Materials needed include:
- Two large ferrite U cores. TSC international is my favorite place for getting ferrite cores.
- Plenty of magnet wire, 28 gauge is preferred.
- Electrical tape, any color but black. Get the really nice 3M stuff, the cheapo dollar store stuff is crap.
- Teflon pipe thread tape.
- Liquid electrical tape.
- An exacto-knife.
- Super glue.
- Regular wire, preferably silicone insulated.
- Lots of time.
This is mostly a pictorial instructable, because pictures are a lot easier to follow than words.
LET's DO IT!
Step 1: First...
Then wrap that tube in about 6 layers of electrical tape, and then proceed to wrap some magnet wire around it.
- Do not take the magnet wire all the way to the ends of the tube.
- Don't make the entire winding layer more than a half inch wide. If you do there will be insulation issues.
- Wrap tightly and make no crossed turns.
Step 2: Second...
...wrap 5 layers of teflon plumber's tape around the coil. This will provide most of the transformer's inter-layer insulation, something critical to prevent it from going up in flames. 5 layers should be good for 4kV, but I personally wouldn't trust it with more than 2.
To calculate your inter-layer voltage, take the output voltage you're aiming for and divide that by the number of layers, then multiply that by 2.
Say I want 30kV and I have 40 layers. (30,000/40)* 2 = 1.5kV inter-layer voltage, not too bad considering I used 4kV worth of teflon.
Step 3: Third...
...put on one layer of electrical tape, then start winding again.
Secure the wire with super glue, then cut strips of electrical tape and place beside the coil. In the picture there is only one strip (on the left), but two are needed to support the next layer.
Step 4: Fourth...
...repeat until your brain melts!
I decided to put 40 layers in my fryback, a task that took me 25 hours! Albeit I was watching TV at the same time, but it's still a daunting task.
Take care to not break the wire coming out of the center! If you do, fun's over.
Step 5: Fifth...
...solder wires to the magnet wire and glue the ends in place with super glue.
This will prevent you from breaking the fragile magnet wire. I chose to use silicone insulated wire because it absorbs super glue like a sponge, but it's not necessary.
Step 6: Sixth...
The liquid tape preforms 4 functions:
- Prevents water from getting in.
- Prevents the electrical tape from sliding off of the cardboard tube.
- Adds some insulation.
- Makes the thing look that much better.
Step 7: Seventh...
...make the primary coil.
This isn't too tricky, all you need is some wire and craft skills to make one. I chose to make a 4+4 turn primary (wires' doubled up so it appears like 8+8).
Step 8: Eighth...
...assemble your fryback!
I used the friction of the paper tubes to hold my cores in place, and when powered up the magnetism clamps the ferrites together. One tip, don't use a metal fastener. It will inductively heat and steal most of your power!