Can I use the DX.com one in the link ?
http://dx.com/p/dc-6v-90v-15a-pwm-motor-speed-control-switch-governor-green-black-160094

What PWM system can I use to control this motor ?
Low, medium, fast speed.

Small Motor (Bought 104 Disc Capacitor to protect it )
6V
0.04A

<Previously. Tried only 500Kohm potentiometer but failed>
Power supply: 9V block battery

 

There is a 555 timer circuit that you can use to create a PWM and control a motor with a variable resistor? Maybe someone else can expand, I can't remember the circuit too well, but it did seem to work quite well. I used it on a home made slot car set that we made as a group project at school.

 

It probably would work, but that's a 15 amp controller to drive a 0.04 amp motor, so seems like overkill. Then again, the voltage and price are right. And, I don't see anything (Googling) that's better.

Ken

 

Doesn't it already have a POT for speed control?
Seems like it also allows you to remove that pot and use a PLC or other PWM generator to provide more "automatic" speed control.

 

Thanks.
+ Now I only have to wait China's snail mail. Awww... at least 6< weeks to letter arrive .