Hello, I am starting a project which requires the control of a motorised potentiometer. I am using the ALPs RS60N12M9000A, I am looking at controlling the motor using PWM. The fader has 6 pins, the DC voltage for the motor, Audio tracks, and servo tracks. Can I control the positioning of the fader just by supplying the PWM to the servo tracks, or will I need the use of a H-Bridge to allow the control of the motor to go both ways? Eventually I would like the code to be able to save the position of the fader, and then be able to reload that position.

Any help on this would be greatly appreciated

Hi Kane,

The servo track is the feedback of the sliders position (mostly a linear potmeter). If you want to control it with a PWM signal you need RC like servo electronics to drive this kind of potentiometer. You could use RC Servo electronics, they consist of a PWM controlled H-Bridge with a potmeter for feedback.

Difference between these kind of potentiometers and RC servos is that they are only actively driven when they need to be positioned,a RC servo will hold the set position firmly. So you need an extra circuit which cuts the power from your servo electronics when you are not controlling it from the mbed otherwise you would not be able to adjust the slider manually (it will just bounce back to the former position).

Once you have adjusted your PWM code for maximum and minimum setting you can store different values for different positions.

You will need an H-bridge, see: http://mbed.org/cookbook/Motor

for my control solution see: http://mbed.org/users/networker/code/ipod/