I found this quite interesting:
http://www.edn.com/index.asp?lay...
If you don't have an available ADC for an LDR this is an option. Anyone have any good ideas in what applications this might be useful?
LED as light sensor
Author
Message
Level: Raving Lunatic
Joined: Fri. Jun 11, 2004
Posts: 2405 View posts
Location: Vilanova (Barcelona)
Backlight control/regulation, Contrast control regulation, heliostat aiming, light control/dimmer, etc.
Guillem.
Very interesting. Thanks for sharing.
@Guillem:
You might as well use an LDR for those applications..
Now the cool thing would be if you could do this with laser-diodes and measure the light in one specific point far away :D
Level: Raving Lunatic
Joined: Tue. Nov 1, 2005
Posts: 7033 View posts
Location: Hilversum - the Netherlands
Not too long ago there was a thread in this forum about this.
Just as a reminder: don't try to witness this effect by attaching an oscilloscope-probe to the LED: no matter how good quality it is, 10* or 100*, the circuit will not work. The impedance of the probe being the reason. It felt a kind of freaky .... it works but as soon as you have a "look" with the scope, it no longer works.
In quantum theory research they found the same effect: watching a phenomenae has an effect on the phenomenae ..... wooohoooo .... spooky ....
Nard
edit: I tried to find that old topic, but this is all what I could find: https://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&t=53465&highlight=led
They are called Rosa, Sylvia, Tricia, and Ulyana. You can find them https://www.linuxmint.com/
Dragon broken ? http://aplomb.nl/TechStuff/Dragon/Dragon.html for how-to-fix tips
Level: Raving Lunatic
Joined: Sat. Sep 20, 2003
Posts: 6156 View posts
Location: Underneath the Cotswolds escarpment, England.
Quote:
You might as well use an LDR for those applications..
Except that you may already have an LED in your device.
Level: Raving Lunatic
Joined: Fri. Jun 11, 2004
Posts: 2405 View posts
Location: Vilanova (Barcelona)
LED's also have some other interesting features: sensitivity to different wavelengths, directivity, RoHS, double use, etc. that may (or may not) force to use them instead of LDR, for particular uses.
Another use that I saw: a 'touch screen' over a LED matrix, that use this effect just to detect the 'pressed LED'.
Guillem.
Level: Raving Lunatic
Joined: Tue. Nov 1, 2005
Posts: 7033 View posts
Location: Hilversum - the Netherlands
Guillem, that's the one I was looking for.
Darn, cannot find it ....
It was in the OffTopic too, but that is more than a year ago.
They are called Rosa, Sylvia, Tricia, and Ulyana. You can find them https://www.linuxmint.com/
Dragon broken ? http://aplomb.nl/TechStuff/Dragon/Dragon.html for how-to-fix tips
here is a link to a youtube video : http://uk.youtube.com/watch?v=7k...
Level: Raving Lunatic
Joined: Tue. Nov 1, 2005
Posts: 7033 View posts
Location: Hilversum - the Netherlands
That's indeed the one that year-back thread was about. Neat huh ?
cheers
They are called Rosa, Sylvia, Tricia, and Ulyana. You can find them https://www.linuxmint.com/
Dragon broken ? http://aplomb.nl/TechStuff/Dragon/Dragon.html for how-to-fix tips
yup, I just wonder how well it will work in a light room....
it took a little googling to find it. couldn't find the original thread.
That touch screen is indeed very neat :-)
I guess this can be used similar to capacative sensing, very neat for boxes that needs to be waterproof but you still need a light to show you the buttons. Underwater etc..
In my opinion that EDN article is a direct copy of MERL article about the same subject.
Too bad I just bought an AVR book by the same EDN article writer, Dhananay V. Gadre, he also wrote a book called Programming and Customizing the AVR microcontroller. Very beginner level stuff, I think I'll sell that book to some newbie or donate it to the university electronics club.
If I had remembered who the EDN writer was, that book would still be in the store :)
- Jani