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bryen
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how can i modulate a detected voltage signal from a light emitting diode(LED)?   

6 members have voted

  1. 1. how can i modulate a detected voltage signal from a light emitting diode(LED)?

    • LED as photovoltaic then amplified
      0
    • LED as photodetector then amplified
      0
    • LED modulator circuit
      0
    • light-induced LED voltage circuit then amplified
      3
    • LED optocoupler
      1
    • LED link communicator
      0
    • LED as photodetector
      1
    • photovoltaic characteristics of LED
      1


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Hi Bryen,
Welcome to our forum.
I've tried it. A LED makes a very inefficient photodetector. With an extremely bright light up close or light from a similar LED up close, they produce a little more than 1 volt with hardly any current. They also conduct hardly any current.
Why not use an efficient photo-transistor or photo-cell, that's what they are designed for.

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First of all could some moderator move this to either the theory or design ideas section as LEDs are not high voltage.

Secondly, a poll is not for this question is totally unnecessary.

Anyway Bryan, what sort of data are you transmitting, and by what means (optical fibre or free air)?

I have had very good results using LEDs, they tend to be most efficient at the wavelength they emit, I measured about 3V from a 400nm near UV LED when it was placed near to a black light florescent tube. With a weaker light source the voltage would be less but you could connect it to an amplifier to give a suitable voltage output.

Photo-transistors provide more gain than photo-diodes but they're slower to, I would advise using a purpose built photo-diode rather than an LED unless you want to detect a specific wavelength only.

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  • 2 weeks later...

audioguru:
Hi Bryen,
Welcome to our forum.
I've tried it. A LED makes a very inefficient photodetector. With an extremely bright light up close or light from a similar LED up close, they produce a little more than 1 volt with hardly any current. They also conduct hardly any current.
Why not use an efficient photo-transistor or photo-cell, that's what they are designed for.
------------------------------------
to overcome the insensitivity you could use a high-speed opamp
on the other hand yes youre right why not use what youvemention or infrared reciever,transmitter leds costing no more than a regular led

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  • 2 weeks later...

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