How do you convert 12 volts to 8 volts?

Answer 1

For a.c. you can use a transformer; for d.c. you can use a voltage divider resistor network.

You can use a circuit that uses a transistor to regulate the voltage down to 8v by adding resistance under control of a reference zener diode.

There are dedicated voltage regulators with three legs like a transistor, the 7808.

Other circuits use an inverter. Where the 12v is chopped up and fed via a computer controlled transistor, recified and stored in a capacitor for output.

It all depends on how much current you want to use. The voltage divider will only give you a small current, usually for reference only.

Adding resistance (via transistor) will produce large amounts of heat as the extra voltage is wasted.