Variable DC motor controller

[Mr Rob]

As part of a college project i need to find circuit designs for a 48V DC motor, with variable speed aswell as forward/reverse. Could you point me to any such site or give ideas of your own, thanks.

[ViperTX]

Hmmmm...college project....think PWM....then google it. Check out Freescale, Siemens and take a gander at Microchip's website.

[2muchstuff]

I know that Vantec makes one and a whole series of others for radio controlled models. Otherwise try what Viper suggested. They are quite easy to build, basiclly a LM556 chip and a couple of high power mosfets for the output.

[fly_champ]

You are looking for a circuit called an H-bridge
it involves four transistors, probably fet's
how are you going to signal the motor for speed?
the most common way is to use PWM

if you have an old R/C servo with good electronics and stripped gears, you can make a cheap and easy motor controller with four FET's and a few resistors.
the servo will work with either a pwm signal or you can use the output pot to drive the motor.