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I want to build a sound detector circuit for my project. I am free to use any amplifier but not much complex circuitry. I googled and found this circuit using LM 386.

Is this good enough or is there any better and more efficient circuit and/or amplifier ? I have to use MSP430 instead of arduino.

nidhin
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Anuj
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1 Answers1

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There is no way on earth I'd feed the output of this audio amplifier directly into a sensitive little pin of any MCU: -

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The output is capacitively coupled and this means the audio signal coming from the microphone will be an AC signal into the pin and more importantly....

NO CURRENT LIMIT to protect the analogue input.

Put a 10k resistor in series with the output capacitor C4.

Andy aka
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  • I wouldn't use the LM386 at all for this project. – Matt Young Mar 17 '15 at 20:14
  • @MattYoung ditto – Andy aka Mar 17 '15 at 20:40
  • Can you suggest any other amplifier or other better circuit for this ? – Anuj Mar 18 '15 at 02:47
  • I'd follow recommendations in my answer in this question: http://electronics.stackexchange.com/questions/68889/controlling-led-with-300mv-ac-signal/68923#68923 - it actually produces a DC level that feeds into the ADC and in your code you just look for that DC level rising above some digital threshold. This type of circuit should run from a 5V rail - take the output from the emitter of Q2. No need for Q3, R5 and the LED unless you want them for debugging. – Andy aka Mar 18 '15 at 09:22
  • Why would you need to limit the output current since a micontroller's input is high impedance? – m.Alin Apr 18 '15 at 06:34
  • @m.alin if the micro is running from a 3v3 supply or a smaller supply than the386. – Andy aka Apr 18 '15 at 08:54