An Easy Way to Build an Arduino Powered Motion Sensor Alarm

Have you ever wanted to build a project that had could detect the presence of a person in a room? If so, then you can do this very easily using the PIR (Passive Infra Red) Motion sensor. This Arduino motion sensor can detect the presence of a person in a room. Therefore, you can build projects such as burglar alarms and automated appliances. Attach this motion sensor along with an Arduino and place it in your room to build an intruder detection system.

An Easy Way to Build an Arduino Powered Motion Sensor Alarm

This tutorial will show you to interface a motion sensor with an Arduino and to use it to build a burglar alarm. This system detects the presence of an intruder in your room and sends a signal to the Arduino. The Arduino then creates an alarm sound using a buzzer to scare the intruder away.

Required Materials


  1. Arduino or an Arduino clone board (freeduino), or you can make your own custom Arduino board.
  2. PIR Motion Sensor.
  3. A piezo buzzer or an 8-ohm speaker.
  4. 9V Battery and connector.
  5. Connecting wires.


Arduino IDE

How Does it Work?

Here, we are using a PIR motion sensor. PIR stands for Passive InfraRed. This motion sensor consists of a fresnel lens, an infrared detector, and supporting detection circuitry. The lens on the sensor focuses any infrared radiation present around it towards the infrared detector. Our bodies generate infrared heat and as a result, this gets picked up by the motion sensor. The sensor outputs a 5V signal for a period of one minute as soon as it detects the presence of a person. It offers a tentative range of detection of about 6-7 m and is highly sensitive.

schematic - An Easy Way to Build an Arduino Powered Motion Sensor Alarm

When the PIR motion sensor detects a person, it outputs a 5V signal to the Arduino. Thus, an interrupt on Arduino is triggered. We define what the Arduino should do as it detects an intruder. Here, we are creating an alarm sound through a piezo buzzer. When the sensor detects an intruder, an alarm sound will get triggered through the buzzer.


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