LED as light sensor

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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?

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Backlight control/regulation, Contrast control regulation, heliostat aiming, light control/dimmer, etc.

Guillem.

Guillem.
"Common sense is the least common of the senses" Anonymous.

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Very interesting. Thanks for sharing.

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@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

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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

A GIF is worth a thousend words   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

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Quote:
You might as well use an LDR for those applications..

Except that you may already have an LED in your device.

Four legs good, two legs bad, three legs stable.

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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.

Guillem.
"Common sense is the least common of the senses" Anonymous.

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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.

A GIF is worth a thousend words   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

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here is a link to a youtube video : http://uk.youtube.com/watch?v=7k...

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That's indeed the one that year-back thread was about. Neat huh ?

cheers

A GIF is worth a thousend words   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

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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.

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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..

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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