Capacitor Run Motor Speed Control

No quotes in the title apparently.. it is really Capacitor Run Motor "Speed Control" Partial circuit of an Alliance HD-73 antenna rotor controller. Trying to understand how the "Speed Control" works. AC Motor, the slower rotation option appears to be just a diode and capacitor. Capacitor values are from the HD-73 antenna rotor schematic, resistance value for the motor is a wild guess. (I was too lazy to measure the actual device) =D Flip the switch up to go full speed, switch down will bring the diode and capacitor into the circuit and demonstrate the "slow" speed mode. After running this it would appear that the diode just "chops" half of the AC wave, I assume this just lowers the overall power delivered to the motor. Does the 220uF capacitor provide a bit of opposite voltage to keep the motor from stalling?

published 8 years ago