LEDs flashing for no reason

Discussion in 'General Electronics Chat' started by matthew798, Jan 17, 2014.

  1. matthew798

    Thread Starter Member

    Jan 16, 2013
    Heya guys,

    I bought a light fixture for my aquarium, and it comes with 4 boards (2 X 4-pin LEDs each) wired in parallel. My problem is that one of the boards does not work at all. Fine and dandy, the LEDs are burnt. But what has me going nuts is that one of the boards is blinking rapidly, like the HDD light on your comp. Sometimes it stops for a few seconds and starts again. Meanwhile, the two last boards are unaffected. I yanked the blinkers out and tried them directly on a power supply (dont worry, i limited the current) and, surprise surprise, they blinked. Now the real kicker is this: When I hook them up to an equivalent voltage but with BATTERIES, the lights work like a charm!!

    What the hell is going on? Is it that the batteries aren't driving as much current as the driver??? I think these leds are running on 100-200mA. Seems to me a battery should be fine with that.

    Yet another disappointing ebay experience... :mad:

  2. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    Photos? Diagram? Information regarding your power supply type? :)
  3. Richie121

    New Member

    Jan 12, 2014
    I know some of the high brightness LEDs take more current to get them to turn on, so find out what the turn on current for them should be. You could be giving them just enough but once turned on may be draining a cap to bring them under the threshold again.
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    from my experience.. with drivers and LED's is that when they blink its because the forward voltage of the string is less than the minimum dc output range of the driver..as such the constant current driver cannot regulate the current properly..and they blink.
    I'd bet that because you have 1 bad board I'd bet it was in series with the other.. So now the voltage drop is half of what it should be.
    GopherT likes this.
  5. Wendy


    Mar 24, 2008
    I have seen the flashing as a failure mode also, when the LEDs have been across a power supply with no current regulation. They get burnt.

    My theory is they become delicate, current, thermal shutdown (a failure mode), they cool, light up again briefly.

    LEDs, 555s, Flashers, and Light Chasers