In this instructable I will guide you trough all the things you need to do to get your flyback transformer working. I hope everything is explained in the instructable, but if there is anything you don't understand, you can ask it here. It's a very simple project with very few components, and it's a lot of fun to make!
About a flyback transformer:
A flyback transformer is a transformer with a low number of primary windings, and a high number of secondary windings. The inductance of a flyback's primary coil (this is the resistance of that coil) is really low when working at low frequencies.
When a voltage is applied to that low resistance coil, it will draw a lot of current. To lower that current, the resistance of the coil needs to become higher. We can do that by using a higher frequency. Xl = 2.π.f.L Where Xl is the resistance of the coil, and f is the frequency. (L is the inductance of the coil, which is constant).
This high frequency will be provided by our transistor. It will switch the coil on, at a frequency around 30kHz. We have now limited the current, but it still isn't perfect, so the transistor will get very hot.
That's why it needs to be cooled with a heat-sink. We will also use a MOSFET (Metal Oxide Screen Field Effect Transistor) because it can switch high currents, and is almost indestructible (it can handle high currents, up to 10A, 30A peak).
The core of the flyback transformer is made out of Ferrite, because ferrite works a lot better then iron when working with high frequencies.
Warning: High Voltage!
This guide is meant for people who have experience with high voltage. I gave a lot of safety instructions in all steps, so that people know what can be dangerous and what is safe. Please read my instructions about safety on every step, it's important. I am not responsible for any accidents.
Step 1: Components
- a Power MOSFET (I used a K2996 - Datasheet: -link- ) (any MOSFET should work, it doesn't need to be exactly this one)
- a good heatsink, the MOSFET will get hot
- 2x 1kohm resistor (0.25W)
- a Flyback transformer (no feedback winding required)
- wires and a soldering iron, or aligator clips and or a breadboard.
- a power supply or battery (12V DC)
- a healthy mind, we're working with High Voltage here!
Flyback transformers can be found in devices with a CRT screen (Cathode Ray Tube) or on Plasma Globes. They generate high voltage, and release the electrons in a cathode ray tube (your screen) When the electrons land on the Fluorine layer on your screen, it lights up.
MOSFET's can be found in many devices. I found mine in magnetron's and also in LCD screens.
Normal transistors will probably also work, but I havn't tested it yet.