Wiring/Electrical question

[nakeworks]

 :

Maybe this is an easy fix but I know little about electricity and wiring...here goes.

I am wiring my 5v ultralux buttons from Ultimarc.  I recently got a completely separate power supply from an old dell computer.  I hooked the positive end into the red wire (per instructions) and the negative end to the black of a 4-pin molex connector.  The light turns on just fine.  When I hook a second into the circuit (positive to negative to positive etc) it works just fine.  When I hook a third one up, nothing.  Fourth one, nothing.  I have rechecked the wiring and  verified that all the lights work individually and as pairs but nothing when a third or fourth is added in.  Am I missing something obvious?  Could my wires not be "holding" the current well enough?  The computer power supply is not powering anything else.  Thanks for the help in advance.  You guys and gals are great.   

[Nephasth]

(positive to negative to positive etc)

  - Do you mean in series?

Put all positive leads to the red wire, and all grounds to the black (wired in parallel).

[nick3092]

For graphical purposes....

Code: [Select]


+++++++++++++++++++++++  +5v
   |   |   |   |   |
   O   O   O   O   O  LED
   |   |   |   |   |
-----------------------  -5v


[SuprSprint]

Put all positive leads to the red wire, and all grounds to the black (wired in parallel).

+1 either your #3 led is bad, or you wired it backwards. 

Also, do your LED's require a stepdown resistor?  An LED is a diode, and without a load or stepdown, they can draw quit a bit of power, perhaps more than your supply can provide.  Normally in a situation like your describe you will see gradual dimming along the chain, but not always.