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All the guides I've found suggest to use an external PSU to power an RGB matrix like this.

However I know it is possible to blink the LEDs at high rates (eg. 2ms) and still give the impression to the eyes they are fully on. I've verified this myself on a small 4x4 matrix, but I am not sure if the same can be done with these bigger matrices.

In my case I could tolerate reduced brightness and color space, but I'd like to power the matrix with the Arduino's 5V pin directly.

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  • give it a try, you won't break anything. probably won't break anything. that said, 512 LEDs is a lot to power from an MCU...
    – dandavis
    Mar 21, 2017 at 15:48
  • @dandavis: I will power only 1 led at a time, not all 512 at the same time! btw i've also found this monocromatic matrix that can also be powered directly by an arduino. In this case they suggest to not connect the 5V pin at all. Maybe i should do the same with my RGB matrix?
    – eadmaster
    Mar 22, 2017 at 1:23
  • Don't those matrices already have bypass capacitors on the backside?
    – Gerben
    May 23, 2017 at 17:29

2 Answers 2

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When powered through USB, the total current consumption is limited to 500mA by the USB interface. If you are using the power connector, the total current is limited by the on board 5V regulator to 1A.

The board will also require some current, so you can draw around 400mA, if powered through USB or 900mA, if powered through the connector; from the 5V pin.

While the matrix on average may not draw than 300 - 400mA, the voltage regulator can overheat and shut off temporarily, and you will never be able to reach 900mA. The regulator is linear, so any extra voltage you supply will result in waste heat.

It is best to get a buck converter or power the matrix externally. You won't be wasting as much power, and avoiding possible thermal shutoff.

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  • but, as you said, if i power the whole thing via a single usb port i can skip the regulator, so there is no risk of shutoff. And if the matrix ICs takes less than 400mA i should be fine because i will have max 1 led on at a time. Now the big question is if the arduino can refresh all the 512 leds at acceptable speed to avoid flickering.
    – eadmaster
    Mar 21, 2017 at 6:12
  • based on my "charger doctor" readings, few USB sources provide only 500ma; 0.8-1.6A is common.
    – dandavis
    Mar 21, 2017 at 15:42
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I've received yesterday the 32x16 LED matrix I've ordered from AliExpress and I've done some measurements with a multimeter in series with the power wire.

LED multiplexing does not seem a good idea as the matrix is already doing that internally.

Instead I've found that using the minimum color intensity helps a lot reducing the current usage.

E.g. for blue use matrix.Color333(0, 0, 1) instead of matrix.Color333(0, 0, 7); for white use matrix.Color333(1, 1, 1) instead of matrix.Color333(7, 7, 7), etc.

With the minimum brightness I've measured:

  • All blue LEDs lit = ~170mA
  • All LEDs lit as white (red+blue+green) = ~400mA

In the average case (not all LEDs are lit) I am getting around 250mA, so I should definitely be fine powering the matrix directly from the 5V pin if I keep the brightness as low as possible.

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