Hi all! On 19.07.2014 16:36, Gene Heskett wrote: > On Saturday 19 July 2014 08:28:09 andy pugh did opine > ... > > Power thru the rings seems easy enough to do, but shipping the encoder > back thru adjacent slip rings would seem to be to subject to a huge amount > of interference from the servo motors cummutation noises. If he can steal > power for the bluetooth from the servo's power with a teeny switcher > stepdown, then get the encoders signals out the end of the shaft, then 3 > bluetooth buttons like they use for computer mice with each on a different > channel could do it, arranged in a circle, with 3 bt receivers rigged to > see only one transmitter by way of 3 concentric horns. With the correct > physical polarization, I'd think the 2x per revolution signal nulls could > be dealt with when the range is <3". If not, then 2 receivers at 90 > degrees with the outputs or'd might do it. > > That would be awfully complex to manufacture though. With anything that > rotates more than 170 degrees, carrying the transmitters with it, the > signal nulls when the transmitter and receiver are exactly 90 degrees in > signal polarity is going to be a major problem. Those nulls would be 2x > per revolution. > ...
Though you /might/ be able to get something like this working more or less reliably, it will most likely be as far away from realtime as one can get. When the encoder should generate the feedback for the servo controller, then it should not be subjected to a lot of (variable) delay. Same goes for the home/limit switches of course, though a constant delay could more easily be dealt with for those. So I'd definitely prefer an inductive or optical solution for the data and slip rings for power if really necessary. A cheap alternative to slip rings for signal lines are ball bearings, but only if you can tolerate some noise in the output while rotating. So not really useful for an encoder signal as well. Maybe for the limit switches. Regards, Philipp
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