DC Motor Speed Controller

Posted on Feb 5, 2014

This circuit takes advantage of the voltage drop across bridge rectifier diodes to produce a 5-position variable voltage supply to a DC fan or other small DC motor. It is not as efficient as a switch-mode circuit but it has the virtues of simplicity and no switching hash. The four full-wave bridges are connected so that each has two pairs of serie

DC Motor Speed Controller
Click here to download the full size of the above Circuit.

s diodes in parallel, giving a voltage drop of about 1. 4V, depending on the load current. The rotary switch should have make before break  contacts which should be rated to take currents up to about an amp or so. For higher currents, higher rated bridge rectifiers and a suitably rugged rotary switch (or solenoids) will be required. If you want smaller voltage steps, you could use the commoned AC inputs on the bridge rectifiers to give intermediate steps on the speed switch.

Leave Comment

characters left:

New Circuits



Popular Circuits

McCAD PCB software
10 Band Audio Equalizer
Audio power amplifier
Step-Down Converter Controller
relay Do I need a protection diode here
Ardurino Logger
monostable multivibrator 555 timer
Tesla Coil
Two motor speed control circuit and the main level indicating circuit