to filter out any of
the original RF carrier from the output
audio. R4 is needed to prevent C7’s
feedback affecting the demodulator’s
RF operation.
R3 provides conventional negative
feedback from the output stage’s anode
back to the demodulator and thus to
the output grid.
Moving-iron loudspeaker
The loudspeaker requires special
mention. For a start, it is a movingiron arrangement, with the cone attached to an iron pole-piece instead
of a voice coil, as in a conventional
dynamic speaker.
Second, it has a very high DC resistance of 2kW and an even higher impedance of 17kW at 1kHz, which means
that this can be driven directly from
the tetrode's plate rather than using an
output transformer. The plate current
flows through the loudspeaker's field
coil but it is only 12mA and not likely
to cause much additional distortion.
The pressed cardboard “basket”
may seem pretty agricultural, but it
does not need the steel basket we see
used in dynamic speakers (needed to
hold the voice coil, magnet and cone
in alignment).
The moving-iron type’s “motor”
contains all parts except for the outer
rim of the cone. Since this outer rim
does not need precise positioning,
the pressed-cardboard basket gives
adequate strength and stability while
economising on costly steel. Eliminating the output transformer also saved
steel and wire; highly necessary in
pre-war Germany.
The moving-iron speaker can
also use a high-impedance winding
that matches directly to the output
valve. This eliminates the costly and
bulky output transformer needed for
siliconchip.com.au
matching to the low voice coil impedances of dynamic speakers.
The lack of a power transformer has
already been mentioned. One side of
the mains supply is fed through the
double-pole switch S2 to the anode
of the rectifier diode, VY2.
The output from the cathode feeds
a standard pi filter, with two 4µF
capacitors, C9 & C10, together with an
iron-cored choke. R6, between the negative terminals of the two capacitors,
develops the back bias for the grid
of the output tetrode, as mentioned
above. C8, across the diode, is there
to reduce rectifier buzz.
Appearance and controls
The DKE38 has a very spartan Bakelite cabinet with simple controls: the
left-hand knob, volume, adjusts the
coupling between the aerial coil primary and its tuned windings.
The central tuning control tunes
either the Long Wave or Broadcast
bands, with the change-over occurring at the middle of its 360° travel.
The right-hand “regeneration” control
adjusts feedback from the triode’s anode to a regeneration winding on the
aerial coil assembly.
The set is constructed on a fibre
composite chassis with point-to-point
wiring. It’s pretty much a doublesided breadboard radio. My set’s mains
cord anchoring consisted of one mains
wire doubling through a hole in the
chassis – not even close to safe.
The top view of the chassis (on the
last page) shows the 8-pin VCL11
socket at top left, above the aerial coil.
The VY2 rectifier socket is towards the
right, above the filter choke with the
two main filter capacitors at the righthand edge. The tuning capacitor occupies the lower centre.
Original parts are easily spotted: any
large enough to be branded bore the
Reichsadler “Imperial Eagle” symbol.
The underside view shows the aerial
coil at lower right, with the large tuning knob in the centre. Minor components are wired point-to-point under
the fibre/composite chassis.
The aerial coil primary offers two
tappings for different lengths of aerial wire, with a third connection via
300pF capacitor C1. The adjustable regeneration and tuning capacitors both
use plastic dielectrics.
This makes them compact but also
easier and cheaper to manufacture
than air-spaced versions which must
siliconchip.com.au
The DKE38 shown with the original moving-iron loudspeaker. Note the
vertical tapped resistor which is used to set the filament current in the
rectifier and the triode-tetrode. The preset control is R6 which was adjusted
by the factory to set the back bias for the tetrode section.
be made to high precision to preserve
plate spacing. There’s a bonus for the
tuning capacitor – it can rotate through
a full 360°, allowing the set to change
bands (as noted below) simply by turning the knob past the end of the current band.
The picture directly below shows
the “flat” solid-dielectric tuning capacitor on top of the chassis, with its
tuning knob below. The band-change
contacts are just visible on top of
the tuning capacitor. The vertically
mounted reaction capacitor is on the
right-hand side with its tuning shaft
pointing forward to pass through the
front of the case.
Making it work
As purchased, the physical condition
This shot shows the tuning knob which covers the LW and MW bands. The knob
on the right is the regeneration control.
July 2017 95
This underside view of the
set shows that it is a nonmetallic chassis. This causes
problems when using any
of the controls, because of
hand-capacitance effects.
of the set was good, although the chassis was understandably dirty and dusty.
A brush had little effect, so I turned to
one of those microfibre kitchen scourers. Used dry, it cleaned off all the dust
and left a light polish on the fibre composite chassis.
The Bakelite cabinet was shiny with
no noticeable blemishes, it had the
original knobs, and the Reichsadler
emblem was undamaged. You’ll find
some examples where that emblem
has been defaced, presumably due to
its association with the Nazi Party. A
second set, bought while this article
was in preparation, was defaced. However, I used it for some internal photos
as it’s pretty well original.
Electrically, the review set had been
restored “to some extent”. Many components had been changed and the
original moving-iron speaker had
been replaced by an oddball dynamic speaker of some 300W impedance
and a 3600W series resistor. Not surprisingly, I couldn’t get a peep out of
it. A junkbox 240~30V transformer
gave a pretty good match for the substitute speaker and I was able to get
some operation.
I also noticed a 200pF capacitor connected between the Earth connection
96 Silicon Chip
on the aerial socket bar and the “low”
side of the mains. I’m guessing this
was to capitalise on mains earthing
and eliminate the need for a separate
earth wire. Be aware that, if such a capacitor fails (or even becomes leaky),
you’ve got a 50-50 chance of putting
your aerial system at lethal 230VAC
mains potential.
Even so, the set still didn’t work as
well as I expected, so I popped in a
spare VCL11 I’d bought some time ago.
Then it was time to take it for a test
drive. All measurements were made
with an isolating transformer and a
220VAC supply, as I didn’t want to
stress this rare set with the full mains
voltage.
So how did it go? For a set made
some 80 years ago, with just two
active elements; pretty well. But if
you’re expecting “superhet convenience”, you’d be disappointed.
At maximum sensitivity, the Kleinempfänger suffers from hand capacitance effects when tuning or adjusting
it – the Bakelite case and chassis simply can’t provide the levels of grounding and shielding we take for granted
with a metal chassis. This set also demands careful adjustment for optimal
performance.
I measured the sensitivity first.
Using the standard dummy antenna between my signal generator and
the set, for 50mW output, the LW
band needed 25mV at 145kHz, and
3.5mV at 400kHz. For the MW band,
it was 1.4mV at 600kHz and 600µV
at 1400kHz. Removing the dummy
antenna improved the 150kHz sensitivity to 600µV, implying that actual
performance will depend on aerial
wire length.
