Step 3: The speed Pot
PWM circuits uses a Pot (Potentiometer)to adjust the speed from 0 RPM to Max RPM . The Potentiometer can be of the rotary type or linear sliding type. The potentiometer is usually rated 5 or 10K Ohms. Typically 0 Ohms is no movement and 10K Ohms is full speed (unless you have your Pot High and Low wires swapped...then it's visa versa). Keep in mind the motor may not even begin moving till 2 or 3 K Ohms (actual value varies) and you can't really start the pot at 2 or 3K Ohm position either because the treadmill motor controller requires 0 Ohms on start-up (Kind of annoying).
The Pot talks to the circuit board through 3 terminals usually marked High,Wiper and Low (or H,W,L).
Some controllers use a digital console to change the motor speed. You dont want to scroll through programmable selections, excercise routines and heart beat monitors just to change the motor speed on your lathe.
Solution: Throw it away and replace it with an appropriate Pot(usually 5 or 10K Ohm Pot). The digital console interfaces the PWM Circuit board the same way that The speed Pot does. through those 3 terminals (on some marked G O H or L W H and colored black, white and red or S1,S2,S3, colored Blue, Grey, Orange.
You should also use a switch for ON and OFF. The Pot is for speed control once the machine is running.