SW-420 Vibration Sensor NC For Arduino. A vibration sensor can detect tiny vibration, like the ground shaking. The signal sent by a vibration sensor is very short. You must use an interrupt to catch it. For most sensors, you could just poll them. Polling means that you check the state of the digital pin, wait a while, and then check again. With an interrupt, you can tell Arduino to run a function whenever some event happens. Interrupts make it harder to follow the flow of the code you write, but they allow you to catch very short-lived events, like a pin going up and then down quickly.
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