circut boards

Does anyone have a wiring digram to make a circut board to control linear motion using a potentiometer and trim pots to control a 12 volt DC motor?

Do you mean that you want a circuit for a simple servo motor ?

If you have a potentiometer tied to the mechanical output of the motor, you can use the output of that in an op-amp against your set point voltage to produce an error voltage. Use this to drive a H-Bridge amplifier.

It's very simple and will produce hunting, but it might suit your needs.