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Power Supply for Adafruit RGB Matrix HAT + RTC
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Please be positive and constructive with your questions and comments.

Power Supply for Adafruit RGB Matrix HAT + RTC

by tommika on Thu Apr 22, 2021 10:04 pm

I'd like to use the Adafruit RGB Matrix HAT (https://www.adafruit.com/product/2345) with the 64x32 RGB LED Matrix panel (https://www.adafruit.com/product/2278).

Based on the matrix power supply requirements in the HAT description, the max current for this setup would be ~7.7A.
To calculate the max current of your matrix set up, multiply the width of all the chained matrix by 0.12


However, the description also says
you can plug a 5V 4A wall adapter into the HAT and it will automatically protect against negative, over or under-voltages!


Can a 5V 10A power supply be plugged into the HAT, or is 4A the max?

thanks

tommika
 
Posts: 3
Joined: Thu Apr 22, 2021 9:38 pm

Re: Power Supply for Adafruit RGB Matrix HAT + RTC

by blnkjns on Thu Apr 22, 2021 11:26 pm

You attach the PSU directly to the panel, not through the hat. I never use the power connectors on the hat. They are also the wrong type.... A 10A power supply has screw terminals, and the cables that come with the matrix panels fit fine directly in those screws. Never seen DC plugs on power supplies over 3A, and they are specced at 2A max:
https://en.wikipedia.org/wiki/EIAJ_connector
Here you can see how I wire these panels. I even feed the board from the panel power supply in the HUB75 connector:
https://youtu.be/aSBq0EFhfE4?t=196
I personally never use a Pi on these panels, always Metro M0/M4 Express or ESP32. The example shows a custom made hat. You can see the panels come with pretty serious power cables and double wires, you don't want to have that current go through the hat.
I assume you power the Pi from the 3A USB-C PSU. So feel free to desolder the EIAJ socket to remove any confusion.
If Adafruit pops by: see the video on the RIGHT connector we need on those matrix hat boards, put that on you hats as well: A single Molex 4 pin one to power the board from the panel PSU!

blnkjns
 
Posts: 461
Joined: Fri Oct 02, 2020 3:33 am

Re: Power Supply for Adafruit RGB Matrix HAT + RTC

by tommika on Fri Apr 23, 2021 1:05 pm

Thanks @blnkjns for your reply, and I appreciate your insight.

This particular application requires use of a Raspberry Pi, the Adafruit RGB Matrix HAT, and a 64x32 RGB LED Matrix panel. As I understand it, that panel can draw up to ~7.7A.

The HAT description says,
> you can plug a 5V 4A wall adapter into the HAT ...

The question is, can we power the matrix through the HAT using a supply >4A (for example, this 5V 10A supply https://www.adafruit.com/product/658), or is 4A the max if powered through the HAT?

thanks

tommika
 
Posts: 3
Joined: Thu Apr 22, 2021 9:38 pm

Re: Power Supply for Adafruit RGB Matrix HAT + RTC

by blnkjns on Fri Apr 23, 2021 2:09 pm

Again, don't power through the HAT. It is totally unnecessary and you could end up using the board traces as fuse. Get the PSU shown below and use the power wires that come with the panels without tampering. No "powerbricks" at this amperage! The mean-well is even half the price and smaller. I can follow the risk-evading attitude of Adafruit here, a Meanwell has AC current within reach of fingers, but the DC jack solutions are quite dirty and way beyond the specs of the connectors.... Especially when they recommend the use of U-connectors and put half of the connector in a screw terminal.
Here you can see the contents of the package:
Image
The forks at the end of the red/black cable are meant for this supply:
Image
Another reason you don't want all current to flow through the hat is this:
https://html.alldatasheet.es/html-pdf/1 ... OD417.html
The power MOSFET on the board is rated at 2A continuous with short 6A pulses peak.

Adafruit, if you see this topic: please fix your hats in a way the extra MOLEX connector on the cable can power the board the hat sits on, instead of trying to power the matrix from the hat. That way we don't need a second power supply for our M4 Express, Feather or Raspi.
These products badly need a 2.0 version with the DC and screw terminals replaced with a single 4-pin MOLEX:
https://www.adafruit.com/product/2345
https://www.adafruit.com/product/2601
https://www.adafruit.com/product/3036
https://www.adafruit.com/product/3211

blnkjns
 
Posts: 461
Joined: Fri Oct 02, 2020 3:33 am

Re: Power Supply for Adafruit RGB Matrix HAT + RTC

by tommika on Fri Apr 23, 2021 3:33 pm

Thanks again blnkjns. That's some great information, and I get your point now. So, even a 5V 4A adapter, suggested in the hat description/tutorial, would be pushing it.
I was hoping to power the panel through the hat, just to keep things simple and consistent with the hat tutorial. But will investigate powering it directly as you recommended.

tommika
 
Posts: 3
Joined: Thu Apr 22, 2021 9:38 pm

Please be positive and constructive with your questions and comments.