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Electronics LED voltage and Amps?

Discussion in 'Modding' started by Dragonite, 7 Apr 2011.

  1. Dragonite

    Dragonite Minimodder

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    I have a number of different LED:s in my storage box. The problem is that I for some unexplainable reason that I can't remember have throw away the original bag where the voltage and amp are posted. So now I have some small difficulties to know what resistance I should use so that I don't burn the LED:s So is there anyway to determine what volt and amp they are on a voltmeter or something? Amps would be the easiest one but it would be hard to determine voltage I could be wrong though. So anyone that's better on electronics that could answer this?
     
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  2. mvagusta

    mvagusta Did a skid that went for two weeks.

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    I dunno if there is a way to reliably do that :confused:

    You can give them 1.6v, and slowly turn up the voltage if neccessary until the led turns just begins to turn on. An led's recommended voltage is usually ~.15v above the minimum.

    The current however is the hard part... you can give a low brightness led 20ma more than it's supposed to, and it will seem to be very happy, shining brightly... but then it dies a hour or so later, as it wasn't rated for that much current :waah:
     
  3. D-Mon Taurus

    D-Mon Taurus What's a Dremel?

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    I also think i highly depends are the kind of LEDs using.
    If i read correctly and the knowledgeable may correct me if i am wrong. Cause like you i am also new on this and trying to learn as much as possible.
    Most LEDs have a voltage around ~3V depending on color, the amps go from 20mA up to 30mA depending on the kind of LED using.
    That is forward voltage and forward current. And if i am not wrong i also read youo wanted to use dual color LEDs making it slightly more difficult i guess.

    Using the idea Mwagusta gave by starting with 1.5V looking at the minimum and add the ~1.5V to find the forward voltage seems to be a good way to start.
     
  4. D-Mon Taurus

    D-Mon Taurus What's a Dremel?

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    Found this solutions right after i wrote the other comment hope it helps you in some way.

    And to correct myself a little on the above comment. The voltage is depending on the LEDs as well. Old LEDs use about 1.5V-2,2V approx and the new ones can handle a bigger Voltage
     
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  5. Tealc

    Tealc What's a Dremel?

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    This is what I have written down and is good as an indicator when calculating resistance required:-

    Red 1.8-1.9v
    Yellow 1.8-2.1v
    Orange 1.8-2.2v
    Green 2.8-3.2v
    Purple 3.2-3.6v
    Blue 3.2-3.8v
    White 3.2-3.8v

    These are based on Ultra bright 20mA LEDs. Standard or Indicator LEDs will probably draw less current.
     
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  6. mvagusta

    mvagusta Did a skid that went for two weeks.

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    +1

    Much easier to find the correct voltage this way, no variable regulated psu necessary :duh:

    The only note i'd make to this is that many new leds need 50ma or more to deliver full brightness, which is wear it becomes risky, as low power leds won't last long at 50ma :miffed:
    I guess if you don't go past 20ma for small leds, and don't go over 30ma for 5mm leds, then they should be fine.

    Resistor calculator clicky: http://led.linear1.org/led.wiz
     

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