How to Power a Pi?

My team struggled with undervolting our Raspberry Pi 3 B+ last year, and this year if there are useful vision targets we will likely have 2 Pis on our robot. What’s the correct way to wire a Pi to provide it the correct current?

We used a 12V to 5V step-down converter that was plugged in to one of our PDP slots. You can use the output of this converter for your Pi.

3468 has used this 12v->5v regulator for a Raspberry Pi for an off-season project where the Pi with an Arduino Hat was the primary controller. There haven’t been any issues with it that we’ve noticed. Between all the USB Options, and its 3A of current, which means it should work well for the newer Pi 4, we really like them for any USB powered devices.

Nice find. My only concern would be the 8v min input. This one has 6.3v min input and is still 3A/5V out. I’ve not yet found a buck/boost in a similar form factor.

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We used this to power an RPi camera in 2019. Based on the manufacturer and specs, I think it’s basically a non-potted version of yours. (This one advertises 5V minimum input, but I’ve found the output stability suffers under 6.5 V or so.) I’d prefer the sealed version for reliability, but the bare-board version offers the ability to adjust the voltage and current limits.

May I ask, why do you need two Raspberry Pis?

We’ve used a battery pack advertised for phone recharging. The rules last year limited the pack to 2.5A and 20K mAh, which was fine for a 3 B+, but would likely not work for a Pi 4. It was nice not to have to worry at all about undervolting the Pi. Even if the rules change for 2020 to allow more than 2.5A per battery output port, it might be hard to find battery packs designed for higher current draw. 2.4A max seems to be very common.

we just plugged our pi’s usb cable into the robo rio for power

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We’ve done this too but have also gotten occasional undervolting this way. Does anyone know what the RoboRio’s USB spec is? I’d be curious to know what it’s current limit is.

image
this is from their specifications PDF

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also as a side note has the rio always had an FPGA in it and I just didn’t notice somehow

The roboRIO cannot provide enough power to properly power the raspberry Pi. See https://www.raspberrypi.org/documentation/faqs/#pi-power for the recommended power supply sizing, and the consumption from the Pi itself.

I think it might depend on the pi that you have. they all draw different ammounts

For every version of the Pi except for the Raspberry Pi A and Raspberry Pi A+, the manufacturer recommends using a power supply of over 1A. Typically 2.5A.

The typical usage of a Pi does not require that amount of power, however the peak power usage of a Pi that can be seen under extreme circumstances(namely vision processing) can require more power than can be supplied by the Rio. The average current draw of a 3B while under stress is 850mA, as measured by the manufacturer.

The roboRIO has.

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Here is a graph showing power usage for each generation of PI both under load and idle for what it’s worth.

We used a PI last year and just plugged a micro usb in from the RoboRIO to the Pi

No, I’m not allowed to say until kickoff. Sorry!

One is used as a homemade Limelight, though.

just out of curiosity what are the units

It says that it is Watts