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How do you make a LED to short itself?

Discussion in 'Electronic Basics' started by Mr. Man-wai Chang, Jul 5, 2013.

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  1. ;)

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  2. I just want to know whether it could be done. Everyone said it's safer
    to assume that LED would short itself.

    Now, how could we prove that LED would really do it using experiments?

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  3. Daniel Pitts

    Daniel Pitts Guest

    Yes, put an amp meter in line with the LED and start raising the voltage
    across. You'll see the amperage raise rapidly as you approach the
    voltage drop of the diode, indicating it acts like a short until it
    burns out.

    Another way to do this is to put a resistor and LED in series with a
    variable voltage source. Measure the voltage across the Resistor as you
    increase the voltage of the source. After you reach the rated voltage
    of the LED, you'll see the rest of the going across the resistor, no
    matter how much more voltage you add (until you burn them both out, of
    course).
     
  4. Jasen Betts

    Jasen Betts Guest

    I did that once, 100mA at 5V about 1 hour on a fairly ordinary red LED,
    then it failed open. which if the semiconductor junctions is
    responsible for 2V of the drop a inticates about 33 ohms ohmic
    resistance.
     
  5. whit3rd

    whit3rd Guest

    If there is a need for a diode to fail in short circuit, there ARE some
    surge-protection diodes that do that (Zener types).
    As for LEDs, the failure modes can include low light output
    or fused (open circuit) bond wires. Or, presumably, short circuit.

    But, I'm not aware of any LED types that can be expected to become short
    circuits under any reasonable conditions. If you really WANT
    the LED to be replaced with a short, use a relay.
     
  6. Just wanna prove that LED could short itself under the right
    conditions.... :)

    --
    @[email protected] Remain silent. Nothing from soldiers and magicians is real!
    / v \ Simplicity is Beauty! May the Force and farces be with you!
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  7. Daniel Pitts

    Daniel Pitts Guest

    Did you read my earlier reply? It answers exactly why it should be
    *treated* as a short, even if it doesn't fail as a short.
     
  8. That's why I am interested in devising an experiment to make it
    happen... :)

    What all of you said is: do NOT treat a diode as a resistor or a fuse.

    --
    @[email protected] Remain silent. Nothing from soldiers and magicians is real!
    / v \ Simplicity is Beauty! May the Force and farces be with you!
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  9. Daniel Pitts

    Daniel Pitts Guest

    And I devised such an experiment. Did you try it? What did you observe?
     
  10. Not yet... busy with something else. Relevant messages copied. :)

    --
    @[email protected] Remain silent. Nothing from soldiers and magicians is real!
    / v \ Simplicity is Beauty! May the Force and farces be with you!
    /( _ )\ (Fedora 19 i686) Linux 3.9.9-301.fc19.i686
    ^ ^ 20:45:01 up 19 min 0 users load average: 0.00 0.03 0.08
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  11. Daniel Pitts

    Daniel Pitts Guest

    In other words, you've run out of steam to troll on the topic?

    You've been obsessed with this since it was first mentioned, and once
    someone gives you a 30 minute experiment to try, suddenly you've got no
    time?
     
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