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Thread: Demystifying LEDs.

  1. #11
    Overclocked Guttenaffe's Avatar
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    Default Re: Demystifying LEDs.

    jdbnsn: careful googling about LEDs over 1/2 the stuff I've seen on LEDs is flat out wrong. This article is 100% correct I have a few posts with this same info in it on this board.

    xmastree:You stole my story I been writing a larger and longer article on LEDs on and off for a bit, though I will still finish it I got some cool animations and what not I made for it. I've been too busy with school and work to finish it. :/

    I'd like to add the following:
    LED's arenít the same as normal diodes as their reverse breakdown voltage is WAY lower (which can cause problems though we electronic engineers normally just put a Si, or Ge if need be, diode in series to prevent damage to a LED.)
    -Gutte
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  2. #12
    SOB Fettler xmastree's Avatar
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    Default Re: Demystifying LEDs.

    Quote Originally Posted by Guttenaffe
    jdbnsn: careful googling about LEDs over 1/2 the stuff I've seen on LEDs is flat out wrong. This article is 100% correct


    xmastree:You stole my story I been writing a larger and longer article on LEDs on and off for a bit, though I will still finish it
    Great. More information is always good, so long as it's not conflicting. Since you agree 100% with what i wrote, I guess that won't be a problem. I'm interested to see your animations though...

    I'd like to add the following:
    LED's aren’t the same as normal diodes as their reverse breakdown voltage is WAY lower (which can cause problems though we electronic engineers normally just put a Si, or Ge if need be, diode in series to prevent damage to a LED.)
    True, they aren't as tough as rectifier diodes, but they're not meant to be either. As for putting a diode in series, isn't it better to put one in inverse parallel? The resistor will still control the current and you won't get more than .6V across the LED in reverse.

  3. #13
    SOB Fettler xmastree's Avatar
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    Default Re: Demystifying LEDs.

    There's a good write-up on wikipedia, but it's a bit too technical for most users, as it goes on about which chemicals produce which light etc. I concentrated on their use, since that's what concerns us modders more than the fact that the newest method used to produce white light LEDs is based on homoepitaxially grown zinc selenide (ZnSe) on a ZnSe substrate which simultaneously emits blue light from its active region and yellow light from the substrate.

    Erm, yeah... right...

    The best bit of info there, is this line:
    "Because the voltage versus current characteristics of an LED are much like any diode, they can be destroyed by connecting them to a voltage source higher than their turn-on voltage."

  4. #14
    Fox Furry crenn's Avatar
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    Default Re: Demystifying LEDs.

    Hmmm... you should also mention there are some very high powered LEDs and also ones which can take upto 6V due to the fact they have a small IC in them and 3 coloured LED chips.

  5. #15
    Overclocked Guttenaffe's Avatar
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    Default Re: Demystifying LEDs.

    crenn, there are LED "bulbs" that require 3A to light and 5A for max brightness. There are all kinds of LEDs out there. This was just an overview of "general" leds.
    -Gutte
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    Some parts are missing.

  6. #16
    Fox Furry crenn's Avatar
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    Default Re: Demystifying LEDs.

    True, very true. There are a lot of different types of LEDs, I'm not denying it, but most of the time, the brightness is dependant on the current going through it.

  7. #17
    SOB Fettler xmastree's Avatar
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    Default Re: Demystifying LEDs.

    Yep.

    This wasn't meant to be an exhaustive article covering every available option. It was mainly meant to cover 'standard' types which most of us will use for our mods. Typically, running 10-20mA LEDs from a 12V supply.
    Covering the more specialised types would probably make it more confusing so I didn't go there.

    I mainly wanted to help people understand how an LED needs a certain current rather than a voltage, and how to achieve that. Once you understand that concept (which I admit, can be difficult to grasp) the rest is easy.

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