Two Speed Motor

Project Number: 54

Description: Set the slide switch (S5) to position B; the fan spins and the red LED (D1) turns on, indicating slow mode. The LED helps protect the motor (M4) from getting the full voltage when the slide switch is closed. Part of the voltage goes across the LED and the rest goes across the motor. Pushing the press switch bypasses the LED and now all the voltage is across the motor, so it spins faster. While the fan spins, carefully use your finger to speed it up; the LED should turn off. As the motor spins faster, its resistance increases and the voltage across it rises. Now there is not enough voltage to light the LED until the motor slows down again.

Snappy: [Not Talking]