Missed this earlier. The software divides the output of this circuit into 4 windows of about 1V range (I.e., 0-1V, 1-2V, 2-3V, and 3-4V).When the audio is clipping then many amplitude fluctuations will be missing and your robot's mouth will appear to be frozen.
Your simple passive envelope detector's voltage loss also covers up minor amplitude fluctuations that would be fixed by using an ACTIVE envelope detector (the diode's voltage loss is cancelled because the diode is inside the negative feedback loop of the opamp).
I put the diode there as a half wave rectifier to prevent negative voltages reaching the op amp + input. My earlier circuit didn’t have this diode and appeared to work fine, but I received many comments that configuration would damage the op amp.The Schottky diode is preventing the opamp (+) input to be biased at any voltage since the input bias current of the input pulls it positively.
Why is the diode there?
Why do you use such a low value of 20 ohms?
The 0.1uf capacitor feeding 20 ohms forms a highpass filter that cuts frequencies below 80kHz (all audio frequencies are cut and frequencies are reduced at -6dB per octave).
Thanks for the feedback and the error message. I have an idea as to what’s happening. I’ve edited the post and re-uploaded the images,Can't see them. Extracting the links and clicking on them returns 'not authorized to view this page'.
Try editing your post, deleting and using UPLOAD FILE again?
Sorry you're having trouble. Frustrating.
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by Jake Hertz