Using a 12V 100W (8A) LED driver for several different 10W LEDs

Discussion in 'The Projects Forum' started by arob, Oct 24, 2017.

  1. arob

    Thread Starter New Member

    Oct 24, 2017
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    Hi there,

    I hope I'm posting this in the correct place. This is my first post here, I like this forum and enjoy people's ideas. I have looked at other people's LED projects here and want to build my own. I have two 12V 100W 8A drivers and two 22-38V 30W drivers. But the LEDs I have are different voltages and currents, but all rated '10w'. These are the LEDs I want to light and their specifications:

    Blue 450nm 9-12v@900mA x4
    Red 660nm 6-8v@900mA x5
    Coldwhite 10-15k 9-11v@900-1000mA x2
    Red 640nm 6-7v@1050mA x2
    Blue 420-430nm 9-12v@1050mA x3
    Warmwhite 2800k 10-12v/30-32v@300mA x2

    Bringing it to a total of 18 LEDs. The product description is very vague on how these work, and I think there is not any current limiting in them. My question is, which of my drivers are better compatible and how to use them for these, and how to wire them? In parallel or otherwise? I have done a lot of research but haven't encountered someone with the same idea with documentation.

    If someone could point me in the right direction or give me an idea, thank you a lot.
     
  2. arob

    Thread Starter New Member

    Oct 24, 2017
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    I know about current limiting resistors, but I heard this wastes a lot of energy and heat, is there a better way to do it on this scale? Eventually I want to add MOSFETs to control the lights with arduino
     
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    All 16 LEDs in the first 5 links could theoretically be driven by 2 of the 100W drivers combined, but each LED would need a respective current-limiter (causing heat) and there would be little or no margin to allow for tolerances and any over-optimistic driver ratings. So you might need more than 2 drivers in practice.
    The LEDs in the sixth link, according to the website, need a 30-32V supply, but the 30W drivers are a constant-current type with a (fixed?) 1.5A current which would be unsuitable for the LED's 300mA rating.
     
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  4. arob

    Thread Starter New Member

    Oct 24, 2017
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    First of all, thank you for your help. These LEDs won't all be on at once, either almost all red and a little bit blue or the other way around will be on. This will lower the usage to an allowed amount, right? And to what voltages and currents should I limit to not push it too far?

    Also, so I need a new driver for those LEDs. Then I will look for one. Thanks again
     
  5. arob

    Thread Starter New Member

    Oct 24, 2017
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    How do I wire them? Then I can try a few resistor values
     
  6. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    The preferred operating method would be to use constant-current drivers for all the LEDs. Although dropper resistors have the advantage of simplicity they can't easily allow for LED tolerances.
    Personally, I wouldn't run any of the LEDs at more than about 80% of their rated current.
     
  7. arob

    Thread Starter New Member

    Oct 24, 2017
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    What about the red LEDs, they are 6-8v, do I connect them to 12v in series of 3 with each led having its own current limiter?
     
  8. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    If you connect 3 of the first lot of red LEDs in series their total forward voltage at 900mA would, according to the spec, be anything from 3 x 6V=18V to 3 x 8V=24V. At a lower current the total forward voltage would be somewhat lower. If I were using those LEDs and needed 3 in series I'd opt for a current of, say, 700mA and look for a constant-current driver which could be set for 700mA at a voltage around 26V to 28V. I haven't checked to see if such an animal exists. Does your 30W driver have an adjustable controlled current? If so, it would be fine for 3 of the red LEDs.
    If you meant in parallel, rather than in series, then you could use a respective resistor of around 8Ω with each red LED and drive 9 or so such combinations with a 12V 100W supply. The current per LED would be (12-Vf)/R, where Vf is in the range 6V to 8V and R is the resistor value. Each resistor would, however, have to dissipate up to around 5W, so a 10W rated one would be advisable.
     
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