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I made a crane from Merkur( something like Meccano). It has two motors, one with encoder. The position of the hook is sensed by the encoder and the position of the second moving part is sensed by potenciometer. It comunicates with computer via serial port. It is controlled by a gamepad.
This is a companion discussion topic for the original entry at https://community.robotshop.com/index.php/robots/show/robotic-crane