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[DPRG] Using an IR LED as IR photodiode
Subject: [DPRG] Using an IR LED as IR photodiode
From: DeltaGraph at aol.com
DeltaGraph at aol.com
Date: Tue Oct 24 12:23:12 CDT 2006
>Maybe slow response from the LED is because of the inherent
>capacitance which can be bled off using, say a 100K resistor ?
Hmm. Maybe. When the LED detector "goes black" adding the resistor would
help to discharge the detector if used in your original configuration, but it
would attenuate the output while the detector is being hit with IR.
> Can you send me a schematic of the design you made with part values.
The application note link I sent had an example of photoconductive mode
(page 19 I think)
Single 1M resistor, diode and op amp.
My addition to your circuit was a 100K resistor in parallel with LED sensor.
> A response output bundled with it will be just great !
> Can you do that please ?
No. Sorry, demands of job / life prevent me from doing that now.
> I found understanding how resistor dividers work through simple application
> of Ohm's law to be very helpful before taking on understanding op amps.
> Certainly there are some very nice explanations of all of this on the
> internet...
Why ? Did I mess up somewhere ?
No, if you derived that equation you know what you are doing for sure.
-Ron
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