Arduino Anti-Theft Device

This DIY anti-theft device is a fun, hands-on project for anyone looking to create a simple security system. Using an Arduino Uno and an ultrasonic sensor, it detects movement and triggers an alarm if the monitored distance changes. A combination of tactile buttons lets you arm and disarm the device, with a buzzer and flashing LEDs signaling any alert. It’s an ideal project for building practical skills in electronics and programming while creating something useful to keep items secure.

*** Side Note: After step 6, the remaining parts of the project are optional, as it functions fully without the aesthetic enhancements.

Downloads

Arduino Working.mp4

Supplies

1 Arduino Uno

Purpose: The microcontroller to run the logic for the device, monitor the sensor inputs, and control outputs (alarm, lights, etc.).

1 Ultrasonic Sensor

Purpose: Measure the distance from the object to detect movement. When the distance changes by more than 1 inch, it will trigger the alarm.

2 Tactile Buttons

Purpose:
One Button: Start the system by pressing a button. It will begin monitoring the distance.
Two Buttons: To disarm the alarm, press a specific sequence of two buttons in the correct order.

1 LED RGB

Purpose: Flashing lights when the alarm is triggered.

3 Resistors (330Ω)

Purpose: To limit current for the LEDs and buttons.

1 AA Battery Holder

Purpose: Power the Arduino Uno and components when not connected via USB.

17 Jumper Wires and 1 Breadboard

Purpose: Connect all the components without soldering.

4 Male - Female Wires

Purpose: Extend the connection between the board and LED RGB

1 Micro Servo

Purpose: Adds actuation (movement) to the device

3D Printer

Purpose: Create covers for the wires and board
This is purely optional as covers can be made with any other material

1 Bell

Purpose: Produces noise when hit

1 Nail/Extension

Purpose: To extend the Micro Servo arm

Hot Glue/Tape

Purpose: Hold the cover pieces together

Thread/Wire

Purpose: Hang the bell from the stand

Gather Supplies

Gather all of the necessary supplies for the project as listed above

Power Connections

Materials Needed:

2 wires
Battery holder

Assembly:

Connect the 5V pin on the Arduino to the positive rail (5V) of the breadboard.
Connect the GND pin on the Arduino to the ground rail (GND) of the breadboard.
Ensure the AA Battery Holder is connected to the Arduino's 5V and GND pins if using battery power instead of USB.

Ultrasonic Sensor Connections

Materials Needed:

Ultrasonic Sensor
4 wires

Assembly:

Connect the Ultrasonic Sensor to pins: J24 (VCC), J23 (TRIG), J22 (ECHO), J21 (GND)
The sensor should face away from the board.
Arduino and Breadboard Wiring:
TRIG → Digital Pin 7
Wire I23 to Pin 7
ECHO → Digital Pin 6
Wire I22 to Pin 6
VCC to 5V rail
Wire I24 to 5V
GND to the GND rail
Wire I21 to GND

LED RGB Connections

Materials Needed:

RGB LED
3, 330 Ω resistors
4 Female - Male connector wires

Assembly:

RGB LED:
Connection to the breadboard is temporary (as shown in the photos)
Attach each of the F-M connector wires to the legs of the RBG LEB
Connect the F-M wires of the LED to pins J1, J2 (GND long leg), J3, and J4
Breadboard and Arduino:
Connect resistors to the LED on the breadboard
Resistor 1: F1 to E1 (connected to Arduino Pin 9) (Wire A1 to Pin 9)
Resistor 2: F3 to E3 (connected to Arduino Pin 10) (Wire A3 to Pin 10)
Resistor 3: F4 to E4 (connected to Arduino Pin 11) (Wire A4 to Pin 11)
Connect the common cathode (GND pin) of the LED RGB to the ground rail on the breadboard. Wire (A2 to (-)GND)

Tactile Button Connections

Materials Needed:

2 tactile buttons
4 wires

Assembly:

Button 1 (Red): F8, F10, C8, C10
Connect one side to (-)GND on the Arduino. (Wire A8 to GND)
Connect the other side to Digital Pin 5 on the Arduino. (Wire A10 to GND)
Button 2 (Blue): F14, F16, C14, C16
Connect one side to (-)GND on the Arduino. (Wire A14 to GND)
Connect the other side to Digital Pin 4 on the Arduino. Wire (A16 to GND)

Micro Servo Connections

Materials Needed:

Micro servo
2 wires

Assembly:

Connect the signal pin of the servo to Digital Pin 3 on the Arduino. (White wire)
Connect the power (VCC) pin to the 5V rail on the breadboard. (Red Wire)
Connect the ground (GND) pin to the GND rail on the breadboard. (Black Wire)

Download Code

You need to complete this step now so that the Arduino stores the code in its memory. This ensures it can operate independently, running off batteries later, instead of relying on being plugged into a computer to execute the program.

Code download is at the bottom of this step.

