So I'm finding it a little difficult to figure out how I should be powering my setup. I'll have Waveshares IO board here: https://www.amazon.com/gp/product/B08VJBGD1Q/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1 along with the Compute Module 4 Lite (8GB RAM) and I'd like to have the capability of fully powering one of those PoE ports and at least 1 USB port.... plus the Pi of course. So assuming both the PoE and USB device are drawing power at the max, what does that result in? I started reading about voltage, amperage etc and realized I don't want to blow anything up (Pi 4s are rare and very expensive these days) because of my misunderstanding so I tried looking up some power supply calculators but all seem to be for PC desktops. I'm pretty confident that this: https://www.waveshare.com/ord-psu-12v2a-5.5-2.1.htm is enough, but I wanted to check with you Pi folks first. That would provide enough power, right? Please feel free to link any good calculator sites out there as well, already got a nice collection for my new Pi 4 rolling :)

1 Answer 1


Warning The Raspberry Pi 4 DOES NOT requires a 3.0A minimum - that is a recommendation.

That will not work. The Raspberry Pi 4 requires a 3.0A minimum. Start by adding the worse case current for each or the other hardware devices then add 20% now add the 3A minimum the Pi requires, this gives you a minimum requirement for your power supply. Take into account the loads you add to the board. Your link does not give any information for current or wattage for the Waveshares IO board. Be careful that you use the correct voltages.

  • It says "POWER INPUT--7V~36V" on the waveshare amazon web page. So I add all the amps together... the Pi is 3, the USB is 2.5, and the PoE is also 2.5. I need an 8A 7V power supply with a dc jack, right? I read that wattage is volts times amps, so I should be on the look out for a 56w power supply. I think 65 is pretty common, so I'll grab one of those universal ones and just make sure it meets the minimum amperage + volt needs, right?
    – Riptide
    Jan 18, 2022 at 10:16
  • Ok I can't find anything over 3.5a on amazon, I must be missing something. I'm just going to get some sleep and worry about it tomorrow.
    – Riptide
    Jan 18, 2022 at 10:25
  • Sorry to inform you Amazon does not have everything! ebay, Newark, and others have them. Going over on the amps is ok.
    – Gil
    Jan 19, 2022 at 0:40
  • I'm A-OK going somewhere else, but most of my search results bring me to a shady 3rd party off-shore website with poor wording and limited random stock. I guess it would help if I knew exactly what I was looking for. You said I should be careful about what voltage I use, but the Waveshare link I provided in the OP says a range of acceptable voltage values... this leads me to believe that I'm misunderstanding you or them. And the only way to find out what works is start buying things I think would work and probably end up with an exploding Pi haha. Can you give me an example of what would work?
    – Riptide
    Jan 19, 2022 at 10:35

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