Basic question: controlling WS2813 LED Strip with powerbank

Hello everyone,

First off, Im new to this platform so if anything is not according to guidelines, please do tell me. I am looking for a place where someone can help me with this pretty basic question:

I have a strip of WS2813 LED strips, 30 per meter. I am making 2 7-segment digits out of these, each digit containing 42 LEDs, that's 84 in total. Even though each LED is RGB, I am only going to use the blue ones. 84 x 20 mA = 1.680 Amps. I have purchased a 10.000 mAh (5V, max 2.1A) powerbank to power this contraption of mine for around 4 hours. However, I was wondering if there is anything I need to pay attention to. I will be controlling the data input with my Arduino Uno R3, for which I luckily only need 1 wire.

Now, I have stripped a mini-USB cable and taken the two power cables to form a USB power lead. If I connect this lead directly to the powerbank, control 84 LEDs, is there a need for any resistors, checking the current, voltage drops or anything of the sort. I know the WS2813 has built-in capabilities of regulation, but power sources hooked up directly to any kind of actuator always gets me nervous.

Throw in any advice you can think of, cheers!

by jacksodus
January 28, 2018
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1 Answer

Answer by mikerogerswsm

I think the simple answer is yes, go for it. The WS2813 looks to be a very good choice. Perhaps for safety one might connect just the one unit to test everything is ok. Powerbanks are bodacious in their capabities, and the WS2813 will run on 3.5 - 5.3 volts so you have headroom available to add a supply polarity protection diode and some fold-back protection if you wish. https://en.wikipedia.org/wiki/Foldback_(power_supply_design) In the early days of electronics we could purchase seven-bar displays as a set of eight leds in a suitable package. You are not limited to seven-bar and I'd suggest you try programming in various fonts. Good luck! mike

+1 vote
by mikerogerswsm
January 29, 2018

Thanks for the swift answer, Mike! Great to hear! I am waiting for the powerbank to arrive today. One curious fact is that, when I used my custom USB power lead on a small USB plug (Output: 5V, 750 mA), I somehow fried Arduino's Serial circuit. Whenever I tried to have the number 2 display (5 out of 7 LEDs), the entirety of the strip shone bright red and green. 2 colours x 150 LEDs x 20 mA = 6A (or 750 mA max, I guess), my Arduino didnt stand a chance. Would you have any idea what hardware error could trigger this? In the software there is no mention of red or green, let alone 150 LEDs.

by jacksodus
January 29, 2018

Aarrgghh! Not good! If using library FastLED WS2812 then you should connect the specified Arduino Data pin to BOTH input pins of your display.

by mikerogerswsm
January 29, 2018
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