Slip rings, rotary connectors, reels, etc.

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EpicentrE
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Slip rings, rotary connectors, reels, etc.

Post by EpicentrE » Thu Feb 14, 2013 2:34 pm

I'm looking for some advice on something I need for a non-robot related project.

I need an extendable/retractable (preferable with a rachet and spring, so that it automatically retracts when a button is pressed) USB lead, or a lead with at least 4 wires which I could use for USB. There are many of things such as this around, but they have some problems which make them unsuitable. They extend in both directions from a central hub, rather than in only one direction; they generally have very thin wimpy cables, and I need cables of at least standard USB thickness, i.e that it can take being wound and unwound regularly, as well as being stood on, without any issue; and they're usually fairly short, whereas I'd like something at least in the 5-6ft range.

I've considered the possibility of custom making something using a slip ring/rotary connector, a length of cable, a coil spring and some magic, but it would certainly be a pain (I hate working with springs!), and I've read that slip rings aren't great for digital connections.

Does anyone have any suggestions of a suitable product, or any other advice related to this sort of thing? It doesn't matter if it's not designed for USB originally, I can always put my own plugs on it if it has enough connections.
Scott Fyfe-Jamieson, Captain of Epic Robotics. Champion of AWS38/41/42.
http://www.epicrobotics.co.uk

daliad100
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Re: Slip rings, rotary connectors, reels, etc.

Post by daliad100 » Thu Feb 14, 2013 5:34 pm

Couldn't you build something roll up extension lead style? No slip rings plus extends from one end.

No auto retract though but you could buy a cheap retractable tape measure, swap the tape for wire, run one end out a hole made in the centre of the reel and case and the other through the tape hole. Might not be very pretty and I'm not sure as to how much cable you'd fit in one but it should do what you want
Team Imperial - What is that, metric?

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BeligerAnt
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Re: Slip rings, rotary connectors, reels, etc.

Post by BeligerAnt » Thu Feb 14, 2013 6:48 pm

If you find a solution, performance will depend very much on what sort of USB peripherals you intend to use on it.
Keyboards and mice will probably be OK, low speed USB is only 1.5Mbps
Full speed (12Mbps) is going to be a whole lot more fussy about impedance mis-matches etc.
High speed (480Mbps) is really fussy. With a wavelength of only just over 600mm a fairly short section of less-than-ideal transmission line can represent a significant problem at signal frequencies although it will be fine at DC.

USB is specified to run over 100 ohm balanced line, so you need a twisted pair for the data lines.
Any significant deviation from this arrangement will cause an impedance mis-match will will degrade the signal which will eventually result in data errors etc.
Usually the power wires are thicker to carry the required power current. At least 500mA (per node) must be available without any significant voltage drop (a couple of hundred mV should be OK).

Good luck with it!
Gary, Team BeligerAnt

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EpicentrE
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Re: Slip rings, rotary connectors, reels, etc.

Post by EpicentrE » Fri Feb 15, 2013 12:10 pm

So to add some context, my Arcade Fightstick's USB cable is getting frayed due to constant wrapping, unwrapping, etc. and I'd like to replace it with something a bit fancier and easier to manage (as folding up a cable to slot into a tiny compartment is annoying and takes a while).

I'd like to cut the casing up and have room for the reel inside. Unfortunately one of the reels that rotates as the cable is pulled out (this kind of thing) wouldn't really be suitable.

Thanks for the advice so far, though. I have no idea what speed or tolerance is used for Xbox/PS3 USB controller connections, but I'll have a scout around and see what I can find out.

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Re: Slip rings, rotary connectors, reels, etc.

Post by BeligerAnt » Fri Feb 15, 2013 6:02 pm

Hmm, nothing immediately springs to mind.
On the plus side, being an HMI device it should operate at low speed, so the least fussy type when it comes to communicating :)
Gary, Team BeligerAnt

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