As expected, bandwidth varied
with the degree of regeneration. For
the LW band at 145kHz, it was only a
few hundred Hertz at full regeneration
and ±800Hz with a 10dB reduction. At
its top end (400kHz), full regeneration
gave a bandwidth of ±800Hz, with a
10dB reduction giving ±1200Hz.
For the MW band, full regeneration
480kHz bandwidth was under ±200Hz
(really!) and ±500Hz at reduced regeneration. At 1630kHz it was ±3900Hz
and ±7900Hz respectively.
These figures reinforce the general
problem with Tuned Radio Frequency sets of all kinds: bandwidth varies
drastically with tuning and regeneration simply exaggerates the effect. At
the low end of the MW band, just at
the point of oscillation, radio broadsiliconchip.com.au
This is the top view of
the set. On the righthand
side are the two 4µF filter
capacitors and the ironcored filter choke.
casts sound like they’re coming down
a drainpipe.
What if we eliminate regeneration?
Disconnecting it completely demanded some 270mV of input at 600kHz for
50mW out. Remembering that optimal
adjustment gave 50mW out for only
1.4mV in, this implies a “regeneration
gain” of up to 200 times; as much as
an extra (very good) RF amplifier. It’s
evidence of Armstrong’s revolutionary improvement to receivers in those
long-ago “pre-superhet” days.
What about responses to signal
strength? Output rises from zero signal to a certain level (depending on
aerial coupling and regeneration),
then flat-lines. For a 50mW output
setting, I could increase the input by
some 50dB and get no significant rise
in output power.
What’s happening here is that, as
signal rectification increases grid bias,
anode current and thus stage gain both
fall off as the input signal increases.
In circuit, there’s a marked rise in the
triode's anode voltage with rising signal strength.
Audio performance will depend
partly on the speaker (for a movingarmature type) or on the output transformer for a dynamic speaker. Using a
siliconchip.com.au
representative output transformer, the
low-frequency –3dB point was 130Hz.
High-frequency response varied greatly, as the RF bandwidth figures indicate. High-frequency response is
markedly reduced at maximum regeneration.
Maximum audio output varied frustratingly with aerial coupling, tuning
and regeneration. The best was some
140mW but a more reliable clipping
figure of 100mW gave some 10% THD
(Total Harmonic Distortion).
While 100mW is much less than
the customary valve mantel with a
6V6 output stage, it’s comparable to
many transistor mantels such as the
Astor M5.
At 50mW output, THD was around
5%, about 7% at 10mW output. Direct audio injection gave a maximum
output of some 500mW with visible
distortion. In practice, it reaches 10%
THD at around 200mW.
Is it as good as the Astor DLP? The
answer has to be no. The DKE38 is not
as sensitive, its audio response varies
widely, it has lower audio output and
is much harder to get the best results
from. The DKE38 makes the case for
the combination of superhet circuitry
and ganged tuning capacitors.
Would I buy another one? During
this project, I did. It came at a good
price but with one drawback. Otherwise pretty original (including the
speaker), it had its Reichsadler symbol defaced, as noted above. You can
expect to pay upwards of $1,000 for an
all-original, working DKE38.
All told, the Kleinempfänger DKE38
is a remarkable piece of minimalist
engineering, and one of the last regenerative sets made in large numbers and
offered for sale to the general public.
Further reading
Ernst Erb’s Radiomuseum has an
extensive collection of circuit, photos
and German-language operating manuals. Go to the home page and enter
DKE38 into the search bar:
www.radiomuseum.org/
There’s an extensive article on Phil’s
Old Radios:
http://antiqueradio.org/KleinempfaengerDKE38.htm
I’ve focused on the DKE38’s technology in this article. For a reminder of
its actual political environment, with
examples of propaganda posters, try
Phil’s Old Radios on the VE301:
http://antiqueradio.org/VolksempfaengerVE301dyn.htm
SC
July 2017 97
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
PIC programming
questions
I have downloaded MPLAB 8.92
which seemed to be the up-to-date
version to use to program the PIC32MX170 for the Micromite (www.
siliconchip.com.au/Project/Micromite).
The MPLAB downloaded and installed,
even downloading some support files!
I was going to use this program with a
PICkit 3.
On checking the configuration,
I could not find the device PIC32MX170. The devices listed went
from MX150 to MX210 (plus other letters). I tried searching for updates of
the main program and ways of updating the data. Unfortunately, I couldn't
find anything to help me. After several
hour of frustration, I thought I need to
ask for help.
I must be jinxed with programming
PICs as I tried to get the programmer
from May 2008 (www.siliconchip.
com.au/Article/1824) to work but WinPic didn't want to cooperate back then,
but it did give me the idea to use an IC
socket into which a ZIF socket is used
for holding the PIC to be programmed,
as per the old Jaycar kit.
I also want to try programming a PIC
using an Arduino, as described in the
November 2015 article titled "Cheap
programmer for the PIC32 microcontroller" (http://www.siliconchip.com.
au/Article/9403). So, I have a question
on that, too. I have downloaded and
I think installed the pic32prog successfully from GitHub but when I try
to open it I get a small window opening up and then it disappears. Is this
because I haven't opened a command
window? How do I do that on XP/Windows 8.1? (R. P., via email)
• The latest version of MPLAB is
MPLAB X v3.61.
It's likely that you will not get support for the PIC32MX170 without using MPLAB X, which superseded earlier versions of MPLAB such as the
8.xx versions.
Regarding your second question;
yes, you need to run pic32prog from
a command prompt. In Windows XP,
you can open one by going to the Start
menu, selecting the Run option and
then typing "cmd" and pressing enter.
In Windows 10, Microsoft changed
the way the "Start" menu works; it
doesn't seem to be called that any more
but it works similarly. Simply click the
button in the lower-left corner of the
screen to open the menu, type "cmd"
and press enter. Windows 8.1 should
operate in a similar manner.
LED downlights
I am replacing some Kogan LED
downlights in my kitchen with
Philips units since the Kogan ones
produce too much RF interference
(see related letter in Mailbag in this
issue). I have eight of these halogenreplacement downlights that I want
to combine.
I know that LEDs need DC but
these downlights are non-polarised;
they just plug in to where halogen
lights were previously. I could make
up a 12V DC supply to power the
lot but aren't the downlight transformers that you get from electrical
suppliers AC only? Does that mean
98 Silicon Chip
that each LED has its own rectifier
in-built?
Perhaps I should buy 12V transformers from Bunnings and just wire
the LEDs in parallel, making sure
that the combination is well within
the ratings of the transformer(s). (I.
