In this article, I will show you how to easily build your own motion sensor alarm using an Arduino board and a few simple components. This project is perfect for learning the basics of Arduino and electronics, and has practical applications for home security or other monitoring needs. The total cost is under $30, and it can be built in about 10 minutes once you have gathered all the parts.

What You Will Need

To build the motion sensor alarm, you will need the following parts:

That's it! These basic electronic components are all you need to build your own motion sensing alarm with Arduino. Now let's look at how it all goes together.

Assembling the Circuit

Step 1) Connect the PIR motion sensor, buzzer, and resistor to the breadboard as shown in the diagram below:

How to Build a Low-Cost Motion Sensor Alarm With Arduino in 10 Minutes

The resistor should be placed between the buzzer and Arduino pin to limit current.

Step 2) Use jumper wires to make the following connections:

Step 3) Connect the 9V battery to the power socket on the Arduino board. Make sure the power switch is in the OFF position for now.

That completes the motion sensor alarm circuit! Now it's time to program the Arduino to activate the alarm when motion is detected.

Programming the Arduino

Step 1) Download the Arduino IDE software to your computer and open it.

Step 2) Copy the following code and paste it into a new sketch:

const int pirPin = 2; // Input for PIR sensor
const int buzzer = 3; // Output for buzzer

void setup() {
pinMode(pirPin, INPUT);
pinMode(buzzer, OUTPUT);

void loop() {
if (digitalRead(pirPin) == HIGH) {
digitalWrite(buzzer, HIGH); // Sound alarm
else {
digitalWrite(buzzer, LOW); // No alarm

Step 3) Upload the code to your Arduino board.

Step 4) Flip the power switch on the Arduino to ON to power up the board.

That's it, the motion sensor alarm is now ready to detect movement and sound the alarm!

The PIR sensor will detect motion up to 6-10 feet away. When it sees movement, it sends a HIGH signal to the Arduino, which then turns on the buzzer to sound the alarm. This creates a simple but effective motion-activated security system.

Customizing the Alarm

There are many ways you can customize this project to suit your needs:

By further expanding on this basic build, you can create all kinds of cool motion-sensing projects using the Arduino platform.


Building a motion sensor alarm with Arduino is simple, inexpensive, and only takes about 10 minutes. With just a few basic components, you can set up your own Arduino-based security system to detect intruders or other motion when you need to.

This project is also a great way to get started learning Arduino programming and electronics. You can easily build upon the simple motion sensor circuit to create more advanced projects and gain valuable skills along the way.

So grab an Arduino board and a PIR sensor, follow the steps outlined in this guide, and you'll have your own DIY motion alarm up and running in no time! Let me know in the comments if you have any other questions.