using a UV LED as a detector

[Peter Lynch]

The plan is to build some sort of meter for measuring the UV light
intensity from the sun. Now I'm not talking about UV-indexes or any sort
of medical/lab-quality measurements, just a hobby level goofing around
project.
I know that a normal LED can be used "backwards" as a detector, so
one option I'm considering is to use an ultraviolet LED, with emmissions
around 395 nm as the detector. I realise it will probably detect
normal light too, but hopefuly with a bit of experimentation using LEDs
of different colours I can take this into account.

Has anyone got any experience of this kind of thing and in particular
will a uv LED actually detect at long-uv wavelengths?

Pete

...........................................................................
.. never trust a man who, when left alone ...... Pete Lynch .
.. in a room with a tea cosy ...... Marlow, England .
.. doesn't try it on (Billy Connolly) .....................................

 

[AZ Nomad]

The plan is to build some sort of meter for measuring the UV light
intensity from the sun. Now I'm not talking about UV-indexes or any sort
of medical/lab-quality measurements, just a hobby level goofing around
project.
I know that a normal LED can be used "backwards" as a detector, so
one option I'm considering is to use an ultraviolet LED, with emmissions
around 395 nm as the detector. I realise it will probably detect
normal light too, but hopefuly with a bit of experimentation using LEDs
of different colours I can take this into account.

Has anyone got any experience of this kind of thing and in particular
will a uv LED actually detect at long-uv wavelengths?

Why don't you just use a proper sensor?
They can be had for around $20:

http://www.mouser.com/search/Produc...O18virtualkey63510000virtualkey718-PC1-2-TO18

 

[John Popelish]

The plan is to build some sort of meter for measuring the UV light
intensity from the sun. Now I'm not talking about UV-indexes or any sort
of medical/lab-quality measurements, just a hobby level goofing around
project.
I know that a normal LED can be used "backwards" as a detector, so
one option I'm considering is to use an ultraviolet LED, with emmissions
around 395 nm as the detector. I realise it will probably detect
normal light too, but hopefuly with a bit of experimentation using LEDs
of different colours I can take this into account.

Has anyone got any experience of this kind of thing and in particular
will a uv LED actually detect at long-uv wavelengths?

I experimented a bit with LEDs as detectors, and found that,
generally, only wavelengths shorter than they emit are
detected. You might have to use a blue LED to detect long
wave UV. The problems you might have include low detection
efficiency, and packaging material that absorbs UV.

 

[Al]

The plan is to build some sort of meter for measuring the UV light
intensity from the sun. Now I'm not talking about UV-indexes or any sort
of medical/lab-quality measurements, just a hobby level goofing around
project.
I know that a normal LED can be used "backwards" as a detector, so
one option I'm considering is to use an ultraviolet LED, with emmissions
around 395 nm as the detector. I realise it will probably detect
normal light too, but hopefuly with a bit of experimentation using LEDs
of different colours I can take this into account.

Has anyone got any experience of this kind of thing and in particular
will a uv LED actually detect at long-uv wavelengths?

Pete

Check out:

http://www.electronicdesign.com/Articles/Index.cfm?AD=1&ArticleID=15980

and

http://www.iscid.org/forrest-mims.php

Forrest Mims is the guru on the subject.

Al

 

[Peter Lynch]

Why don't you just use a proper sensor?
They can be had for around $20:

http://www.mouser.com/search/Produc...O18virtualkey63510000virtualkey718-PC1-2-TO18

..... and, sadly, another $33 shipping to --------+
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...................................................|.......................
.. never trust a man who, when left alone ...... V .
.. in a room with a tea cosy ...... Marlow, England .
.. doesn't try it on (Billy Connolly) .....................................

However, John holds out some hope that a blue/UV LED will detect at
shorter wavelengths. I guess I'll pick up a variety of LEDs and do a
bit of playing - see what I come up with.

As I said, it's only a hobby project. If nothing comes of it at least
I'll have learned something and had fun in the process

Pete

 

[John Popelish]

However, John holds out some hope that a blue/UV LED will detect at
shorter wavelengths. I guess I'll pick up a variety of LEDs and do a
bit of playing - see what I come up with.

As I said, it's only a hobby project. If nothing comes of it at least
I'll have learned something and had fun in the process

I think this short wave blue (428 nm) would be an
interesting candidate:
http://www.avagotech.com/assets/downloadDocument.do?id=2549
They should be responsive to 380 nm.

 

[Tom2000]

Check out:

http://www.electronicdesign.com/Articles/Index.cfm?AD=1&ArticleID=15980

and

http://www.iscid.org/forrest-mims.php

Forrest Mims is the guru on the subject.

Al

WOW!

The EDN article is an eye opener. I knew that LEDs could be used as
detectors, but had no idea that they were so selective. That opens
the door to all sorts of cheap amateur colorimetry experiments.

Thanks, Al.

Tom

 

[John Popelish]

The plan is to build some sort of meter for measuring the UV light
intensity from the sun. Now I'm not talking about UV-indexes or any sort
of medical/lab-quality measurements, just a hobby level goofing around
project.
I know that a normal LED can be used "backwards" as a detector, so
one option I'm considering is to use an ultraviolet LED, with emmissions
around 395 nm as the detector. I realise it will probably detect
normal light too, but hopefuly with a bit of experimentation using LEDs
of different colours I can take this into account.

Has anyone got any experience of this kind of thing and in particular
will a uv LED actually detect at long-uv wavelengths?

I ran across some related links, and discovered that Digikey
sells a a couple small GaN UV detectors.

http://www.cinstrum.unam.mx/~martha.rosete/Leds.htm
http://nina.ecse.rpi.edu/shur/Tutorial/GaNtutorial3/index.htm
http://media.digikey.com/pdf/Data Sheets/Photonic Detetectors Inc PDFs/PDU-G106B-SM.pdf
http://www.advancedphotonix.com/ap_products/pdfs/PDU-G105A-SM.pdf