We may have a Limelight on the bot for the first time in 2024. We actually have 2 so we are trying to plan ahead for what that might look like. This also means we will have a network switch on the bot for the first time.
How should we get power into multiple POE cables for Limelights or other devices? Do teams use something like the REV Mini Power Module and multiple REV POE injector cables (POE Injector Cable - REV Robotics)? Or do you use a custom cable, or a small board of some kind? I’m a little concerned about multiple connections with the REV cables. Not sure if that’s well founded.
I’ve spend a few hours reading CD info on switches and other wiring details. It was all helpful, but the above is a gap in what I could find. If I just missed it, thanks for your patience in linking to the answers!
You can go with the REV poe injectors driven by the REV mini power module. We tested that configuation using an eternet switch as outined in the limelight documentation, mind you it does not show the poe injectors in the diagram. Be sure that the injectors are on the output side of the switch towards the cameras.
You will also need to supply power to the ethernet switch separately from either the PDH or from the expansion board
I had to post once on CD that I wasn’t paying attention and put it on the input side; fried an expensive switch. Mistake-proof this the best you can with labels and anything else you can think of.
There seems to me some concern out there about the REV POE cables having data connection issues over time. Maybe this is an issue for cables of this design in general and not a REV issue? Any insights about reliability?
By “REV poe injectors”, are you referring to the Radio Power Module (RPM)? I ask because the Limelight wiring guide has a note at the top of the page specifically warning against this particular setup… The RPM, takes a 4.75-18v input, and always outputs 18v, which is higher than the limelight is rated for.
Thanks for pointing that out. I missed the link in the OP, and the RPM can easily enough be referred to as a “POE injector” at times. At the least, hopefully my post may cause a team in the future to pause/rethink powering a limelight off an RPM…
All good on the RPM, as noted by Joe. Thanks for the diagram and interest, cad321
This is also not intended to bash the REV product, we are just considering options like making our own. I see hints of how to do this for FRC applications, but haven’t found a full description. We get the wiring part, it’s the details of making them robust that we’re looking for.
Run an ethernet cable from the output of the switch and you can either clip directly into the lime light or use an eithenet adapter with another cable to lengthen the run to the Limelight. Then you need to power the POE low current channel on the PDH or on the extender board.
I’d recommend that over REV’s passive injector cable. As a CSA, it’s just year after year with that cable. I don’t think I’ve seen a full season go by without at least one failing on a team mid-match at an event I was at, most years it’s more than that.
If you do find yourselves using the orange cable, make sure it’s stain relieved well and avoid tight bends at all costs, even temporarily. Don’t let anyone idly fidget with it before it’s on the robot.
(FWIW, I’m the same poster you linked to in your above comment.)
