# How to test a faulty encoder?

I'm trying to understand how to test if a rotary encoder is operating correctly. I understand that there are 3 pins, A B C, and that as you rotate the encoder A and B will connect to C offset 90º. When nothing is connected, neither A or B read as connected C as I rotate the encoder. Does it only make this connection once voltage is present on A and B?

Also, when I connected 5v to either A or B through a 100k resistor, and connect C to ground, A and B continue to read 5v regardless of the encoder position. Is this a faulty encoder?

After taking some readings, it looks like it's flashing to LOW for a couple milliseconds before going back to HIGH. This happens on every detent. It's happening with 2 encoders too! There's a chance I may have connected 5v to the A and B pins without any resistors, though, if that fries them (I was using the internal arduino pullup).

Unless you give us a link to your encoders, how are we supposed to answer? Since you mention detents, do you, perhaps, have a BCD or binary encoded rotary switch?

Paul

Figured it out – they're both working correctly! For the curious: on further inspection, all 4 pulses happen IN BETWEEN the detents. That was making it hard to troubleshoot, but it's all working correctly now!

dmayman: I'm trying to understand how to test if a rotary encoder is operating correctly. I understand that there are 3 pins, A B C, and that as you rotate the encoder A and B will connect to C offset 90º. When nothing is connected, neither A or B read as connected C as I rotate the encoder. Does it only make this connection once voltage is present on A and B?

Also, when I connected 5v to either A or B through a 100k resistor, and connect C to ground, A and B continue to read 5v regardless of the encoder position. Is this a faulty encoder?

I'm having a lot of trouble trying to understand what you were trying to convey in the above. It's very difficult to understand it due to the way it was expressed.

But it is good to hear that you sorted out whatever it was.