Post 3 :
I have received the boards now. I will be showing initial experience wuth the boards in the coming days. For now i am trying to interface sound in the system.
For this sound detection i will be using adafruit microphone amplifier breakout.
Adafruit Electret Microphone Amplifier : It is used to measure sound levels. The specification of the amplifier is :
Supply Voltage: 2.4v-5v
Output: Rail-to-Rail - up to to 5vp-p
Frequency Response: 20Hz - 20 KHz
Adjustable Gain 25x-125x
Connection :
The amplifier has only 3 connections:
GND -> GND
VCC -> 3.3V
OUT -> Analog input
VCC can be anywhere from 2.4-5VDC. For the best performance, we use the 3.3v pin.
The amplifier gain is adjustable from 25x to 125x.
The output will have a DC bias of VCC/2 so when its perfectly quiet, the voltage will be a steady VCC/2 (1.65v).
Measuring Sound Levels : The Audio signal from the output of the amplifier is a varying voltage. To measure the sound level, we need to take multiple measurements to find the minimum and maximum extents or "peak to peak amplitude" of the signal.After finding the minimum and maximum samples, we compute the difference and convert it to volts.
Although the amplifier is capable of a rail-to-rail signal (3.3v in this case), we map it to a 1v peak-to-peak signal. This output is compared to a reference to know if sound is low, normal or high.
The overall design for sensor is :
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