Powering LED Strip directly from USB

Hi

I have a project which needs to be very mobile and light, I'm using the tiniest board I found (pololu a-star 32u4) and I have 4 strips of WS2812B Leds, Each strip has 3 leds so total 12 leds controlled by the same data pin (with 220ohm capacitor) , the leds positive and ground are connected to 3xAA batteries with 220uf 16v capacitor.

Leds are controlled by FastLed and running in 50% brightness.

The batteries are too heavy, and from what I've read it will be too much for the board to drive the leds from the 5v pin. I wanted to ask about using the same usb cable for the board and split it's positive and ground to drive the both the board and leds, should I do it?

If you power you board from USB you can power your LEDs from 5V pin since it connected to USB VBUS. But if you do this - do not power your board using Vin pin. Because in that case power goes through voltage regulator which is not powerfull enough.

alesam: If you power you board from USB you can power your LEDs from 5V pin since it connected to USB VBUS. But if you do this - do not power your board using Vin pin. Because in that case power goes through voltage regulator which is not powerfull enough.

Thanks for your answer, however the board I'm using can only provide maximum of 100mA via the 5v pin.

Yes, 100mA is a power which linear regulator can provide when powered from Vin. When you power your board from USB only - linear regulator disengaged.