HD-SDI signal through a PCB Slip Ring? - Page 1
Forum section: electronics / beginners

author: Jackster
author_rank: Frequent Contributor
timestamp: May 26, 2020, 01:24:41 pm
content: How much trouble is it going to be to engineer a slip ring that can send HD-SDI signal through?One of these...Need it to be around 250-300mm wide radius.

author: Yansi
author_rank: Super Contributor
timestamp: May 26, 2020, 01:28:27 pm
content: Easy. But I'd suggest to reclock and buffer the signal after it.

author: Jackster
author_rank: Frequent Contributor
timestamp: May 26, 2020, 01:31:57 pm
content: Quote from: Yansi on May 26, 2020, 01:28:27 pmAwesome! Stright passthrough not an option?

author: AndyC_772
author_rank: Super Contributor
timestamp: May 26, 2020, 01:38:49 pm
content: Easy? Really?If you're looking to run a signal at over 1 Gbps then that means an edge rate of well under 1ns per transition - in other words, trace topology and proper termination are critical.Those rings will act as wave guides that allow signals to propagate endlessly round in circles, splitting the wave and exchanging energy between them each time the wavefront reaches the wiper. I don't see how you could ever possibly terminate such a topology correctly, and without proper termination, you'll have no eye opening.

author: Jackster
author_rank: Frequent Contributor
timestamp: May 26, 2020, 09:22:09 pm
content: Quote from: AndyC_772 on May 26, 2020, 01:38:49 pmOh this sounds bad.Any idea on how something like this could be done?I need to move a camera around in a circle but I don't have a center point for a signal cable to rotate on like one of these premade items.

author: Yansi
author_rank: Super Contributor
timestamp: May 26, 2020, 11:02:36 pm
content: Who did say you need to have it connected in circle?How about having a terminated split in one place of the ring?How about having the ring split in sectors each fed separately /and terminated/ to create shorter stub length? (Passive resistor splitters are cheap and quite suitable)Or even using multiple wipers? And cheap signal switching so you don't have serious dropout when crossing sector boundary. Heck the signal could even be switched likely using cheap PIN diodes (interesting, never thought about this myself!)No expert and never done any designs like this. However have a heap of old broadcast tech laying around and like to experiment with it. You may be underestimating what the receivers can recover. Hence why I have suggested using a reclocker after the slipring.

author: wizard69
author_rank: Super Contributor
timestamp: May 27, 2020, 07:02:24 am
content: There is also the issue of mechanical reliability. the application is a big factor but don't expect perfect electrical contact during high accelerations or shocks. By the way this isn't even normal operational issues from debris and wear on the rings and contact. this is where it may worth paying for an expensive coupling that has been well engineered and validated by the manufacture.So it may be worth considering entirely different ways of transferring the data.

author: Gyro
author_rank: Super Contributor
timestamp: May 27, 2020, 09:34:47 am
content: Quote from: Jackster on May 26, 2020, 01:24:41 pmUghh, PCB slip rings. Just think cheap multimeter dials, and then trying to put high speed signals through them!You want to look for 'hollow bore' or 'hollow shaft' slip rings. There are several manufactures if you web search. Even then, frequency could well be an issue.