Also, gate driver IC3 could have
been damaged when the IGBT failed
by applying a high voltage to the drive
pin via the gate. The series-connected
thermistor could also have become
faulty, so check or replace that.
Suitable white LED for
tachometer
I have several machine tools, some
with variable speed drives (up to
12,000rpm) for which a reasonably
accurate tachometer would be very
useful. I have a couple of cheap Hall
effect tachos but find them rather
limited. After looking through many
designs, I selected your August 2008
design as a suitable basis for a built-in
tachometer (siliconchip.com.au/
Series/52).
I have all the parts required for construction except the PCB. I produced
very mediocre results with toner
transfer and failed completely with
the paint ablation method using a 7W
laser. I am now waiting for the delivery
of photo-sensitive film, with which I
hope to get satisfactory boards.
I have been experimenting with
cupric chloride etchant and have
been very pleased with the results.
I made the initial cupric chloride by
direct solution of copper metal into
hydrochloric acid with air bubbling
(as widely referenced on the web)
before realising that I could have
started with readily available copper
sulphate/hydrochloric acid and saved
some work.
I think a strobe could be useful, so
I added it to the project. However, I
find that the types specified (eg, Cree
XR-C white) appear to be no longer
available. Jaycar does list them but as
a discontinued line. An internet search
found many high-intensity LEDs, but
I struggled to find any that seemed
equivalent or suitable. Can you offer
any suggestions? (D. F., Bentleigh, Vic)
• We suggest that you use the 1W
LED available from LEDsales (www.
ledsales.com.au), which is listed as a
replacement for the star or Cree LED
specified: siliconchip.com.au/link/
ab9a
SMS Controller is out
of date
I bought a kit to build the SMS controller project, described in two parts
in your magazine in 2004 (October
& November; siliconchip.com.au/
Series/100), but I never got it working.
I want to have another crack at it and
was wondering if it is still possible to
purchase a copy of the articles. (D. W.,
Currumbin Valley, Qld)
• You can purchase back issues
through our website. Those two particular issues are available at the following links: siliconchip.com.au/
Shop/2/423 & siliconchip.com.au/
Shop/2/425
For those back-issues that are
unavailable (eg, due to being sold out),
you also have the option to purchase
the digital version or an article scan.
Having said that, we don’t think you
would be able to get the SMS Controller working now since all GSM
networks in Australia have been shut
down.
You would need to build something
like our 4G Remote Monitoring Station
instead (February 2020; siliconchip.
com.au/Article/12335).
SC
Advertising Index
AEE ElectroneX........................ 25
Altronics...............................87-90
Ampec Technologies................... 9
Dave Thompson...................... 111
Digi-Key Electronics.................... 3
element14................................... 7
Emona Instruments................. IBC
Hare & Forbes....................... OBC
Jaycar............................ IFC,53-60
Keith Rippon Kit Assembly...... 111
LD Electronics......................... 111
LEDsales................................. 111
Microchip Technology.................. 5
Mouser Electronics.................... 11
Ocean Controls......................... 94
PMD Way................................ 111
Silicon Chip Shop...........104-105
Switchmode Power Supplies....... 8
The Loudspeaker Kit.com......... 95
Tronixlabs................................ 111
Vintage Radio Repairs............ 111
Wagner Electronics................... 10
Notes & Errata
Advanced GPS Computer, June 2021: in the parts list on p29, the catalog code given for the laser-cut lid was SC5083, but
that is the original ‘inset’ lid to suit the 3.5in touchscreen. As mentioned in the article, a different lid is needed to give enough
clearance inside the box. The correct catalog code is SC5856.
Mini Arcade Pong, June 2021: if you can’t get the 7450 or 74LS50, you can use the 74LS51, which is more readily available.
To use the 74LS51, pins 11 and 12 need to be tied high (they must be left open if using the 7450). You can do this by bridging
them together and then running a short wire link to pin 14.
Refined Full-Wave Motor Speed Controller, April 2021: we have created an alternative version of the PIC firmware, 1010221B.
HEX. This works identically to the original (A) version, except that it won’t start the motor if the speed pot is not at zero when
power is applied. You need to rotate the speed pot to zero and then back up to start the motor. This safety feature could be
useful in some situations.
USB Flexitimer, June 2018: in the circuit diagram (Fig.1) on page 26, LED2 and LED3 are swapped. LED2 (ON) connects to pin
5 of IC1 via a 3.3kW resistor, while LED3 (OFF) connects to pin 2 via another 3.3kW resistor.
The August 2021 issue is due on sale in newsagents by Monday, July 26th. Expect postal delivery of subscription copies
in Australia between July 23rd and August 10th.
112
Silicon Chip
Australia’s electronics magazine
siliconchip.com.au
