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Led light setup. need help, will this work?

Discussion in 'LEDs and Optoelectronics' started by trebor, Apr 30, 2017.

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  1. trebor


    Apr 30, 2017
    hey guys!

    first of im new to the forum, hope i posted in the right place.
    so, ive decided to make an led light setup, but i have no basic knowledge of electronics and/or electricity in general, so after alot of research i came up with this setup, and i would like to know if this will work and if it does, if its a safe setup.

    for main power source i have modified an old pc power suply. on the 12v rail its rated at 11A wich would give me a total of 12v*11a = 132W, lets say 100-110W tops to be on the safe side.

    with this psu idd like to power the following LEDs:
    1) 1x 50W cob led @ 30-36v / 1.5A (with active cooling) + driven by a dc boost converter from ebay with the following speccs:

    Input voltage: DC 10V-32V.
    Output voltage: DC12V-35V(adjustable).
    Output current: 10A (MAX).
    Input current :16A (MAX) (more than 10A please strengthen heatsink).
    Output power: natural cooling 100W (MAX), strengthening cooling 150W (MAX) real power.
    Conversion efficiency: 94% (when Input 19V 2.5A Output 16V, Reference).
    Output ripple: 2% (MAX).

    50w led -> boost converter -> 12v dc power suply (pc psu)-> wall plug
    2) 10x3w led 10 in series. 1 led is rated 3.2V-3.4V 560mA-700mA, so i figured 10 would be 32/43v @ 0,7mA + 30W constant current driver also from ebay with the follosing speccs:

    Input Voltage: DC9-24V
    Output Voltage: DC30-38V

    10x3w in series -> constant current driver -> 12v dc power suply (pc psu) -. wall plug


    from what i have calculated i figured the 50W led would draw from the psu around 54W and the 10x3w leds would draw roughly 31W with a total power draw from the 12v power suply of 85W (12v*7A)

    so my questions are:
    1) is the 50w setup and the 10x3w setup ok? will it run safelly?
    2) after desoldering the extra wires from the psu, i have 6 yellow (12v) wires left. i thought of using 2 wires (2yellow +2black) to power the 50W led, 2 wires (2yellow +2black)to power the 10x3w leds, 1 (yellow + black) wire to power coolers, and leave 1 wire aside. will this work? considering its a YES on question one
    ive seen people on youtube using psu-s as 12v power suplies connecting all yeallow wires togheter so i figured it would be safer to use 2 wires to power each led setup.

    thank you very much in advance, hope to hear your opinions!
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Welcome to electronicspoint.

    The basic ideas are o.k., but flawed in detail.

    add 1:
    a) Sounds like the boost converter has a voltage regulated output. To drive an LED you will need a current regulated output aka an LED driver. The voltage will adjust automatically to the LED's operating voltage at the set current.
    b) Sounds like the 30 W LED driver is rated at 1000 mA output current. Unless it is adjustable down to 700 mA it is not suited for your application.

    add 2; You may connect all 12 V wires together, as well as all ground wires. Or any combination thereof. Within the PSU these all go to the same connections anyway.
  3. trebor


    Apr 30, 2017
    exactly the things i was not sure about!
    @50 led: if i set the boost converter to 35V, im guessing the output wount be 10A (boosters max output), but it will be more than 1,5A (what the led needs). 3,7A, if im correct, wount the led draw just the 1.5a it needs? or will it blow from the 3.7A?
    Last edited: Apr 30, 2017
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    LEDs are not like tungsten lightbulbs!
    You don't supply an LED with a constant voltage in the hope the current will adjust. You supply a constant current and the voltage wil adjust. This is what LED drivers are for. If you are interested in details, read this ressource.

    Once you ned to buy an LED driver anyway, you can buy one that directly operates on mains, foregoing the PSU as an intermediate circuit.
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