Sometimes you want to slow down a brush type DC motor. The most efficient way to do this is with a pulse width modulation (PWM) technique. The hobby circuit below can operate from about 3 volts to 15 volts. The frequency is fixed at about 2KHz but the pulse width can be varied from nearly 100% to 0%. By using a multi-turn pot, you can accurately select the desired motor speed. With the components indicated, the peak motor current can be about 2 amps.  For higher currents, you will have to use an n-channel FET with a lower drain to source resistance.

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