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multiple LEDs

slimboyfatboyslimslimboyfatboyslim Posts: 6
edited 2004-08-24 17:31 in BASIC Stamp
hi,

I'm going to built a LED sculpture, which requires to light 3x-40 leds at the same time (either from 1 pin or severals).
Stamp can't output more that 50mA, I've read somewhere about wiring 8 Leds with IC but the information is not complete.

Does anyone have any experience on it or more information about that? More simple question, is my project possible?

Comments

  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2004-08-24 06:45
    The Stamp can drive aout 70ma total. Individual pins about 20-25 ma depending on source or sink.

    To drive more, you need a 'driver' of some sort. the UNL3803A (darlington array) will drive much more (500ma), has 8 outputs and connects directly to the Stamp. You can buy one from Parallax and appears to be what you need (a one-additional-chip solution).

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    G. Herzog in Taiwan
  • slimboyfatboyslimslimboyfatboyslim Posts: 6
    edited 2004-08-24 07:44
    hi Herzog,

    Thanks for your reply, do you have any reference link or schematic diagram?
    I'm quite new to electronics
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2004-08-24 15:11
    You might consider using a string of (3) MAX7219 LED drivers. Each one of them can handle 64 discrete LEDs, and their modulated so you can control the current to all connected (to each MAX7219) with a single resistor.

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    Jon Williams
    Applications Engineer, Parallax
    Dallas Office
  • slimboyfatboyslimslimboyfatboyslim Posts: 6
    edited 2004-08-24 16:14
    Thanks Jon, Do you have any schematic diagram for reference or more information on that driver?
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2004-08-24 16:18
    Google is your friend -- download the specs from the Maxim site. You can find an experiment with the MAX7219 in our StampWorks book, and also a couple Nuts & Volts columns dealt with it (you can find the reprints on our web site). Just so you know, those part aren't cheap, but I would use them given the parameters you've already expressed.

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    Jon Williams
    Applications Engineer, Parallax
    Dallas Office
  • UAEmbeddedUAEmbedded Posts: 5
    edited 2004-08-24 17:26
    May I suggest the MAXIM-IC MAX6954.· It will drive up to 128 LEDs under control of an SPI interface.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2004-08-24 17:31
    You can purchase the MAX7219 & Download the Datasheet from here:

    http://www.parallax.com/detail.asp?product_id=603-00001

    I have a few of these, and although I haven't used any of them yet, I have great plans for them, and have seen projects using them.



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    Chris Savage

    Knight Designs
    324 West Main Street
    P.O. Box 97
    Montour Falls, NY 14865
    (607) 535-6777

    Business Page:·· http://www.knightdesigns.com
    Personal Page:··· http://www.lightlink.com/dream/chris
    ·
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