I wanted to buy a bunch of UV LEDs by Internet. Some sellers on ebay offer items of 2000~3000 mcd (millicandela) while some others offer 400 mcd. It's a big difference. (The candela is a unit designed for visible light, but UV is invisible). Which one is more reliable in saying the truth? So, I decided to measure the UV output of a sample of UV LEDs by myself.
Looking for information I found the following post:http://www.thenakedscientists.com/forum/index.php?topic=20305
A man wanted to help his son to find out a way to measure UV from a CFL, what is in some way the same thing that I plan to do (respect to the LEDs).
After reading this, I got in contact with Techmind, a contributor in that thread. Summarizing, he has asked me two questions:
* if I need very deep UV.
* what do I need the LEDs for.
(Now I decided to post here the subject just in case some others can take advantage of this information as I did with the thread before mentioned.
Of course, this is a project of my own, so I'm not in the idea of using expensive measuring intruments out of my reach).
Why do I want to measure UV? As I said, I would like to buy some LEDs based on their [UV output/price] rate. I'm pretty sure that the cheapests could work well for my project, but I want the 'optimum' ones. It has become more a challenge than any other thing.
And what project for? The project is to make an ozone generator, not very big. Something small enough to get into a PC power source box. I must say that I have made already one with an UV 'fluorescent' lamp, but the lamp crashed after short time because of its fragility. So, I decided to move myself to the LED grounds.
I don't need much ozone neither deep UV light, just 'close' UV light enough to produce ozone when a flow of air is passing through the beam.
So, I want to buy a bunch of UV LEDs from Internet (in the shops of my town they are much more expensive), but I want to be sure that I'm buying the right thing, I don't want to be conned thinking that I'm buying UV LEDs just because I "see" violet light getting out of them. The seller was unable to provide me a datasheet of the LEDs, but he has sent to me a couple of free LEDs to make my own checks.
Based on the materials I can use at home, I have thought the next experiment to "measure" (even relatively) the UV outputs:
* to open one tube edge of one CFL that got out of service.
* to put the LED inside the CFL tube pointing the beam outside the glass wall.
* to light the LED on.
* to take a picture of the illuminated point (from outside) in a dark room. I plan to use a DSLR camera with a tripod.
* to repeat with the other LED in the same conditions.
* to compare both pictures in a Photoshop type software.
What do you think? Will it work? At least, will I be able to check that the LEDs are yielding UV light? Should I diffract the light with a CD/DVD before take the photos?
How can I avoid the violet (visible) light to get to the lamp (to be sure that I only photograph the white light produced by the UV light)?.
Thank you for any help and/or information. Comments and suggestions are also wellcome.