Vibration sensor made from a piezoelectric transducer and an LM358 microcircuit

While disassembling the car alarm, I discovered a spring attached to a piezo buzzer. It's some kind of sensor, but what does it do? It's a vibration sensor. When the car is hit, the spring vibrates, and this motion is transmitted to the piezo buzzer, which converts it into electricity. Connect an LED to the piezo buzzer and gently tap it with your finger—the LED will start flashing.

I decided to make a vibration sensor. To do this, I attached a spring to a piezoelectric transducer, as shown in the photo. I connected a voltmeter to the transducer. If I hit the table, the voltmeter reads approximately 11 mV.

This voltage from the sensor can be fed to the input of an alarm device based on the LM358 microcircuit. When an impact occurs, the LED will light. Another alarm source can be connected instead.