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I have an idea to use WS2812B as animating light on some old equipment. And I have some doubt. The equipment is 12v so I want to use WS2812B directly on 12V, namely I want to use 5 WS2812b in pararalel, as they usually are on strips, BUT what resistor to use to limit current?

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    \$\begingroup\$ What do you mean run them in parallel? They run on a serial bus and need to be daisy chained. Can you draw a diagram to show what you mean? \$\endgroup\$ – Harry Beadle Sep 9 '19 at 20:52
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WS2812B are strictly 5V devices, so you'll need a regulator of some sort, not just a resistor. Either the classic LM7805 linear regulator (which will get hot) or an equivalent switching regulator.

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Are you wanting to use 5 strips of WS2812B or are you talking about 5 individual WS2812B? Whichever it is, the data sheet says 3.5 - 5.3V for the power supply. Since the current drawn by each individual device will vary from 0 to about 50mA depending on what colour and intensity you have selected, a simple resistor isn't good enough. You will have to generate 5V from the 12V supply.

If it is only 5 individual WS2812B you may get away with a resistor and a 5V zener diode. If it is 5 strips you will need a 12V to 5V buck regulator of sufficient capacity to drive them all. A strip of 30 LEDs will draw up to 1.5A so 5 of them requires up to 7.5A. Alternatively a separate, cheap 5V 10A PSU, widely available on line.

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  • \$\begingroup\$ Zener is a good idea maybe Ill use it. BUT I want to do it "as cheap as possible". I know that ws2812b works on 3.5-5V, on the other hand "all" other diods work at the "same range". But for example we can put diod train with smd3528 (also wants 5V) with limeter resistor.So why ws2812b so special? \$\endgroup\$ – smartes Sep 10 '19 at 14:01
  • \$\begingroup\$ Looking at the data sheet the smd3528 LED is a single colour device with a single LED chip. Some versions, made up into strips, can run off a 12V supply, so presumably there are 3 or 4 wired in series with a resistor to limit the current. On the other hand the WS2812B contains 3 LEDs (R,G & B) plus a control chip that drives each LED separately to one of 256 levels. This gives 16,777,216 possible combinations. But this control chip runs off 5V and not 12. The RGB LEDs are are not in series and hence also only need a lower voltage overall. \$\endgroup\$ – Peter Jennings Sep 10 '19 at 18:10
  • \$\begingroup\$ That is true. But there are 2 things which suppose me to think that 12v is possible. 1) the 3 dionds on WS2812B are still diodes and they are depend on current only (doesnt metter 5V or 12V). 2)control chip runs off 5V but this is depends on microcontroller which I use (mostlikely arduono 5v). \$\endgroup\$ – smartes Sep 10 '19 at 20:13
  • \$\begingroup\$ No, the WS2812B is a 4 wire device, 0V, 5V, Data in, Data out. There is no separate supplies for the chip and the diodes, they are powered from the same 5V source. You cannot separate them. 12V will undoubtedly blow the chip and the diodes. The current through each diode comes from the 5V input, via the control chip. Read the data sheet here \$\endgroup\$ – Peter Jennings Sep 10 '19 at 20:53
  • \$\begingroup\$ There are a couple of useful websites with more information than you could ever need regarding their use here and here \$\endgroup\$ – Peter Jennings Sep 11 '19 at 10:54

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