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Arduino Ultrasonic Alarm

Using an Arduino UNO, an Ultrasonic Sensor, and a RFID Reader, you can create a simple alarm which when placed near a door, senses if that door has been opened or if someone has come in and triggers an alarm which would sound a buzzer and flash a set of LEDs until its shut off. With an Ultrasonic Sensor, the alarm goes off when the individual or object passes the sensor at less than a certain distance set in the Arduino (ie. 36 inches), thus creating a restricted perimeter near the door rather that detects an object going in. Once the alarm has been triggered, it remain on until either the alarm is deactivated, power is cut to the Arduino, or a certain amount of time passes (ex. 10 minutes), whichever comes first. Activation of the alarm is controlled using an RFID Reader which renders the alarm on and off when the appropriate tag/card is flashed in front of the reader. If an unauthorized tag/card is detected, the reader will reject it, and the alarm’s state will not change. The tag/card can be used to activate and deactivate the alarm when entering or leaving, as well as deactivate the alarm when triggered.”

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