Blue light sensor with wavelenght 400-500nm

Dear all,
i am working on a project with the aim to measure a blue light from different devices.
I am searching a sensor for arduino able to measure Blue light between an interval of wavelenght of 400-500nm. Actually i found different sensor but their range are too much larger (400-700 or something similar). Do you know which is the best sensor for my range (400-500)?

Another question, i am searching different blue light source (always in the 400-500 range), do you know if exist some device that is able to generate it? Thanks a lot!

There are several RGB sensors out there. The B part of that sensor may be just what you need (just ignore the other two channels).

I am not sure that a RGB sensor should work. I prefer (if exist) a sensor similar to this:

But with range 400-500nm.

I am not sure that a RGB sensor should work.

Did you try or do any research? Anything in the data sheet that suggest it's not useful for you?

The blue channel of the TCS34725 is pretty much covering the 400-500 nm range with very little above the 500 nm. Pretty constant sensitivity over that range with sharp cut-offs on both sides. Looks exactly like what you're looking for.

The S9702 is another strong contender for your 400-500 nm requirement.

You should also have a look at the BH1749NUC sensor. The blue channel is also very nicely in the 400-500 nm band.

Thanks for you reply, probably i will use the TCS34725.
Searching on the web, i see that all the exist code report as out the value of R G B variable.

How can i convert this value into nanometers? Thanks

Just ignore the R and G value. The B is what you’re after.
And there’s no “conversion to nanometers” of course. You get the intensity of the light in the 400-500 nm range. How to convert to brightness, check the data sheet on what values it produces and the meaning of those numbers.

Ok but what i want to measure is the exactly nanometer detected by the sensor. I understood that if i switch off the R and G, i retrieve the B wavelenght (400-500nm) but what i want to measure is a specific value for the range (for example 423nm).

The sensor you mentioned in #2 is a brightness sensor, what you're now asking for sounds more like a spectroscope, that's a VERY different thing, and I'm not aware of any such device in existence for an Arduino. The AS7265x sensor array is the closest to a spectroscope but still far from nanometer resolution (it's a pretty sweet set of sensors, trying to turn one of these into a PAR sensor).

Yes probably is what i am searching. So actually there isn't a solution? For a raspberry? Thanks for your support

Not that I'm aware of.

I have seen some DIY projects using an old CD as diffractor, if you could manage to project that onto a CCD (camera) something like a RPi may be able to read the actual spectrum.

There must be commercial spectroscopes out there as well, used them in the lab myself a few decades ago. Make sure you have a generous budget if you want to go that route.

Cheap, DIY spectrometer

i am searching different blue light source (always in the 400-500 range)

Use a blue LED.