Let's Make Robots!

Conducting electricity through sealed bearings?

I was considering the idea of a 360 degree rotating sensor. To rotate through 360 degrees the wiring would twist up obviously.

My theory:

So simplify the sensor idea for a second. Say you want a one-wire sensor (just pretend) to rotate. Take a bearing, wire the sensor to the inner race and wire up the outer race for the signal or power or whatever it is you want to connect (it's just pretend, remember).  The electricity would move from one race through the ball bearings to the other race. With the proper mounting to the respective races it would allow for free rotation without wire tangling.

Assuming this would work, my question is:

As sealed bearing are packed with grease, do you think the grease would interfere with an analog signal? Maybe some resistance would be imparted from the grease? Or maybe use simple shielded bearings, forego the grease, and use powdered carbon lube instead? I fear shielded bearing's susceptibility to corrosion from my old radio control and skateboard days so I'm not really keen on them in general. 

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Because of the grease you will not get a good connection. If any arcing occurs then the bearing will become pitted and not run smoothly. An optical connection is the best for data as it will be noise free. This can be two way as the LED and receiver do not need to be dead center. Aside from slip rings, power can be transferred by induction.

This is something I`ve been thinking about how to get around for use in free spinning robot arm bits. My idea was to use an LED and phototransistor mounted directly in the center of the bearing and use them to transmit serial in between the joints. This would probably only be 1 way communication though.

It might be worth trying, but it might also generate a bunch of noise. The headphone jack idea has been done and definitely works. Commercial slip rings are pricey and hard for most of us to get hold of.

Of course, you seem to be the king of salvage from your company's junk pile. Does anything they may have a rotating part that might yield a slip ring connector?

Slip ring connector. Never heard of it until now. I don' t think there is one in the equipment  we have or I would have seen it and said "OOOOOH! HELLS YEAH!" I don't think our stuff is designed with cool things like slip rings in the build list.

After a quick Wiki about slip rings I see motors and their commutators are used as an example. Duh. I feel slightly retarded for not recognizing that earlier.

Yes, noisy, I thought about that. Maybe stop rotating when taking a reading from the sensor, I don't know. I have some bearings handy that I was going to use. I found three that could nest together, giving me enough for one 3-wire device.

I will have to look into the headphone thing. Googling now...

Headphone jacks work great too.

Out-fricken-standing. I knew there was something out there already.

Why didn't I think of that!