Need help choosing an LED driver.

Discussion in 'The Projects Forum' started by specialedster, Jun 19, 2010.

  1. specialedster

    Thread Starter New Member

    Dec 21, 2009
    4
    0
    Admittedly, I do not have much experience in this area. I am trying to drive 10 individual groups of 6 LED's each. Each of these groups of 6 LEDs will be controlled with an arduino so that any combination of the 10 groups can be on/off at the same time. I don't need to have any control over the dimming since the LED's will either be completely on, or completely off.

    Each LED needs ~25mA and has a forward voltage drop of ~2.5V. I am using a basic 250 ATX power supply with 5V and 12V rails. Not having much experience in this area I was hoping I could get some help choosing a driver that will be able to handle enough power (60 total LEDs) and with enough channels (10) that will not be a nightmare to work with. I looked at a couple of matrix LED drivers but the problem is that my LED's are not in a matrix and it would be a pain to wire them so that they were. Does anybody have any suggestions or experience with this kind of thing?

    Thanks in advance!
     
  2. nickelflipper

    Active Member

    Jun 2, 2010
    280
    35
    Look for an enhanced 8 bit shift register, like the tpic6595, that will handle the total package power requirements (1W). Cascading 8 devices should do it. No fancy series strings, just 5V with corresponding resistor per led. This assumes that your 5V tap can supply the required 2A+.

    Should be plenty of Arduino code out there for running the '595 style shift registers.
     
  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,176
    397
    If you drive the LED's individually from 5V they will draw about 1.5A. Would suggest each group be two paralled strings of 3 LEDs & 180 Ω in series with a transistor driver. Each group of 6 LEDs would draw 50 mA so all 10 will draw 500 mA from 12V supply. There are 10 control lines, one for each group.
     
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  4. specialedster

    Thread Starter New Member

    Dec 21, 2009
    4
    0
    I think I will go with the transistor driven circuit that you supplied. Thank you very much for the detailed schematic!

    - Alex
     
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