The flyback ZVS driver [Published]

KatzenklavierKatzenklavier Regular
edited April 2011 in Life
Warning: No fancy text. Blunt as fuck. Also, reply to my god dammed thread!

This is how you can make high voltage arcs with a flyback transformer. These can be found in anything with a cathode ray tube. (Glass TVs, old computer monitors).

You have a choice to either use the IRFP260 MOSFET, which can handle 48A, or the IRFP250 which can handle 33A. More amperes = longer hotter arcs, but the 260's are a dollar more. No matter what, both FETs must be put on their own heat sink (can't share one!). You can pull sinks from a computer monitor. Also make sure to use thermal paste ($3 at radioshack).

The inductor can be anywhere from 47uH to 200uH @ 10+ amps. More microhenrys = higher voltage but less amps. Less microhenrys = more amps but less volts. You can use the inductor donut (toroid) from a computer power supply if you don't want to buy one. Wrap 30 turns of 20AWG enamel magnet wire around the toroid and you'll have a 50 something uH inductor.

Power source is 2 car batteries in series. This will give you 24V. If you have only 1 car battery, you can use it but replace the 1k 5watt resistors with 470 ohm 3W ones. The arcs won't be too impressive at 12V however. If you want even more power, use 3 car batteries. The circuit will start to get quite hot though. If you really want to push it to the limit, 4 car batteries MAX. The FETs won't be able to handle any more power. If you want more power, you can replace the FETs with IGBTs. At around 30 bucks a pop, they aren't cheap. You'll likely blow up the transformer before an IGBT though. You can also use computer power supplies in place of the batteries too.

Any more than 24V, regularly kill the power and feel the FETs' heatsinks. If they're too hot to comfortably touch either run the thing intermittently, put a fan on it (big help!), or get bigger sinks.

Because the majority of you are electrically illiterate, I drew a picture only brandon could fuck this up with.

You can substitute the 1k 5w resistors with 470 ohm 3 watt resistors. It works just as well if not better.

All the blue wire and all the red wire must be thick (<18AWG). The yellow wire can be thin, but no thinner than 24AWG. The coil on the transformer should be two sets of 5 turns (20AWG enamel magnet wire), with the "middle ones" connected. The entire primary coil MUST be wound in only 1 direction.

If all goes well, you can do this. With a 50uH inductor, a 20" computer monitor flyback and IRFP260's,
12V should give you 4,000V @ 30mA (1.5 inch long arcs).
24V should give 12,000V @ 50mA (3.5" long arcs).
36V should give 15,000V @ 80mA (5" long arcs).
These figures are highly variable though.

Notice the guy is using a stick. That's quite important because you don't want to get shocked by this thing because it can be deadly. His stick is excessively long however; you can use a rubber handled screwdriver. The high voltage comes out of the red wire and he supplies the ground. The best way to find the HV ground is to attach a thin wire to the HV out, and with it taped to your srewdriver bring it near the bottom pins on the flyback. It will arc to at least one of them if things are working OK. Solder a wire to that pin so you don't burn the transformer when you play with it.

Parts are below. I recommend getting extra parts, namely the diodes and FETs. This way if you blow up the driver you can replace all the silicon and get it working again. You'll know when something's wrong because MOSFET chunks will go a flyin'.

1k 5W resistor or 470 ohm 3W. The latter works better.
>400V Ultrafast diode
IRFP260 (high power) or IRFP250 (low power)
.68 uF Capacitor
56 uH Inductor
10K resistor
12v zener


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