I need to use a IR sensor in a project and I would like for the system to actually tell me what the wavelength that is detected is. I can't seem to find any examples that do that. The closest thing I've found is color finding projects. That is almost what I want to do. I believe that equations exist for telling what the wavelength is by the voltage produced by the light sensitive diode used in the sensor but that it exists is as far as my knowledge goes on the matter.
Put on your thinking cap. The voltage already conveys the level of illumination.
Not so. If you want wavelength information, filters or a diffraction grating are required.
This sensor has IR filters for six wavelengths: https://www.sparkfun.com/products/14351
Thank you, I'll have to look into filters and diffraction gratings. I'm basically working on the design for a flame sensor for an environment with a lot of IR blackbody radiation from IR drying lamps. I need it to be able to tell the difference between the IR lamp radiation and fire.
The AS7263 spectral sensor linked above might be all you need.
So… I'd be interested to know how you will test this part and/or the final device that uses it. 
a7
There is free software and a spectrometer you can build with a certain type of old web camera.
Below is a starting point.
https://alternativeto.net/software/theremino-spectrometer/about/
Apparently many "flame detectors" work in the UV portion of the spectrum, because flames emit more UV than other indoor lighting...
See: https://www.crowcon.com/blog/what-is-a-flame-detector-and-how-does-it-work/
(I don't know if those work with all types of flames, though.)
the sort of far-infrared (heat) that you're trying to detect is outside the range of most normal electronics, BTW.
@westfw has a good point. If you are using this sort of IR drying lamp the dominant emission is in the range of .8 to 4 microns, with little to none in the UV.
Noncontact thermal sensors like the MLX90614 or MLX90640 sense IR around 10 microns, but depending on what sort of fire you anticipate, UV/Vis detectors and smoke detectors would probably be much more appropriate.
So the IR lamps we use peak at 1.2 microns. I took that to mean that it starts lower but I'll have to test that since the specs don't say. We basically make machines that dry paper in industrial printing presses. Fires in printing presses typically happen either from a page slipping out of the grippers that guide it through the machinery and falling under one of the IR lamps or from accumulated dust and powders combusting from inadequate cleaning of the equipment.
I'm thinking that I might just be able to point the IR sensors downward away from the lamps. IR radiation can be blocked by conductive materials so maybe shield it with aluminum foil or something.
On sensors and to answer your question @westfw, from my research it seems like a sensor that uses one UV sensor and one IR sensor and an and gate is what the industry uses for cases like mine. It basically only trips is there is a sudden change in the radiation and one that flickers. They call it a UV/IR flame sensor with the simple voting method. Now if only I knew how to do that.
The AND gate is a logical operation that can be done with a discrete chip that you buy, or with the smallest, simplest microprocessor.
What they mean is that fire output is activated if (IR sensor is activated) AND (UV sensor is activated).
You can do that with Arduino compatible sensors and just a few lines of Arduino code. The Arduino could then send a text message via SMS, an email via the web, sound an alarm, blink a light, etc.
Keep in mind that Arduino is a hobby and teaching tool. It is not intended for use in safety-critical applications or industrial settings!
So think of smoke detector.
Smoke happens before fire in many instances.
No, energy cannot be blocked. It can be reflected. The foil will absorb and re-radiate the IR at perhaps a different wavelength.
I considered that avenue and it might help though they likely have them in place already. I was thinking of adding a flame sensor as an added feature to the equipment we sell since the former of the two types of fires usually happens near or right under our dryers. The second type of fire is caused by a buildup of the powder they use for parts of the drying process. You're supposed to clean that stuff up, if it accumulates static electricity can cause it to explode with little to no smoke beforehand. Thats another reason I'm considering a combo UV/IR sensors because even though most of the radiation from fire is IR the initial blast from an explosion has a lot of UV light in it and UV sensors are good at detecting that. The flame sensor type I mentioned earlier is designed to trip when it sees both UV light as well as a sudden spike in IR radiation.
Yeah, I'll probably only use Arduino for the prototyping stage. I'm doing some research on the best SBCs to use. There are a surprisingly large number of good options. Depending on how much coding is required, I might use a respberry pi pico. If it gets too sophisticated I'll use something more powerful.
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Yeah, its true that arduinos aren't really meant for much real use but they can be an excellent starting point for a real project. I've found a few flame sensor projects, but they aren't very accurate which mostly the cheap sensor I'm using of course, but I'm trying to look into pass filters to narrow things down a bit to get fewer false positives.
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