I have a nice PMDC motor with an encoder that was pulled from an old DEC printer and I'm trying to figure out the pinouts for the encoder. I could find no data sheet on Google.
It has 4 wires so I'm assuming I have a ground, +5V, A channel and B channel.
These are the values I measure:
Blue-yellow: 500 ohms
Blue-red: 173 ohms
Yellow-red: 327 ohms
Black is open when connected to any wire.
Any ideas?
Doesn't sound like a typical quadrature encoder. It's suspicious that blue-red + yellow-red = blue-yellow. That suggests there's a potentiometer in there with red as the wiper and blue/yellow as the fixed ends. Black could be a frame ground independent of the potentiometer.
Can you try turning the shaft? I'm betting you'll still get blue-yellow=500 ohms but the other values changing and adding up to 500.
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Can you try turning the shaft? I'm betting you'll still get blue-yellow=500 ohms but the other values changing and adding up to 500.
I just tried that. Nothing changes. It is curious that blue-red and yellow-red values add up to the 500 of the blue-yellow pair, though.
There are two trimpots on the encoder (the white thingies with red dots) but I have no idea what they would be for. On the underside are a pair of 180 ohm resistors.
By all appearances it looks like an optical encoder. It's a metal slotted code wheel (by a rough calculation probably 500 slots which would be typical) which does not contact anything. There are two tiny pcb's but they're glued in so I can't get it apart to follow the traces.
A common wiring scheme is to use Red & Black as + & - supply. you would proabaly be safe with 5V across those 2 wires. Measuring with a meter doesn't give much information.
The encoder might be open collector which means that it switches to ground, you need a pullup resistor. Or it might switch between Supply and Ground.