I have a seemingly simple question but I am getting stumped.

I have a power supply providing +12v +5v GND and -12v. I would like to have an LED for each input voltage showing that they are working correctly. The '+' Voltages are all simple, However, I am having trouble with the -12v input.

Any help or a point in the right direction would be appreciated.


  • \$\begingroup\$ What is the problem you are having with the -12V input? It might help us help you if you showed a schematic of your circuit. \$\endgroup\$ Apr 4 '18 at 19:42
  • \$\begingroup\$ I think the problem was with the -12v input on my cheapo power supply. So flipping the led was, in fact, working in that it was not illuminating because there was no - input at all. The irony. \$\endgroup\$ Apr 4 '18 at 20:14
  • \$\begingroup\$ Perfect, so your LED correctly told you that the -12V was missing :) \$\endgroup\$
    – Selvek
    Apr 4 '18 at 20:16

All you need to do is turn the LED around.


simulate this circuit – Schematic created using CircuitLab


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