need to convert 12 volts to 6 volts @ about 4-6 amps

The standard mechanism for efficiently controlling power to DC motors is pulse width modulation (PWM). IOW, you turn the current on and off rapidly.

The alternative (dropping voltage across a load resistor) is going to waste 50% of your power. If the motor draws a lot of current, you would need a high-power resistor, which may well cost more than the components required for PWM.

Essentially, you need:

1. A transistor (bipolar or MOSFET) which can take the motor current.
2. A diode with the same current rating.
3. A square wave oscillator, typically running at a few KHz (for a fixed ratio, a 555 is the obvious choice).

Connect the motor between the +12V supply and the collector or drain of the transistor. Connect the emitter or source to the ground (0V) line. Feed the square wave to the base or gate (for a bipolar transistor, via a resistor). Connect the diode across the motor with the *cathode* to the

If you can provide the specifications of the motor (preferably the current; failing that, the power), someone may be able to recommend specific components.

This question should be in sci.electronics.basics.

If you are needing something in a 12 volt system, but need to pull 6 volts off to power something else, couldn't you just use two 6 volts batteries wired in series to run the 12 volt stuff, but then tap directly into one of the 6 volt batteries to power the 6 volt motor?