Led lighting problem - LED's flashing

Discussion in 'General Electronics Chat' started by gadgetboys, Sep 18, 2016.

  1. gadgetboys

    Thread Starter New Member

    Sep 18, 2016
    3
    2
    Firstly may i say hello to anyone reading this. I am a new user to the site and found the site whilst looking for a solution to the problem below.

    Quick question for all you LED boffins, its driving me mad. I have recently made a light for the wifes greenhouse using some Cree CXA3070s (all working fine) with the addition of 50 Deep blue 3w LED's http://futureeden.co.uk/products/3w-royal-blue-led-epiled-440-450nm-with-star-pcb-heatsink and 100 3w Deep red LED's http://futureeden.co.uk/products/3w-deep-red-led-epiled-640-660nm-with-star-pcb-heatsink
    All wired in banks of 10's wired in series and each ten driven with its own driver http://futureeden.co.uk/products/constant-current-led-driver-600ma-28w-30-50v Both the Red and Blue's are wired in the same way

    Now the problem i am having is that the sets of 10 blues all work perfectly yet the sets of 10 reds all flash on and off at 2 sec intervals. The red and blue led's are the same wattage and the same voltage. I have checked all solder joints, LED polaritys and also tried changing the LED drivers wired to the blue ones to the reds but with the same results. I have noticed that when wired the Blue circuit LED driver outputs measures between 32 - 38v as would be expected yet the Red LED drivers only measure between 14 -18v. I Any ideas would be gratefully received as I out of ideas
     
  2. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,879
    371
    The voltage of the red and blue LEDs are not the same. The blue ones are specified at between 3.4V and 4.0V @750mA while the red ones are 2.2V to 2.8V @800mA. The driver provides 600mA so you would expect the LED voltages to be lower than that spec as the current is lower. The driver output voltage is specified at between 30V and 50V.
    Your ten blue LEDs are going to drop between 34V and 40V or a bit less as the current is less. Comfortably within the voltage range of the driver.
    Your ten red LEDs would drop between 22V and 28V (actually less than that) and this is outside the voltage range of the driver and I expect that is your problem.

    Try 15 red LEDs in series.
     
  3. #12

    Expert

    Nov 30, 2010
    16,248
    6,744
    This sounds more like, "try 20 reds in series to get to 28 to 36 volts".
    If that doesn't work, try 25 reds in series to get to the right voltage range.
     
  4. gadgetboys

    Thread Starter New Member

    Sep 18, 2016
    3
    2
    Thanks for that guys, Dont know how I missed that I must of just checked one and presumed the other the same :rolleyes: Thanks a lot will let you know the result tomorrow :):)
     
    #12 likes this.
  5. gadgetboys

    Thread Starter New Member

    Sep 18, 2016
    3
    2
    Many thanks for the help guys, It took 15 and the flashing stopped. 10 more on order to complete the 2 :) Great forum also Really glad i found it.
     
    #12 likes this.
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