LED project - need some guidance

Discussion in 'The Projects Forum' started by davenc, Apr 27, 2010.

  1. davenc

    Thread Starter New Member

    Apr 27, 2010
    Hi all,

    I was a little hesitant to post yet, because I don't want this to seem like a "please do this for me post", but I could use some advice. :)

    I am working on a project to use LEDs to back light translucent plexiglass panels. I am looking at using PLCC2 surface mount type LEDs (current 2ma, 3.0 min voltage). I need something small (physically) so that I can sandwich the LED's between two sheets of plexi.

    I expect to have around 25 panels in the project, and with my current level (lack of:D) of knowledge, was thinking that each panel would have 5 LEDs in series and all panels wired in parallel (125 LEDs total). If I am correct, that will be 2.5amps total (.02ma x 125 = 2.5a).

    If these numbers are correct, what voltage power supply will I need? From a wizard I found online, I believe 24volts is needed, but with my limited knowledge at this point, I am not sure how to confirm that. And if 24volts is right, I've come up with needing a 470 ohm resistor for each panel.

    Am I even close to being on the right track?

    I obviously want a toggle switch to cycle power, but I also want the ability to dim the LEDs and don't have a clue what I need for this.

    To give you some background, I have dabbled with electronics before, but nothing on this scale. I am currently reading the E-book which is helping tremendously (and was also how I found this forum) but I still have much to learn. I've also ordered several different types of LEDs to experiement with as I am really a "hands on" learner. However, I want to be sure I am not going to hurt myself either! :)

    Thank you!

  2. retched

    AAC Fanatic!

    Dec 5, 2009
    Bill_Marsden has written an article, (or series of articles) that will help you.

    PWM is what you will want to use to dim your leds. You should read this, then come back with your questions.

  3. Bernard

    AAC Fanatic!

    Aug 7, 2008
    With 5 LEDs @ 20mA.in series that is still just 20mA/ panel X 25 = .5A. Resistors of 450 to 470 @ 1/4 W should be OK with 24V supply.
  4. davenc

    Thread Starter New Member

    Apr 27, 2010
    Thanks guys! Trying to read through the article now, but I think it will take several attempts to comprehend.
  5. Wendy


    Mar 24, 2008
    No problem, we have a lot of people who don't mind answering questions, myself included. Don't hold back because you think it sounds silly, this is how we learn.