[philso]

Whatever sensor you chose to use, put some thought into how you will test your system. Think about what happens if your sensor is not set up correctly or the software does not read the sensor correctly. Will the mechanical system get damaged?

For example, you may want to disconnect the motor from the arm, command the arm to move one way, move the arm manually and verify that the software stops the motor with the arm at the correct angle.

Be sure to allow for the momentum of the mechanical system and the reaction time of the system so that you are not trying to sense the position just as the arm is hitting a hard stop. If you do that, the motor may try to drive the arm past the hard stop.