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Resistors for IR LED's not working?

Discussion in 'LEDs and Optoelectronics' started by Bowman, Jun 6, 2018.

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  1. Audioguru

    Audioguru

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    Sep 24, 2016
    Your IR LEDs are burned out because:
    1) They show a forward voltage of infinity on your diode test.
    2) Their current limiting resistor has no current in it.
     
  2. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    Or one or both of them are connected backwards.

    Bob
     
  3. Audioguru

    Audioguru

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    Sep 24, 2016
    Maybe the LEDs are not IR LEDs. The LEDs are in a clear case so their color could be white or blue and have a forward voltage too high for the multimeter to measure or too high for two in series to light from only a 5V supply.
     
  4. Bowman

    Bowman

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    Feb 1, 2017
    Righty, i have figured what was done wrong.

    I assumed the clear LED's would be the IR LED's, and the dark tinted ones would be the phototransistors, since the tint is supposed to block all visible light except for IR wavelengths. (So i read)

    But with these ones this is not the case, so my bad, these clear ones are in fact the phototransistors. The tinted ones are the IR Emitters oddly.

    Found out by messaging the seller from which i got them and it was clarified:

    So yeah my bad :D It was late :rolleyes: Wonder if i can still use them after this?
     
    Last edited: Jun 7, 2018
  5. Audioguru

    Audioguru

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    Sep 24, 2016
    Yes, a mistake was made about the IR LEDs or photo transistors. I am glad you didn't mistake them for candy and ate them.:)
     
  6. Bowman

    Bowman

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    Feb 1, 2017
    Haha yeah, i was pretty tired when i first put this together, but i doubt i would make that mistake. ;)
     
  7. davenn

    davenn Moderator

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    Sep 5, 2009
    actually, not oddly ... it is pretty much ALWAYS the case
     
  8. Bowman

    Bowman

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    Feb 1, 2017
    Well then if it is always the case then how come i have 2 bags of 850nm and 940nm IR LED's that are clear.

    Also my CCTV camera outside has built into it 8 or so clear 850nm IR LED's for its night vision that are clear...

    These look like any other LED until you turn them on, appearing red to the naked eye that's a very noticeable glow in the dark, whereas 940nm is almost unnoticeable even in darkness as its on the edge of the visible spectrum and depending of their intensity if you will see any glow or not.
     
    Last edited: Jun 8, 2018
  9. Bowman

    Bowman

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    Feb 1, 2017
    Well after this i have managed to complete the project, which was a chronograph to measure the FPS of my Airsoft RIF's. it works pretty well!

    Thanks for the troubleshooting suggestions peeps despite it being a mistake on my behalf.
     
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