PoE Question

I’ve got a question about PoE. Of the teams that powered their radios by PoE, did you use a passive injector(if so…which one?) or did you manufacture a custom cable? The reason I’m asking is that with a passive injector there are three more connection points…three more places for a failed connection. I’m wanting to minimize wiring failures. We were plagued with issues at both regionals and they stemmed from the radio power connections(and a loose ground in one instance).
I’m leaning toward making a custom cable…no muss…no fuss. Please share your experiences with this issue.

We were lent a manufactured PoE at champs. It had some issues.
Though we ran it to our switch, then to the radio. So I suppose the intermittent comm drops we got could have been the switch dropping the power.

Don’t remember the brand of PoE.

Per R43 last year, the radio had to be powered from the VRM… so regardless of how you hooked it up, you were going to have some connection points that could cause issues. The blue box under R43 specifically notes that the rule prohibits any PoE injector device, but allows passive connectors for that purpose.

What I would like to see, personally, is a redesigned VRM with two ethernet ports on it - it would pass through data and inject POE for the radio.

That said, my team didn’t use PoE at all, and we never dropped comms during the season. So the barrel plugs aren’t horrible if you use them right.

Actually, would be cool to see alternatives to the VRM allowed. I’m sure this product idea is in the head of a couple FRC vendors out there.

We opened up the middle of a short Ethernet “port saver” cable and tapped into the appropriate wires. The plug end went into the roboRIO, the power wires went directly to the VRM, and the jack end accepted a patch cable to the radio.

That would make the VRM larger and more expensive, for a feature that wouldn’t always be used. I believe in modular design – that’s why the VRM itself is a separate component and not part of the PDP.

I made a small passive POE connector as a proof of concept. It’s just a normal Ethernet coupler with a short pair of wires coming out the side. A bit of hot glue would attach it to the side of a VRM and provide basically what you’re looking for.

We jumped at the chance to use POE. Not because of potential connector issues, but because it meant we simply didn’t have to worry about routing the power wires. The single Ethernet cable going to the radio made it easy to find a place for it, and to move it if necessary.

There’s also something to be said for using a cable with a mechanical latch on it to power your radio, rather than one that relies on a barrel connector staying in. Granted, the tab on an Ethernet cable isn’t the strongest thing in the world, but it won’t vibrate loose.