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Looking for IRED/photodiode pair: 4260nm. — Parallax Forums

Looking for IRED/photodiode pair: 4260nm.

Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
in General Discussion
I'm looking for an IRED/photodiode pair with a peak wavelength emitter/response of 4260nm. An identical IRED for sensing, instead of the photodiode, would also be acceptable. I'm planning to modulate the IRED, so the detector should have a moderately short response time.

I've been approached by a senior at the local high school, looking for a mentor and a senior project (a graduation requirement in Washington State). One idea I have is a from-the-ground-up CO2 sensor.

Any ideas/sources?

Thanks!
-Phil

Comments

  • jmgjmg Posts: 15,144
    Digikey shows AK9700A Emitters, with a peak of 4300nm ?
  • Tracy AllenTracy Allen Posts: 6,656
    Try Roithner LasertechnikGmbH, mid-ir_application_co2.pdf
    They sell the LEDs, both for CO2 and for compensation in a dual wavelength scheme.

    Here is another LED supplier.
    http://www.lasermonitoring.co.uk/IR LED's.html
    I don't know the company, but the page has some good advice.


    Here is a nice article
    https://www.analog.com/en/analog-dialogue/articles/complete-gas-sensor-circuit-using-nondispersive-infrared.html
    It uses a traditional white light through interference filters onto a differential thermopile. They have a nice presentation of the issues. The whole enchilada has its power-hungry lamp, filters and thermopile and really adds up in complexity and cost. Yes another exotic technique now becoming popular uses the photoacoustic response.

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    4300nm might work. Above 4260nm the water-vapor absorption coefficient starts to climb again, so 4300nm is not really the sweet spot for CO2 level sensing. Might require an rH sensor for compensation.

    Thanks,
    -Phil
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    Tracy,

    You're a fountainhead of knowledge, as usual. My main objective is to keep it as simple as possible for someone of high-school-level capabilities. My thought was to modulate the IRED and AC-couple the detector output to a receiver like the one I used for receiving radio stations with the Prop. I don't think an op-amp would even be necessary.

    I know that dual-channel NDIRs are the way to go for accuracy and longevity, but for a high school project, proof of principle with a single channel should be adequate. There's still plenty of neat physics to explore.

    Thanks!
    -Phil
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