S., Glenhaven, NSW)
• Any LED that is intended as a
plug-in replacement for a 12V halogen lamp will have its own built-in
rectifier and current drive circuitry
so they can run from the original 12V
AC transformers. A single 12V 50VA
transformer should easily handle all
eight LED lamps.
Alternatively, in Windows Vista and
later, you can hold shift and right-click
in a folder to give you the menu option to open a command window in
that folder.
Majestic speaker
dimension misprint
I am currently building several of the Majestic speakers (www.
siliconchip.com.au/Series/275) but
I am confused about the hyperbolic
horn construction.
The follow-up article in the September 2014 issue shows different dimensions for the horn panel in Fig.3 but the
panel still seems to be too long to be
secured at the critical points of attachment. I am assuming that the length
of 660mm as stated may be a typo as
is the front anchor point of 377mm.
(R. L., Cornubia, Qld)
• The figure of 377mm on the diagram
on page 89 of the September 2014 issue is a misprint; it should be 37mm,
as in the original diagram on page 27
of the June issue. Thank you for bringing it to our attention. The dimension
of the curved horn panel is correct at
660mm. The misprint has been corrected in the online issue.
Stationmaster frequency
lower than expected
Recently I finished building your
Stationmaster train controller, published in the March 2017 issue (www.
siliconchip.com.au/Article/10575).
However, it does not work and I'm
wondering if you can help me troubleshoot it?
The red LED comes on when DC or
AC is applied but when trimpot VR1
is turned, no other LED comes on. I
have followed instructions in the magazine and the voltage across VCC1 and
VCC2 is correct but when the frequency is checked across SYNC, it only
comes up with 50Hz, not the required
8-10kHz. (A. M., Lidcombe, NSW)
• The SYNC output seems to be opencircuit if you are only picking up mains
siliconchip.com.au
Adding over-current protection to Speaker Protector
Could over-current protection be
added to the next version of Silicon Chip's excellent speaker protector from the November 2015
issue (www.siliconchip.com.au/
Issue/2015/November/A+Universal
+Loudspeaker+Protector)?
This would mean that if someone
accidentally shorted the speaker
cables, the speaker protection will
detect the huge voltage drop across
the amplifier's emitter resistors and
then the relay will be switched off.
One added resistor can be used
to define the speaker impedance,
so if the speaker's impedance is
below 6W, the protection circuit will
refuse to turn on the relay.
This way we are protecting an
amplifier that is designed to work
with 6 to 8-ohm speakers from a
load of significantly lower impedradiation on your frequency meter (the
most likely explanation for a reading of
50Hz). Check at pin 7 of IC1 directly.
Make sure IC1 has 5V at pin 4 and 0V
at pin 11. This oscillator should work
if the components are correctly placed
and soldered in with no dry joints.
The voltage at pin 2 and pin 5 of
IC1 should be at half supply, ie, 2.5V.
Deep Cycle Battery
Charger confusion
I have built the Deep Cycle Battery
Charger described in the November
and December 2004 issues of Silicon Chip (www.siliconchip.com.au/
Series/102).
However, there appears to be an
anomaly in the connections to bridge
rectifier BR2. The circuit diagram
shows no connection to the negative
pole of the rectifier but the board layout shows it connected to the battery
negative terminal. Could you please
clarify which is correct. (G. C., Stanthorpe, Qld)
• We can see the source of your
confusion; the PCB overlay for that
project in the December 2004 issue
is labelled in a confusing manner.
Referring to the PCB overlay on page
31 (Fig.6) and the wiring diagram on
page 33 (Fig.9), the terminal labelled
“TO BR1 NEGATIVE OUTPUT” in
Fig.6 does indeed go to the negative
siliconchip.com.au
ance (eg, if a 4W or 2W speaker is
connected instead).
• At first sight, this could be a
useful enhancement, even though
it would a bit tricky to do without
the potential for false tripping, as
the impedance of all speakers can
dip well below the nominal value.
For example, an 8W speaker can
definitely have an impedance below
4W at certain frequencies.
You might consider using a microcontroller or some tricky circuitry
to pass a small AC signal through
the speakers at switch-on to detect
the impedance at a few different
frequencies and decide whether to
switch the outputs off or not.
However, the more one considers the idea, the less desirable it
becomes, especially if we add a series resistor, as you suggest, to “deoutput terminal of BR1, as shown
in Fig.9.
However, the terminal labelled “TO
BR2 NEGATIVE OUTPUT” in Fig.6 actually goes to the AC terminals of BR2,
as shown in Fig.9. These effectively
act as the negative output in this case,
even though they are not labelled “-”.
That’s because only half of the diodes
in the bridge rectifier are used.
So the PCB overlay and wiring diagram are consistent with the circuit
diagram in the November 2004 issue, as
long as you understand that the “negative output” of BR2 is not actually
the terminal marked “-” in this case.
Quirks encountered
with Micromite tutorial
I have just completed the Micromite
LCD BackPack project from the February 2016 issue (www.siliconchip.com.
au/Article/9812) but I am having a few
issues that I hope you might be able to
help me sort out.
I am a total novice when it comes
to these little microprocessors and any
programming, although I did have a go
with BASIC when I was in high school,
with a DSE VZ200 computer!
I was prompted by the articles on
getting started with the Micromite in
the February, March, May and June
2017 issues (www.siliconchip.com.
au/Series/311). I was considering the
fine” the speaker impedance. Any
such resistor will degrade the damping factor of the amplifier and possibly also degrade the overall distortion performance.
We take the view that any amplifier should be capable of coping with
the inevitable dips in the impedance
curve at some frequencies, for all
loudspeakers. That means it should
cope with very brief signal bursts at
those critical frequencies without
any interruption to the output signal.
Even a brief short circuit between
the outputs of an amplifier should
not cause any problems, particularly if the signal level is low. Of
course, much longer severe overloads, which might happen when
the amplifier is really cranked up to
high volumes, should be protected
by the supply fuses blowing.
Arduino or Raspberry Pi platforms
but choose the Micromite as it is a local product and hopefully help is not
too far away.
I have it up and running and configured as per the February 2016 article.
The screen is calibrated, the touch/
draw functions work etc.
However, when I write out the test
program for the clock/calendar in
MMEdit and attempt to run it, it loads
the program, acknowledges the Micromite and then I get the error message
"DO WITHOUT LOOP", even though
I have typed the program exactly as
printed, including the loop command
at the end.
I then thought I’d make up the little
diode & resistor circuit and connect
the anode via a 470W resistor to pin
14 and the cathode to GND and run
the little program on page 20 of the
February 2017 issue.
The result of this is an error message "pin 14 reserved at start up". I am
using MMEdit version 3.69 and Terra
Term Version 4.93 on a Windows 10,
64 bit desktop computer. I am using
the PIC32MX170F256B-50I/SP which
I programmed myself with a PICkit 3.
