As in last year’s model, the LEDs draw 60mA (at 5V) per pixel. I’m now planning 76 pixels, so that’s about 4.5A — if they were all on bright white at the same time, which is rare. Nonetheless, that’s a lot of power.

I’ll bring the power from the battery to the pixels in buses, that is, relatively thicker wires (22AWG) that can handle the current. The positive (red) and ground (black) have little cuts in the insulation through which the conductive thread wraps each pixel to each bus. Here’s an image of the buses:

blinky-power-bus-markedAfter I marked them, I used a wire stripper to make a little break at each mark. Then I separated the sections of insulation just a tiny bit, lining them up, so the pixels can be wired into them.

The buses connect to the battery through voltage regulators that bring the power from whatever it is at the battery (7.2V in the batteries I’ll use in the coats, but 8.4V in the battery I’m using for testing) to stable 5V that the LEDs need. The FLORA can take whatever voltage we give it. The wiring from the battery looks like this.

blinky-power-harnessStarting on the far right, the molex plug connects to a battery. The negative (black) wire goes to the wire snap on the top; the wire snap connects all the wires in the snap: the battery ground, the ground wires for the input for the 3 regulators, and the ground for the JST that powers the FLORA. The red wire for the molex connects to the positive for the 3 regulators, and the positive for the FLORA.

The regulators each handle about 1.5A, so we use three of them. We’ll bring the positive from each regulator to a subset of the LEDs. The ground is common for all of them. The 4-pin JST on the bottom left will connect to wires that carry the current to the buses on the back of the coat.

Here’s an overview: