Preamps & Amplifier advice please

Discussion in 'The Projects Forum' started by JDR04, Jul 21, 2013.

  1. JDR04

    Thread Starter Active Member

    May 5, 2011
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    Hi All. I'm looking at learning about preamps and amplifiers.

    My goal is to have a sound detector circuit connected to a microcontroller so I can control a humble LED.

    Some of the questions I have are;

    Is it best to connect a preamp directly to a microcontroller or should it first go through an amplifier?
    Can a preamp or amplifier circuit be run off a single 5V power supply?

    Any suggested circuits to help me learn all this will be greatly appreciated as well.

    Thanks again. JDR04
     
  2. bertus

    Administrator

    Apr 5, 2008
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  3. JDR04

    Thread Starter Active Member

    May 5, 2011
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    Thanks Bertus, how do I figure out what transistors to use?
     
  4. bertus

    Administrator

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  5. JDR04

    Thread Starter Active Member

    May 5, 2011
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    Thanks Bertus, I'll give that a try and see how it works out. Thanks again.
     
  6. JDR04

    Thread Starter Active Member

    May 5, 2011
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    So, am I correct in assuming the following;

    A preamp amplifiers very small signals so that a amplifier can amplify them?

    If a circuIt has a preamp feeding a signal to an amplifier chip then the circuit will be far more sensitive to sound than a circuit with only a preamp? Am I right???

    Thanks guys - JDR04
     
  7. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    What would be the expected signal level at the micro controller entrance?
    What would be the expected output level of the used microphone?
    The difference would give the needed amplification.

    Bertus
     
  8. JDR04

    Thread Starter Active Member

    May 5, 2011
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    The microphone should be sensitive enough to pick up avarage conversation and right up to something as loud as a pistol shot.

    I need between 3 and 5V dc to go into the microcontroller.

    So, I would need the amplifier to put this out at least. Is this possible or am I misunderstanding the whole thing??
     
  9. donpetru

    Active Member

    Nov 14, 2008
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    Pay attention to the amplifier that you choose. An amplification factor too high can damage the microcontroller ADC input. I recommend you choose, instead of a classic circuit transistor, an operational amplifier circuit operated at a voltage of 5V.
     
  10. BobTPH

    Active Member

    Jun 5, 2013
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    You will need a gain of about 1000 to get microphone level to 5V level. Two op amp stages would work fine.

    Bob
     
  11. JDR04

    Thread Starter Active Member

    May 5, 2011
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    Thanks donpetru, would you be able to suggest a circuit at all or an IC chip to use and I can take it from there? Thanks again.
     
  12. JDR04

    Thread Starter Active Member

    May 5, 2011
    339
    4
    BobTPH, thanks for that. When you say two stages, I assume the signal is amplified twice. Can this be done with one Amplifier IC? If you could suggest a circuit I would be grateful. Thanks a lot - JDR04
     
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