As I sit here typing this note I have
the screen constantly drawing those
lovely little coloured circles of the GUI
TEST LCDPANEL command.
I am using the same Serial to USB
converter as in the article and it seems
July 2017 99
Fixing incorrectly sized Senator speaker cabinets
I had a cabinet maker supply and
cut out the panels using the dimensions given in the Senator loudspeakers article from September
2015 (www.siliconchip.com.au/
Series/291).
But I forgot about the later correction to the cabinet size with the
result that the cabinet maker made
the width 320mm. He very cleverly
almost matched the depth and
height, but the width was left at
the 320mm.
If my calculations are correct, I
now have enclosures that are 4.63
litres too large. If memory serves
me correctly from previous articles
on vented enclosure design, this is
a significant variation to design parameters.
It cost a packet to get the cabinet
maker to supply and cut the imitation-wood coated MDF and this
used my allocated budget for this
project (which is why I built the
budget Senator).
to work fine. Here is the program I'm
trying to run. Where am I going wrong?
(P. C., Woodcroft, SA)
CLS
BOX 0, 0, MM.HRes-1, MM.VRes/2,
3, RGB(RED), RGB(BLUE)
DO
TEXT MM.HRes/2, MM.VRes/4,
TIME$, CM, 1, 4, RGB(CYAN),
RGB(BLUE)
TEXT MM.HRES/2, MM.VRES*3/4,
DATE$, CM, 1, 3, RGB(GREEN)
IF TOUCH(X) <> -1 THEN END
LOOP
•
We tried typing in the same sample program (from Fig.6 on page 28 of
the February 2016 issue) into MMEdit,
just like you, and we too got the "DO
WITHOUT LOOP" error.
However, as you say, the LOOP
line is there so we tried doing exactly the same thing again from scratch
and would you believe it worked the
second time? We're quite baffled by
this and we think maybe it is a bug in
MMEdit which somehow mangles the
code when it is first uploaded to the
chip. So please try again.
Note that we've had other readers complain of the "DO WITHOUT
100 Silicon Chip
Would adjusting the box/port
resonance frequency to match this
different volume be easier than rebuilding the boxes?
Without doing the maths (which
I could use some help with – I don’t
have software to do it for me), can
you suggest a box/port resonant
frequency to match my slightly larger
cabinet volume?
When I refer to the box/port
frequency I’m assuming this means
only changing the port length, which
would be the easiest option.
Alternatively, can you recommend some open-source software I
can use to do the required calculations? In case it helps, here are the
exact dimensions of each panel cut:
* Front and rear baffle: 730mm
x 315mm
* Side panels: 730mm x 414mm
* Top panel: 347mm x 414mm
* Bottom panel: 315mm x 382mm
Another difficulty created by the
cabinetmaker was that they only
LOOP" error however they were trying to type the program directly into
the console.
The error is produced as soon as you
type the "DO" line in that case. You
need to use the Micromite's built-in
EDIT command, or MMEdit, to enter
the sample program (or any program,
for that matter) as commands entered in
the console are executed immediately.
As for the program on page 20 of the
February 2017 issue, that was intended
to be used on a bare 28-pin Micromite.
Your LCD BackPack is already using
pin 14 to communicate with the LCD
(it's the SPI IN pin).
You have two options: either disable
the LCD to free up the pin or change
the code to use a different pin. The
latter is probably easier. Pins 4, 5, 9,
10, 16, 17, 18, 21, 22, 24 and 26 are
all available.
It's unfortunate that the example in
the tutorial uses pin 14 when it won't
work on the LCD BackPack. Had we
realised, we would have changed it.
To solder the pad on the
underside of SMD ICs?
I am currently building your Compact 8-digit Auto-Ranging Frequency
used 16mm MDF. Thinner MDF
means I’ll need some small-volume
bracing which may restrict me to using aluminium angle.
If I used MDF for bracing, some
close calculations of volume would
be needed. A cross-brace in 16mm
MDF would be 16x315x100 which
works out to 0.5 litres if I used a
100mm width. I hope Allan LintonSmith won’t be too horrified. (E.
McA, Capel, WA)
• By our calculations, the change in
volume is just over one litre which
means that there should be negligible change in performance.
We calculated this by ignoring
the overall cabinet dimensions and
just using the internal dimensions.
The published cabinet is 73 × 32 ×
38.1cm = 89 litres, while your cabinet is 73 × 31.5 × 38.2cm = 87.84
litres
A small amount of added bracing
would be unlikely to have much
effect.
Meter project from the August 2016
issue (www.siliconchip.com.au/
Article/10037).
On inspection of the surface mount
ICs1-3 (ADA4899 high speed op
amps), I noticed that they have a pad
on the underside in the middle and so
does the circuit board, with a platedthrough hole.
Do I need to solder that pad of the
circuit board from the underside? The
instructions of how to solder the ICs
don't mention it. Or do I have to put
pressure on the IC, so there is contact?
Is this pad perhaps used as a heatsink?
I would appreciate your help.
On another note, I purchased the
Banggood DSO138 scope kit, described in the April 2017 issue (www.
siliconchip.com.au/Article/10613).
That is a terrific little project and
proved easy and fun to build. Thanks
for presenting it and I am looking forward to more of your excellent technical articles.
And to the readers who think this
or that article does not belong to an
electronics magazine, if you can learn
something then it is definitely worth
having it! (H. M., Bowral, NSW)
• You are right, the article left out
mention of soldering the pad on the
siliconchip.com.au
ONLINESHOP
SILICON
CHIP
PCBs and other hard-to-get components now available direct from the S
.com.au/shop
ILICON CHIP ONLINESHOP
NOTE: Not all PCBs are shown here due to space limits but the SILICON CHIP ONLINESHOP has boards going back to 2001 and beyond.
For a complete list of available PCBs, back issues, etc, go to siliconchip.com.au/shop Prices are PCBs only, NOT COMPLETE KITS!
