Power supply - missing "ground" symbol - but what's that?

Discussion in 'General Electronics Chat' started by MagicMatt, Aug 5, 2014.

  1. MagicMatt

    Thread Starter Member

    Sep 30, 2013
    I bought a power supply from eBay - 12VDC, 30W (to be used to power some LED strips).

    I was expecting to find the usual v+, V- for the DC, and the L, N, E for the mains... but there's no Earth, and instead a circle with a plus... is that the same thing, or something different?

    I've attached an image for reference. I didn't want to just wire it up as I'm sure you can appreciate, without knowing whether it's right!
  2. crutschow


    Mar 14, 2008
    I would guess that is the ground terminal. Check continuity between that and the metal chassis to determine for sure.
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    "Guessing" about safety is never a good idea.

    I've never seen that symbol to indicate ground, in fact I've never seen that symbol.

    The power (earth) ground is not always used, especially if this is an isolated supply.

    However, a continuity check as mentioned should indicate where the mystery terminal goes.
  4. MagicMatt

    Thread Starter Member

    Sep 30, 2013
    It's connected to the chassis for sure - measuring less than 1ohm between terminal and chassis. Would it be sensible to attach it to ground anyway? It will be inside a much larger enclosure which is made of wood, so it's electrically isolated anyway, however it seems sensible to me to ground anything that can be grounded.
  5. MaxHeadRoom


    Jul 18, 2013
    You should still carry a earth ground to the terminal, if this confirmed that it is actually connected to the case.
  6. studiot

    AAC Fanatic!

    Nov 9, 2007
    I see the terminals L and N.

    What is the resistance between these and what is the impedance between the the unknown terminal marked with a pozidrive screw symbol.

    While you are at the ohm-meter, check form this terminal to V+ and V- as well.

    If you can see into the box, make sure this terminal is not an output zero.
  7. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    Could this be a dual supply (i.e. +12V, 0V, -12V) ?