@knud-rishøj yes it's the same than led dimmer except you add a RC filter because the motor will be very noisy if you set on/off like it's done for the LEDs. Your circuit would be inserted between existing connection to motor and the motor. For the screw I don't know what it does, so you have to check the circuit to see how it influences the output voltage. Not such an easy project to start with IMHO