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Thread: LED's and Resistors Guide

  1. #31
    Fresh Paint Nameless's Avatar
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    Default Re: LED's and Resistors Guide

    Quote Originally Posted by calumc View Post
    I wouldnt worry at all about that, it would come into play only if you had a large amount of leds. If I was doing it I'd just wire them all up to a 47ohm resistor on the 5v line
    Would that work on a 5v line? 3.0+3.0+2.6+2.6=11.2V

    Now I realize that just wouldn't work in series, and that it probably would if I just hooked them up in parallel, but then I'm sticking resistors on each LED.

    I just want to make sure I'm doing my math right mainly, like I said, because I'm way out of practice.
    'I weep for noone, and noone weeps for me.'

  2. #32
    t3h f3cKiN 33Ji7 calumc's Avatar
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    Default Re: LED's and Resistors Guide

    A quick diagram for you:
    Quote Originally Posted by Crazy Buddhist View Post
    I'm starting to worry that I may become genuinely funny at some point. Then there will be no hope.

  3. #33
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    Default Re: LED's and Resistors Guide

    Quote Originally Posted by calumc View Post
    A quick diagram for you:
    BAH! I can't see it from work, damn Army network, so I'll check it out when I get home. Thanks!

    *scribble scribble* Yea... Gotta make sure I stop and get my resistor on the way home.
    'I weep for noone, and noone weeps for me.'

  4. #34
    SOB Fettler xmastree's Avatar
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    Default Re: LED's and Resistors Guide

    Quote Originally Posted by Nameless View Post
    Edit: After thinking about this, since two of my LEDs require different current I think I need to run my Red LED's in Series and my Yellow LED's in Series, and then run the two different colors in Parallel to the 12V power source, since I don't think 5V or 7V can push this. Is that right?
    That's what I would do.

    As for the equation, for the red ones:

    2x Red LED's @ 2.6VDC/28mA

    So the total volt drop across the LED's is 5.2V, leaving 6.8V (12 - 5.2) across the resistor.
    R=V/I so 6.8/.028 = 242.

    So 240 ohms is the nearest one there.


    2x Yellow LED's @ 3.0VDC/20mA

    6V/.02A = 300 ohms

    Don't try calumc's suggestion. Sorry, but putting LED's of different voltages in parallel will never work. The red ones will clamp the voltage to 2.6V, so the yellow ones won't conduct at all.

    Quote Originally Posted by aintnothang View Post
    Think of a way to simulate a real bullet hole, like shooting it.

  5. #35
    Spam Sniper SgtM's Avatar
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    Default Re: LED's and Resistors Guide

    Quote Originally Posted by Nameless View Post
    BAH! I can't see it from work, damn Army network, so I'll check it out when I get home. Thanks!

    *scribble scribble* Yea... Gotta make sure I stop and get my resistor on the way home.
    Quick word of advice for you.. don't buy Radio Shack stuff. Nothing but crap from them. Check out www.lsdiodes.com. Great stuff.

  6. #36
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    Default Re: LED's and Resistors Guide

    Quote Originally Posted by xmastree View Post
    That's what I would do.

    As for the equation, for the red ones:

    2x Red LED's @ 2.6VDC/28mA

    So the total volt drop across the LED's is 5.2V, leaving 6.8V (12 - 5.2) across the resistor.
    R=V/I so 6.8/.028 = 242.

    So 240 ohms is the nearest one there.


    2x Yellow LED's @ 3.0VDC/20mA

    6V/.02A = 300 ohms

    Don't try calumc's suggestion. Sorry, but putting LED's of different voltages in parallel will never work. The red ones will clamp the voltage to 2.6V, so the yellow ones won't conduct at all.
    Much thanks! That's what I was thinking, but it never hurts to ask just to be sure.
    'I weep for noone, and noone weeps for me.'

  7. #37
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    Default Re: LED's and Resistors Guide

    Quote Originally Posted by SgtM View Post
    Quick word of advice for you.. don't buy Radio Shack stuff. Nothing but crap from them. Check out www.lsdiodes.com. Great stuff.
    Nice site. Any reason Radio Shack LEDs are crap in particular? I already got the ones I'm using in this project from there, but I'm sure I can use the site you posted in the future because they seem pretty sharp.

    I was just wondering if you had some experience you'd like to relay about Radio Shack LEDs or stuff in general, as it sounds like you've had a bad experience or two.
    'I weep for noone, and noone weeps for me.'

  8. #38
    Spam Sniper SgtM's Avatar
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    Default Re: LED's and Resistors Guide

    Just more expensive for the same thing. $4 for 1 LED vs .45 for 1 LED and freebies. I'll order from lsdiodes any day of the week.

  9. #39
    Modders block rendermandan's Avatar
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    Default Re: LED's and Resistors Guide

    Quote Originally Posted by SgtM View Post
    Just more expensive for the same thing. $4 for 1 LED vs .45 for 1 LED and freebies. I'll order from lsdiodes any day of the week.
    Ditto! I have an order in with them right now!

  10. #40
    SOB Fettler xmastree's Avatar
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    Default Re: LED's and Resistors Guide

    Quote Originally Posted by SgtM View Post
    Radio Shack stuff. Nothing but crap from them.
    Quote Originally Posted by Nameless View Post
    Any reason Radio Shack LEDs are crap in particular?
    Quote Originally Posted by SgtM View Post
    Just more expensive for the same thing.
    So not really crap then, just over priced?

    Quote Originally Posted by aintnothang View Post
    Think of a way to simulate a real bullet hole, like shooting it.

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