Need help modifyin the code to use a vibration switch instead of an analog senso

[J-M-L]

One challenge in this code is

#define MOTION_PIN     13 // Vibration switch from here to GND

.....

if(MOTION_PIN == LOW) { // Pin change detected?

There is really zero chance that MOTION_PIN will ever be LOW. I think your code Should probably be a if (digitalRead(MOTION_PIN) == LOW) { instead