Optical Encoder Problems

[Hitchhiker 42]

Hi y'all,
It's way past build season, but our team's still working on our robot. A couple days ago, both of our optical encoders on our drivetrain have stopped working. We have already checked our wiring, and tried switching out the encoders for new ones, yet the problem persists.

Is there any way to fix this? Thanks!

[techhelpbb]

Originally Posted by Hitchhiker 42

Hi y'all,
It's way past build season, but our team's still working on our robot. A couple days ago, both of our optical encoders on our drivetrain have stopped working. We have already checked our wiring, and tried switching out the encoders for new ones, yet the problem persists.

Is there any way to fix this? Thanks!

Assuming quadrature encoders:

Do you have an oscilloscope?
Power up the encoders and look at the A/B channels and see if they produce square wave forms as the encoder shaft rotates.
If not, there's a problem.

If you don't have an oscilloscope, maybe a DMM with a frequency function?
It's a little less friendly but you could test 1 channel at a time like that.
You'd have to rotate the encoder shaft over and over to make this work and at a consistent velocity.

If you are handy with TTL/CMOS you could make a little board with a counter on it, hook it up to each channel with an LED on the highest order bit...that bit should blink.
Again this requires rotating the encoder shaft over and over at a fairly consistent velocity.

Do you have an encoder you know works?
Put that on one of the encoder inputs...be very careful not to mess up how you power that encoder...and see if you can see that input in your robot.
If that works and yet your other encoders do not...pretty good chance those not working encoders are shot.

[AdamHeard]

Since both stopped working, it might indicate that the power being source for them has gone bad.

Assuming they are powered off the roborio, is the 5v and ground rail shorted?

[bobbysq]

The discs may be scratched or out of place if they won't read properly.

[frcguy]

Originally Posted by AdamHeard

Since both stopped working, it might indicate that the power being source for them has gone bad.



Assuming they are powered off the roborio, is the 5v and ground rail shorted?

Highly suggest checking this. All of our problems with erratic RoboRio behavior turned out to be shorted power rails.

[tr6scott]

Originally Posted by AdamHeard

Since both stopped working, it might indicate that the power being source for them has gone bad.

Assuming they are powered off the roborio, is the 5v and ground rail shorted?

+2 This, look for shrapnel in the roborio.
Rail status is also reported on the driver station.

(Be thankful you are not playing in the semi finals for MSC right now, like when it happened to us... then be thankfull that the drive coach chews gum, and the lead electrical person has much sharper eyes than me, and you get to play in the finals.)

[frcguy]

Originally Posted by tr6scott

(Be thankful you are not playing in the semi finals for MSC right now, like when it happened to us... then be thankfull that the drive coach chews gum, and the lead electrical person has much sharper eyes than me, and you get to play in the finals.)

We discovered ours right in between qual matches on Curie field, so I definitely hear you! Luckily, we had the foresight to get an additional RoboRio, and our drive team worked through lunch to swap it out. One of the most tense moments of the season for me.