zakqwy/bikelight

bikelight

It's a blinky red light for the back of my bike helmet.

The circuit uses an ATtiny412 to control four red LEDs, along with a Microchip MCP73831 lipo charge controller for battery management and a micro-USB jack for charging.

The circuit is designed to be milled on a single sided chunk of FR1 using a 1/64" end mill. If you use mods, the three layer *.svg files (holes, outline, and traces) are in the /pcb directory. After assembling and programming with pyupdi and an FTDI cable, I masked off the USB jack and slide switch and sprayed it with a few coats of clear varnish.

The pcb attaches using M3 hardware to two laser cut acetal clips, which then snap into my helmet. If you have the same model, this will probably work for you too, otherwise you'll need to figure something else out. Laser cut files for these parts are in the /cad directory, intended to be cut from 2.5 mm acetal.

I used a 1200 mAH lipo battery since we had a few on hand; it's secured to the rear of the pcb using VHB tape. I snagged a JST PH off a spare Feather, but if you plan ahead you can buy the part here. Note that lipo batteries are inherently dangerous, so don't build this circuit unless you're familiar with their quirks (and make sure to use one with a built-in protection circuit). Yes, if my helmet ever actually has to do its job, my head will likely catch fire.

bikelight! blink blink blink blink blink