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Team 180 used a pair of Grayhill series 61k optical encoders from Digikey:GH3065-ND. We sent the output to a custom circuit board where we processed a pair of RC digital inputs for each encoder for distance and an RC analog input for speed. The circuit used a CD4040 binary counter and an LM2917 frequency to voltage converter. With the way the encoders mounted on our gearbox, the "2-bit" distance inputs gave us 3.125 inch resolution in hi gear and 6.5 in low gear. We used the distance inputs in autonomous mode for dead-reckoning. The speed inputs gave us a low speed threshold for "shift-on-the-fly" and input for a pid speed controller we're working on, but never used in competition. So, we'll prototype the speed control in the off-season and check out its usefulness for both autonomous and manual mode.
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