# Transformer coil design? HELP!

1. Feb 5, 2012

### hobbs125

I am in need of a transformer which has the following characteristics:

Operating frequency 20kHz
Turns Ratio 1:8
Primary 12V square wave @ around 100mA max
Dual secondary coils (wound together with equal turns)
(Note: Only 1 secondary coil will operate at any given time)
Secondary 96V square wave at 1mA max
Load is simply a high watt resistor.

Now, my question is, with this information could I design a coil myself?

Is there any easy to learn transformer design software I could use for this?

I contacted an engineering company and they wanted 1,000 dollars just to start the project....I don't need this for anything important, it just for a hobby, nothing long term either, jsut something to play around with and learn from....

Last edited: Feb 5, 2012
2. Feb 6, 2012

### dzimmerm

20Khz is an audio frequency. Transformers that handle that frequency could be looked for at places such as Radio Shack.

The problem with using a transformer to raise the voltage level of a square wave is that you will loose the high frequency components of the square wave due to the action of the transformer as a filter coil. You can input a square wave, but the output will be rounded to resemble a sine wave.

A square wave is a sine wave with high frequency components the make the sharp edges added to the basic sine wave. Since any inductor will have more resistance at higher frequencies than lower frequencies those high frequency components get blocked leaving you with a sine wave.

If you have a square wave output at 12 volts you would need to have it feed a circuit that has the capability of pulsing a 96 volt signal. A transistor circuit would probably be your best bet and be sure to choose a transistor with a emitter collector voltage never exceed of greater than 200 volts.

3. Feb 6, 2012

### Staff: Mentor

Primary and secondary currents are related. So if max secondary is 1mA, with your turns ratio primary should be not much over 8mA (or double this, if you have a pair of secondaries). If your output is 96v at 1mA, you won't need a high power resistor for such a load.

V · I ≈ 0.1 watt

A small ferrite toroid about the size of an ostentatious wedding ring might do. Thread your enamelled wire through it. Try 40 turns for the the primary if you can't think of a better number.

4. Feb 6, 2012

### fbs7

Keep in mind that if you can deliver a DC voltage to your resistor (instead of a square wave), then it's easy to build a 8x voltage multiplier from diodes and capacitors only.