EVERYONE,
Sincere THANKS for your continued discussion on this topic. I am embarrassed to say that I didnt notice the thread continued beyond Page 1. So I apologize for the radio silence.
Just to catch up, please allow me to respond en masse to your questions and comments:
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I think I might have found an IC that does what you are recommending.
http://www.analog.com/en/circuits-from-the-lab/cn0185/vc.html"]AD7400A[/PLAIN] sigma-delta modulator
My hunt also led me down the path of dynamic noise reduction (DNR) and Dolby filtering, specifically a lineage of...
I will investigate your suggestions.
Please enjoy your family... this project has languished for years, it can wait a few more days. In the meantime, I'm learning about various noise reduction ICs... hoping to stumble on an inexpensive and simple solution: ala noisy signal in - clean signal...
I cannot thank you enough for the time and effort you've been putting into this problem.
I'm very eager to implement your idea of chopping/modulating/demodulating the signal. Just wish I knew how. The AD630 is definitely an elegant one-stop-shopping chip, but a bit impractical for this...
Thanks again for your thoughtful suggestions. The most encouraging and exciting think you wrote concerned the idea of chopping or heterodyning (or is it homodyning?) the signal. I understand this in principle, from my experimentation with Radio as a kid. But I never designed such a circuit...
I apologize if the attachments didn't get uploaded. I am trying again to attach them here.
I'm actually not modulating the light signal, per se. We're using SMT proximity sensors, with LED and phototransistor in the same package. The IR LED's are driven by a current source. And the...
Thanks again for your suggestions. Attached is the schematic, which I forewarned was rather simple. You'll see that there are already two stages of low pass filtering, but they don't seem to do the trick.
This circuit is not my design, per se. I actually paid someone to design it for me...
Thanks very much for your replies!
The signal I am transducing is surprisingly enough, a harmonica reed. Actually a set of ten reeds, summed. The noise appears to intensify with each additional sensor, rather than canelling out :-( But I'm intrigued by the idea of signal averaging... which I...
Citizens of Physicsforums.
I would greatly appreciate your advice.
I've been wrestling with a pesky noisy phototransistor for quite a long time, and am at wit's end.
The sensor is being used to transuce an audio signal in the 1-5kHz range. Unfortunately the shot noise is introducing...