I am an absolute beginner in both electronics and LEDs.

I would like to power my WS2812B LED strip (5m, 300 LEDs) with an old PC power supply.

The power supply has 600W so more than enough power.

To trick the power supply into thinking it is connected to a mother board, I cutt the green wire from the 20 pin connector and connected it with a black wire.

After that I cut a red and a black wire and measured the voltage using a multimeter.

I got 5V so everything works as expected.

But if I connect it to the LED strip nothing happens. I expected some kind of reaction from the LEDs.

What I am missing here?

  • 3
    \$\begingroup\$ I don't know WS2812B well enough, but isn't their default state "0 brightness on all channels", and you'll need to "pipe" in some data to set them to something visible? \$\endgroup\$ Commented Jan 23, 2021 at 19:44
  • \$\begingroup\$ Simply giving power to LEDs won't do a thing, they need data from a controller to set the color. Also, a 600 watt powes supply will not give all the power on the 5V supply, and depending on which era ATX supply it is, it may give most power out on the 12V line instead of 5V line. And since it is run without load on any other output, it may lose regulation and turn itself off when LEDs are suddenly turned off. So you better check how many amps the LEDs need 5V supply, and how many amps it says the PSU can provide. \$\endgroup\$
    – Justme
    Commented Jan 23, 2021 at 19:51
  • \$\begingroup\$ Thats a good point. I got an arduino connected to the data pin. The Arduino is connected to an Raspberry PI running hyperion. I can verify that the everything works. But the LEDs dont turn on. \$\endgroup\$
    – dknaack
    Commented Jan 23, 2021 at 19:52
  • 1
    \$\begingroup\$ Is it 3.3V data out or 5V data out? \$\endgroup\$
    – Justme
    Commented Jan 23, 2021 at 20:11
  • \$\begingroup\$ Many/most PC supplies specify the max current on each output voltage. You won’t get the full 600W at 5V but you should get a significant amount of power. \$\endgroup\$
    – Frog
    Commented Jan 23, 2021 at 20:16

1 Answer 1


WS2812 is IC with internal 3 color LED driver and LEDs inside a case. By default then turning on power no lights supposed to be on. Some data should be pushed inside. And specific communication protocol should be applied through serial interface. For each chip 24 bits in sequence, which define brightness of each color. No data - no lights.


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