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Adding a ground to row of LEDs

Former Member

Hi all,

 

I am trying to make a lid with rows of LEDs on it (connected in parallel). The setup is attached as a diagram of the PCB to this post, but mainly what I will be doing is attaching a voltage source to each potentiometer (it will act as a variable resistor) and then since the LEDs are connected in series with the copper wire bussed into the board (I think this is how it is on the board - can someone confirm this is how it will work?). My question is whether I will need a ground at the end of each row (pretty sure I would) and if so, how would I put that in (I tried looking online and it said to go to 'supply' but I couldn't find it in there). Thanks for the help in advance.

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  • I can't see your image, however you mention having the LED's connected in

    parallel - in general, that will not work unless each one has a current

    limit resistor in series with it.  No two LED's will have exactly the same

    voltage when "on", so you will get very bad load sharing (brightness) if

    they are just connected in parallel.  Without seeing your diagram, I can't

    be sure, but is sounds like the intent is to run a bunch of LED's and

    control the brightness with a variable resistor.  Generally, that will

    result in exceeding the power/current rating of the pot - a better approach

    is to use some sort of switching regulator to adjust brightness.  If I

    mis-interpreted what you are doing, this doesn't apply, but I was not able

    to see the circuit.

     

    mikey

     

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  • in reply to autodeskguest

    My bad - was able to see your image (why can't I edit my post?).  Anyway,

    my comment about parallel LED's stands.  I think you will find you have

    lots of problems with them bussed together like that - each one should have

    it's own current limit resistor (or put them in series and drive it with a

    higher voltage and one current limit resistor).  This is especially true

    with "bargain" LED's (which is what most of us would be using) - their Vf

    will be different for each one.  Others may have a different idea, but that

    is my initial reaction to a bunch of diodes in parallel.

     

    mikey

     

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    Web access to CadSoft support forums at www.eaglecentral.ca.  Where the CadSoft EAGLE community meets.