Looking for IRED/photodiode pair: 4260nm.

Phil Pilgrim (PhiPi)

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

jmg

Digikey shows AK9700A Emitters, with a peak of 4300nm ?

Tracy Allen

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)

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)

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