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RGB Matrix Bonnet Diode
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RGB Matrix Bonnet Diode

by wolfpants on Sat Sep 18, 2021 5:05 pm

Hello, I'm trying to understand the role of diode D1 on the RGB Matrix Bonnet. My understanding is that this is a power safety diode protecting the micro-USB cable from unintentionally powering the RGB matrix itself, per the Raspberry Pi Hat spec.

I have a couple questions about this: (1) If the Pi were to somehow use more than 1A, and I'm powering the whole setup solely from a 5V 10A power supply connected to the barrel jack on the bonnet, is it safe for this diode (a 20V 1A Schottky) to be used in this way? (i.e., This is probably a very basic question, but is a 20V 1A diode capable of being used at 5V up to 4A, because it's rated up to 20[V] x 1[A] = 20W, or is that not how it works?)
(2) Is a safer course of action to split the output of the 10A supply to go separately to the Pi's micro-USB input and to the barrel jack on the hat, so that I can take advantage of the Pi's power protection, instead of powering everything through the bonnet's barrel jack, per this other thread?

Thanks!

wolfpants
 
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Re: RGB Matrix Bonnet Diode

by mikeysklar on Sun Sep 19, 2021 2:12 pm

@wolfpants,

You probably saw this on the RGB Matrix Bonnet page:

https://learn.adafruit.com/adafruit-rgb ... -2982416-4

The driving Raspberry Pi must be powered separately, from the Pi's microUSB port but we do have a 1A diode on board that will automatically power the Pi if/when the voltage drops. So if you want, just plug in the 5V wall adapter into the bonnet and it will automagically power up the Pi too!


You should plan on powering your Pi from a micro USB and not rely on this the matrix bonnet to power the Pi.

mikeysklar
 
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Re: RGB Matrix Bonnet Diode

by wolfpants on Sun Sep 19, 2021 2:25 pm

Thanks for your response, mikeysklar! Yes, I have seen that - but just for my edification (I'm trying to better understand circuit design), can you help me understand why? And when you imagine powering the Pi separately through the micro-USB port, do you mean via two different power supplies, or is the Y-splitter that adafruit_support_carter mentioned just as good of an option if the power supply can supply the required current?

wolfpants
 
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Re: RGB Matrix Bonnet Diode

by mikeysklar on Mon Sep 20, 2021 11:26 am

@wolfpants,

The Raspberry Pi 3B+ has a current recommendation of 2.5A. 1.3A for the main board (proc/mem/video) and 1.2A for the USB ports. Trying to a Pi on less than 1A is problematic.

The Y splitter would be fine or two seperate DC wall adapters. Either way is good as long as you are providing enough current to the Bonnet and Pi.

mikeysklar
 
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