Steps:

Plug in the board to the HDMI port of your device (computer/laptop)
Download the Arduino IDE app
Select Arduino Uno in the app
Press the checkmark (Verify) and arrow (Upload) buttons in the top left to run the code

// Arduino Anti-Theft Code

// C++ Code

// Seting up servo and distance vars

#include <Servo.h>

Servo myservo;

float getDistance(); // function to measure distance from sensor

float distance; // variable for stracking current distance

float initialDistance; // intital distance measured when armed

float thresholdDistance = 05; // allowed tolerance of movement

// variable for tracking system states

bool isArmed;

bool alarmTriggered;

//Declare pins

int trigPin = 7; // sensor pins

int echoPin = 6;

int startButtonPin = 5; // button pins

int disarmButtonPin = 4;

int servoPin = 3; // servo controller

int redpin = 9; // LED pins for different colors

int bluepin = 10;

int greenpin = 11;// on physical board, green and blue pin are switched

// Function to measure distance from ultrasonic sensor

float getDistance() {

long duration;

float currentDistance;

digitalWrite(trigPin, LOW);

delayMicroseconds(2);

digitalWrite(trigPin, HIGH);

delayMicroseconds(10);

digitalWrite(trigPin, LOW);

duration = pulseIn(echoPin, HIGH);

currentDistance = (duration*0.034) / 2; // Convert time to distance in cm return distance

return currentDistance;

}

void setup()

{

//setup pins

pinMode(trigPin, OUTPUT);

pinMode(echoPin, INPUT);

pinMode(startButtonPin, INPUT_PULLUP);

pinMode(disarmButtonPin, INPUT_PULLUP);

pinMode(redpin, OUTPUT);

pinMode(bluepin, OUTPUT);

pinMode(greenpin, OUTPUT);

//servo

myservo.attach(servoPin);

myservo.write(100);

//Initial system states

isArmed = false; // System starts unarmed

alarmTriggered = false; // alarm starts untriggered

}

// Function to handle the main logic

void loop()

{

//first, check if alarm is triggered

if (alarmTriggered == true)

{

//pulse red and move servo back and forth to hit noisemaker

analogWrite(redpin, 255); // red intensity 1

analogWrite(bluepin, 0);

analogWrite(greenpin,0);

myservo.write(20);//position 1

delay(400);

analogWrite(redpin, 0); // red intensity 2

analogWrite(bluepin, 0);

analogWrite(greenpin,0);

myservo.write(120);//position 2

delay(250);

}

//if alarm not triggered

else

{

// Arm/Trigger logic

//start button pressed

if (digitalRead(startButtonPin) == LOW)

{

//not armed

if (isArmed == false)

{

initialDistance = getDistance(); // Set initial distance

isArmed = true; // Arm the system

analogWrite(redpin, 0);

analogWrite(bluepin, 0);

analogWrite(greenpin,255); // Green

delay(250); // Debounce delay

}

//already armed -->flash red

else

{

analogWrite(redpin, 255); // Red

analogWrite(bluepin, 0);

analogWrite(greenpin,0);

delay(250);

analogWrite(redpin, 0);

analogWrite(bluepin, 0);

analogWrite(greenpin,255); // Green

delay(250);

}

//still under 'if alarm not triggered'

// When the system is armed, track distance and check if alarm needs to be triggered

if (isArmed == true)

{

analogWrite(redpin, 0);

analogWrite(bluepin, 0);

analogWrite(greenpin,255); // Green

distance = getDistance(); // Measure current distance

// If the alram isn't triggered, and the sensor moves out of the threshold, trigger alarm and move servo

if (alarmTriggered == false && (abs(distance-initialDistance) > thresholdDistance))

{

alarmTriggered = true; // Set alarm state to triggered

}

/* Disarm logic

- has to be outside the 'if alarm is triggered' statement

because we want to be able to disarm it even if it's not triggered

*/

if (digitalRead(disarmButtonPin) == LOW)// Disarm button is pressed

{

isArmed = false; // Disarm the system

alarmTriggered = false; // Reset alarm state

analogWrite(redpin, 0);

analogWrite(bluepin, 255); // Reset LED to blue (unarmed)

analogWrite(greenpin, 0);

myservo.write(100);

delay(1000); // Debounce delay

}

if (isArmed == false) //system is on and unarmed

{

analogWrite(redpin, 0);

analogWrite(bluepin, 255); // Blue

analogWrite(greenpin, 0);

}

Downloads

Final Code.ino

Print 3D Models

Files to Print:

2 Extended Button Rods
1 Breadboard Cover
1 Arduino Cover
1 Bell Stand

Downloads

Anti-Theft Bell Stand.SLDPRT

Anti-Theft Breadboard Cover.SLDPRT

Anti-Theft Arduino Cover.SLDPRT

Anti-Theft Button Rods.SLDPRT

Assemble

This step does NOT utilize the bell stand.

Assembly:

Lay newly printed pieces on top of assigned place
Thread LED RGB and Micro Servo into correct places
Tape the battery pack to any desired place

Extend Micro Servo

Materials Needed

1 screw

Assembly:

Secure the screw with tape to the micro servo's arm

Bell Installation

Materials Needed:

3D printed bell stand
1 bell
Thread/wire
Hot glue

Assembly:

Glue the stand to the device, directly between the two covers
Tie and hang the bell to the stand using a thread or wire

Run the Code

Congratulations! The project is complete. Once the Arduino is powered on, the system is active. Press the red button to arm the device, and hold down the blue button to disarm it after movement is detected.