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Power Requirments

A project log for WS2812 Controller

A cheap & cheerful widget to control those RGB strips everyone has

jesse-farrellJesse Farrell 01/30/2022 at 02:240 Comments

To determine the power requirements, I’ll turn a string of 5 led’s onto max brightness and monitor the input. At max brightness the recorded power consumption at 5V was about 950mW (190mA), and with all LEDs off its about 100mW (20mA). This corresponds to approximately 175mW (35mA) per LED. Note that these are just ballpark figures, with very questionable accuracy. 

After getting a general idea of the power requirements I plugged a string of 100 WS2812s and recorded similar per LED power draw. I recorded 15.4W for 100 LEDs, so about 153mW per LED (adjusted for quiescent). For power supply recommendations I will go with the larger figure, 175mW per LED + 100mW.

I have a wall wart rated for 5V@3A, so I’ll be able to drive about 85 LEDs at max brightness (3A/0.035A). Of course, I don’t need to run these at max brightness, but I’d rather be safe than sorry. The final power supply recommendation is:

I= 0.035n + 0.02 [A]                            //5V supply current rating for 'n' LEDs

Just a final aside about the power planes on this board. I measured the power rails and its about 100mV pk-pk. I'm happy with this so I won't bother tweaking the bulk capacitance ect. 

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