Slip rings

[Fredrik Andersson]

"A slip ring (in electrical engineering terms) is a method of making an electrical connection through a rotating assembly." - Wikipedia

So... yeah, that is what I need. I've googled a bit for it but only found sliprings for the industrial market. Is there any hobby level internet shop that sells slip rings?

Or could i easily make one myself? I was thinking of making them myself using ball bearings but when i checked the conductivity it seemed the resistivity was high. Thats probably because they are oiled inside. Would it work well if i cleaned out the oil? Is there another easy approach?

I found this: http://www.maybevideodoes.de/howto/slipring.html

But this slip ring wasn't made for any type of communication. I want to do I²C through it.

[Rebelgium]

I²C, or any bus protocol for that matter, is very sensitive to disturbances that could be caused by slip rings, so you'll need to have a perfect continuous contact...
I'm very curious how you'll solve this .

I recommend to go wireless 

[izua]

you can design the collector thing on the circular wiper(ring) in several points instead of one, and average, so you will even out bumps. but this will limit your overall speed.
explaining your purpose might bring out more ideas

[Fredrik Andersson]

This is the robot I'm gonna build:





It's basically a hexapod with a cylindrical body shape and tree legs on each flat side. The middle section will feature a camera and some other sensory. The robot will be able to roll so I need that section to be able to stay on the same angle. The other parts will feature two servo controllers, one on each side. Thats why i need I²C as it's even worse to wire another slip ring for two serial connections.

[AndrewM]

You could make one similar to a brushed DC motor.  Use two small pieces of copper tubbing over a plastic tube (small gap between), wires run down the inside of the plastic tube and connect to each piece of copper (I2C is two wire, right?).  A graphite brush (generally used for brushed DC motors) presses against each piece of copper tube completing the circuit.  You can attach the plastic tube to a bearing for stability while it spins.

I'll try to draw up a picture if what I am describing doesn't mke any sense

[Fredrik Andersson]

I've searched a bit about slip rings, but found nothing for the hobby marked, just industrial products. This does seem nice however:
http://www.polysci.com/slipringexpansion.htm

I feel really confused on these kind of sites. How would I order from here? And would they accept small hobby buyers?

[GHF]

You could make one similar to a brushed DC motor.  Use two small pieces of copper tubbing over a plastic tube (small gap between), wires run down the inside of the plastic tube and connect to each piece of copper (I2C is two wire, right?).  A graphite brush (generally used for brushed DC motors) presses against each piece of copper tube completing the circuit.  You can attach the plastic tube to a bearing for stability while it spins.

I'll try to draw up a picture if what I am describing doesn't mke any sense

You do get a lot of unwanted signals when the brushes hit dirt and other non-conductive spots on the rotating part. I guess he could just use a lot of brushes to maintain contact.

-Xo W.

[Trumpkin]

froogle "slip ring"

[bukowski]

Fredrik,
Have you had any luck? You got me curious, and I have been looking myself, but I havent found much in the hobby world (might want to form a company!). I know that in large high quality slip rings you really dont have the unwanted signals GHF was talking about. I worked on radars when I was in the service and they used slip rings (obviosly). Trust me, there was no unwanted signals coming through.