I am designing a device which must power a number of RGB LEDs. I am currently looking at WS2812 "NeoPixel" style LEDs, which have a max current draw of 60mA each. I would like to have a large number of these, but running at lower brightnesses.
The problem is that I want to supply this from a standard USB port, and I have more critical functions that run off of the same USB power, so I want some sort of current limiter/protection to ensure that the LEDs don't consume so much current that the USB controller shuts off the device.
- Would a simple PTC/Re-settable fuse work?
- Or something like this current limiter from Wikipedia.
- Or should the supply be cut completely?
I don't need very high accuracy,but I would like to keep current under ~250mA±30mA.
Also since I need >100mA from the USB VBUS should I include a MOSFET or other way to disable the supply while the microcontroller is starting/restarting.
Finally I have seen some people recommend large(100-1000uF) smoothing capacitors to the LED's VCC. Which side of the protection should this be on?