Teensy 3.2 power rails and max mA output.

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knox

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Hey guys. Trying to hook up ~140rgb apa102 rgb leds in a string to my teensy 3.2. I have seen multiple projects hook the power directly to the bottom on the teensy on the 3.3 output. (https://learn.adafruit.com/supernova-poi/wiring) I am not clear on how this pin works, does it share a common power rail with voltage input rail or does it have its own voltage regulator. On the side of the board it also has a 3.3 output, but says 250mA max, does this apply to the output pin on the bottom, because the max mA is not marked on this spot? Thanks for the long read.
 
First to answer your question:

On the side of the board it also has a 3.3 output, but says 250mA max, does this apply to the output pin on the bottom, because the max mA is not marked on this spot?

Yes, it absolutely does apply. There's only one 3.3V power on the board, so this spec applied to it no matter where you connect.

But there are more issues here...

First, APA102 LEDs need 5V power, not 3.3V.

Second, Teensy 3.2 has a 500 mA PTC fuse in line with the USB power, and most USB ports are designed to deliver up to only 500 mA. But some sources, like unpowered hubs, can only provide 100 mA.

Third, you will need MUCH more power for 140 APA102 LEDs. A good budget is 50 mA per LED, which means 7 amps of current. For this many LEDs, you really must use an external 5V power supply. There's no way to get this much power from Teensy!
 
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