encoder jumping between two values. please help!

[badger3.14]

On our robot, we are trying to use the 360 clicks per revolution encoders from us digital to regulate our speed for our shooter, but when powering up the wheels and reading the values in labview, the encoders read steadily until 20833.3 clicks per second. When going above that, the values jump from 20833.3 to 41666.7 clicks per second.

Any thoughts or answers???

[Tom Line]

You may be exceeding the capabilities of either the encoder or the cRio. Research the limitations of both with regard to data rates for the DI/O and the encoder you have chosen. Reading over 20000+ samples a second is significant overkill. Consider getting a different encoder wheel to tone that down to 100, 32, or even 16.

[wireties]

Originally Posted by badger3.14

On our robot, we are trying to use the 360 clicks per revolution encoders from us digital to regulate our speed for our shooter, but when powering up the wheels and reading the values in labview, the encoders read steadily until 20833.3 clicks per second. When going above that, the values jump from 20833.3 to 41666.7 clicks per second.

Any thoughts or answers???

The counting circuits in the FPGA are only good to 40000 counts per sec. How fast is your wheel turning? You had better use the k1X setting. We are going with 32 cpr encoders for this reason.

[j.cole]

Just had the same problem today. Got it fixed. The problem is the Decoding rate (at least that's what it's labeled as in LabView). If it is set to 4x the variation is huge, at 2x its smaller, and at 1x its almost nothing. Talk to the programmer and see what it's set to.

[badger3.14]

thanks for the input, our team ordered two new 32cpr encoders today. i am hoping that this will fix the problem.