Society of Robots - Robot Forum

Mechanics and Construction => Mechanics and Construction => Topic started by: scomcleod on March 03, 2009, 06:57:07 PM

Title: Where can we find slip rings?
Post by: scomcleod on March 03, 2009, 06:57:07 PM

Hey all,

I'm looking for a cheap 2-contact slip ring.  It seems the only slip rings commercially available are industrial quality ($$$).
This robot will be simply transmitting low power to a microprocessor (5V@100mA) at speeds at ~600RPM (10Hz).  I'm not concerned about the noise levels, and the slip ring can be through hole or end mounted.  It seems like I want something as simple as a 3.5mm headphone jack (but designed to rotate continuously).

Does anyone know any places to find a pre-built slip ring for a decent price?

Title: Re: Where can we find slip rings?
Post by: Soeren on March 04, 2009, 12:29:12 PM

Hi,

Like you mention yourself, jack plugs and sockets can be used, but I'd go for the 1/4" variant.

Title: Re: Where can we find slip rings?
Post by: scomcleod on March 04, 2009, 02:46:39 PM

That's a good thought to go with a larger jack..

Since audio jacks aren't designed for continuous rotation, I wonder how long they will last or if they will fail relatively quickly.

Title: Re: Where can we find slip rings?
Post by: SmAsH on March 04, 2009, 02:49:31 PM

jacks are pretty good, my guitar lead gets plugged in many times a day and has lasted me a fair while. but what about a circular plate with brushes?

Title: Re: Where can we find slip rings?
Post by: scomcleod on March 04, 2009, 03:09:02 PM

Ideally, I would like to minimize the amount of custom construction as I plan to make 4 elements with these slip rings.

With this type of build, are you suggesting ordering carbon brushes and making the circular plate similar to a bullseye or the Target logo?

Title: Re: Where can we find slip rings?
Post by: Soeren on March 05, 2009, 01:51:21 AM

Hi,

If you wanna go that route, bronze spring arms are better than carbon.

A thing to note: You need to have extra capacitors after the slip ring, since it will bounce off for short intervals (µs to ms) every now and then and a µController will tilt, if it sees that kind of interruptions.
At 100mA draw, 2'000 µF will buy you 5ms before the voltage has dropped 0.25V and that should be enough - unless the slip ring is very poorly made.

Title: Re: Where can we find slip rings?
Post by: scomcleod on March 05, 2009, 11:55:26 AM

Thanks Soeren for the advice on the spring arms / caps.
I just worked the math... your calculation was F = I*t/V?