I had some tough experience with using slip-rings on a military Ku-band data link. The mechanical mount was an X-Y platform carrying a 1-meter parabolic antenna and electronics package, so there was a slip-ring at each axis, carrying DC power, DC logic, servo drive, low frequency servo feedback and a couple of channels of Ethernet. The design required continuous, no limit axis rotation. We initially had horrible RE & RS problems, and still had them after double-shielding and Eesealing every cable. Turns out that the slip-ring assemblies were not EMI shielded, despite looking very nice externally. After going back to the slip-ring vendor and explaining our problem, he was very happy to sell us the military-grade shielded slip-rings; same form-factor, just cost a lot more.
We never got to ESD testing with the unshielded commercial slip-rings, but after the shielded slip-rings were installed, all the RE & RS problems went away, and we proceeded to remove most of the cable fixes we had tried. When we got to ESD, we had no problems at all. I don't know what the differences were inside the rings, but performing the MIL-STD-461 CS114, CS115 & CS116 tests on the cables on each side of the slip rings produced no problems at all, so I assume that the cable shields were carried through the slip-rings in a way to prevent coupling to the inner cables. Ed Price WB6WSN Chula Vista, CA USA From: David Carney (Neenah) [mailto:[email protected]] Sent: Wednesday, March 19, 2014 3:03 PM To: [email protected] Subject: Re: [PSES] Slip Rings and EMI Just wanted to provide some updated info from our project's use of a slip ring. We didn't end up having any emissions issues due to the slip ring. However we were not able to pass the ESD tests. The rotating part of our enclosure was grounded through a connection through the slip ring. Discharges to this part of the enclosure caused radiated noise to couple onto signal wires and cause board resets and lockups. Making a direct connection of all the wires through the slip ring by removing the slip ring eliminated the problem. We're pretty sure it was ESD noise radiating from the slip ring because the issues were from signals on other cables in the system, not associated with the slip ring in any way other than proximity. So our experience was that the slip ring was fine for emissions, but difficult for ESD if you have to pass your ground connection through the slip ring. From: Bill Owsley [mailto:[email protected]] Sent: Friday, June 01, 2012 12:17 AM To: [email protected] Subject: Re: [PSES] Slip Rings and EMI We've had an intermittent one recently during development. Running Gigabit Ethernet across it and USB too. Otherwise it runs ok. _____ From: John Woodgate <[email protected]> To: [email protected] Sent: Thursday, May 3, 2012 1:35 PM Subject: Re: Slip Rings and EMI In message <eb1085fdca2c0d47832130cbdf9b36a010079...@co-mail-001.ms1.plexus.com>, dated Thu, 3 May 2012, "David Carney (Neenah)" <[email protected]> writes: > We?re considering a slip ring in a design to pass some wires through a rotating motor shaft, and we have never used one before. Are there any EMI concerns with this architecture? How much current and source voltage? This is critical, as different considerations apply according to these values. > If there are concerns, what types of mitigations are used for EMI when slip rings are used? It can be a matter of 'art' - choosing the right brush and ring materials. Consult a brush manufacturer, e.g. Morgan. > If slip rings are to be avoided for certain types of signals due to EMI concerns, what other alternatives should we consider? Rotary transformer, as in VHS VCRs. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk Instead of saying that the government is doing too little, too late or too much, too early, say they've got is exactly right, thus throwing them into total confusion. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) <http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher <[email protected]> David Heald <[email protected]> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
