I connected a segment of a led strip (12v) to a line coming from a standard ATX PSU (12v line, of course). I just wonder if it is safe to put a toggle switch to turn on/off the led strip, or may be this really simple circuit requires additional components. I should say the ATX PSU is actually powering a PC and I want to power also the led strip, and turn it on/off while pc (psu) in on.

  • \$\begingroup\$ It should be fine. \$\endgroup\$ – Horror Vacui Nov 20 '20 at 16:38

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.
  • 8
    \$\begingroup\$ Second point is outdated.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\$ – duskwuff -inactive- Jun 28 '17 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 '17 at 22:15
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    \$\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 '17 at 22:21
  • \$\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 '20 at 18:03

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