Medium IR (4,260nm) LED?

Discussion in 'The Projects Forum' started by wayneh, Feb 12, 2011.

  1. wayneh

    Thread Starter Expert

    Sep 9, 2010
    Anybody ever see an LED that emits at this wavelength (4.26µ)? I gather there are several sensor technologies - including consumer video cameras - but I haven't seen any LEDs that emit at this wavelength. If you're wondering, it's the wavelength at which CO2 absorbs and water doesn't, allowing you to detect CO2. I'm wondering if it's possible to build an LED-based capnometer = CO2 meter. "Real" capnometers are in the $3K range.
    GhoshM likes this.
  2. AlexR

    Well-Known Member

    Jan 16, 2008
    wayneh likes this.
  3. Adjuster

    Late Member

    Dec 26, 2010
    To the best of my knowledge, most consumer cameras use silicon photo-detectors. These may see into the near infra-red to about 1100nm, (that is, 1.1μm) but not much beyond that. I think that you will need to look for a special detector designed to give an adequate response at these long wavelengths.
  4. wayneh

    Thread Starter Expert

    Sep 9, 2010
    Yes, I think you're right. I haven't found a detector to use yet, but at first glance it looked like they're more available than the emitters, which I now have a great lead on.
  5. jpanhalt


    Jan 18, 2008
    I think you may find some inexpensive detectors in the new wave of non-invasive glucose monitors that are based on near and mid-infrared. Technical details are basically lacking in the free links I found, but given what they are detecting, the range should be about right for some of them. Your selectivity will, of course, depend on how monochromatic your source is, not your detector.

    None of these links is right on, but they may give you some ideas of places to look. In any event, a home glucose monitor will cost less then a bolometer for astronomy.

    http://www.growthconsulting.frost.c...BF773D86525714E003DB451/$File/TI Alert NA.htm

  6. wayneh

    Thread Starter Expert

    Sep 9, 2010