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What to do with historic electronic gear
I have come across an old PMG test
instrument in the family storeroom –
the old Gracemere Station office. It is
an AWA Type R667 Capacity Unbalance Measuring Set. A calibration note
attached to the lid is dated 15/2/68,
but the instrument might be older than
that (see the images below).
I have little idea what it was for; I
presume for improving crosstalk in
either open-wire lines or cables. I have
not opened it, so I don’t know what
is in it. It has a vernier dial reading
Capacity in uuF/nF (I think – not very
clear). It has a battery compartment –
again, I have not opened it, but I suspect it has some active components –
valves, I presume. It also has two mic
earpiece headsets.
I don’t have any idea how it came
into the family. It is in Rockhampton but I live in Brisbane. It is secure
where it is, but there may be a more
appropriate place for it to live, such
as a museum. Do you have any suggestions?
Patrick Durack,
Ashgrove, Qld.
Comments: we aren’t sure what to do
with this device but perhaps one of
our readers has a suggestion.
4
Silicon Chip
USB Cable Tester & SMD Test Tweezers
What a challenge, especially with
soldering the USB-C ports. I completed
the USB Cable Tester (November &
December 2021; siliconchip.com.au/
Series/374) without any soldering
remediation or fault finding, and it will
be useful on my hobby bench.
My soldering skills and techniques
were definitely tested and improved.
This experience highlighted that traditional magnifiers now need to be
supplemented with a digital scope for
quality control, although my phone
camera set to super macro assisted
this time.
The recent SMD Test Tweezers project (October 2021; siliconchip.com.au/
Article/15057) is also a great and useful project and was a fun build.
Barry Hinz,
Charleville, Qld.
Farewell Geoff Nichols
Those who followed ETI Magazine
would have been familiar with Geoff
as a staff member/Project designer.
My good friend Geoff passed away
on the 19th of October, aged 64, of pancreatic cancer.
Craig Laybutt,
North Ryde, NSW.
Australia's electronics magazine
Test Tweezers survived reverse polarity
I am delighted to report that you
can insert the battery the wrong way
and it will still work after correcting
that error!
Horst Leykam,
Dee Why, NSW.
Comment: We believe that it’s possible for a new CR2032 cell to supply
more current (100mA) than the maximum specified for the microcontroller’s clamp diodes (20mA). However, it
may be that components in the OLED
module are also shunting current.
PICs are pretty robust and will generally withstand much higher currents
than the maximum ratings if they are
of limited duration.
Beware of fake solar panel ratings
I bought a solar panel from a toprated seller on eBay. The panel was
rated at 200W, but after receiving it, I
became suspicious that its rating was
incorrect.
I later realised that the panel was
unusually cheap for 200W, a warning
sign I should have paid more attention to.
The panel measures 0.58m2 (820 x
710mm). This is smaller than is physically possible for a 200W panel.
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FEBRUARY 2021
37
Helping to put you in Control
ESP32 Controller
Arduino-compatible ESP32 controller with
2 relay outputs, 2 transistor outputs, 2
opto-isolated inputs, 2 0/4-20 mA analog I/
Os, 2 0-10 VDC analog I/Os and 4 GPIOs.
Interfaces using USB, RS-485 serial, I2C,
Wi-Fi or Bluetooth. DIN rail mountable.
SKU: KTA-332
Price: $251.90 ea
CS Series Closed-Loop Stepper Driver
Closed-loop stepper motor driver with encoder
feedback input and encoder A/B/Z outputs.
Operating at 20-50VDC, max 7A output current.
Suits 2 phase CS Series Closed Loop Stepper
Motors.
SKU: SMC-162
Price: $215.60 ea
Low transformer output mystery solved
Ethernet Closed Loop Stepper Driver
CS3E-D507 is a new Ethercat closed-loop stepper
motor driver with encoder feedback input, operating at
20-50 VDC. Suits 2 phase stepper motors up to 7.0 A.
Has digital inputs and outputs for control such as limit
switch and brake.
SKU: SMC-171
Price: $439.95 ea
CS Series Closed-Loop Stepper Motor
3.0 N·m, 2 Phase NEMA 24 closed loop stepper
motor with 1,000 line encoder for feedback.
