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Discussion in 'General Electronics Discussion' started by davez, Aug 3, 2015.

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  1. davez


    Oct 11, 2014
    I tried hooking up an led directly to a 9v battery(hahaha)
    but what happened is it kinda switch color from red to dark orange then dies can someone give a good explanation why this happens
  2. Tha fios agaibh

    Tha fios agaibh

    Aug 11, 2014
    Too much power blew it up.
    A red led runs on about 2 volts and draws about 20ma.(depending on led)
    If you want to run it on a 9v battery, the current needs to be limited. If you add a resistor that drops the voltage difference you would get (form ohms law); 7volts divided by .02amps that equals 350ohms. So a 350ohm resistor would limit the current and cause 7volts to drop across it, leaving 2v for the led.
  3. Gryd3


    Jun 25, 2014
    I think the op was asking why it changed color as it died?

    I've noticed too, and if this is indeed the questions, I'm unsure myself and a little curious.
  4. davenn

    davenn Moderator

    Sep 5, 2009
    for the same reason my meat under the grill goes from red to brown to a charred black
    if subjected to too much "power" ;)
    Martaine2005 likes this.
  5. Martaine2005


    May 12, 2015
    I like the above posts. But the OP was why?
    I know it burnt out and too much current was applied.
    As Dave said, red meat to charred meat.
    But in the electronics world, the led needs a certain forward voltage to EMIT. (light up).
    And current too. If that current exceeds the operating parameters of the led, it will die.

    Think of an incanescent light bulb. A 240v light bulb will work great.
    Plug that same light bulb into 500v. It will work for a second but die out rather quickly. It will also change colour before dieing. The led also is a diode and only works ONE way. The 'bulb' works both ways.
    Over current and over voltage kills a semiconductor.

    davenn likes this.
  6. Robert Hill

    Robert Hill

    Mar 5, 2015
    My suggestion as to why it changed colour is that perhaps the plastic or resin or whatever encases the metal parts of the LED got burnt/melted as the inards of the diode got too hot and blew up. If you melt clear plastic it takes on a browny colour sometimes so maybe this is what is happening. Just a thought.
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