FRIDGE/FREEZER ALARM
ARDUINO MULTIFUNCTION MEASUREMENT
PRECISION 50/60HZ TURNTABLE DRIVER
RASPBERRY PI TEMP SENSOR EXPANSION
100DB STEREO AUDIO LEVEL/VU METER
HOTEL SAFE ALARM
UNIVERSAL TEMPERATURE ALARM
BROWNOUT PROTECTOR MK2
8-DIGIT FREQUENCY METER
APPLIANCE ENERGY METER
MICROMITE PLUS EXPLORE 64
CYCLIC PUMP/MAINS TIMER
MICROMITE PLUS EXPLORE 100 (4 layer)
AUTOMOTIVE FAULT DETECTOR
MOSQUITO LURE
MICROPOWER LED FLASHER
MINI MICROPOWER LED FLASHER
50A BATTERY CHARGER CONTROLLER
PASSIVE LINE TO PHONO INPUT CONVERTER
MICROMITE PLUS LCD BACKPACK
APR 2016
APR 2016
MAY 2016
MAY 2016
JUN 2016
JUN 2016
JULY 2016
JULY 2016
AUG 2016
AUG 2016
AUG 2016
SEPT 2016
SEPT 2016
SEPT 2016
OCT 2016
OCT 2016
OCT 2016
NOV 2016
NOV 2016
NOV 2016
03104161
04116011/2
04104161
24104161
01104161
03106161
03105161
10107161
04105161
04116061
07108161
10108161/2
07109161
05109161
25110161
16109161
16109162
11111161
01111161
07110161
$5.00
$15.00
$15.00
$5.00
$15.00
$5.00
$5.00
$10.00
$10.00
$15.00
$5.00
$10.00/pair
$20.00
$10.00
$5.00
$5.00
$2.50
$10.00
$5.00
$7.50
AUTOMOTIVE SENSOR MODIFIER
TOUCHSCREEN VOLTAGE/CURRENT REFERENCE
SC200 AMPLIFIER MODULE
60V 40A DC MOTOR SPEED CON. CONTROL BOARD
60V 40A DC MOTOR SPEED CON. MOSFET BOARD
GPS SYNCHRONISED ANALOG CLOCK
ULTRA LOW VOLTAGE LED FLASHER
POOL LAP COUNTER
STATIONMASTER TRAIN CONTROLLER
EFUSE
SPRING REVERB
6GHZ+ 1000:1 PRESCALER
MICROBRIDGE
MICROMITE LCD BACKPACK V2
10-OCTAVE STEREO GRAPHIC EQUALISER PCB
10-OCTAVE STEREO GRAPHIC EQUALISER FRONT PANEL
10-OCTAVE STEREO GRAPHIC EQUALISER CASE PIECES
NEW THIS MONTH
RAPIDBRAKE
DEC 2016
05111161
DEC 2016
04110161
JAN 2017
01108161
JAN 2017
11112161
JAN 2017
11112162
FEB 2017
04202171
FEB 2017
16110161
MAR 2017
19102171
MAR 2017
09103171/2
APR 2017
04102171
APR 2017
01104171
MAY 2017
04112162
MAY 2017
24104171
MAY 2017
07104171
JUN 2017
01105171
JUN 2017
01105172
JUN 2017
$10.00
$12.50
$10.00
$10.00
$12.50
$10.00
$2.50
$15.00
$15.00/set
$7.50
$12.50
$7.50
$2.50
$7.50
$12.50
$15.00
$15.00
JUL 2017
$10.00
05105171
Prices above are for the Printed Circuit Board ONLY – NO COMPONENTS OR INSTRUCTIONS ETC ARE INCLUDED! P&P for PCBS (within Australia): $10 per order (ie, any number)
PRE-PROGRAMMED MICROS
Price for any of these micros is just $15.00 each + $10 p&p per order#
As a service to readers, SILICON CHIP ONLINESHOP stocks microcontrollers and microprocessors used in new projects (from 2012 on) and
some selected older projects – pre-programmed and ready to fly!
Some micros from copyrighted and/or contributed projects may not be available.
PIC12F675-I/P
PIC16F1455-I/P
PIC16F1507-I/P
PIC16F88-E/P
PIC16F88-I/P
PIC16LF88-I/P
PIC16LF88-I/SO
PIC16LF1709-I/SO
PIC16F877A-I/P
UHF Remote Switch (Jan09), Ultrasonic Cleaner (Aug10),
Ultrasonic Anti-fouling (Sep10), Cricket/Frog (Jun12), Do Not Disturb (May13)
IR-to-UHF Converter (Jul13), UHF-to-IR Converter (Jul13)
PC Birdies *2 chips – $15 pair* (Aug13), Driveway Monitor Receiver (July15)
Hotel Safe Alarm (Jun16), 50A Battery Charger Controller (Nov16)
Microbridge (May17)
Wideband Oxygen Sensor (Jun-Jul12)
Hi Energy Ignition (Nov/Dec12), Speedo Corrector (Sept13),
Auto Headlight Controller (Oct13), 10A 230V Motor Speed Controller (Feb14)
Automotive Sensor Modifier (Dec16)
Projector Speed (Apr11), Vox (Jun11), Ultrasonic Water Tank Level (Sep11),
Quizzical (Oct11), Ultra LD Preamp (Nov11), 10-Channel Remote Control
Receiver (Jun13), Revised 10-Channel Remote Control Receiver (Jul13),
Nicad/NiMH Burp Charger (Mar14), Remote Mains Timer (Nov14),
Driveway Monitor Transmitter (July15), Fingerprint Scanner (Nov15)
MPPT Lighting Charge Controller (Feb16), 50/60Hz Turntable Driver (May16)
Cyclic Pump Timer (Sep16), 60V 40A DC Motor Speed Controller (Jan17)
Pool Lap Counter (Mar17), Rapidbrake (Jul17)
Garbage Reminder (Jan13), Bellbird (Dec13), GPS Analog Clock Driver (Feb17)
LED Ladybird (Apr13)
Battery Cell Balancer (Mar16)
6-Digit GPS Clock (May-Jun09), Lab Digital Pot (Jul10), Semtest (Feb-May12)
PIC16F2550-I/SP
Batt Capacity Meter (Jun09), Intelligent Fan Controller (Jul10)
PIC18F4550-I/P
GPS Car Computer (Jan10), GPS Boat Computer (Oct10)
PIC32MX795F512H-80I/PT Maximite (Mar11), miniMaximite (Nov11), Colour Maximite (Sept/Oct12),
Touchscreen Audio Recorder (Jun/Jul 14)
PIC32MX170F256B-50I/SP Micromite Mk2 (Jan15) – also includes FREE 47F tantalum capacitor
Micromite LCD BackPack [either version] (Feb16), GPS Boat Computer (Apr16)
Micromite Super Clock (Jul16), Touchscreen Voltage/Current Ref (Oct-Dec16)
Micromite LCD BackPack V2 (May17)
PIC32MX170F256B-I/SP
Low Frequency Distortion Analyser (Apr15)
PIC32MX170F256D-501P/T 44-pin Micromite Mk2 (Now with Mk2 Firmware at no extra cost)
PIC32MX250F128B-I/SP
GPS Tracker (Nov13), Micromite ASCII Video Terminal (Jul14)
PIC32MX470F512H-I/PT
Stereo Audio Delay/DSP (Nov13), Stereo Echo/Reverb (Feb 14),
Digital Effects Unit (Oct14)
PIC32MX470F512H-120/PT Micromite PLUS Explore 64 (Aug 16), Micromite Plus LCD BackPack (Nov16)
PIC32MX470F512L-120/PT Micromite PLUS Explore 100 (Sep-Oct16)
dsPIC33FJ128GP802-I/SP Digital Audio Signal Generator (Mar-May10), Digital Lighting Controller
(Oct-Dec10), SportSync (May11), Digital Audio Delay (Dec11)
Quizzical (Oct11), Ultra-LD Preamp (Nov11), LED Musicolor (Nov12)
dsPIC33FJ64MC802-E/P
Induction Motor Speed Controller (revised) (Aug13)
dsPIC33FJ128GP306-I/PT CLASSiC DAC (Feb-May 13)
ATTiny861
Thermometer/Thermostat (Mar10), Rudder Position Indicator (Jul11)
ATTiny2313
Remote-Controlled Timer (Aug10)
When ordering, be sure to nominate BOTH the micro required AND the project for which it must be programmed.
