>>>READER-TO-READER QUESTIONS AND ANSWERS
stiff enough. The steel leads are
sometimes plated with gold to prevent
corrosion and improve conduction.
For the carbon film resistors, I
suspect the iron — or soft steel — is
an inexpensive but sturdy core that
can be coated with ceramic or glass,
then the carbon.
[#11075 - November 2007]
Years ago, I built several "Nothing
Boxes" that fascinated friends. They
were boxes with six to 10 flashing
NE- 2 lamps. They needed over 120
volts, usually from three surplus 45 volt
batteries which were hard to find.
Can anyone provide a simple but
efficient power supply that could be
used with 6 to 12V and provide the
120 to 140 volts needed by the NE- 2
oscillators? I would probably use C or
D cells so that the boxes would run for
several months on one set of batteries.
Figure 2 is a simple power supply
schematic gleaned from part of
that kit. The power supply is a simple
oscillator that runs on 6 VDC with
a single PNP transistor. The oscillator
output is stepped up to around 100-
150 VDC with the transformer. Almost
all components are off the shelf.
The transformer is an audio output
transformer, like those used in
many older audio amplifiers. You can
probably find one in a discarded radio
from the 1970s.
E. Kirk Ellis, KI4RK
Helpful hint: Do NOT wet your finger
and touch the capacitor contacts
when it is charged!
Sid Knox, W7QJQ
#3 How about a free power supply
and as a bonus, a free battery to run it?
Go to a photo developing store and
ask for a used disposable camera.
When you take it apart, look for these:
1) Contacts that when closed,
energize the flash option.
2) The large (slightly smaller than
an AA cell) high-voltage storage
Close the contacts (1) to begin
charging the capacitor. After a few
seconds, the small neon lamp (similar
to an NE- 2) will flash. With a meter,
you can measure the capacitor voltage
which will be around 300 VDC. This
will run your "Nothing Box," although
you may want to change the resistor
values if the flash rate is too fast.
If you want to see the camera
strobe lamp flash, hold the contacts
(1) closed and simultaneously close
the contacts that are connected to the
shutter release mechanism.
Mr Google has links to dozens of
sites related to hacking these cameras.
#4 The answer can be found with
the MAX1932. The standard circuit for
this part makes 90V and operates
from 3 to 5V input, so three AA cells
is all that is needed. This circuit also
has a nice current limit so it will make
it safer than a garden variety boost.
The datasheet and circuit are
(works for Maxim)
#1 Jameco Electronics sells a 12V
power supply for fluorescent lamps
that may work for you. Its output is
180V or so; Part #239636. It will probably work on less than 12V, as well.
#2 Years ago, I assembled a “goofy
night light” P-Box kit from RadioShack.
That kit had five neon bulbs that could
be configured to flash in sequence or
randomly. The kit was made to run off
of six volts DC and advertised that
if you used four D cells or a lantern
battery, it would run for months.
#5 I built one of those many years
ago and used 110 volts right out of the
wall. Many more years later, I built
another one using a bunch of nine volt
batteries in series. That was safe but
did not last long. I later used a DC-to-DC converter fed by five AA cells. It
worked well and would probably last
for months with D cells. The converter
I used was a PICO 5B48S. I used small
neon bulbs without sockets and 2. 2
meg resistors. Put the whole thing in a
clear plastic box. Piece of cake. Good
luck and keep having fun!
#6 Buy 12 nine volt batteries and
snap them together in series for 108
volts at the two remaining terminals.
The neons may light at as low as 90
volts. Add more batteries to the series
string if you think you need more than
[#12072 - December 2007]
I subscribe to cable phone with a
company that provides a bundle of
high-speed Internet access, television,
and phone service. A cable problem can
cause any one or all three to crash. My
primary concern is about the phone.
When it goes out, you won't know it
until you try to use it and get no dial
tone, or if someone tells you later that
they could not reach you. This has
caused me to miss important calls and
deliveries. Is there a circuit I could build