ULN2003 usage question

Discussion in 'The Projects Forum' started by ajaxoftherockies, May 10, 2013.

  1. ajaxoftherockies

    Thread Starter New Member

    Apr 7, 2012
    17
    0
    Hi Gang,
    I have a circuit with three outputs that switch channels of a ULN2003 Darlington array to drive an RGB LED Module - one output to each color.
    Right now, it works perfectly. I want to add another module and have a question. can I just tie each output to two of the 2003 channel inputs, then tie the outputs to the two separate modules? Or do I need something between the 2003 inputs?
    Here's what I have in mind:
    [​IMG]

    This way? or something else?

    Thanks!

    - a -
     
  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,173
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    I see no problem with paralleling inputs.
     
  3. ScottWang

    Moderator

    Aug 23, 2012
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    You only have one channel left to drive the LED, if you changing to ULN2803 then you have two channel s to use.

    Do you need to in series a resistor with the input of 2003, it's depends on your input voltage, if the voltage of signal is <=12V then it's OK, no need.
     
  4. ajaxoftherockies

    Thread Starter New Member

    Apr 7, 2012
    17
    0
    Thanks, Scott. I'm not clear, though. Would you please elaborate? I'm using three of the transistors (i've called them channels) to drive the three colors - one transistor per color - in the first module and propose to use another three to drive another module.

    Right now, I have no resistor from the 2003 to the LED Module and the supply is 12v
     
  5. ajaxoftherockies

    Thread Starter New Member

    Apr 7, 2012
    17
    0
    Thanks! I was hoping for that answer to keep complexity down


    - a -
     
  6. ScottWang

    Moderator

    Aug 23, 2012
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    767
    Sorry, it's my mistake, I just thought the circuit is the old one and you want to adding another three LEDs in it, but not show in the circuit.

    The circuit only need 6 resistors in series with each LED to limiting the current of LEDs, otherwise it may reducing the life of LED.

    Now you using three channels to drive three LEDs, the new three LEDs In your circuit that they can in parallel with the same colors, someday if you want to adding more LED, then you may need to do this way.
     
  7. absf

    Senior Member

    Dec 29, 2010
    1,493
    372
    Make sure that the total current of your LED modules dont exceed the 600mA of the ULN2003. What kind of module are you using?

    Allen
     
  8. #12

    Expert

    Nov 30, 2010
    16,316
    6,818
    Is this drawing what you want?
    If your LEDs don't have current limiting resistors in them, this is how you do it.
     
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