LED wiring help!

Discussion in 'The Projects Forum' started by ...jay..., Mar 18, 2010.

  1. ...jay...

    Thread Starter New Member

    Mar 18, 2010
    4
    0
    Hello all and good evening!

    i found this forum whilst frantically searching the internet for help with a university project that i have undertaken, needless to say i am an electrical novice with very little wiring knowledge!

    i am currently in the middlle of building an array that consists of

    9 yellow LED's
    1.8 - 2.2 forward voltage
    30mA forward current

    24 Blue LED's
    3.2 - 3.8 forward voltage
    30mA forward current

    56 Red LED's
    1.8 - 2.2 forward voltage
    30mA forward current!


    the power supply i have is
    5V output 0.2a

    to begin with is this suitable?

    secondly
    i assume this quantity will require parrallel wiring but i have no idea what colour LED's to start with and where to place resistors of what value to ensure that it all works!

    i know this is a big ask but is there anybody that understands me and if possible could point me in the right direction

    i have tried LED calculators but didnt believe they would work due to the Blue LED's having a higher forward voltage!

    regards

    Jay
     
  2. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    Well, the power supply is way too small for your project. You MIGHT be able to light 3 leds with it at full brightness.

    You have to add together the forward voltages of each string.

    A string of 9 x 2.2v red leds will need 9x2.2v=19.8v

    This will help, read:
    http://forum.allaboutcircuits.com/blog.php?bt=674
    It is a blog from a member here, Bill_Marsden.
     
  3. ...jay...

    Thread Starter New Member

    Mar 18, 2010
    4
    0
    wow, ok i was well off the mark then!
    after adding all of those values up it leaves me with 234.2V

    being around the out put on a normal house ring main does that mean i should just use a normal plug with a length of 2 core cable on it or am i completely missing the idea here?

    Jay
     
  4. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    no, You will wire them in series sets, then wire the sets in parallel.

    When you wire in series, you add up the voltages, in parallel, you add the current.

    Read the link I gave you. It will show you the math and the process.

    Look at this too. It is pretty much what you want to do:
    http://forum.allaboutcircuits.com/showthread.php?t=32398
     
  5. ...jay...

    Thread Starter New Member

    Mar 18, 2010
    4
    0
    ok, sounds a wee bit confusing! i shall have a read!

    thanks for the link by the way!

    Jay
     
  6. k7elp60

    Senior Member

    Nov 4, 2008
    478
    69
    In simple terms you can connect two yellow in series or two red, or one red and one yellow alone with a reistor to light on 5V. You do not need to use the 30mA of current. LED's will illuminte on very low current the intensity varies with voltage. I use normal LED's on 5-10mA all the time and they are clearly visible.
    With 5V you can only illuminate one blue LED.
    Off course all the circuits require a resistor in series with the LED's to limit the current.
     
  7. Wendy

    Moderator

    Mar 24, 2008
    20,764
    2,534
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