RC hobby servomotors were just made for hacking. What’s not obvious is how much you can hack them — with a few tricks, you can use a servo to control almost anything.
Hobby servos consist of a DC gear motor, a potentiometer (usually 5K), and a control circuit. The output shaft is the output of the geared motor. The shaft also turns the pot, which returns a position-dependent voltage to the control circuit. When the servo receives a command to move to a new position, it runs its motor in the necessary direction until the pot indicates that the output shaft has reached the desired location.
What if you want motion more powerful or complex than a standard servo can give — can you do it? Certainly! Just replace the little motor with a bigger one (and whatever driver is needed) and/or replace the pot with one that senses the movement that you really want.
Let’s get started with extreme servo hacking. At Evil Mad Scientist Labs, we’ve modiﬁed a standard hobby servo to control an automotive jack. The result is a powerful, sub-$100 actuator that can move a heavy load with precise control, with a total stroke of 5"–10". It’s a powerful weapon in the maker’s arsenal for theatrical and Halloween props, CNC projects, and robotics applications.