How to power a Raspberry Pi

[Denchief1]

In our six hours time before our competition this weekend we developed a raspberry pi based opencv vision tracking program. We were going to take a phone charger and wire it to the VRM but upon further inspection of the rules that does not seem to be allowed. Therefore we want to know:

A. Can we power the raspberry pi off of the VRM? and if not
B. How else can we power it? (If all else fails we can try and use the classmate)

[Al Skierkiewicz]

You may use a second VRM. Under R48 you can have up to three additional VRM modules.

[Denchief1]

Originally Posted by Al Skierkiewicz

You may use a second VRM. Under R48 you can have up to three additional VRM modules.

Thank you, would you wire it off of the same position that the VRM is wire from the PDP.

[Al Skierkiewicz]

Yes, but the rules do allow you to feed two VRM by splicing the leads together.

[rbutani]

My team used a Raspberry Pi this year (for the same purpose: vision) and we ended up powering the Pi off of the 5V 2A rail of the VRM, through the Raspberry Pi's GPIO. (Pins 2 and 6 in this diagram, 5V Power and Ground respectively, lend themselves nicely to powering the Pi since you can use a standard 3 pin PWM cable)

You should be able to connect the 5V Power/Ground wires straight to your VRM, unless you're already using the 5V 2A rail of your VRM. In that case you can add a second VRM; which you probably want to wire up to one of the wago ports and not to the VRM weidmuller connector with the fuse (don't want to trip that fuse!)

[rich2202]

Originally Posted by Al Skierkiewicz

Yes, but the rules do allow you to feed two VRM by splicing the leads together.

I presume that "same position that the VRM is wire from the PDP" means the VRM/PCM connectors at the end of the PDP that is protected by the 20 amp mini fuse.

Per R44, "no other electrical load shall be connected to these PDP terminals". I presume that means "directly or indirectly".

Are you saying that 2 VRM's can be connected via a splice to the VRM/PCM power supply terminals at the end of the PDP?

I see that R48 lets you have 3 VRM/PCM's off one 20 Amp circuit, but I presumed that applied to the WAGO terminals, and not the special power supply terminals.

I had presumed that R44 intended to give extra headroom to the VRM providing power to the Radio, and the PCM that would be powering the Compressor.

Let's say that you wanted to connect 2 VRM's, and no PCM's. R44 would require you to use a splice (only a PCM can be connected to the other terminal). Why wouldn't you allow a VRM or PCM to be connected to the 2nd terminal (with the restriction that a PCM could not be spliced off). In other words, the allowable combinations would be:

1) VRM
2) VRM, PCM
3) VRM, VRM
4) VRM/VRM (via splice), PCM

[Al Skierkiewicz]

R44 is confusing. It begins with saying the VRM supplying the radio must be connected here and it allows that one PCM may also be connected at that point.
R44 does go on to say "no other electrical load shall be connected to
these PDP terminals". So I gave you wrong info.
If it were me, I would not power a VRM, a PCM on a single 20 amp fuse. My recommendation would be to power additional VRMs and PCMs separately from two 20 amp breakers. Most compressors exceed 20 amps in start.

[GreyingJay]

We ran a micro USB cable to the 5 volt, 2A output of the VRM and had no trouble with this. Last year this port was exclusive for the D-Link robot radio but this year it was open so we used it.

Teams have also powered it by plugging it right into the USB port on the RoboRio.

[engunneer]

I wouldn't power a rpi from the roborio USB except for testing. A normal USB port only guarantees half an amp, and the rpi can easily draw more than that, depending on what you have connected to it.