Arduino-Based Early Warning Prototype for Left Vehicle Key Indication Using SW-420

Abstract

This study designed an early warning prototype system to prevent user negligence of leaving
keys in the vehicle ignition. The system utilized an Arduino Uno microcontroller and a vibration
sensor (SW-420) to monitor physical activity around the parked vehicle. The warning logic was
configured to activate visual (light-emitting diode) and audio (buzzer) indicators if no vibration was
detected for five seconds. Testing results showed that the sensor responded perfectly to high
vibration (100%) and well to medium vibration (80%), but lacked sensitivity to low vibration (20%).
In conclusion, the vibration-based early warning prototype successfully operated according to the
designed delay timing, although its main limitation was the inability to physically detect the direct
key position.