I connected a segment of an LED strip (12 V) to a line coming from a standard ATX PSU (the 12 V line, of course).

I just wonder if it is safe to put a toggle switch to turn on/off the LED strip, or if maybe this really simple circuit requires additional components.

I should say the ATX PSU is actually powering a PC and I want to power the LED strip also, and turn it on/off while the PC (PSU) is on.

  • \$\begingroup\$ It should be fine. \$\endgroup\$ Nov 20, 2020 at 16:38

1 Answer 1


This should be fine.

  • Generally the +5 V or +3.3 V line is accurately regulated and the +12 V (and -12 V, if provided) are relying on the turns ratio on the SMPS transformer to keep them in proportion to the 5 V supply.
  • Watch your current. The 12 V rails were only designed for hard drive motors which are not high power. The PSU label should give you the limits.
  • 12
    \$\begingroup\$ Second point is outdated. Modern motherboards and video cards derive Vcore from 12V, so power supplies have tons of current available on 12V. (43A on a typical 550W supply I just checked.) \$\endgroup\$
    – user39382
    Jun 28, 2017 at 21:39
  • \$\begingroup\$ I will only power a few segments of the led strip, so I think it will be fine. What about the toggle to switch on/off the led strip while the pc is on? I was thinking between the 12v-GND and led-GND. \$\endgroup\$
    – Dario
    Jun 28, 2017 at 22:15
  • 2
    \$\begingroup\$ Convention is to leave GNDs connected and switch the supply rails. That way the line is isolated when switched off. Many transistor circuits switch the negative with an NPN transistor. Car circuits often have switched negatives too. \$\endgroup\$
    – Transistor
    Jun 28, 2017 at 22:21
  • 3
    \$\begingroup\$ In fact they are now planning to make power supplies with only 12V. 12V is the most important voltage in a modern computer power supply. \$\endgroup\$
    – user253751
    Nov 20, 2020 at 18:03

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