Slip Rings

You got it half right. Slip rings are usually copper but the brushes are usually carbon because they are softer than copper and self lubricating.

Yeah like in motor brushes, it was only meant as a short term thing to start with, I didnt have any suitable motors I was prepared to sacrifice to use the brushes from though.

maybe some car dynamo/alternator brushes would suffice but would be tricky to mount.

I did just have a brainwave though, if I uses a second identical pcb instead of the brushes and have some brass discs making contact between the two pcbs free to rotate but guided by a spider, bit like an axial roller bearing.

thanks Colin =^.^=

I think it would be simpler to just use pencil led, just measured the resistance of a .5mm, it is low, but fragile, so why not use a carpenters pencil? Just shape your point and cut to length, cost negligible. Remove 3/8" of the wood from one side and drill a small hole for a small screw to fasten your wire.

Rolf

That might be better than a slips ring/brush, since the rollers will not be sliding over the ring surface. On the other hand, the sliding effect does keep the surfaces clean. A roller will just roll across any crap that may settle on the ring surface.

For the data, you might want to consider some sort of low range RF (BlueTooth, ZigBee, etc.) so as not to be subject to noise on the data slip ring (if that's a problem). The power on the moving pat can be filtered and a big cap or two can carry the system over the od slip ring glitch.

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Yes thats a point, still there wont be any need for grease to get gumed up with dust etc. maybe a felt pad to clean the surface .. and multiple narrow rollers (brass washers) to cut through any debris.

Theres a 5v headroom on the power line with ULDO regulator and rechargeble batteries to cope with interruptions, the data is very low frequency, a .1uf cap and high impedance ip on the stationary side is enough to smooth out any glitches, a seperate reference ring is used rather than power 0v.

Yes I havnt waded through all whats available in the short range RF stuff yet. I think my mothorboard has some kind of wirless LAN facility. maybe even a ring of leds and a sensor would be a solution.

Colin =^.^=

What happens if you try the super mangy slip rings on telephone cords?

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Many thanks,

Don Lancaster                          voice phone: (928)428-4073
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Put a dab of plain vaseline on the contacts. This removes the grime and gives true metal-to-metal contact. It leaves a thin film that keeps the surface clean. This reduces the contact resistance by a factor of ten and stabilizes it. Works on most electrical connections that operate at room temp.

Try it on the CMOS clock battery, pcb and ram connectors, flashlight battery connections and on/off switch, intermittent and scratchy noises in telephone connectors, electric light bulb sockets (also makes them much easier to remove when they burn out), car battery terminals, and any other connection that operates at room temperature. Repeat every six months or so when the connections start acting up again.

This is an old trick used by transmitter radio engineers since the 30's. When the antenna wouldn't tune properly, they would unbolt the feedline bars, clean the connections, apply vaseline, and reassemble. This solved the tuning problems.

Regards,

Mike Monett

If you have the $$ see if you can find out what happened to Litton -- before they got bought up by Northrop-Grumman they had some 'budget'

12-contact slip rings for $200 ea. Whatever N-G division they've become they may still sell them.

Even if you don't want to spend that much for slip rings they had a pretty educational website on how the things were manufactured. If I recall correctly they used real brushes -- bundles of silver wire that rode in a 'v' slot in a disk to make contact. There's obviously a great deal of science behind what they do, but their sliprings last forever.

Alternately, what's keeping you from going to Radio shack and buying some DC motor brushes? They come wrapped in a cheap DC motor that you have to take off and throw away, but they'll be designed to run against copper which is what you're using now. If you can mount them so they maintain pretty good contact you should be OK.

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if your really serious about it then maybe using a inductive method will work for you?

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I found a site that sold slip rings but my local distributers didnt stock anything like it, and they were quite expensive. dont recall seeing any details of how they were constructed, maybe they want to keep that a secret to themselves, also very interesting was fibre optic slip rings

However the 'real brush' idea is quite interesting, wonder if a brush made from copper wire aka 'a short bit of ordinary stranded wire' will do

Good idea dont know why I didnt think of that before, oh I tend to just try and use what I have at hand, just looked for some cheap motors on ebay found

5 quite cheep, stil dont like trashing new stuff, however found 4 cheap motor brushes. they have round carbon type brush and coil spring wich is a challenge to try and mount, however the brushes have a shoulder on them wich i might be able to mount in a hole in the end of the contact strip.

thanks Colin =^.^=

For about two years now I've been applying Silicone Spray on light bulb threads. No more getting out the 15' ladder to remove frozen-in-the-socket bulbs.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

I used rotating transformers for the Hubble 'scope mirror electronics. (The mirror floats on a magnetic field.)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Good book: The Hubble Wars by Chaisson.

John

Haven't heard of it. Quick synopsis?

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

Brushes are usually used when conduction path has more than one route, like in armatures and variacs, otherwise they would short. I have seen big slip rings before. Had some analog DC servo stuff around here some time ago. High currents and low voltage are not really good in slip ring use. An AC to DC supply would probably work better as a supply with HV AC on the rings say 48 volts. gs

...

Take apart a scrap car alternator?

Good Luck! Rich

Colin:

Check out the Rotating connectors at:

I don't know the cost, but they claim to have lower noise than slip rings.

Don Cleveland

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wow they look cool, liquid metal .. mercury ?

Colin =^.^=

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Will the application permit the use of mercury?