LED Project

Discussion in 'The Projects Forum' started by chrisab508, Sep 30, 2009.

  1. chrisab508

    Thread Starter New Member

    Sep 30, 2009
    3
    0
    Hey Guys,
    I understand that LED projects are popular, and that you get a lot of questions regarding them so I apologize if what I'm asking has been covered.
    I am making an LED sign (essentially a neon sign but made with LEDs). My plan is to make the outline of a christmas tree with green LEDs, and some "christmas lights" inside the tree with red LEDs. I have a fairly large perf board because I wanted to make it pretty large. My question to you guys is how do you think I should power it? Given the size I'm looking for, I could be using quite a few LEDs, so I'm guessing a simple battery (e.g. 9v) will not be sufficient. I could do the calculations, however, I feel that someone here has probably tackled this situation previously.
    I also have a similar question. I will probably be operating somewhere in the range of 100 LEDs (perhaps more), so I would imagine that I do not want to wire them all in series, or all in parallel (which would be a mess), would you guys recommend splitting them into lines of 10? 20? n?

    I can get a DC power adapter pretty easily. A 12v, 500mA is easiest for me to get (won't have to order it online), however, a quick ebay search shows me that I can get a 12v 2A power adapter as well. Thoughts?


    Thank you in advance, any help is appreciated.

    - Chris
     
  2. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
    16
    Chris,

    How many LEDs are you planning on powering? I would suggest a LED driver; they have different ones for how many LEDs you plan to run. Like the LT3598 from Linear Tech can drive up to ten of them. Some go even further, I have one that can drive up to 60 LEDs.
     
  3. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    That power supply would work fine. LED colors act a bit differently than each other, so you need to take that in account for your design.

    Have you read this?

    LEDs, 555s, Flashers, and Light Chasers

    One other question, is the 12VDC power supply regulated? If not then it will likely need something. Basically a stable voltage only needs a resistor to light an LED. Your project will be a mix of both parallel and series LED circuits, the article the link points to explains this.

    Just a thought, something I've been tempted to do, but get a piece of plywood and drill holes that are slightly undersized, then use point to point wiring in the back. It is extremely simple.
     
  4. chrisab508

    Thread Starter New Member

    Sep 30, 2009
    3
    0
    Sorry it took me so long to respond, I assumed I would get emailed notifications of the replies to my thread.
    In response to Electronerd, I'm not quite sure how many LEDs I'll be using. I have to place them in the perf board first, and then count them. However, I would estimate somewhere in the 60-100 range. You mentioned a driver for the LEDs? Obviously it will drive the LEDs, but how exactly does it work? Is it possible to see the design for your 60 LED driver?

    In response to Bill, I'll read through your link. At some point I would like to make a flashing modification to an LED circuit, and I have read about 555s to help make that work. The 12v DC power supply is not regulated. Would I need a rectifier to help regulate it? Would it be complicated to regulate? Should I think about just getting a regulated one?

    Thanks again guys.

    - Chris
     
  5. Mohanram

    New Member

    Oct 2, 2009
    1
    0
    Hi,
    You can use resistances for limiting the voltage. LED drivers are for limiting the current. For ordinary LEDs you dont need the drivers as only high bright (HB) LEDs need them. An LED is about 3V. For a 12 V DC you can connect a maximum of 3 LEDs in series with suitable resistors (Resistance calculators are available on line). These strings then have to be connected in parallel. Only if your battery is powerful enough you can have about 60 to 100 LEDs as you plan. All the best.
     
    Last edited: Oct 2, 2009
  6. chrisab508

    Thread Starter New Member

    Sep 30, 2009
    3
    0
    I have not done any tests with my particular LEDs, but I was under the impression that my green LEDs were roughly 2v, which would allow me to connect roughly 5 of them in series for each string (with proper resistance of course).

    - Chris
     
  7. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Suggestion, read the link I gave you. I think it will answer almost all your questions, including how to do special effects.
     
  8. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,172
    397
    Try for a higher V supply, or stack 2 12V supplies for 24 V , so that you can use longer strings. Can use an LM317 to regulate at about 20V.
     
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