This is similar to what I suggested as a starting point; however, I added looking up what the microphone's output impedance was and to put a matching resistor in the measurement circuit. If the microphone you were using had an output impedance of >10 Kohms, the difference probably won't matter; however, if it was 150 ohms it might make a considerable difference in being able to accurately measure it.He said that all I had to do was feed my ringtone into a microphone with an input of 20 kHz that was connected to an osilloscope to find the volts in the ring tone.
He may very well be correct; however, many operational amplifiers, particularly those that have two or four on the same IC substrate can interact with each other because of parasitic coupling and can oscillate on their own at high frequencies (MHz range) especially if the gain is high and the signal to noise ratio is low. Throwing in 25 KHz low pass filter is just a simple way to help eliminate that possibility. My suggestion of using a double pole high pass filter may also be overkill and a single pole high pass filter may be all that is needed. Neither he nor I can predict without knowing what the signal level you are going to get when you run your first test.He said that I only need a high pass filter and that a low pass filter was not required.
This might work because a filament light bulb has some integration properties; however, if it doesn't or gives you too many false positives or negatives you will have to come up with something more descriminating. The concept of AC coupling into a small signal diode with a tuned tank RC circuit with separately tunable charge and discharge times followed by a threashold comparator is a much more sophisticated approach. Again, it maybe overkill; however, by changing the resistance values, you can easily do some tuning to improve the detection with this more sophisticated design.My final step would be to hook the rc circuit to a 3 or 6 volt light bulb.
No disagreement on that point, if you read back to one of my earlier replies I mentioned that the cost of the breadboard would probably be a significant part of the cost of the project.He t[o]ld me that my whole device would be connected on a breadboard.
Definitely NOT! If he is going to be there helping you as you run into problems, then his approach to getting you started is similar to what I might have used. Circuits are developed a stage at a time. No need to get too far ahead of what the person you are mentoring can grasp and deal with at one time. You can always learn together. By being remote, I didn't have the luxury of down playing any of the stages. I had to take the steps that OneBrightGuy layed out in simplistic terms earlier in this thread and provide you a good recommendation on what I felt could definitely be made to work and to open your eyes all at once to everything that might be needed.I think the advice he gave me was incorrect. Was it?
Your local mentor on this project may have plenty of practical experience with the particular microphone you have and know you aren't going to run into any problems making a VERY simple circuit work.