Hi! The new pi 5 power supply is, with a difference, the cheapest way to get a 5a 5v power supply.
Will it provide 5a to a load of LEDs plugged into a Plasma 2040? Or is there some reason that wouldn’t work?
Thanks!
The specs certainly imply that 5A is the default current output, so it should? There might be only one way to find out.
The screw terminals are probably rated for 10A, but I am not sure if the trace from USB-C to the terminal will be sufficient. Since Pimoroni does not provide a board layout, they are the only ones who know.
Perhaps someone from customer service will appear and help us out…
You can find an interesting read here: Simple way to use USB Type-C to get 5V at up to 3A (15W) - #3 by Kristof_2649 - Power - Electronic Component and Engineering Solution Forum - TechForum │ Digi-Key
The Plasma2040 has these 5.1K resistors that the author is talking about. But he also points to the problem of trace-width.
Hm. I think there might be an easier solution here, such as getting the power to the LEDs straight from the USB, without going through the plasma 2040, using something like this:
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Just tried the official 27W PSU with a string of 66 RGB LEDs and it powers them fine, though I don’t think I have 5As worth of LEDs to hand…
Technically 5A @ 5V is outside of USB specs; I don’t know if the Pi5 does some shenanigans to ask their PSU to deliver it, or if it just uses the handshake to know it can safely draw it.
Of course, the store page (correctly) states that the USB C socket on the plasma is only rated to 3A.
Thanks! 5a 5v in that form factor for that price is absolutely fantastic, I’m going to find a way to get it into my lights, even if it’s not via the Plasma.
One option is to just snip the USB C plug off the end. Then strip the wires and attach to the screw terminals. If you have a soldering iron I’d tin the ends. Or add some crimp on connectors.
Disclaimer: I’m not sure you will get 5A, and I’d measure the voltage before hooking it up to the plasma.
EDIT: Keep in mind that doing this will back feed that 5V through the USB connector. Your going to want to unplug the dedicated supply when programing through the USB port.
This is what I did on my Interstate 75 64x64 LED Matrix.
It’s fed by a 5V 4A switching power supply.
One feed to each panel and a feed to the i75.
5V 4A (4000mA) switching power supply - UL Listed : ID 1466 : $14.95 : Adafruit Industries, Unique & fun DIY electronics and kits
There is also a 10A version if you want to be
“blinded by the light” =)
5V 10A switching power supply : ID 658 : $29.95 : Adafruit Industries, Unique & fun DIY electronics and kits
I’m pretty sure that the Pi 5 does some handshaking to get the 5a total…
I have a couple of cables which are USBC (female) → 5V and GND which I could use to avoid soldering/crimping… but I’ll think about it. Thanks!
I think without a PD-chip that does proper handshaking with the power-supply, you won’t get 5A. And I am not sure if these 5A are peak usage only or if the power-supply will really deliver this for a long time.
For LEDs, there are special drivers. Or you could use one of the Mean Well power-supplies.
Yes, there are loads of solutions. But there’s nothing as cheap and small and powerful as the pi supply (i’ve spent a lot of time looking into this!)
I had a rethink about cutting the USB C connector off. I’ve done it on a Pi 4 power supply, on it there is only the +5V and Ground. Same deal with the older Micro USB Pi 3 etc power supply, just the +5V and Ground wires.
Cutting the plug off of the latest Pi 5 supply might make a mess of it, with all those extra wires. And only get you 3 A anyway?
Thanks! I’ll have a look.
You are absolutely right. These Mean Well supplies are rather expensive.
One other idea I had was that you might add an USB-C PD-breakout yourself to do the negotiation. Adafruit does have such a breakout, but it turns out it does not support the 5V/5A mode. Which is a very exotic mode anyhow.
Going to post some relevant observations.
I have a 144 RGB LED strip wired up to a Plasma Stick.
Flexible RGB LED Strip (aka NeoPixel, WS2812, SK6812) – 144 pixels per metre (pimoroni.com)
Plugged into, and powered by my PC’s USB port my test code ran fine.
I cycled through
(255, 0, 0) all Red
(0, 255, 0) all Green
(0, 0, 255) all Blue
(255, 255, 255) all White
It lets me easily spot a dead LED.
I then wired up a Pi 4 5V 3A supply for power.
(255, 255, 255) all White caused the RP2040 to crash and reboot. I’m thinking the power supply overcurrent protection kicked in? I had thought it looked dim when powered by my PC’s USB port, likely due to a 500 ma limit.
I’m now using a 5V 4A regulated switching power supply. The Adafruit one I linked too in my earlier post. I had an extra one not in use. No problem going full bright all white now.