Wiring a router without a VRM

[TheBakerMan]

Our team has while working on the competition robot had the Kit of Parts drive train running as a test bot for the programmers. Our lead programmer wanted me to connect a router so he didn't have to deal with an Ethernet cable constantly connected anymore but when I went to do this I realized that we don't have a spare VRM to connect the router to the PDP with. So the question is do I have to use a VRM to power the router or is there another way to go about this?

[arichman1257]

R51: The Wireless Bridge power must be supplied directly by the 12V 2A output of a CTR Electronics
Voltage Regulator Module (VRM) (P/N: am-2857, 217-4245) and must be the only load
connected to those terminals.

TL;DR you have to use the VRM

But I presume that you are not looking for competition legal. Still, every other power output terminal on the PDP is 10A, 20A, 30A, or 40A max so if there was to be an issue your radio could be destroyed.

Still TL;DR bad idea

[JR0405]

Yes, you need one for competition as stated above but I'm assuming you mean at the moment until you get a new one. As obvious by the fact that the PDP directs power straight from the battery, the PDP does not supply a constant 12V which is why the voltage regulator module is necessary. For know I would think that it'd be ok to connect it to any 12V output of the PDP. The radio can handle up to 24V and if there isn't enough power it will just shut off which unlike in a match isn't terribly important.

TL;DR I'd assume it's ok to connect it to one of the 12V outputs of the PDP the radio could shut off if the power drops to low for testing

[jSchnitz]

Originally Posted by arichman1257

R51: The Wireless Bridge power must be supplied directly by the 12V 2A output of a CTR Electronics
Voltage Regulator Module (VRM) (P/N: am-2857, 217-4245) and must be the only load
connected to those terminals.

TL;DR you have to use the VRM

I read the OP as asking if it's possible / safe to run the radio from a PDP WAGO output instead of the VRM in a pinch, not if it's competition legal.

I personally wouldn't risk it - both sources are 12V, but the VRM is limited to 2A, whereas the PDP outputs are 20A or higher. More importantly the VRM is a regulated 12V source, whereas the PDP outputs provide a variable battery voltage. You probably wouldn't be at risk of frying it, but it would likely reboot if your battery voltage dropped for a moment.

[TheBakerMan]

Sorry I should have clarified, I didn't want to use it during competition just for a few tests. Thank you for the responses I think I'll play it safe and see if I can get it arranged to get another VRM so I don't break anything

[Fusion_Clint]

This is safe, for a testbed in a pinch.

Replace the 10A VRM Fuse on the PDP with a 2A fuse and use the VRM power plugs on the PDP to power your radio.

[BitTwiddler]

Or perhaps you could use one of these https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
It's an adjustable buck/boost voltage regulator that you can set to 12 V output at 25W (a smidge over 2A). I have one and it does a good job.

[Jpatterson1710]

Until teams receive the correct wiring to supply VRM power to their radios, you should be able to power them via ethernet (PoE) from the RoboRio.

[Mark McLeod]

Originally Posted by Jpatterson1710

Until teams receive the correct wiring to supply VRM power to their radios, you should be able to power them via ethernet (PoE) from the RoboRio.

Um, no.
The roboRIO doesn't provide POE. That would require a power injector (powered from a VRM or similar buck boost supply).

[Jpatterson1710]

Originally Posted by Mark McLeod

Um, no.
The roboRIO doesn't provide POE. That would require a power injector (powered from a VRM or similar buck boost supply).

Huh, I was told our by our FTA that the local teams got their robots running at Quick Build via PoE. I'll have to clarify how that worked.

[rich2202]

As a test robot, you can put a 2nd battery that only powers the radio. that would avoid brownout problems. If the robot is not moving, then you can plug the radio into an AC power supply. Or, battery->dc to ac converter -> 110v to 12v dc power supply -> radio

[FrankJ]

If your radio pulls more than 2 amps, it is already broken. The extra ampacity of the PDB just lets the broken radio smoke a little more. The big issue is brown outs will reset the radio. For limited testing I wouldn't have any issues. You can always put an in line fast blow fuse,

[Mark McLeod]

Originally Posted by Jpatterson1710

Huh, I was told our by our FTA that the local teams got their robots running at Quick Build via PoE. I'll have to clarify how that worked.

POE setup requires a way to inject power from a VRM into the radio alongside the roboRIO-to-radio Ethernet communications.
Here's an example:

[Brutick]

Originally Posted by Mark McLeod

POE setup requires a way to inject power from a VRM into the radio alongside the roboRIO-to-radio Ethernet communications.
Here's an example:

You can use 12V passive PoE to power the radio? The silk screening claims 18-24V PoE only. Unless you're using the 802.3af port which would violate R63?

We're looking into doing this, I ended up ordering some boost converters, but if I don't need them then I'm not going to use them.

[Mark McLeod]

Originally Posted by Brutick

You can use 12V passive PoE to power the radio? The silk screening claims 18-24V PoE only. Unless you're using the 802.3af port which would violate R63?

We're looking into doing this, I ended up ordering some boost converters, but if I don't need them then I'm not going to use them.

Read the label on the back of the OM5P-AN radio.
Note: This is only for the older OM5P-AN radio. The New OM5P-AC is looking for 24v on the Passive POE port.

POE Input:12-24v in the port closest to the barrel input.
The 802 port wants 48v