microcontroller in the VU/Peak Meter
with LCD Bargraphs (May 2007 issue;
siliconchip.au/Article/2232).
Lapel Mic Adaptor
SNR & PCB query
I am curious about the signal-tonoise ratio for the Lapel Mic Adaptor
described in the January 2004 issue
(siliconchip.au/Article/3330). Sadly,
you do not have the PCB in your
inventory, but I understand you can’t
have everything in stock. (P. S., Mount
Pleasant, SA)
● The signal-to-noise ratio (SNR)
was not measured for the published
specification as it depends on the noise
from the electret lapel microphone
itself. That information can be found
in the electret microphone manufacturer data. We expect the circuitry to
provide an SNR of at least 100dB with
respect to 1V RMS output.
When tested at the time it was published, the noise was not audible and
was better or at least comparable to a
Advertising Index
Altronics.................................29-32
Dave Thompson........................ 111
Digi-Key Electronics...................... 3
Emona Instruments.................. IBC
Jaycar........................ IFC, 9, 11, 13,
............................. 23, 43, 71, 91, 95
Keith Rippon Kit Assembly....... 111
Lazer Security........................... 111
LD Electronics........................... 111
LEDsales................................... 111
Microchip Technology.............OBC
Mouser Electronics....................... 4
good-quality commercial radio microphone system.
The SNR could be improved to as
much as 114dB with respect to 1V
output by using an NE5532 op amp
instead of the TL072.
We could add this PCB to our Online
Shop if you want to order some. There
are two versions of the PCB. If you are
interested, please tell us which one
you want and how many and we can
estimate the cost. In most cases, as long
as we have the artwork on file and the
rights to it, we can get PCBs made for
pre-2010 projects. We already stock
PCBs for pretty much all post-2010
projects (it is now available SC6627).
Variac won’t filter
generator output
I have a 2.5kW petrol generator that
I use to power an older refrigerator,
lights etc if there is a blackout. I don’t
use it for computers, TVs and other
electronic appliances as I suspect these
might be damaged by voltage spikes
and harmonics from the generator.
Is there a straightforward way to
filter the generator’s output to enable
it to be used with electronic items? I
thought of using a 2kW variac since
it is basically a large inductor with
resistance, but I need some advice on
whether this will work and be safe.
On another subject, I recall reading Jim Rowe’s articles in Electronics
Australia many years ago describing
how he built a home computer. This
was long before IBM developed the
PC architecture, so components such
as memory, communication systems,
software, processors etc couldn’t be
bought off the shelf.
If I remember correctly, he was the
first person in the world to complete
a working home computer, or was narrowly beaten by an American. It might
interest readers to hear Jim’s recollections of his achievement and the challenges he faced. (I. P., Fullarton, SA)
● The autotransformer probably will
provide little filtering, especially at its
full voltage setting. A commercially-
available line filter will remove some
of the RF hash, and a surge-protected
power board can reduce voltage
spikes.
Concerning the computer, it was
just about the first published home
constructor article for a computer but
was beaten by a month. The computer
was called the EDUC-8, and a scan
of its 80-page manual is still available to purchase at siliconchip.au/
Shop/3/1816
Help with a power
supply kit from AEM
I assembled a power supply from a
kit many years ago. As I was an Electronics Australia subscriber at the
time, I assume it was one of theirs.
The only information I have on it is
that it is labelled “VERSATILE LAB
SUPPLY” and “AEM2521” on the
front panel. It is a 30V supply with
an ammeter and an inbuilt crowbar
circuit inbuilt. I have no idea where I
purchased the kit.
Do you have any information on this
supply? (O. A., Boort, Vic)
● The AEM2521 is from Australian
Electronics Monthly magazine. Unfortunately, we do not own the rights to
that magazine, so we cannot provide
copies of articles. The National Library
or your state library would have a
copy; the main challenge is figuring
out the month of publication; we suspect that the project was published in
the July & August 1988 issues.
As far as we know, Dick Smith Electronics sold the kit for the AEM2521
supply.
SC
Oatley Electronics..................... 111
Silicon Chip 500W Amplifier..... 12
Silicon Chip PDFs on USB......... 94
Silicon Chip Shop.................60-61
Silicon Chip Subscriptions........ 42
Silicon Chip VGA PicoMite...... 109
The Loudspeaker Kit.com.......... 93
Tronixlabs.................................. 111
Wagner Electronics....................... 7
112
Silicon Chip
Errata and Next Issue
SC GPS Analog Clock............... 107
Bass Block subwoofer, January 2021: the specified Altronics C3055 driver
is no longer available. The SB Acoustics SB16PFCR25-8 is a suitable
substitute available from Wagner Electronics for $46.50 at the time of
writing. See the February 2023 Ask Silicon Chip column for advice on
tweaking the design to suit this new woofer.
High-Performance Active Subwoofer, December 2022: in the parts list,
two 3.7-4mm crimp eye terminals are required, not one, and the 377 × 140
× 1.5mm aluminium sheet listed is slightly too small. It needs to be at
least 377 × 150mm.
Next Issue: the March 2022 issue is due on sale in newsagents by Monday,
February 27th. Expect postal delivery of subscription copies in Australia
between February 24th and March 15th.
Australia's electronics magazine
siliconchip.com.au
