Supershifter Encoder Reliability Problems?

[Qbranch]

Ok, so we were driving the snazzy new chassis I posted pictures of recently today, and within just a few minutes our encoders on our supershifters ceased to function. No, it isn't a software problem, I've examined the output of the encoders with an oscilloscope on both sides of the robot. One is almost constantly high (5v) and occasionally comes low if you spin the transmission shaft fast enough. The other randomly gets pulses occasionally when you spin the transmission shaft fast enough.

Has anyone else had reliability problems with the supershifter encoders? We're probably going to end up making a coupler and all then mounting different encoders as the open-frame us digitals (being open frame) are more prone to short life if there is any runout in the shaft of the transmission.

*hint hint* Any suggestions Andy?

-q

p.s. Where are my manners: the shifters pull great and the gear ratios were well figured. Nice shifter. Servo shifting not so hot, switching to pneumatic.

[Schnabel]

I would open the encoder cases up and check to see what is going on inside of them. When you take the back case off, there is a metal disc inside. Take this disc off, if it comes off with a little struggle, then that part is good. If it loosley comes off, the it was not fitted to the shaft properly. To do this, gently use a pair of pliers to squeeze the four parts that go over the shaft (on the side of the disc facing the transmission) until each gap is closed. Make sure not to close them in too tight. Another thing to check is the side of the disc that faces the transmission (with the near microscopic lines on it) and make sure that there is no debree(sp) or scratches on it. If so then the disc is bad. Make sure to not touch this side at any time. Also make sure the red sensor on the green board is clean. Again do not touch this part. When you put the disc back on, do not push it all of the way down. It is best to use a tool designed to put the disc on, but if you do not have one, leave a little more than a milimeter between the disc and the top of the sensor. Let me know if this helps any!

[Dad1279]

Did you change the shafts or pull them out of the transmissions? If so, you will need to pop the covers off as stated above, and attach the encoder wheels.

[Qbranch]

We've already examined the encoder wheels and such, and have found no problems with it.

However, what we have nocied is that our super shifter's encoder shaft has more than the allowable axial play listed on the US digital website. By setting the transmission down on a flat table and using a dial caliper, we've discovered our transmission's encoder shafts have about 0.050" play (total, not +/-). So, to remedy this, we're next-day-airing some US digital fully housed and ball bearinged 250ct encoders and installing a HeliCal flexure coupling between the transmission and the encoder to isolate the encoder from possible damage by the transmission shaft.

And, completely unrelated, our plasma cutter quit and crashed (physically) today while running all of the parts for our final version of our shooter, as well as all the brackets to mount our pipes. I've had a rough day.

Thanks for your help and thought,

q

[SteveJanesch]

Q,

Thanks for bringing this up. We're using supershifters for the first time this year, and I'll have ours checked out tonight before going on the chassis (yes, we are a little behind where we'd hoped to be).

Originally, we weren't aware that there were coders built into the transmissions, so we designed one wheel axle on each side longer than necessary, to extend beyond the bearing and back into the main portion of the chassis, where we had intended to mount COTS encoders. Would something like that be easier for you to do, rather than unmount and disassemble the transmissions?

Steve

[Guy Davidson]

Q,

We've had some reliability problems with our encoders. They seem to be retuning odd values, or none at all at times. I'm planning to look at the return values with an oscilloscope and some simpler code to see what is actually going on.

Please let us know how the couplings work for you, we might try the same thing.