Light wavelength meter recommendations ?

[TheDefpom]

Hi All,
It has occurred to me that I do not have anything that can measure the wavelengths of light being emitted by items such as LED's etc.

This is mainly as I have some unknown wavelength invisible light LED (probably some version of IR) which I need to replace, being able to measure the wavelengths of the light coming out would be perfect.

Does anyone know of anything (very cheap) that can give a wavelength measurement of a light source (I'm less concerned about power, but that could be handy too).

I've seen some very cheap items on Ebay but I don't really think they are what I want, as it seems to only give which block the wavelength is (850nm, or 980nm etc), I want more precision than that, unless you think this doesn't really matter.

I think my budget would be in the region of less than US$200. it isn't something I would use often, just something to have for those rare times I need it.

[tautech]

There's a few spectrometers on Aliexpress but maybe outside your budget, however while doing a quick look around it seems there's iPhone apps that delve into this territory.
Just one:
https://spectrumgenius.com/website/app

[TheDefpom]

A couple of years ago (when my house was flooded and we were living in the motorhome/garage) I had purchased a tester for window tint, it had various measurements on it and I'm pretty sure one was of IR transmittance/wavelength, and of course now I cannot find it.

[awallin]

If your into DIY then try DVD disc as grating, web-cam as sensor?
https://publiclab.org/system/images/photos/000/026/339/original/DSLR_spectrometer.pdf

[james_s]

You can do it with nothing more than a decent quality diffraction grating of known pitch provided the light source is bright enough that you can mask it into something resembling a point source and project it through the grating onto a flat surface. I remember doing that in highschool and using a meter stick to measure the wavelength of a HeNe laser.

[jpanhalt]

Your choices for near IR wavelength LED's are limited. 

I suggest determining the voltage and current used/needed and buying one IR LED that fits those criteria of each available wavelength.  You will probably find that wavelength does not matter and you have solved the problem.  If wavelength does matter, you will also have solved the replacement problem for a lot less than $200.