using a LED as a light sensor

"BrunoG" <noreply@micro-examples.com> wrote in message 
news:4492c725$0$991$ba4acef3@news.orange.fr...
> "Rufus V. Smith" <nospam@nospam.com> a &#4294967295;crit dans le message de news: 
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>>
>> "BrunoG" <please_reply_in_the_forums@www.micro-examples.com> wrote in 
>> message news:445d31a5$0$19698$8fcfb975@news.wanadoo.fr...
>>> Hi,
>>>
>>> Here is an idea about using a LED as a light sensor, to dim a 7-segments 
>>> LED display :
>>>
>>> http://www.micro-examples.com/public/microex-navig/doc/096-led-light-sensor.html
>>>
>>> Questions & comments are welcome !
>>>
>>> Thanks,
>>>
>>> Bruno
>>
>> Very cool.
>>
>> Unfortunate about the color of the casing filtering incoming light.
>>
>> Could this detect the signal coming from an IR remote (well enough to
>> decode), I wonder?
>>
>> Rufus
>>
>>
>
> Hi, thanks !
>
> It's worth a try, but I don't think so, because the response time of the 
> diode & PIC DAC would be too long.
>
> Bruno
> http://www.micro-examples.com/public/microex-navig/doc/096-led-light-sensor.html

OK, not quite 40kHz territory, but this looks fairly quick:

http://mrl.nyu.edu/~jhan/ledtouch/index.html

from here:

http://www.hackaday.com/entry/1234000873073550/

Deep.
> 

On 8 May 2006 04:22:25 -0700, "Antti" <Antti.Lukats@xilant.com> wrote:

>well I was able to make a iopad oscillator that had frequency change
>10% based on light intensity, and even that was possible bad solution,
>eg the change could be even larger.
>
>but getting stable absolute reading is probably more difficult or
>impossible due to temperature, effects, etc
>
>Antti

LEDs are decent candidates for RF VFOs (variable frequency
oscillators) in place of specialized varaiable capacitance diodes.
What we've found is that the LED-based VFO must be kept in a
light-shielded enclosure due to the effect described.  Not usually a
problem, since the VFO should be in an RF-shielded enclosure anyway.