On Saturday 19 July 2014 08:28:09 andy pugh did opine And Gene did reply: > On 19 July 2014 08:15, Steve Blackmore <[email protected]> wrote: > >>I wouldn't want to be anywhere near a BT transmitter/receiver that > >>you can run a servo off of :-) > >> > > Why not? Plenty of wireless controls in industry. > > He is trying to run a servo through the slip rings. > > I was trying to be funny. > > He needs power as well as signal.
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. I think I'd try three, maybe 4 (one for bt power & ground) pieces of foil shielded coax squeezed into the middle of the power rings, feeding a much smaller set of rings on out on the end of the shaft for the encoder signals first. I think the small rings could be grooved to receive a gold plated wire borrowed from an rj45 jack, in fact if the rings were small enough and close enough together, one could make a set of brushes by milling away the far side of an rj45 jack insert, making a few of them so when one did wear out, a fresh one could be inserted thru a well aligned hole in the side of the swarf eliminator housing in just 5 minutes of downtime. Cleanliness in this case being a quite holy attribute for long life. Somewhere in my travels, I saw an 8 ring slip ring assembly in a broadcast Video tape machine, not at all shielded from dirt, and I don't recall they were a huge maintenance problem. My mind eye says they were about 3/8" in diameter Air hosing the cooling air's dirt & dust out of them periodically seemed to be all the machines needed. There, the rings rotation was uni-directional at 60 rps. The machines basic design however had tape tracking problems such that its reputation precluded it ever being an industry std format so the experience I had with it was not extensive. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS ------------------------------------------------------------------------------ Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
