conductive cylinder for homemade slip-ring

Hello guys .

i am intending to me make a homemade through-hole slip ring of an internal diameter of 8mm . all of the pre-made ones are too expensive since they seem to be using precious metals for some reason . i won't be driving any fancy signals through it , only a power supply and low frequency serial for an arduino . my thoughts are to buy some sort of conductive material in the shape of a thin Tube . cut the tube , place it on my rotating shaft and then get a stationary conductive rod to come into contact and have friction with it . now my problem is with the tube , i can't figure out where to find it . i can't figure out where to find something conductive and thin shaped like a cylindrical tube .

the length doesn't matter at all because i can cut it , all that matters is a the diameter which has to be strictly superior than 8mm and less than 15 . i kept searching for "copper cylinder" , "copper tube" , " conductive cylinder" and so on .. and i found nothing at all . do you guys know the name of something that can assist to make this ?

thank you very much .

"copper tube" would be a rare thing, "copper pipe" is a very common thing. "brass tube" is a better choice, copper is very soft and would wear rapidly.

hello sir , thank you for your response .

yes actually "brass tube" brought some interesting and useful results . the copper tubes seem be kind of thick though , that wouldn't be a problem tight ? because of resistance and all .

A layering of bearings and insulators would work as the basis of a slip ring assembly. I found a number of bearings on the I-net using my favorite search engine with an inside dia. of 8mm.

Not sure where you reside in the world but (small, private) hobby stores here in the USA carry a good supply of brass tubing used in the construction of model aircraft and railroading. Here is a sample of what is available from one of the major suppliers of such product:

http://www.ksmetals.com/26.html

You will often see a rack from that supplier in a major hardware store too. Ace hardware usually has it, but each Ace is an independent franchise so they don't all have it.

Gold is required in this application for long-term corrosion resistance. If you live near the beach, brass and copper will have an unacceptable amount of corrosion in a week. Inland, it may last a few years.

Do they still make chromium plated brass or copper tubing that was once popular in exposed bathroom plumbing?

Have you considered this: https://www.adafruit.com/product/736

Commercial slip rings are not very expensive. $15 adafruit, and similar ones from china are on ebay for under $5, or in the $20 range for higher spec ones. Why are these not suitable???

And yes, commercial slip rings use gold plating on the contacting surfaces (thicker by a significant margin than, say, enig PCB surface treatment) - non-noble metals are subject to corrosion, which is fatal for something like a slip-ring. If doing it without gold, you need enough friction between the rotating and stationary element that the corrosion will be scraped off as it turns - which in turn means that one or more likely both of the surfaces will wear and need routine replacement.

amine2: Hello guys .

i am intending to me make a homemade through-hole slip ring of an internal diameter of 8mm . all of the pre-made ones are too expensive since they seem to be using precious metals for some reason . i won't be driving any fancy signals through it , only a power supply and low frequency serial for an arduino . my thoughts are to buy some sort of conductive material in the shape of a thin Tube . cut the tube , place it on my rotating shaft and then get a stationary conductive rod to come into contact and have friction with it . now my problem is with the tube , i can't figure out where to find it . i can't figure out where to find something conductive and thin shaped like a cylindrical tube .

the length doesn't matter at all because i can cut it , all that matters is a the diameter which has to be strictly superior than 8mm and less than 15 . i kept searching for "copper cylinder" , "copper tube" , " conductive cylinder" and so on .. and i found nothing at all . do you guys know the name of something that can assist to make this ?

thank you very much .

Would a transformer work instead? I've not done it myself but my cousin builds rotating stuff with a transformer to carry power and data between the fixed and rotating parts. Enough power for a controller and some LEDs.

Hello again , i am very sorry for my late response and feed-back as i have too much work up my back these days . - Idahowalker , thank you very much for the suggestion , but that won't work , as the bearings i have seem to be too resistive and they are not that suitable for conducting similar signals .

  • Wattsthat , thank you very much sir that is very helpful ,that's the closest thing to what i need at the moment.

  • MorganS and Outsider , thank you guys , yes i have considered corrosion , but i have no choice :( ill probably just end up changing it periodically

  • LarryD , thank you very much Sir , that's a capsule slip ring , those have quite a good price , but i can't use those . because the mobile part is moved with a motor and the slip ring is between the motor and the rotated part . so i need a "Hole slip ring" with 6 channels and a through hole of a minimum of 8mm . those are indeed very expensive , and the delivery prices are often too high . thank you very much sir .

  • DrAzzy , thank you very much , that's actually very interesting to know and consider . through hole slip-rings are often too expensive , capsule slip rings are cheap but they are not suitable

  • Hello Mr Berry , thank you very much for your attention , i don't think that can work , especially with this specific project , it would be very interesting to see how that works if you have a link for it though , thank you sir (y)

Indeed bearings are unlikely to work, as a continuous film of lubricant is the very essence of a decent bearing - no metal to metal contact is supposed to happen in a moving bearing, so its electrical behaviour will be poor/intermittent at best.

I would suggest a copper tube, perhaps a water pipe from a plumbing store. This type of pipe is a little harder than most motor commutators but should work.

The brushes can be found in most hardware stores as replacements for hand tools with DC motors.

The tricky part will be to make sure the surface of you ring (copper pipe) is true to the rotating center and with little radial variation.

Interesting thing about commutators, the graphite brushes carrying current, kind of burnishes the slipring surface making the life much longer than one would expect looking at just mechanical wear.

Oh - yeah, use brushes for motors to make the contact! They are usually made from graphite, which helps scrub the surface of the thing it's contacting, while also providing some lubrication.

  • Hello Mr Berry , thank you very much for your attention , i don't think that can work , especially with this specific project , it would be very interesting to see how that works if you have a link for it though , thank you sir (y)

I think you mean me, but where 'Mr Berry' came from I'm not sure.

This is the device I am talking about, it uses a transformer between the fixed and rotating parts, the transformer carries power and data Minimag rotary clock

Old video recorders used concentric rotating transformers to couple to the spinning head assembly. Tricky to make your own as casting ferrite is a high temperature industrial process as far as I know.

If you use copper slip rings and graphite brushes, burnish the copper. I just chuck the tube in a drillpress on a high speed and use a >2000 grit paper to clean it, then use a stainless steel washer and press it into the rotating tube.

It helps with corrosion and arcing, which would not play nice with any sort of signal.