led pcb mystery

Discussion in 'General Electronics Chat' started by Heikki, Sep 7, 2014.

  1. Heikki

    Thread Starter New Member

    Sep 7, 2014
    3
    0
    Pcb has 2 x 21 strings in series
    leds are 3w and of 7 different kind
    is it even possible to make such strings
    with out burning the house down
     
  2. Heikki

    Thread Starter New Member

    Sep 7, 2014
    3
    0
    Here is the pcb

    20140907_125646.jpg

    20140907_125646.jpg
    The leds are 3w and ranging from 2-9v and 300-750ma
     
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,770
    970
    Sure you just need a driver with an output voltage higher than the series strings forward voltage rating.

    For safety many drivers only go to 48-52V (60V SELV) max DC output.. There are some that go higher.


    Hope you realize too that ALL the leds in each string will get the same current so you can't mix 300mA and 750mA (well if you do you should only drive them at 300mA) .. They will all be driven at the same current level.
     
  4. ISB123

    Well-Known Member

    May 21, 2014
    1,239
    527
    You could use LM317AHV to build the supply.
     
  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,058
    3,820
    Assuming most white LEDs are 3.3 volt forward voltage, each string will have a 70 volt drop and 126 watts (3x42) on a 150x200 mm plate? Fire? It is possible.

    Note that fire is possible from poorly designed electronics and circuitboard but, instead, from radient energy. LED flashlights of 30 watts and more can heat place paper or electrical tape to combustion (depending on focal length and distance).
     
  6. Heikki

    Thread Starter New Member

    Sep 7, 2014
    3
    0
    Hmm i guess i ll skip the white ones then and figure out a combination of the rest for a 21 string..

    i have 2x 300x120x20 heatsinks i intend to use and 4 x 100mm fans for each 2xheatsink
    20140907_204059.jpg
    20140907_204059.jpg


    I was hoping it would be possible to connect 2 x pcb on the heatsinks and then controll it all via arduino,

    20140907_204128.jpg
    20140907_204128.jpg


    Thanks for all input and critic , now its back to the drawing board and back here for a revisit ,

    tip of the hat..
     
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