I have a vertical geophone sensor that records seismic vibrations in the range 0-20 mV . I want to use this sensor to generate an external interrupt to wake up my arduino from PWR_DOWN mode.
So ,I will be needing a low level interrupt . From a previous experiment , I found out that to wake up an arduino from PWR_DOWN mode , you need a consistent high signal that rapidly changes to a low signal and stays low for some time before getting high again.
Basically , I have to amplify the signal input from the geophone and set a low threshold value(around 0.2 V) such that for inputs greater than 0.2 V , I get a logic value =1 and 0 otherwise .Then use a NOT gate to reverse logic and generate an effective low interrupt.
But , the problem is , what kind of comparators to use?No standard comparators work at such low thresholds . Is there any alternative?