"N_Cook" wrote in message
...
Getting a bit flakey on a Behringer SL2442 mixing desk.
Just 3 control lines out , ground and 2 lines taken high via 4K7 to 5V.
What
would be inside , 2 sets of 10 resistors? All wrapped up again , different
problem repaired and only noticed at final checks so cannot investigate.
Owner only uses one effect so fingers-crossed will not need replacement or
its fellow




The ones I've seen have 2 printed concentric zero ohm tracks, in a "square
wave" pattern.
Each track is supplied with 5v by the pullup resistors, the wiper shorting
out the tracks as it is turned, producing 2 square wave outputs.

The tracks are printed such that turning it one way makes one output lead
the other, turning it backwards makes it lag the other.

It is then possible to use these as data lines to a uP port, where software
determines direction of rotation and increments or decrements a counter to
show how far it has been moved.

Obviously it is not possible to determine absolute position.



Gareth.