Sound sensor help needed

Hello, I have the mic preamp from the attached picture and i need to modified it so that i can use it as sensor for an Arduino. The preamp works, but the output signal is centered at around 2.2V and i need that 2.2v to become 0(at analogRead from sensor pin - i only need the upper "positive" part of the wave to be taken in to consideration). Basically i need to bodify this preamp to be used as a sound level sensor 0(0V on Arduino input)- no sound 1023(5v on Arduino input ) very loud sound

Can anyone help me to modify this circuit? PS: I would like to keep the gain on each stage of the amp if it is possible OMG: How can i attach an image here? http://www.edaboard.com/viewtopic.php?p=1280130#1280130

Here is a link to my sensor http://www.grozeaion.com/download-menu/arduino.html I can't figure it out what I'm doing wrong

Take R6 and replace it with a pot with the wiper going to pin 3 and the ends to +5 and ground. That should allow you to control the DC level. However it will not turn it into an envelope follower which is I think what you want. For this put a diode in line with the output feeding into an R&C to ground. Then feed that into the analogue input of the arduino.

You are right, i want to create a envelope follower
In my previous attempt i use an RC delay with R=47K and C=100n because i need a small delay (0 will be perfect :slight_smile: ) but instead of a diode i used a 100Ohm resistor.
Regarding the R6 replacement, if i will use a pot then i will have an offset voltage. If no sound (or sound above a threshold) is present the i need my output to be 0, in this case i don’t think it is possible. I am wrong?

I am wrong?

yes you need a DC offset, currently you have a DC offset of 0V with respect to the signal ground. However this signal ground it 2.5V above the arduino ground. therefore you want to have a DC offset of -2.5V. This then would give you 0V for no signal.

but instead of a diode i used a 100Ohm resistor

No you need a diode for this to work.

I've modified the circuit Do you think that will do the job?

Here it is the link http://www.grozeaion.com/download-menu/arduino.html

Putting R8 will stop you setting the DC bias as low as you want. Take it out ad give it a try.