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OT- leds as sensors

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  • OT- leds as sensors

    Ok, sort of out of the blue, but today I wondered whether the new breed of led is also more sensitive as a sensor than those of the past. I once built a circuit that used an led as both a transmitter and a receiver. A few steps above the two tin cans and string- it worked as a sender of modulated light, then became the receiver instead of a photocell or phototransistor. At any rate I'm just wondering if anyone has played with this-
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    I'd wanted to monkey with it, but Near-IR receivers are so cheap it didn't seem worth the effort.

    The answer on sensitivity depends on whether the quantum efficiency for the direct-emission LEDs has improved drastically since then, as that's really going to be the only factor affecting the photon-to-electron conversion. While we've seen big improvements for the white LEDs, it bears repeating that they're actually a phosphor-based light, so you'd actually need to use the excitation frequency (usually around the UV) to get a voltage out of one. Best bet in this application is going to be Red, Green, Yellow, or Near-IR as there's no intermediate step. I've not actually tracked any of the trends in quantum efficiency, so I couldn't say whether there have been appreciable improvements.

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    • #3
      IR emitters sure have improved. I've got one for my night scope that "lights up" a target out to 300 yards. The IR emitter is driven to 850mw! The light is no bigger than those burglar-blinding lights you see advertised on TV.

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      • #4
        Originally posted by CCWKen View Post
        IR emitters sure have improved. I've got one for my night scope that "lights up" a target out to 300 yards. The IR emitter is driven to 850mw! The light is no bigger than those burglar-blinding lights you see advertised on TV.
        I would be interested in the brand of scope and illuminator. Night vision has advanced to the point where I might get one for less than the price of a nice used car.

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        • #5
          Originally posted by michigan doug View Post
          I would be interested in the brand of scope and illuminator. Night vision has advanced to the point where I might get one for less than the price of a nice used car.
          I've got the ATN X-Sight II 5x20. It comes with the IR illuminator. Besides night vision, it also works well during the day and takes video and snapshots. It has a RAV (Recoil Activated Video) mode you can set to record a video segment of before, at and after the shot. There's lots of videos on YT about the scope. The major drawback I see with it is weight. It gets heavy mighty fast so use with a x-pod or in a blind is suggested. I have it on a S&W AR15 and the whole rig tips the scales at 12.5 pounds! The scope alone is about 2.5 pounds but I run an external battery pack. (A required accessory if you're out for more than 1-2 hours.)

          I'd post a picture but it's not worth the effort anymore.

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