Need some urgent help related to this Arduino Audio processing

Hi Raviraz,

Yes there is a difference between the two microphones. The 33-3038 is a dynamic microphone which means that it is a coil of wire in a magnetic field. Sound waves vibrate the diaphragm and this moves the coil in the magnetic field and produces the electric signal. The Spark Fun microphone is an Electret condensor mic and it uses a different system involving a charged metal plate and a capacitive effect to convert the sound into an electric signal. The Electret also has a built in FET amplifier to amplify the electric signal to a usable level. I am sure that the Sparkfun mic will work but you will have to provide power to it from your board as it is has three wires Ground, Signal, and Power, whereas the Radio Shack Mic has only two wire Ground and Signal. Sparkfun usually has good documentation and they will likely include instruction to make the mic work with your project.

John

John, one more query,

As sparkfun  Electret microphone has already inbuilt op-amp, So do I need to discard op-amp circuitry in instructable site or  just proceed with op-amp circuitry ?

could you please confirm me.

John, one more query,

As sparkfun  Electret microphone has already inbuilt op-amp, So do I need to discard op-amp circuitry in instructable site or  just proceed with op-amp circuitry ?

could you please confirm me.

You shouldn't need the additional op-amp.

The following page gives an example connection diagram 

Electret Microphone Breakout - IPDL Seed

Hi Raviraz,

Edited and Reposted as I had a mistake in the first posting.

Sorry I couldn't get back to you sooner, I have looked at your Instructable schematic:

This is doing more than just amplifying the microphone signal. The two 100K resistors near the arduino are centering the DC bias and the 10 uF cap is removing the DC component of the output signal from the OP Amp. For your design to work these components would still be necessary. The next consideration is if the output of the Electret mic is anywhere near the output of the original Dynamic mic / op amp combination. You could hook it up and see what you get. My experience has been that the Electret with the internal Op Amp has about the same output amplitude as the Dynamic Mic on its own.. If this is true you will still need the amplification of the second OP Amp to meet the input parameters of your Arduino program.

Here is the schematic of the Electret Mic from Sparkfun:

If we hook this up directly to the Arduino it will work as a microphone but without the 100K resistors and 10uF cap the signal will not be centered as required by the Arduino program. Perhaps without the second Op Amp you may not have enough signal amplitude. There are no modifications that can be made to the Electret circuit as it is internal to the Mic and must be used as designed. The Vcc for the Electret is 2.7 to 5.5 volts so you will have to go to the Arduino 5 volt tap and not use a 9 volt battery or other power source greater than 5.5 volts. Hopefully this has clarified and not confused the question.

John

Thank you very much for your detailed explanation.

Actually as per one of the above comment I have continued to plug the electret mic to the arduino and can see some inconsistancy in output(frequency Hz) values.

After seeing your recent reply I can see where I went wrong.

Thanks again.

As per my understanding in Instructable site, I can see two things one is amplifying and other one is DC offset, So Both amplification and DC offset circuitry have to be involved just instaed of dynamic mic I will be using Electret mic, am i correct

Yes I think your approach will work. You have gain control of the second Op Amp using the 10K variable resistor so you can adjust the amplitude to the arduino. I would also probably experiment with putting a resistor ( try 1K ) in series with the output of the Electret as it goes into the input of the 2nd Op Amp. I tried to see what the impedance of the Radio Shack 33-3038 mic is but true to form Radio Shack has very poor documentation. The Electret is probably lower output impedance than the dynamic mic would be but I'm not sure. This is a great project for a little experimentation. Please post back your results when you get it working properly.

John

Thanks once again John.

I am pretty new bee in Arduino.

My basic theme is to calculate the frequency of the sound generating from my test device",So i have chosen this  instructble to help.

I will try to put the circuit up and will post you the results.

Hi John,

  Need your suggestion here,Can I use LM741 IC instead of TI802 IC,Could you pls clarify me, Currently I don't have TI802 IC immediately with me.

Waiting for your response.

Hi Raviraz,

I think you mean TL082 J-Fet Op Amp. Here is the Data Sheet:  http://www.ti.com/lit/ds/symlink/tl082.pdf

The LM 741 (Here is the Data sheet):  http://www.ti.com/lit/ds/symlink/lm741.pdf  is a more general purpose BJT transistor Op Amp but for your application it should work just fine. Even the pinouts are the same and the voltages match OK. Give it a try as it can't hurt anything.

John

Hi John,

  I have builded the circuit with LM741 opamp, and Can see values in serial as -1Hz always, not sure why it is happening, any help pls.

If you have some way to check the input to the Arduino with a meter do so. We need to verify that the amplifier is working. If you have a signal generator you could also put an artificial signal into the Arduino to see if it is processing the input properly. Lacking this you can post your schematic and code so it can be looked at on the forum. If we are going to get help from some of the arduino coding experts they will need a clear explanation of what the code is suppose to do.

John