This is my DIY high voltage power supply. It
puts out up to 30kV DC and expects to be fed by
a source giving 0 - 24V DC. The input is through banana plug connectors.
I usually feed it using my
homemade 24V power supply
but as shown below, I've also used a wall adapter and a laptop power
supply. Also below is a video
showing step-by-step how to make this high voltage power supply
along with some demonstrations.
One modification I made is to make the FOCUS HV output from the multiplier (in this
case also called a tripler since it triples the voltage) available. With the 30kV
output wire I could get at low as 4kV but I
wanted lower. So by making the FOCUS HV output wire available as an alternative
I was able to get the range 1.2kV to 4.6kV.
It uses a flyback transformer to step the input voltage up to around
10kV AC and then feeds this into a multiplier which brings it up
to around 30kV DC.
I've looked at the output on my scope and it's fairly flat.
The flyback transformer was purchased from
Don Adsit's "The Experimenter's Store" (which seems to gone from the web). I actually
purchased two of
them but burnt out the first one when I tested without the multiplier
hooked up yet. Don sent the flyback schematics along with the flybacks
and on the schematics it gives the resistance across various parts of the
flyback secondary. Using an ohm meter you can easily test whether the secondary
of the flyback is any good. After I ruined my first flyback one of the
segments of the secondary measured infinity (the wire was clearly broken).
So make sure you get those schematics!
For the primary of the flyback I removed the wire that came with it
and put on my own wires as per the schematic and as shown in the following
photo. After wrapping the wires into place and taping them with black electrical
tape, I then coated the result with a few layers of black liquid electrical
tape for durability, gluing the whole thing.
New wires as per schematic.
The multiplier was ordered from a local electronics
store and is NTE 521 from NTE Electronics, Inc.
It has two inputs (hot and GND) and two outputs (focus and the 30kV output).
NTE supplies a thick book of all their semiconductor
parts (available at any store that specializes in NTE parts) and the
schematic for the multiplier was in the book.
Top/front view. The weird clear plastic extension
on top is because my flyback and multiplier were taller than I orignally
expected. The 30kV HV output is the red wire at the top left of the picture.
Front view showing the transistors and the heat sinks.
The input is via the banana plug connectors on the right.
Top view showing the insides. The multiplier is
the beige rectangle near the back and the black thing just below
it is the flyback.
Side view. The round black thing is the
secondary of the flyback. The multiplier is to the left of it.
View from the rear showing the transistors better.
Click here for full details of
where I got the heatsinks and
how I mounted the transistors to the heatsinks.
I attached a small round brass ball to the end of
the HV output wire. Here the end of the output wire is sitting
taped to a roll of masking tape to keep it off the floor. The red
tube thing is a Fluke 80k-40 40kV high voltage probe
which I can feed into my multimeter to measure the voltage.
My multimeter is on the right. To the left of
it is my 24V DC power supply. The output
of the 24V power supply is feeding into the 30kV power supply which is
on the left. On top of the 24V power supply is a Variac. In this picture
I am measuring the output of the entire setup.
As I turn up the voltage using the Variac, the first
reading I get from the 30kV power supply is this one, around 12kV. The
meter is on the 30V scale and is showing 1.2V (12,000 volts / 1000 (due to
the HV probe) / 10 (due to being on the 30V scale) = 1.2 volts). If
I then turn the voltage down gradually I can actually get less voltage.
I think I went as low as 4kV at one point. Then it just drops to 0.
Here it is at the highest I was willing to turn it
up, 28kV, for fear of damaging something.
Showing the arrangement for using the 1.2-4.6kV FOCUS wire.
Notice that both wires have brass balls attached to them since both have to
be discharged after use.
Feeding it 0 to 24 volts
As the above circuit diagram shows, this needs a 0 to 24 volt
power source to feed it. I usually use my
homemade 24V power supply
but as the photos below show, I've also used a small wall adapter
and a laptop power supply as well. The wall adapter has a switch for
selecting the voltage, from 1.5V to 12V. The laptop power supply
puts out only 20V and keeps it that way, even if I plug it into
my Variac and try to control the voltage that way.
Wall adapter as 1st stage.
Laptop power supply as 1st stage.
Here's my video showing step-by-step how to make this power supply.
I also demonstrate it flying a
both using my
homemade 24V power supply as
the first stage and using a laptop power supply instead, which more
people have access too.
While experimenting with
ion propulsion added to a Star Trek Enterprise model
I broke this power supply for the first time. I could have avoided it
if I'd followed my own advice and put around 250 kilohms of
resistors (2 watts) in series with the output, but I didn't and
ended up damaging one of the transistors.
The following video shows my steps in finding and fixing the problem.