This is only a preview of the August 2012 issue of Silicon Chip. You can view 30 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. Articles in this series:
Articles in this series:
Articles in this series:
Items relevant to "The Driveway Sentry Mk.2":
Items relevant to "Timer For Fans And Lights":
Items relevant to "Isolated High-Current Adaptor For Scopes & DMMs":
Items relevant to "Wideband Oxygen Sensor Controller Mk.2, Pt.3":
Purchase a printed copy of this issue for $10.00. |
Advertising Index
Altronics.................................. 78-81
Amateur Scientist CD................... 93
Electronex...................................... 9
Embedded Logic Solutions.......... 32
Emona Instruments...................... 71
Geoff Coppa............................... 103
Grantronics................................. 103
Harbuch Electronics....................... 7
Ask SILICON CHIP
. . . continued from p100
are new, having been replaced within
the past few months.
The Light Box Control Timer unit
was a faithful replication of that
described in SILICON CHIP and when
completed performed exactly as described in the article when operated
on the bench with no load attached to
the relay. However, when installed in
the light-box with a fluorescent tube
load connected, it began to behave
somewhat erratically on start-up. Most
of the time it would only generate a
mere flicker from the tubes and then
nothing. Pressing start again usually
had the same outcome, although once
in about five times, before the microprocessor became completely confused and displayed random outputs,
the lamps would fire and run for their
timed period before switching off.
Trying to improve the reliability
of the start-up has proven frustrating
and I have double-checked, tested and
virtually rebuilt the controller board
in several different configurations to
try to isolate and remove the problem,
including re-programming the microprocessor. The differing configurations
included alternative relays (on and off
the PCB), separate input mains power
supplies, full suppression of the mains
input supply etc.
After extended deliberations, I have
concluded after testing the relay with
both DC loads and other AC loads that
the trigger action of the fluorescent
starters seems somehow to be applying a power spike into the input circuitry of the 16F84A, shutting down
operation almost immediately after it
begins, suggesting that some further
decoupling of the micro inputs may
104 Silicon Chip
DOWNLOAD OUR CATALOG at
Hare & Forbes.......................... OBC
www.iinet.net.au/~worcom
Instant PCBs.............................. 103
WORLDWIDE ELECTRONIC COMPONENTS
PO Box 631, Hillarys, WA 6923
Ph: (08) 9307 7305 Fax: (08) 9307 7309
Email: worcom<at>iinet.net.au
Jaycar .............................. IFC,49-56
Notes & Errata
LED Sales.................................. 103
Mix-it! 4-Channel Mixer, June
2012: Fig.8 on page 67 should
show the top switch connecting
to signal ground and the bottom
switch going to pin 7 of IC1b (not
the other way around).
Soft Starter for Power Tools, July
2012: the X2 capacitor specified
in the parts list is a tight fit on
the PCB. Element14 part code
1215460 is a better fit, as is the
Altronics R3129.
well be in order. I would be grateful
if you could provide me with your
thoughts and any possible solutions.
(W. G., Dunedin, NZ).
• The inputs to the PIC are only held
high via internal pull-up resistors and
these may be too high for an application within a fluorescent tube lighting
box. The problem should be solved by
adding 10kΩ pull-up resistors between
the +5V supply and the RB6 & RB7
inputs. Adding 100nF ceramic capacitors between these inputs and the pin
5 ground supply should shunt any
interference to prevent false triggering
(see also the errata in March 2012).
If this doesn’t cure the problem,
the timing board should be shielded
from the fluorescent tubes, starters and
ballast with an earthed piece of tinSC
plate.
Keith Rippon............................... 103
Kitstop............................................ 6
Low Energy Developments........ 103
Matrix Multimedia......................... 11
Microchip Technology..................... 3
Mikroelektronika......................... IBC
Ocean Controls.............................. 8
Quest Electronics....................... 103
Radio, TV & Hobbies DVD............ 99
Reality Design................................ 7
Red Button Technologies............. 63
RF Modules................................ 104
Sesame Electronics................... 103
Silicon Chip Binders................... 103
Silicon Chip Bookshop............... 102
Silicon Chip Order Form............... 95
Silicon Chip Partshop................... 94
Silicon Chip Subscriptions......... 101
Siomar Battery Engineering.... 5,103
Splat Controls............................. 103
Tekmark Australia........................... 6
Truscotts Electronic World.......... 103
Wiltronics...................................... 10
Worldwide Elect. Components... 104
siliconchip.com.au
|