encoder problems

[reuven]

hi everyone!
finally we have wired the us-digital encoder right.
when we try to use the example program. we get "jumps" between 0 and a different value (it changes every time we rest the encoder).
can anyone think what is the problem? and how can we fix it?

[mikets]

Did you follow the instructions when assembling the encoders? In particular, did you use the centering and spacing tools? This is to make sure you did not scratch the optical disc of the encoder. If the disc has scratches, the readings will be unreliable.
Also, please tell us how you finally "wired it right". That phrase does not mean it is really right.:)

[reuven]

for the first question the answer is yes.
we have followed the instructions on how to assemble it and as far as i know there are no scratches on the disc.
for the second question: we have used the diagram printed on the cover of the encoder to know which wire is which. and then we have connected them to the right ports on the digital DIO ports...

[mikets]

I still don't have enough details to tell you what could be wrong. The problem could be physical (defective encoder), wiring or coding.
One year, one of our electrical guys mis-wired the encoder. Although we have corrected it later, it turned out the encoders were fried. Had been scratching our heads for hours until I pulled out an oscilloscope to check the encoder output and found nothing. So the best bet is to first make sure the ecnoders are physically working. Then check the wiring correctness and finally check the code.

[reuven]

i think we probably burned them when we wired them wrong (is there any way to cheek that?).
thanks a lot! :)

[mikets]

We hooked up the encoder outputs to an oscilloscope and turned the wheels to check if we have pulses. I can't think of another easier way to check that.
Do you have robots from previous years that you can swap their encoders?

[reuven]

can we use a voltmeter?

[mikets]

Encoder pulses are fast, voltmeter cannot capture them.

[reuven]

the problem is we don't have an oscilloscope ...
so can you think another method of cheeking that?

[mikets]

Do you have robots from previous years? FIRST included encoders in KOP every year. So unless this is your first year, you should have some lying around or on previous robots.

[reuven]

this year is our second year.
but last year we gave them to a different team (cause we didn't used them at all)
we found a team in the area how don't use theres and they can give them to us on Sunday. i hope that will fix the problem ...

[mikets]

Good, that's what I will suggest next.

[kgzak]

Make sure there are no shorts in your wiring and that all the wires are connected right. We had a problem where we shorted our B signal to ground so it jumped between 0 and .25 when we turned the wheel.