SPECIALISED COMPONENTS
P&P: FLAT RATE $10.00 PER ORDER#
PCBs, COMPONENTS ETC MAY BE COMBINED (in one order) FOR $10-PER-ORDER P&P RATE
NEW THIS MONTH:
STATIONMASTER
ARDUINO MUSIC PLAYER/RECORDER
(JUL 17)
Geeetech VS1053 Arduino MP3 shield $20.00
ARDUINO LC METER
(JUN 17)
1nF 1% MKP capacitor, 5mm lead spacing
MAX7219 LED DISPLAY MODULES
8x8 LED matrix module with DIP MAX7219
8x8 LED matrix module with SMD MAX7219
8-digit 7-segment red display module with SMD MAX7219
(JUN 17)
(MAR 17)
DRV8871 IC, SMD 1µF capacitor and 100kW potentiometer with detent $12.50
ULTRA LOW VOLTAGE LED FLASHER
(FEB 17)
kit including PCB and all SMD parts, LDR and blue LED
$12.50
$2.50
SC200 AMPLIFIER MODULE
(JAN 17)
hard-to-get parts: Q8-Q16, D2-D4, 150pF/250V capacitor and five SMD resistors
$35.00
$5.00
$5.00
$7.50
60V 40A DC MOTOR SPEED CONTROLLER
$35.00
(JAN 17)
hard-to-get parts: IC2, Q1, Q2 and D1
MICROBRIDGE
COMPUTER INTERFACE MODULES
(JAN 17)
MICROMITE LCD BACKPACK V2 – COMPLETE KIT
TOUCHSCREEN VOLTAGE/CURRENT REFERENCE
MICROMITE LCD BACKPACK KIT (programmed to suit) PLUS UB1 Lid
LASER-CUT MATTE BLACK LID (to suit UB1 Jiffy Box)
(DEC 16)
(MAY 17)
PCB plus all on-board parts including programmed microcontroller
(SMD ceramics for 10µF) $20.00
(MAY 17)
includes PCB, programmed micro, touchscreen LCD, laser-cut UB3 lid, mounting hardware,
SMD Mosfets for PWM backlight control and all other on-board parts $70.00
EFUSE
(APR 17)
two NIS5512 ICs plus one SUP53P06 $22.50
DDS MODULES
(APR 17)
AD9833 DDS module (with gain control) (for Micromite DDS) $25.00
AD9833 DDS module (no gain control) (El Cheapo Modules, Part 6) $15.00
POOL LAP COUNTER
(MAR 17)
two 70mm 7-segment high brightness blue displays plus logic-level Mosfet $17.50
laser-cut blue tinted lid, 152 x 90 x 3mm $7.50
CP2102 USB-UART bridge
microSD card adaptor
SHORT FORM KIT with main PCB plus onboard parts (not including BackPack
module, jiffy box, power supply or wires/cables)
$5.00
$2.50
$70.00
$10.00
$99.00
PASSIVE LINE TO PHONO INPUT CONVERTER - ALL SMD PARTS
(NOV 16)
$5.00
MICROMITE PLUS EXPLORE 100 *COMPLETE KIT (no LCD panel)* (SEP 16) $69.90
(includes PCB, programmed micro and the hard-to-get bits including female headers, USB and microSD
sockets, crystal, etc but does not include the LCD panel)
MICROMITE LCD BACKPACK ***** COMPLETE KIT *****
(FEB 16) *$65.00
includes PCB, micro and 2.8-inch touchscreen AND NOW INCLUDES LID (specify clear or black lid)
All items subect to availability. Prices valid for month of magazine issue only. All prices in Australian dollars and included GST where applicable. # P&P prices are within Australia. O’seas? Please email for a quote
PAYPAL (24/7)
INTERNET (24/7)
MAIL (24/7)
– (9-4, Mon-Fri)
eMAIL (24/7)
To
siliconchip.com.au
JPHONE
uly 2017 101
Use your PayPal account
siliconchip.com.au/Shop
Your order to PO Box 139
Call (02) 9939 3295 with
silicon<at>siliconchip.com.au
Place
silicon<at>siliconchip.com.au
Collaroy NSW 2097
with order & credit card details
with order & credit card details
Your
You can also order and pay by cheque/money order (Orders by mail only). ^Make cheques payable to Silicon Chip Publications.
Order:
6/17
Down button not working on Digital Audio Signal Generator
I've been building the Digital
Audio Signal Generator from the
March, April & May 2010 issues
(www.siliconchip.com.au/Series/1)
and have finally gotten it to power up.
The problem I have struck is that I
cannot get the down button to work.
I have tried many things and traced
the circuit right through from the
main board. No luck, except when
I stopped the select button from
being in the circuit. Then it would
go down but it would only go down
a menu item, not take a value down!
All the other buttons work as they
should. I need to have the down
button working so I can have one
channel at 1000Hz and another at
either 500Hz or 2400Hz. Unfortunately, you cannot use the Up button to take it back to zero as it stops
at 24000Hz. You then have to switch
off and restart.
I also had a lot of trouble with
ZD1 and trying to get one that came
underside of these ICs. This was intentional because we found it was quite
easy to allow too much solder to flow
through the hole and this can short out
the pins, which is then difficult to fix.
It isn't critical to solder this pad; it
does improve the chip's heatsinking
but in our circuit, they are not dissipating so much power that it's an issue.
These ICs are designed to be used
with hot air or infrared reflow soldering, where solder paste is placed on the
PCB, then the IC is placed on top and it
is heated to melt the solder paste. You
can use this same approach if you have
a hot air rework station. They are available at surprisingly reasonable prices.
The hole we placed on the PCB is
large enough to fit a very fine soldering tip through and solder the bottom
side of the IC directly. However, this
should not be necessary.