Rated at 5.0 A phase current, Nema 17 to
34 sized motors available and 8.0 mm shaft
diameter.
SKU: MOT-162
Price: $202.29 ea
Liquid Level Sensor Detector
A budget priced level sensor for detecting high
and low levels of water in plastic and glass
vessels or tanks.
SKU: HEI-140
Price: $19.20 ea
LogBox Connect WiFi
LogBox Wi-Fi is an IoT device with integrated
data logger and Wi-Fi connectivity. It has three
universal analog inputs one digital input and an
alarm output.
SKU: NOD-012
Price: $604.95 ea
N322-RHT Temperature and RH Controller 230 VAC
Panel mount temperature & relative humidity
controller with sensor probe on 3 metres of
cable. 2 independent relay outputs. 100 to
230 VAC powered.
SKU: CET-109
Price: $290.35 ea
For Wholesale prices
Contact Ocean Controls
Ph: (03) 9708 2390
oceancontrols.com.au
Prices are subjected to change without notice.
6
Silicon Chip
A general figure for solar irradiance at the surface in
Australia is 1100W/m2. The quoted panel efficiency was
17%, which seems reasonable. We can therefore calculate 0.58m2 × 1100W/m2 × 17% = 108W.
Allowing for empty space, this is probably a 100W panel
being incorrectly sold as a 200W panel.
I also made some electrical measurements. The
short-circuit current is 5.84A in peak sunlight. According to the label on the panel, peak power is at 18V. This
means that the panel can generate no more than 105W.
The open-circuit voltage measured 21.7V.
The sticker on the panel does not show the power rating or short-circuit current, which is most unusual.
The situation was somewhat resolved by the seller
refunding half the purchase cost after I presented these
facts. The panel was worth keeping as it seemed to be of
good quality for a no-name panel.
But many purchasers of solar panels would not be aware
they are getting much less than they paid for. I wonder
how common such fraud is.
Dr David Maddison, Toorak, Vic.
I read the Vintage Radio article in the November 2021
issue of Silicon Chip by Graham Parslow with great interest (siliconchip.com.au/Article/15107). Graham writes in a
relaxed yet informative style, easy to read and with plenty
of detailed photos. I always enjoy his articles.
Graham describes the restoration of a Stromberg-
Carlson model 496 autodyne superhet receiver from 1936.
The cabinet looks stunning and the knobs look the part
too. It’s a real shame the electrodynamic speaker was
unable to be repaired; a reality faced by restorers from
time to time.
Graham mentioned the problem experienced with
the 6.3V heater voltage winding running at 4.9V. This
could be explained by the 6V6 heater being connected
to the 6.3V winding. For example, the 6C6 and 6F7 each
draw 0.3A heater current and the two dial lamps draw
0.3A each, for a total specified loading of 1.2A for the
6.3V winding.
Adding the 0.45A heater current required by the 6V6
modification takes the total load on the 6.3V winding to
1.65A, an increase of 37% above the power transformer’s
1.2A load specification. This could explain why the 6.3V
winding voltage has dropped to 4.9V.
Graham mentioned that this particular radio was manufactured before the 6V6 became available, so I presume
it was manufactured with an AL3 output valve, per the
circuit. Graham stated he received the radio with the 6V6
fitted. To improve the originality of the radio, the retrofitted 6V6 and socket could be removed and replaced with
an AL3 and suitable socket.
This would require the AL3 heater to be wired to the
4V winding, which would also remove the additional
loading on the 6.3V winding. That should allow the 6.3V
winding voltage to return closer to the specified 6.3V figure, overcoming the low heater voltage problem Graham
reported, as well as increasing the originality of this very
nicely restored radio.
Graeme Dennes, Bunyip, Vic.
Graham Parslow responds:
I took some measurements of the 6.3V winding with
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8
Silicon Chip
various loads after receiving the suggestion from Graeme
Dennes. Graeme was correct in his analysis; the winding
cannot cope with the load imposed on it with the 6V6
added. I did not consider this initially because most comparable 6.3V windings can handle multiple amps.
