Wiring Limelight without PDP

Our team is currently using 16 motors on our robot, but we also want to use a limelight. However, since there are only 16 slots on the PDP we can’t fit the wires for the limelight on it. Is it possible to wire a limelight without a PDP?
Team 2265

As far as I’m aware, you basically only have the 12v 1a rail on the VRM. I was noting when teams used 16 PDP slots and a limelight for CADathon judging, which teams miss in real life as well.

Are some of your motors the ones where two can be run from one motor controller? The number of PDP slots is a design constraint that is not obvious.

Do you have a compressor installed? If you do, perhaps one of your functions can be done with a pneumatic actuator instead of an electric one.

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Our team powers limelight through POE (Power-Over-Ethernet).


We connect the LL via Ethernet to Radio. And power wire to PDP. What do you mean by POE?

I would like to know as well. I assume you are hooking the poe to the pdp.

I believe you should be able to power it off of a rechargeable power pack if it’s under 10,000mah? I wonder if you could splice a USB onto power cables and plug it in?

After looking at the rules further it states “100Wh or less (20000mAh at 5V) and 2.5 Amp max”

cc: @Tom_Line

We run a POE injector from the VRM to the radio. This powers the radio. In the female part of the splitter, we run an ethernet cable to the rio. We then run another ethernet line from the radio to the limelight, which powers it.

I’ll send a diagram once I arrive at the shop.

Doesn’t that break rule R47, which says the radio must be the only load on the 12V 2A rail of the VRM?

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Can someone explain why they have that rule and why provide 4 slots when only 2 are legal.

Bag motors are the only ones this year that you can have 2 motors under one fuse.

You can double power your radio from the VRM 12v /2a connections.
We recommend connecting both POE and the barrel connector between the VRM and the radio.
Redundant connections at the radio end.

But a second VRM can also be used to power anything, so the connections can be used there as well.

I can only speculate that since the radio is one of the two most important components on the robot they want to insure the radio has power.

Probably makes inspection easier too.


Please see R30 and Table 9-2 in the Game Manual. There are 6 motor types where two of them are allowed to be connected to one controller.


If you look at R47 it says

"but does not prohibit using any PASSIVE CONDUCTORS to inject the VRM power into an
Ethernet cable plugged into the radio port labeled “18-24v POE”


The Wireless Bridge (Radio) 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.

The important part is “must be the only load connected to those terminals.” The Limelight would be another load (regardless of the wiring approach… POE passing through the radio is electrically equivalent to just directly wiring to the VRM terminals), and thus would violate R47 if its power ultimately comes from those terminals.

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I suggest using this POE Injector and running it over a Ethernet cable. That is what we use, it’s cleaner and efficient.

I agree, but we get the same version from Amazon.

As Peter and I pointed out, placing two loads on the 2 Amp 12v VRM rail is not legal.

Corrected Response:
Per the Q&A clarification, Q290 you must use a breaker for additional circuits. Q171 clarifies that all other circuits may be powered by terminals (distribution panels).

Incorrect Response:
If you are not using a pneumatics controller, you can use the additional port on the PDP to power a second vrm. Power at your limelight off the second vrm.