I want to run power from the blade pcb to the neopixel accent on the crystal chamber in order to save space. Does that connection need to be 22 awg like the battery to blade pcb, or can it be 28 awg?
Thanks!
28 is fine, even 32 would be enough, unless you have a lot of accents.
I use a crude rule of thumb for wire guages, which I dare say strictly speaking isn’t entirely accurate, but it helps will ballpark figures. If 22awg is sufficient to power a full blade - which with a KR 36 inch strip is 132 pixels length on each side, so 264 pixels in total - then you can extrapolate from there:
22 awg - 264 pixels
24 awg - 132 pixels
26 awg - 66 pixels
28 awg - 33 pixels
30 awg - 16 pixels
32 awg - 8 pixels
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Wire is not lineal. I assume 35mA per pixel (that’s a white pixel, two colors are 24mA and a single color is 12mA). From the Proffie V2.2 Manual page 34 you can get the allowed Amperes, so:
AWG Pixels
20 314
22 200
24 100
26 62
28 40
30 24
32 15
We are assuming the stock 5050 WS2812B pixels. 3535 are usually the same. But the 2020 on PCB might use less.
Please note that this is total pixels. A 132 blade is actually a 264 blade. This is why I always use dual 22AWG wiring. If my son wants to use a white blade, I better be safe than sorry.
Again, I’m assuming white pixels. Single color is 1/3 the amps or X3 the pixels.
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Does each R/G/B LED use equal amounts?
Each Neopixel has 3 internal LEDs: green, red and blue. You can drive each from 0 to 255 of power. So each consumes power individually, yes. There’s some waste from electricity flow, and the circuit for data an driver consumes a bit. But roughly speaking, yes, each one is independent. So single color consumes about 1/3 of white. And a blinking style consumes less than a full one.
Roughly. There is a current limiter for each channel. It’s not perfect, but the intention is for them to use the same amount of current.
Once the voltage goes below 3.5 volts or so, then the green and blue LEDs might start dimming, and thus draw less power, while red continues to draw the same amount all the way down to about 2.4 volts.
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