A 120-volt fan can be controlled by a simple dimmer switch.
How you control a fan, depends partially on what type of motor powers the fan. Most DC motors are controlled by changing the voltage applied to the motor's input terminals. AC motors can be controlled by changing the frequency of the voltage, changing the voltage, or using a motor with multiple speed coils. Each of these forms of motor control uses a different type of switch. Building a motor controller can be simple with carefully chosen parts.
Instructions
1. Connect one end of a black piece of electrical wire to the of the 12-volt battery. Connect the other end of that wire to one of the two terminals or the on/off switch.
2. Connect a three inch piece of black wire to the second terminal of the on/off switch. Then connect the other end of that wire to one of the two terminals of the dimmer switch. Connect the remaining terminal of the dimmer switch to the negative terminal of the fan motor.
3. Connect a red wire from the positive terminal of the battery to the positive terminal of the motor. The on/off switch and dimmer switch together form a fan control. The on/off switch is used to turn the fan on and off while the dimmer switch controls the fan's speed by changing the amount of voltage sent to the fan motor.
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