In hindsight, looking at the gauge of the winding, it is
thinner wire than usual (this was not immediately evident
due to being sheathed in spaghetti tubing). I measured
a 5.7V output when loaded with just the two 0.3A dial
lamps; the low voltage is no longer a puzzle.
What is padder feedback, really?
In researching radio designs, I have often come across
the term “padder feedback”. There are plenty of references that explain its purpose (to improve local oscillator activity and reliability), but I have not found any good
explanations of its principle of operation.
It looks like the classic Armstrong oscillator, which puts
a feedback transformer between anode and grid. The classic circuit sees one end of each winding (anode and grid)
return to RF ground: the anode winding to decoupled HT,
the oscillator winding to circuit ground.
The only common variant returns the secondary to
ground via the padder. Since this puts the padder in
series with the inductor, its effect is identical to grounding the secondary and connecting the padder between
the secondary’s ‘hot’ end and the oscillator tuning gang
section. This has the advantage of returning one end of
the padder to ground, minimising ‘hand effect’ during
alignment.
But the padder feedback circuit sees the two cold ends
joined (either directly or via a capacitor; C14 in the Astor
Mickey Oz circuit, see page 80 of this issue for example)
and returned to ground via padder capacitor C12.
Whatever this forms, it is not a true Armstrong oscillator. Is it some kind of Hartley oscillator (two inductors, L5
& L6, with mutual coupling), a modified Colpitts (padder
C12 and tuning capacitor C10 with a single inductor L5),
or a pi-filter resonant circuit (padder C12, inductor L5
and capacitor C10), as used in permeability-tuned radios
(essentially a Colpitts oscillator)?
If it is a Colpitts oscillator, why bother with the transformer primary? I trust that someone is less confused
than I am!
Rather than clog the Editor’s inbox, readers who can
explain its principle/s of operation might reply to me at
the email below.
Ian Batty, Rosebud, Vic. – ianbatty311<at>gmail.com
Hydrogen as a storage medium for renewals
As usual, the July, August, and now the September
issues have been worth reading. I was intrigued to see
that you published one of my earlier letters in the September edition. Unfortunately, I have not progressed very
far with the Li-ion battery charging project or any other
projects. It seems that there is almost a limit on how much
a person can do.
It has been almost 40 years since I began experimenting and creating electronic and mechanical devices plus
PC and embedded programs. I have devised many hundreds of circuits, plenty of mechanical devices, and many
hundreds of programs during that time. It seems that the
effort has caught up with me.
Australia's electronics magazine
siliconchip.com.au
Design Contest Win $500+
Dick Smith challenges you
Win $500 by designing a
noughts-and-crosses machine
that can beat 14-year old me!
Dick Smith has described in his new autobiography how one of
the turning points in his life, at age 14, was successfully building a ‘noughts-and-crosses
machine’ (also known as tic-tac-toe) that could play the game as well as anyone. Keep in mind that
this was in 1958, when nobody had computers; it was a purely electromechanical device.
Email Design to Enter
Design your own noughts-andcrosses circuit and send your
submission to compo<at>siliconchip.
com.au including:
a) Your name and address
b) Phone number or email
address (ideally both)
c) A circuit or wiring diagram
which clearly shows how the
device works
d) The display can be anything as
long as it’s understandable
e) Evidence that your device can
always play a perfect game (it
never loses)
f) A video and/or supply images
and text describing it
g) Entries requiring software
must include source code
The deadline for submissions is the
31st of January 2022.
➠
➠ Win $500 + Signed Copy of Dick Smith's Autobiography
➠
Four winners to be decided, one
each for the following categories:
➊ The simplest noughts-andcrosses playing machine
most ingenious noughts➋ The
and-crosses playing machine
youngest constructor to
➌ The
build a working noughts-and-
DICK
SMITH
crosses playing machine
most clever noughts-and➍ The
crosses playing machine not
using any kind of integrated
processor
The entry we judge overall to be
the best will also be featured in
our Circuit Notebook column and
receive an additional $200.
