Electronics > Electronics

sound control for robot, schematic

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Admin:
hey so im thinking of building a soundvore type robot, that moves to chase loud sounds.

so here is the thing, im having trouble figuring out the circuit that takes microphone noise, amplifies it, and stabilizes it as a voltage that lasts about quarter a second or so.

in the end i want it to go to an ADC of a microcontroller for a reasonable 8 bit reading.

my guess . . .
sound -> audio op-amp (how much do i amplify it?) -> diode (to remove negative voltagess) -> capacitor between signal and ground (for signal smoothing, but what value?) -> ADC of microcontroller

im not doing frequency matching, just amplitude analysis.

ideas?

Militoy:
It sounds to me like what you’re looking for is a simple high-impedance precision rectifier circuit. You can either run right into your op-amp as shown in the circuits in the link below, or increase your input current by feeding through a sensitive UJT, to avoid drift errors associated with input offset current. Integrate the output through a voltage divider and a small cap across the bottom resistor (your output) – the RC time constant and the current through the bottom (bleeder) resistor will determine your holdup time, and the feedback resistors in the op-amp will set your gain (DC out vs signal input).

http://sound.westhost.com/appnotes/an001.htm

Militoy:
Oh, and one thing I neglected to mention - the TL072 op-amp the author of the link reccommends is a JFET type. Though the manufacturer claims they aren't subject to latchup, I've seen them latch, in circuits where layout was less than perfect. I'd reccommend a plain old LM358A instead.

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