(Last Updated On: June 26, 2020) Description: Arduino GSM Alarm System– This project is based on the Security system using PIR Sensor, Arduino Uno, and GSM module “SIM900A”. The PIR sensor is used for Intruder detection. Whenever an unauthorized person is detected a message is sent on the desired number. A relay module is also … Continue reading GSM Alarm System Using Arduino and a PIR Sensor