‘Part Bear Grylls, part Bill Gates,
but
Dick is a great innovator, philanth 100% Aussie larrikin.
ropist and adventurer,
who in my eyes can do no wrong.’
PAUL HOGAN
Conditions of entry
Dick Smith writes
1) You must be a resident of
Australia or New Zealand
2) One entry per family (Silicon
Chip staff and their families
are not eligible)
3) Submissions will be confirmed
within 7 days. If you do not
receive a confirmation of your
submission, contact us to
verify that we have received it
4) Chance plays no part in
determining the winner
5) The judges’ decision is final
6) The winners will be decided by
the 3rd of February 2022 and
will be notified immediately
By 1958 I’d advanced from building crystal radio sets to designing
and building what I called a noughts and crosses machine. It really
was an early computer. I used second-hand parts from a telephone
exchange to build it. It would play noughts and crosses against anyone
and no one could beat it.
This was a great boost to me, because while I was no good at rote
learning and theory, I was fine at practical things. The fact that my mind
was capable of working out how to build this complex machine gave
me confidence as I left school. Now I just had to find a job.
Because this was such a turning point in his life and he’s so
enthusiastic about youngsters learning electronics, he’s putting up
$2000 of his own money to award to people who can come up with
a modern version of his noughts-and-crosses machine. Silicon Chip
will judge the entries.
Winners will be announced in the March 2022 issue of Silicon Chip
magazine and will also be contacted directly for payment information.
siliconchip.com.au
Australia's electronics magazine
January 2022 9
I used to wonder why authors of novels would need to
take substantial rest after writing a novel. Now I know.
Currently, I am finding it hard to do anything involving
electronics and/or robotics. Instead, I have been catching
up on home maintenance and seriously overdue home
projects. Hopefully, in the near future, my electronics
drive will return.
On another topic, there is a problem with the storage
of solar energy using batteries of any type, and that problem occurs when the batteries are fully charged. There is
almost certainly more energy available but it cannot be
stored. However, immediate conversion of solar energy
into hydrogen avoids this problem.
Storage tanks are far cheaper than electrochemical cells.
They do not suffer significantly from cycling, nor do they
suffer from over-discharge. More storage is simply changing to a bigger tank or adding more tanks.
Currently, both electricity-to-hydrogen and hydrogen-
to-electricity converters are available off the shelf. Storage tanks almost certainly would be available as well; if
the high leakage of steel can be tolerated, steel tanks are
readily available.
The main reason for bringing this subject to your attention is that solar energy storage via hydrogen is at the
stage where it is feasible for hobbyists to make their own
systems.
Of course, there are safety concerns, and I have no doubt
that our governments’ health and safety departments will
react in their usual “it’s dangerous” manner.
But hydrogen is far safer than LPG with the ability of
hydrogen to rapidly disperse upwards and not lay around
the lower levels of a house. It is unnecessary to store
hydrogen at very high pressures, and a physically large
tank is not a problem like it is for vehicles.
An external installation in a well-ventilated enclosure
should be far safer than any current fuel storage schemes,
except perhaps fuel oil, coal, coke and wood.
George Ramsay, Holland Park, Qld.
Comments: Most city dwellers, even those with a house,
might disagree about your statement that the size of a
hydrogen storage tank is not a concern. Also, safety concerns aside, the round-trip energy efficiency is not likely
to be that great.
Regarding motivation, try working for an electronics
magazine where you have to come up with and complete
four or so project articles per month. Somehow we’re not
only still coming up with new ideas (admittedly, in many
cases, improved versions of previous ideas), but we’re
turning them into working prototypes and documenting
them after all these years.
Article on electric vehicle charging
I recently sent you an email relating to the logistics of
charging multiple electric vehicles (EVs) in a suburban
front yard. I don’t know whether this topic piqued your
interest, but here is a link to an ABC article that relates
to EV charging and the future of service stations: www.
abc.net.au/news/100627312
The broader issue becomes providing the appropriate domestic and public infrastructure to support an EV
based transport sector.
David George,
Montmorency, Vic.
SC
10
Silicon Chip
Australia's electronics magazine
siliconchip.com.au
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