If you put a little flux paste under
the IC before soldering it in the usual
way, then add a little extra flux paste
into the hole on the other side, simply
applying solder to the pad on the underside should cause it to flow through
the hole and onto the pad on the bottom if the IC.
If you decide to do this, be careful
to only add solder sparingly, though,
102 Silicon Chip
close trying 4.7V and 5.1V units from
many suppliers. They vary so much,
even within a batch. I have finally
found some with a rated breakdown
voltage of around 4.9-5.0V and am
going to get some and try them.
At present, it's close and works
alright with correct voltages at 7.0V
DC. If I go above that by 0.3V, the
screen starts to get an orange background!
Except for the button issues, the
PIC appears to be doing its job and I
was very careful installing it. I would
really appreciate any assistance you
can give me in this as it's not much
use at present and I really need the
analog side to work properly. (P. N.,
Newtown, Qld)
• This is quite baffling. Our prototype certainly didn't exhibit button
problems like you describe, but you
say you've checked the continuity
between the buttons and the micro
and that would have been our first
guess as to the problem.
to avoid the aforementioned possible
short circuits.
Using VK2828U7G5LF
GPS module
I am building the High Visibility 6-Digit LED GPS Clock (December 2015 & January 2016; www.
siliconchip.com.au/Series/294) and
the Deluxe GPS 1PPS Timebase for Frequency Counters (April 2013; www.
siliconchip.com.au/Article/3757),
both using the VK2828U7G5LF GPS
module purchased from your online shop (www.siliconchip.com.au/
Shop/7/3362).
Is a pull-up resistor needed from
the +V line (red wire) to the enable
line (yellow wire) or can the enable
line be connected directly to the positive supply? What value for such a
resistor do you suggest? Is it best to
use 3.3V or 5V to power this module?
(R. P., via email)
• It will work either way, with a
pull-up resistor from +V to EN or with
a direct connection. As long as the EN
pin (yellow wire) is pulled high, the
module should operate. If you do use
a resistor, we suggest something in the
range of 1-10kW.
Normally we would recommend you
try replacing D9 and D11, carefully
check the solder joints for D9, D11,
S5, S7 and CON9 on the front panel
board and CON4 on the main board,
and make very sure that the ribbon
cable connecting the two boards has
been properly crimped.
In the past, the ribbon cable has
been the source of most faults. The
crimp connectors can look good but
you can have a high-resistance connection to one or more pins. In that
case, it's worthwhile re-crimping
both ends just to make sure.
It's especially weird that you managed to get the Down button to work
in the menus but not for changing
values.
It seems like it might be a timing
problem but we can't understand
why. Maybe try a different PIC. As
you purchased the original PIC from
us, we could send you a replacement on the basis that it seems to
be faulty.
We tested it at both 3.3V and 5V
and didn't notice any difference in
performance. Its I/O signal swing is
3.3V regardless of the supply voltage.
Note though that 5V is recommended
and 3.3V is the specified minimum,
so unless your 3.3V rail is precisely
regulated, a 5V supply is a little safer.
If you run the module off 3.3V that
is derived from 5V via a linear regulator, you will be increasing dissipation in the regulator and also reducing
the 3.3V current available to the rest
of your circuit.
Alternatively, if your 3.3V rail is derived via a switchmode regulator, overall power consumption will be lower
than if you power the module from 5V.
So we suggest using a 5V supply unless there is a compelling reason to do
otherwise, but our tests suggest it will
run off 3.3V just as happily.
Personal Noise Source
wanted
I am after an old kit from the September 2001 issue; the Personal Noise
Source, PCB code 01109011. Is it still
available or would I have to make it?
(G. M., Kogarah, NSW)
• Unfortunately, we do not have PCBs
siliconchip.com.au
MARKET CENTRE
Cash in your surplus gear. Advertise it here in SILICON CHIP
KIT ASSEMBLY & REPAIR
KEITH RIPPON KIT ASSEMBLY &
REPAIR:
* Australia & New Zealand;
* Small production runs.
Phone Keith 0409 662 794.
keith.rippon<at>gmail.com
VINTAGE RADIO REPAIRS: electrical mechanical fitter with 36 years
ex
p erience and extensive knowledge of valve and transistor radios.
Professional and reliable repairs. All
workmanship guaranteed. $10 inspection fee plus charges for parts
and labour as required. Labour fees
$35 p/h. Pensioner discounts available on application. Contact Alan
on 0425 122 415 or email bigal
radioshack<at>gmail.com
DAVE THOMPSON (the Serviceman
from SILICON CHIP) is available to help
you with kit assembly, project troubleshooting, general electronics and custom design work. No job too small. Based
in Christchurch, NZ but service available Australia/NZ wide. Email dave<at>
davethompson.co.nz
Where do you get those
HARD-TO-GET PARTS?
Where possible, the SILICON CHIP On-Line
Shop stocks hard-to-get project parts,
along with PCBs, programmed micros,
panels and all the other bits and pieces
to enable you to complete your
SILICON CHIP project.
KEEP YOUR COPIES OF
SILICON CHIP
AS GOOD AS THE DAY
THEY WERE BORN!
SILICON CHIP
ONLY
95
On-Line SHOP
$
1P6LUS
p&p
A superb-looking
SILICON CHIP
binder will keep
your magazines in
pristine condition.
* Holds up to 14 issues
* Heavy duty vinyl
* Easy wire inserts
ORDER NOW AT
www.siliconchip.com.au/shop
www.siliconchip.com.au/shop
FOR SALE
PCB MANUFACTURE: single to multi
layer. Bare board tested. One-offs to
any quantity. 48 hour service. Artwork
design. Excellent prices. Check out our
specials: www.ldelectronics.com.au
tronixlabs.com.au - Australia’s best
value for hobbyist and enthusiast electronics from adafruit, DFRobot, Freetronics, Raspberry Pi, Genuino and more,
with same-day shipping.
LEDs, BRAND NAME and generic
LEDs. Heatsinks, fans, LED drivers,
power supplies, LED ribbon, kits, components, hardware, EL wire. www.ledsales.com.au
PCBs MADE, ONE OR MANY. Any format, hobbyists welcome. Sesame Electronics Phone 0434 781 191.
sesame<at>sesame.com.au
www.sesame.com.au
ADVERTISING IN MARKET CENTRE
Classified Ad Rates: $32.00 for up to 20 words (punctuation not charged) plus 95 cents for each additional word. Display ads in
Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST.
Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, address & credit card details, or phone Glyn (02) 9939 3295 or 0431 792 293.
for this project. You can purchase a
PDF of the artwork from our website if
you want to make the board. But have
you considered that there are pink
noise apps for smartphones? That really seems like a more convenient solution, unless you don't want to use a
smartphone.
