I am starting work on a wearable project (kid's Halloween costume)  I am using

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(David Summers) #1

I am starting work on a wearable project (kid’s Halloween costume) I am using an Arduino Nano, and I want to power the Nano and the LEDS from +5V USB power pack. I have two wiring questions:

  1. Is it OK to just wire the +5V directly to the +5V pin of the nano using a cannibalized USB cable? I have seen conflicting information on the web. Some say it is fine, others say it is no-no. If I wire directly from the power pack to the +5V, can I still connect the USB to my computer for programming while the Nano is powered from +5V without fear of blowing out my USB port?

  2. I plan to have three separate strings of APA102 LEDS (only about 20 pixels per string) just to make wiring easier. Is it OK to connect one string to the SPI pins, and the other to general purpose IO? Is FastLED smart enough to use HW SPI for the string connected to SPI and “bit-bang” the other strings?

(Giligain I.) #2

Umm, plug into computer to program the nano w/out LED load. Then after it is programmed remove from computer and plugin LEDs and use power pack.
You can use computer USB only if the total power current is less than 500mA. You can verify with calculations or using an accurate voltmeter/ammeter (USB detector).

(Marc Miller) #3

For question #2, yes, FastLED can do that just fine.

(Zeke Koch) #4

hi David, i do that all the time. I’m generally using a teensy, but I’ve also done nanos and raw attiny85.

(Luminous Elements) #5

Why wire it in directly when you could just use the programming port as the power input? When you’re done programming it, just plug the same cable into your power bank. Simple.

(allanGEE) #6

When I work with a Mega 2560, I leave it plugged into the computer AND I have power running to the LEDS from a separate source. It just makes it quicker when I’m experimenting and want to see what the effect is.

Keep us posted. I’m trying to get something together for Halloween that consists of 10 wearable 6x12 panels (720 LEDs) – but feel like ‘real life’ is sucking up way to much of my ‘LED life’ time! :slight_smile:

(Randal B) #7

I power my wearables through the USB connector on the Nano’s. And I use the 5v pins to power my lights off it. I’ve had zero problems.

(Royce H) #8

I have a few blown USB ports. Don’t ask me why. :wink: