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

 

Hello,

You might want to look at this circuit made by Eric007:

This comes from this thread made by him:
http://forum.allaboutcircuits.com/showthread.php?t=64687

He want to use the preamp for DSP purposes.

Bertus

 

Thanks Bertus, how do I figure out what transistors to use?

 

Hello,

I think you can use some basic transistors like the BC147 , BC547.
In this TUN (Transistor Universal NPN) list, you will find some more:
http://translate.google.com/transla...&u=http://a29.veron.nl/tuntup.htm&sl=nl&tl=en

Bertus

 

Thanks Bertus, I'll give that a try and see how it works out. Thanks again.

 

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

 

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

 

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??

 

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.

 

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

Bob

 

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.

 

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