Large LCD panels for
the Explore 100
I'm currently building the Explore
100 project (September & October
2016; www.siliconchip.com.au/Sesiliconchip.com.au
ries/304) and have a query regarding
the LCD panels that are suitable.
On page 79 of the September 2016
issue, under display size and in bold
print, it says that the East Rising panel
uses a non-standard interface pin-out.
Does this only refer to the 8-inch
panel or the 5-inch and 7-inch panels
as well? I would like to use the largest panel that has the standard interface pin-out. (I. T., Blacktown, NSW)
• Geoff Graham replies: East Rising
is a company that does not necessarily
follow established standards, so you
need to have a good depth of knowl-
edge and flexibility when using their
products.
The article mentioned the East Rising 8-inch display as that is the only
8-inch display that we could find and
that we tested.
If you are considering 5-inch and
7-inch panels then you would be better
going with more standard eBay products that will plug straight into the Explore 100. These two examples look
OK (note that we have not tested them
so we cannot guarantee anything):
http://siliconchip.com.au/l/aad1
http://siliconchip.com.au/l/aad2 SC
July 2017 103
Next Month in Silicon Chip
LTspice - simulating and testing circuits, part 2
Next month in part two of our SPICE tutorial, held over from this issue
due to space constraints, we describe how to build a basic simulation of a
relay in LTspice. We then make the relay model more realistic by adding a few
extra features.
El Cheapo Modules, part 8: GPS modules
We describe two common GPS modules, their features and how to interface them
to an Arduino or Micromite.
Survey of Radio Telescopes
Silicon Chip has had a number of articles on radio telescopes, the most
recent being on China's gigantic new telescope, in the October 2016 issue.
Now Dr. David Maddison takes a look at radio telescopes around the world,
from the relatively small to the extremely large which use the techniques
aperture synthesis and interferometry.
Using a DDS Module for AM Radio IF Alignment
In this article, we present updated software and slight tweaks to the
hardware of the Micromite BackPack Touchsreen DDS Signal Generator
described in the April issue. These changes make it a cinch to align the IF stage
of a transistor or valve-based superheretodyne AM radio.
Rohde & Schwarz RTB2004 DSO Review
We take a look at this latest offering from R&S which combines a 10-bit ADC and
10.1-inch capacitive touchscreen along with either two or four channels in a compact bench-top unit.
Note: these features are prepared or are in preparation for publication and
barring unforeseen circumstances, will be in the next issue.
The August 2017 issue is due on sale in newsagents by Thursday July 27th.
Expect postal delivery of subscription copies in Australia between July 27th and
August 10th.
Advertising Index
Altronics.................................. 68-71
Dave Thompson......................... 103
Digi-Key Electronics....................... 3
Electronex.................................... 15
element14...................................... 7
Emona Instruments.................... IBC
Hare & Forbes.......................... OBC
Jaycar............................... IFC,49-56
Keith Rippon Kit Assembly......... 103
Laservision................................... 14
LD Electronics............................ 103
LEDsales.................................... 103
Master Instruments...................... 11
Mastercut Technologies................ 12
Microchip Technology............... 5, 39
Mouser Electronics......................... 9
Ocean Controls.............................. 8
PCB Cart................................... 13
Sesame Electronics................... 103
SC Online Shop......................... 101
SC Radio & Hobbies DVD............ 76
Silicon Chip Binders..................... 81
Silicon Chip Wallchart.................. 31
Tronixlabs................................... 103
Vintage Radio Repairs............... 103
Notes & Errata
Improved Tweeter Horn for the Majestic Loudspeaker, September 2014: Fig.3 on page 89 has a misprint in theSC
printed edition, which shows a distance of 377mm between the front of the lower panel of the speaker and the end of
the hyperbolic horn panel. It should read 37mm instead. The online version of this article shows the correct dimension.
Spring Reverberation Unit, April 2017: if using the DC supply option with CON6 (the barrel connector), it's necessary
to either omit CON5 and solder a short length of wire between its two outer mounting holes (without shorting to the centre), or alternatively, fit a 3-way connector for CON5 and connect a wire link across its two outer terminals.
6GHz+ RF Prescaler project, May 2017: As published, this project does not have an output impedance of 75W; it is
300W. This can be fixed by substituting 0W resistors for the 100W resistors and 75W resistors for the 300W resistors.
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
Competition & Consumer Act 2010 or as subsequently amended and to any governmental regulations which are applicable.
104 Silicon Chip
siliconchip.com.au
“Rigol Offer Australia’s Best
Value Test Instruments”
Oscilloscopes
RIGOL DS-1000E Series
NEW RIGOL DS-1000Z Series
RIGOL DS-2000A Series
450MHz & 100MHz, 2 Ch
41GS/s Real Time Sampling
4USB Device, USB Host & PictBridge
450MHz, 70MHz & 100MHz, 4 Ch
41GS/s Real Time Sampling
412Mpts Standard Memory Depth
470MHz, 100MHz & 200MHz, 2 Ch
42GS/s Real Time Sampling
414Mpts Standard Memory Depth
FROM $
469
FROM $
ex GST
579
FROM $
ex GST
1,247
ex GST
Function/Arbitrary Function Generators
RIGOL DG-1022
NEW RIGOL DG-1000Z Series
RIGOL DG-4000 Series
420MHz Maximum Output Frequency
42 Output Channels
4USB Device & USB Host
430MHz & 60MHz
42 Output Channels
4160 In-Built Waveforms
460MHz, 100MHz & 160MHz
42 Output Channels
4Large 7 inch Display
ONLY $
539
FROM $
ex GST
Spectrum Analysers
971
FROM $
ex GST
Power Supply
RIGOL DP-832
RIGOL DM-3058E
49kHz to 1.5GHz, 3.2GHz & 7.5GHz
4RBW settable down to 10 Hz
4Optional Tracking Generator
4Triple Output 30V/3A & 5V/3A
4Large 3.5 inch TFT Display
4USB Device, USB Host, LAN & RS232
45 1/2 Digit
49 Functions
4USB & RS232
1,869
ONLY $
ex GST
649
ex GST
Multimeter
RIGOL DSA-800 Series
FROM $
1,313
ONLY $
ex GST
673
ex GST
Buy on-line at www.emona.com.au/rigol
Sydney
Tel 02 9519 3933
Fax 02 9550 1378
Melbourne
Tel 03 9889 0427
Fax 03 9889 0715
email testinst<at>emona.com.au
Brisbane
Tel 07 3392 7170
Fax 07 3848 9046
Adelaide
Tel 08 8363 5733
Fax 08 83635799
Perth
Tel 08 9361 4200
Fax 08 9361 4300
web www.emona.com.au
EMONA
|