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DotStar matrix (3444) power hookup in video
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DotStar matrix (3444) power hookup in video

by finson on Mon Aug 31, 2020 6:12 pm

Question: In the DotStar matrix (3444) video on the product page , what is the schematic for the power portion of the circuit?


I’m a little confused on how to hook up power to my 8x8 DotStar Matrix (3444).

In the video, there is a Trinket hooked to the back of the matrix and there is a USB cable running to the Trinket. As far as I can see, that’s the only source of power for the combination.

First issue I realized is that my Trinkets are 3.3 V, not 5V, so the arrangement shown is not going to work for me. That’s okay, I have various level converters and can deal with that.

Second issue is: what is the path from the power supply to the DotStar? According to the DotStar description “each LED can draw as much as 40mA (that’s up to 2.5 Amps per panel)” and a 2 amp power supply is suggested. Okay, I can do that.

Now then, how is that power actually provided to the matrix? According to the Trinket 5V writeup, the USB power pin can provide 500 mA. It’s vague on whether or not that is a max value, but on the Trinket M0 pinout drawing it’s quite specific that 500 mA is an absolute maximum.

So, as far as I can tell, in the video, LadyAda is holding a matrix display that is being powered by a 2 amp supply running through a Trinket pin designed for 500 mA max and driving a set of LEDs that might draw up to 2.5 amps.

This doesn’t seem very likely which makes me think my understanding is wrong. I can hook up my own level changer and power supply okay, but I want to understand why the system in the video didn’t destroy the Trinket before I do my own smoke testing.


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