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Need idea for testing Leds

Discussion in 'LEDs and Optoelectronics' started by nicomey2003, Mar 5, 2010.

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  1. nicomey2003


    Mar 5, 2010

    Can anyone tell me how can I test that a certain LED (connected at a certain PORT pin - as output) is broken ?

    Thanks in advance.
  2. Mitchekj


    Jan 24, 2010
    If you have a multimeter w/ a diode checker, you may be able to get it to light up very dimly by forward biasing it in that mode (touching the black lead to the cathode and the red lead to the anode.) Other than that, reading resistance may work. It should be a lower resistance when forward biased, and a near open when reverse biased (assuming the LED has no internal ESD protection diode.) Exact numbers will vary depending on the LED.

    If all else fails, try applying a volt or two to it? Don't go any higher though, or else it will kill it. What type of LED are we talking about here?
  3. neon


    Oct 21, 2006
    A: i don't think a meter is good to light a LED not enough voltage my is 1.25 volts out. LED needs at least 1.8volts somem 5 volts Is you know the polarity of the led try to light it up with an external source or add a diode in seires to force polarity your way.
  4. Mitchekj


    Jan 24, 2010
    Not sure about his particular LEDs, but a decent meter will very dimly light any LED we use here at work (Nichia, Osram, Avago, Lumileds, etc.) when used on diode checker mode, the perfect level to look at the individual die to see if any are out.
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