DC motor speed control with potentiometers


Thread Starter


Forgive my noobishness, I know very little about engineering... Here's My question: I am building a jib for video production, and would like to control some 12VDC motors using a joystick (two potentiometers -- x and y.) The motion of the motor needs to be as smooth as possible, and speed control would be very good. I've thought about using relays (because this would be easy,) but I would rather use transistors if this is possible. I know it is not optimal, since the torque created will not be constant, but this is cheaper, (and maybe smoother) than using pulses to control speed. Is it possible to use transistors, and if so what would the schematic look like? I have a rough idea, but any help would be greatly appreciated. my email is [ wocavanagh at g mail dot com ] (remove the spaces and replace "at" with "@" and "dot" with ".")

Michael Griffin

If you want to build this yourself, look up "DC drive schematic" or "H bridge schematic" on Google. There are lots of examples.

For smooth motion with variable speed, you will want a transistor drive, not relays. The drive should have a PWM frequency in the kilohertz range (20 kHz is fairly standard). PWM frequencies in the 100 to 200 Hz range are used in some applications, but they cause vibration and noise which you might not be able to tolerate.