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Using PC power supply for LED stripes

  • 18-05-2017 10:04am
    #1
    Maccon
    Registered Users, Registered Users 2 Posts: 7 ✭


    Hi,

    I Used my old PC power supply to run about 14 meters of LED stripes. It works however it only draws about 37-38 watts in total and the light is not great.
    The stripes are rated @ 14.4 w per meter so 72 w per 5 meter.
    With 5 meter attached it takes about 24 W.
    The power supply, an old ATX has 16 amp @ 12 volt so this should be sufficient to drive most of the LED.
    I also used a fully charged car battery and the light output seems 30% higher.

    It seems that the PC supply is not working to nowhere near to it's potential. How can I push the PC power supply to let more out?


Comments

  • #2
    bonzodog2
    Registered Users, Registered Users 2 Posts: 6,285 ✭✭✭bonzodog2


    You might try a small dummy load on some of the other voltage outputs, I think I read they need some drain all round to work properly.


  • #3
    Capt'n Midnight
    Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 93,596 Mod ✭✭✭✭Capt'n Midnight


    12V from a car is normally 14.4 volts when driving , dropping down to 11.3 when engine off and battery low.

    12V from a PC power supply is 12.1 volts


    a rare few PC power supplies have an adjustable resistor, but they'd only be very old ones like 20 years old, and you don't mess with switched mode PSU's as they are totally unforgiving


    change the resistors on the led strips


  • #4
    Ubbquittious
    Registered Users, Registered Users 2 Posts: 6,292 ✭✭✭Ubbquittious


    Measure the voltage between black and yellow when the lights are on. If it's significantly less than 12v I'd say the psu is banjaxed


  • #5
    M.T.D
    Registered Users, Registered Users 2 Posts: 396 ✭✭M.T.D


    This might not be relevant in this case.
    I have a 12v psu that will power 100w of incandescent bulbs with no problem but only seems to light 12v leds to about 1/2 brightness. But if I put an incandescent bulb, say 20w, in as well then the leds come on full. Having looked online it seems not all power supplies will work with leds. But adding the resistive load (20w bulb) cured it for me. I your case using strip leds something like a 22ohm 10w resistor might work.


  • #6
    Maccon
    Registered Users, Registered Users 2 Posts: 7 ✭Maccon


    I added 12V car bulbs to the 3V and 5V as dummy loads and and the consumption of the LEDs (ex. PCP 10W and car bulbs 20W) went from 25W to 70W.
    Total consumption is now 100W and the light output is sufficient. This will do for the moment. If I need more I just need to add more car bulbs.

    Thanks :)


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