Here are some pics…see the divisions I marked, 1 cm corresponds to a voltage change of about 0.5 V. Yellow wires go to the motor, brown to the pot connections. The USB brick gives a good 5V supply.
The simple code in this example waits for A to go high. Then if the slider is less than 2 cm from the bottom end, the motor moves it to the 8 cm position, waits 5 sec, then takes the slider back to the 2 cm position.
