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Thread: Soldering Problem

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  1. Default  
    #21
    Join Date
    Feb 2007
    Posts
    48
    Okay, so here's what we know about your LEDs:
    Forward Current - 20mA
    Forward Voltage - 2.2

    If you use a 9v power supply or battery and the LEDs are dropping 2.2v of that, then it means we need the resistor to drop 6.8v (9-2.2). We now know the voltage across the resistor and the current going through it (20ma or .02 amps, same as the LEDs), so we can use Ohm's law.

    6.8v / .02A = 340 ohms

    The next-highest standard value resistor is 390 ohms, so that's what you'd want to use (get 1/4 watt; 1/8 watt isn't big enough).
     

  2. Default  
    #22
    Join Date
    Feb 2007
    Posts
    48
    BTW: technically you could power your 8 LEDs with fewer resistors, but this way you can have as few or as many LED/resistor pairs as you want without having to recalculate anything.
     

  3. Default  
    #23
    Join Date
    Nov 2003
    Location
    Davison, Michigan
    Posts
    1,751
    You could buy a power supply from minispotlight, that way you aren't draining batteries. It seems to me they were like $15.00 or so. That just covers your source though, you still need them resistors.
    Jared Layman
     

  4. Default  
    #24
    Join Date
    Sep 2007
    Location
    Roanoke, VA.
    Posts
    318



    Ha! Who needs night classes when I have you guys, eh?

    Now that I've created something that works, I can start on the real thing.
     

  5. Default  
    #25
    Join Date
    Nov 2003
    Location
    Cedar Rapids, Iowa
    Posts
    396
    congrats, and good work!
    -------------------------------
    http://www.fx13studios.com
     

  6. Default  
    #26
    Join Date
    Aug 2003
    Location
    Alpine, California
    Posts
    509
    By George, I think he's got it.
     

  7. Default  
    #27
    Join Date
    Feb 2007
    Posts
    48
    It's alive!
     

  8. Default  
    #28
    Join Date
    Sep 2007
    Location
    Roanoke, VA.
    Posts
    318
    O' Christmas tree, O' Christmas tree....



    Almost done with my prop.
     

  9. Default  
    #29
    Join Date
    Feb 2007
    Posts
    48
    Nice work. I can't wait to see your prop.
     

  10. Default  
    #30
    Join Date
    Dec 2007
    Posts
    164
    Thats awesome man it looks just like a real workbench with real tools! sweet prop!
    Nate Mitchell|creative consultant
    [n8 creative studios]
     

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