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Thread: Do I need to run a driver?

  1. #1
    Unenlightened
    Join Date
    Mar 2020
    Posts
    1

    Default Do I need to run a driver?

    Hi everyone,

    I bought some LED downlights off ebay:

    12VDC 12W FROSTED WHITE ADJUSTABLE DIMMABLE
    SAMSUNG LED DOWNLIGHT
    FOR USE WITH 12VDC BATTERY SOLAR SYSTEMS
    AUSTRALIAN SAA APPROVED, EMC, CE, Certified

    If I actually run this on a solar system it will see 12-14VDC depending on the time of day and what the battery is doing. All I can see is LEDs and there doesn't seem to be space underneath the actual PCB for any other components (Have not pulled it off to be 100% sure as will have to tear up the glue). I asked the seller if I needed to run a driver or buck converter and he assured me no.

    Now being ebay I assume these are not Samsung LEDs and judging by lack of markings anywhere the lights are not SAA APPROVED, EMC, CE, Certified.

    So are these junk? What happens if they do see 14VDC with no driver? Possibility of burning a hole in my roof?

    Thanks in advance


  2. #2

    Default Re: Do I need to run a driver?

    Probably not a good idea with something as variable in current supply as that sort of system hooked up to a solar panel.
    Yes, you will probably need some sort of current regulator or driver. (But I will say it might theoretically be possible with the right calculations, which depends very much on specifics)



    Quote Originally Posted by m3445 View Post
    What happens if they do see 14VDC with no driver? Possibility of burning a hole in my roof?
    Each emitter is going to be somewhere between 3.2 to 3.4v and they are in sets of 4. Which means 12.8 to 13.6v.
    14v is most likely going to result in a permanent burnout, meaning the light panel will permanently no longer work.

    However, this could be wrong.


    Edit: You didn't really give enough specifics. If those are really downlights that "plug in", rather than a freestanding circuit component, then they should already have a current regulator built in. Those circuits these days don't take up a lot of space. Most likely it would be able to handle 14v, but likely not much more than that.
    However, a cheap design may not have a current regulator built in (only a rectifier). In that case, it is not likely to be able to handle 14v.

    The short answer is I don't really know.

    I could go into a lot more detailed specifics, but it would ultimately be speculation.

    If the downlight is cheap enough, it may be worth trying. The worst thing that would happen is the light would burn out.
    The risk of fire is not very great. But even though I think that risk would be rather small, you may not want to risk it.

    Last edited by JoakimFlorence; 03-29-2020 at 12:09 AM.

  3. #3
    Flashaholic
    Join Date
    Nov 2009
    Location
    Ottawa Ont. Canada
    Posts
    287

    Default Re: Do I need to run a driver?

    Quote Originally Posted by m3445 View Post
    Hi everyone,

    I bought some LED downlights off ebay:

    12VDC 12W FROSTED WHITE ADJUSTABLE DIMMABLE
    SAMSUNG LED DOWNLIGHT
    FOR USE WITH 12VDC BATTERY SOLAR SYSTEMS
    AUSTRALIAN SAA APPROVED, EMC, CE, Certified

    If I actually run this on a solar system it will see 12-14VDC depending on the time of day and what the battery is doing. All I can see is LEDs and there doesn't seem to be space underneath the actual PCB for any other components (Have not pulled it off to be 100% sure as will have to tear up the glue). I asked the seller if I needed to run a driver or buck converter and he assured me no.

    Now being ebay I assume these are not Samsung LEDs and judging by lack of markings anywhere the lights are not SAA APPROVED, EMC, CE, Certified.

    So are these junk? What happens if they do see 14VDC with no driver? Possibility of burning a hole in my roof?

    Thanks in advance
    Do you have access to some basic equipment such as DMM and a 0-15v (or higher) variable dc power supply at >1 amp?
    If so you can characterize the light without further dis-assembly. Start low, crank up voltage slowly and
    watch the current drawn; should not go much above 1A.

    My work with 12v dc LED lights is largely ones with built-in constant-current driver. Not all are like this.
    This light may have some sort of current limiting; resistors mounted on other side of PCB, or below, or perhaps
    one big one.

    I count 20 LEDs which suggests 5 parallel set of 4 in series (5P4S or 4S5P). However, brightness may vary between
    12v and 14v. This range is probably safe to test with if you want to chance it; could connect to small regulated 12v power
    supply to start. For a simple 12v solar/battery system, 12-14v is a reasonable range if fed straight from the battery i.e.
    no converter to tightly regulate output.

    If a switching CC driver is hiding in there somewhere, brightness should stabilize at a certain voltage, and the current will
    decrease as voltage increases, due to constant power of load (more or less).

    I have a 21-LED dome light unit which behaves as rough current limiting mode; current and brightness increase with voltage.
    This one has a clever circuit which allows operation at 24v also, by switching parallel LED strings to series; can't say
    much more as the circuit is potted in clear epoxy!

    Dave
    Last edited by Dave_H; 03-29-2020 at 12:02 PM.

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