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because nobody buys antique
transformers except for scrap, which
might be my best business decision
considering the times. I do have the
transformers and the SCRs. My heirs
can scrap the units out after my
reward. I have lots of scrapables to
play with and nothing else but time.
#1127 Robert Gibson
LCD Display Help
In the recent article on the
web-based thermostat (Sep-Oct’ 11)
an EA DOG-M LCD display was used.
I have two of these displays and
haven't been able to get them
working. I use PICBASIC PRO and it
seems there are a lot of people that
are trying to use this LCD with some
trouble. There isn't much in the way
of information on the forums. Could
someone please show how to initialize the display with PICBASIC PRO in
both SPI and four-bit mode?
Extra Bright Picture/Exit Bulb
I'm looking for help locating or
building a super bright exit/picture/
display style bulb with an E26 base for
My 95 year old mother has
macular degeneration in both eyes.
She still enjoys reading but finds it
harder by the day. Her main complaint
is that she can't get enough light on
the printed page.
I'm asking for help to locate
and/or build a bulb with what I know
as ultra-bright LEDs. It will throw
the equivalent of 200 [fairly cold]
incandescent watts of light down onto
her page. I'm no engineer, but am
handy with a soldering iron and
multimeter. Can anyone help me?
#1129 Rod Reynolds
Half Cycle Magnetizer
I'm looking for a half cycle magnetizer schematic for 60 cycle, 120
volts. I used one at work before I
retired, but it was built for a higher
industrial voltage. I would like to build
one from scratch using the standard
120 volt line. I know that it must be
contained in a protective box, takes
many turns of transformer windings,
and uses a high speed thyristor.
[#11115 - November 2011]
I would like to make a special
power supply/converter with a
difference. It can be supplied from:
• A nominal 12 VDC (nine to
15 actual) from a vehicle supply.
• Or by a nominal 24/28 VDC
supply ( 20 to 32) from a vehicle or
• Or, by international mains (90 to
• All three inputs need to be
isolated and capable of being
accidentally or deliberately connected
at the same time.
• Have all three inputs tolerant to
transients, e.g., mains derived from
The unit needs to have four outputs, all of which are DC and each of
which is configurable internally by a
trim pot to deliver four output voltages
between 10 and 24 VDC (e.g., 12V,
15V, 18V, and 22V).
• Output to be unaffected by
change of input source.
• Once set, each output voltage
needs to maintain a tolerance of ±0.5
VDC, regardless of input changes.
• Each output to be capable of
delivering 120 watts.
• Robust, portable unit.
I understand that these parameters
are often mutually exclusive, but
the following considerations are also
• Low weight.
• Small size.
• Low heat dissipation.
• Low noise.
• Low interference.
• High quality.
If the overall concept is too big,
perhaps someone could direct me to
previous power conversion solutions
that may be married together to give
a solution, and highlight the isolation
issues that may apply regarding
multiple input connections.
My goodness! Four 120-watt
outputs? I think you are pretty well
stuck with switching power supplies
here! I’m not a switching power
supply guru — to put it mildly! — so I
won't try to design that, but I will
suggest an 'architecture.'
Clearly, you need four switching
power supplies for the four different
output voltages (or at least, that seems
the cleanest to me).
I would suggest having three input
switching power supplies to convert
the three differing input voltages to
some handy intermediate voltage that
the four output switchers take as their
input. Set the output of each switcher
such that the mains gives a few volts
more than the other two, and then
pick which one of the other’s you
want to supply the power if both are
hooked up. Isolate these three input
supplies from each other with diodes.
That is, each of these three has a
diode between it and the intermediate
supply rail. With the mains switcher
having the higher output voltage, it
will take (most of) the load even if the
other two are active. The diodes will
keep the three input switchers from
feeding each other.
[#11119 - November 2011]
I was wondering if it would be
possible to cheaply build a system in
which I speak into a CB type radio and
January 2012 79