Components needed Ultrasonic SensorPiezo(buzzer)An LEDA resistorJumper cablesBreadboardArduino BoardA computer with the Arduino IDE installed Completed Circuit The image above is the completed circuit for the security system. We will build a simple security system using an ultrasonic sensor where if something is stolen, the piezo (buzzer) will buzz , and a red light will turn … Continue reading Tutorial 10: Security System using an Ultrasonic Sensor HC-SR04