I built a trip wire for the post box that I'm connecting. It's however based on a mercury tilt sensor so I'm really not sure whether I think it's a great idea putting it to use (at least not with a sturdy case...). However, I can share my code: #define DIGITAL_INPUT_SENSOR 2 // The digital input you attached your motion sensor. (Only 2 and 3 generates interrupt!) #define INTERRUPT DIGITAL_INPUT_SENSOR-2 // Usually the interrupt = pin -2 (on uno/nano anyway) MyMessage msgTripped(CHILD_ID_TRIPPED, V_TRIPPED); void setup() { gw.sendSketchInfo("Postal", "1.0"); gw.present(CHILD_ID_TRIPPED, S_MOTION); pinMode(DIGITAL_INPUT_SENSOR, INPUT); // sets the motion sensor digital pin as input } void loop() { boolean tripped = digitalRead(DIGITAL_INPUT_SENSOR) == LOW; if(tripped) { gw.send(msgTripped.set("1")); // Send tripped value to gw } gw.sleep(INTERRUPT,FALLING, SLEEP_TIME); }