Hello everybody I have a question to all! I need help designing a moter speed controller that can drive a 12vdc moter to different speeds like a pulse width modulator (pwm) but i need to be able to control the speed with a variable voltage from 0-5Vdc from another source. Also i need to be able to control the moter start up voltage for example(3-12v,5-12v,8-12v) If any body can give some advice, websites or keywords to a circuit like this it would greatly be appreciated.

 

Other than this site take a look at:
http://www.thebox.myzen.co.uk/Workshop/Introduction.html
http://www.thebox.myzen.co.uk/Tutorial/Introduction.html
http://playground.arduino.cc//Main/ElectroInfoResources

look into the Arduino with a few compontents it will do all of that and very mucch more.

 

I'm discovering that my Nyko Intercooler for the old fat PS3 system functions almost exactly like you describe.

Maybe you could find one and maybe it would work for you without having to build something?

 

Take a look at this simple pwm based on an lm393. This circuit was sugested by 4qd in this page under "improved circuit".

The frequency of the pwm is given by r2*c1 which is around 21khz in this case. The amplitude of the ramp is given by z1, and the floor of the ramp is given by the voltage drop of d2. It's important to maintain the 10x ratio between r1 and r2 because the current difference makes the voltage drop on d2 slightly higher than d1's to ensure a proper reset of the ramp.

This circuit will go from 0% to 100% with a signal amplitude from the voltage drop of d2 to vz1 that is, from .6 to 4.7v approximately.

The circuit formed by r3, pot and d3 can be replaced by your 0-5v signal.

Here's the schematic and the .asc in case you want to simulate it in ltspice. Hope this helps and if it does have fun building it.