Build an Ultrasonic Intruder Alarm with LED Indicator

2022-12-07 | By Maker.io Staff

License: See Original Project

You probably have seen robotic projects with a device that looks like a pair of eyes and wonder, ‎what is that part? Well, you do not have to wonder because, in this project, you will learn how ‎to build an Ultrasonic Intruder Alarm using an Arduino Uno and a few off-the-shelf electronic ‎components. In this hands-on project, you will learn how to wire an ultrasonic sensor to an ‎Arduino. Further, while wiring the sensor to the Arduino, you will build an electronic tape ‎measure to allow adjusting the intruder detection distance with your electronic alarm unit. To ‎build the Ultrasonic Intruder Alarm with an LED indicator, you will find the electronic ‎components required to build the project at the Digikey SchemeIt BOM (Bill of Materials) ‎website. Here is the electronic circuit schematic diagram and BOM link for the Ultrasonic ‎Intruder Alarm project; https://www.digikey.com/schemeit/project/ultrasonic-intruder-alarm-‎‎6ce7fdbfe769417da2071905044d13bb/. The functional concept of the device is to provide an ‎audible and visual alarm upon detection of a human within a specified sensing zone.

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Ultrasonic Intruder Alarm with an LED Indicator device Concept Diagram

The four main subcircuit components to build the electronic intruder alarm device include an ‎ultrasonic sensor, an Arduino Uno, a piezoelectric buzzer, and a LED circuit. The LED circuit ‎consists of a series limiting resistor and a discrete LED. A block diagram showing the electrical ‎wiring relationship between the subcircuit components is shown below.‎

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The Ultrasonic Intruder Alarm Block Diagram

How Does an Ultrasonic Sensor Work?‎

A device that uses ultrasonic sound waves to measure an object’s distance is called an ‎ultrasonic sensor. Ultrasonic sensor transducers send and receive ultra-high frequency sound ‎waves to obtain an object’s distance or proximity. The transducers are a microphone and a ‎speaker. The ultra-high frequency sound waves are reflected from an object’s surface, creating ‎a unique echo pattern.‎‎ ‎

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An HC-SR04 ultrasonic sensor with transducers.‎

The below image illustrates the ultrasonic sensor’s ultra-high frequency sound waves being ‎reflected from an object’s surface.‎

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Sent and reflected waves: ultrasonic sensor basic operation.‎

Wiring an ultrasonic sensor to an Arduino (TinkerCad Circuits)‎

With a basic understanding of how an ultrasonic sensor works, you are now ready to wire the device to ‎an Arduino. To explore the operation of the ultrasonic sensor, you can build a virtual functional circuit ‎using TinkerCad Circuits. TinkerCad Circuits is a free online circuit simulator that allows a variety of ‎electrical and electronic circuits to be simulated prior to wiring them on a real breadboard. You can ‎even test Arduino projects (including the code) with TinkerCad Circuits. You can gain valuable ‎electronics knowledge through experimentation prior to committing the building the physical circuit.‎

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An example online ultrasonic sensor-Arduino TinkerCad Circuit

Wiring a real ultrasonic sensor with an Arduino on a breadboard

You can use the ultrasonic sensor-Arduino circuit built in TinkerCad Circuits or the electrical wiring ‎diagram shown below to build your intruder alarm device. You can place the ultrasonic sensor as ‎shown on the breadboard and use jumper wires to complete the wiring of the sensing device to the ‎Arduino.‎

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The electrical wiring diagram for the Ultrasonic Intruder Alarm with LED indicator

Here’s the final prototype built using discrete components to create the Ultrasonic Intruder Alarm with ‎an Arduino Uno.‎

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The final Ultrasonic Intruder Alarm prototype

The HC SR04 ultrasonic sensor 4-pin terminals that attach to the Arduino are included in the previously ‎linked schematic diagram. As an additional reference, the below wiring table will assist in wiring the ‎connections between the Arduino Uno and the ultrasonic sensor.‎

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The 4-pin wiring connection of the Arduino Uno to the ultrasonic sensor.‎

Congratulations, you have just wired an ultrasonic sensor to an Arduino. You are now ready to install ‎‎(upload) the ultrasonic sensor code to the Arduino Uno.‎

The Ultrasonic Intruder Alarm code

Attach the Arduino Uno to your desktop PC or laptop computer using a USB cable. You can type the ‎code into the Arduino Integrated Development Environment (IDE) using the code shown below or you ‎can download the code. With the code displayed in the Arduino IDE, you can upload the code by ‎clicking the horizontal arrow.‎

Copy Code

#define TRIG_PIN 11
#define ECHO_PIN 10
int LEDpin = 13;
SR04 sr04 = SR04(ECHO_PIN,TRIG_PIN);
long a;
 
void setup() {
  pinMode(LEDpin, OUTPUT);
   Serial.begin(9600);
   delay(1000);
}
 
void loop() {
   a=sr04.Distance();
   Serial.print(a);
   Serial.println("cm");
   delay(1000);
   if(a < 200) {
     digitalWrite(LEDpin, HIGH);
   }
   else{
     digitalWrite(LEDpin, LOW);
   }
}

Placing your hand or object in front of the ultrasonic sensor will turn on the LED indicator and sound ‎the piezo buzzer. Here is a short video illustrating the Ultrasonic Intruder Alarm’s operation; ‎https://youtu.be/X5-RfRhKBwk. Additionally, by opening the Serial Monitor within the Arduino IDE, ‎you should see distance data scrolling down in the Arduino IDE. Below is an example of the data from ‎the distance measuring circuit. Place a small scale or ruler between the ultrasonic sensor and the ‎object’s distance to measure. How accurate are your readings compared to the actual distance ‎measured? This integrated measurement feature may be used to adjust the sensing distance of the ‎object or intruder you want to detect. You have successfully built an ultrasonic intruder alarm. ‎Congratulations again!! You can detect and observe a variety of objects and their measured distance ‎with an electronic detection device.‎

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