[Alan Anderson]

An encoder requires power (make sure there is +5 on the +5 connection, and ground on the ground connection). It will provide a pair of digital signals on the A and B connections (look at them with a voltmeter or oscilloscope).

The US Digital E4P has an optical sensor pair pointing at a disk with a reflective pattern on it. If you take the cover off the encoder, you will see the non-pattern side of the disk. If the disk is at an appropriate distance from the sensor, as it rotates it will cause the digital outputs to change in phase quadrature (first one output goes high, then the other, then the first goes low, then the other).


If power is not present, it will not work.

If the signal lines are not connected to digital inputs, it will not work.

If the disk is upside down or too far away, it will not work.

If the disk is too close, the pattern surface will probably touch the body of the encoder, get scratched, and soon be damaged to the point where it will not work.