Ultrasonic LED Radar

In this guide, created by Zaitronics, you will learn how to build an LED radar system using an Arduino Nano, HC-SR04 ultrasonic distance sensor, SG90 servo motor, and a pack of LEDs. The sensor will be mounted on the servo to scan the surrounding area, while LEDs will indicate the presence of objects detected by the sensor.

Video available on our Youtube

Let's get started!

Materials Needed

• Arduino Nano
• HC-SR04 Ultrasonic Sensor
• SG90 Servo Motor
• Pack of LEDs (multiple colours optional)
• Jumper wires (assorted)
• Breadboards (at least two, one for Arduino and wiring, one for LEDs)
• Resistors

Arduino Setup:

• Place the Arduino Nano on a breadboard.
• Connect the VCC and GND of the Arduino to the breadboard power rails (+ and -).
• Connect the VCC and GND of the HC-SR04 sensor to the breadboard power rails.
• Connect the trigPin (Arduino pin 9) and echoPin (Arduino pin 10) of the HC-SR04 to digital pins on the Arduino Nano.

Servo Setup:

• Mount the SG90 servo motor securely next to the breadboard.
• Connect the VCC (usually red wire) and GND (usually brown wire) of the servo to the breadboard power rails.
• Connect the control signal wire (usually yellow or orange) of the servo to a digital pin on the Arduino Nano (e.g., pin 8).

• Use the second breadboard for LEDs.
• Place the LEDs in a line facing outward from the centre of the breadboard.
• Connect the longer leg (anode) of each LED to individual lines of positive power
• Connect the shorter leg (cathode) of each LED to a shared ground rail on the breadboard.
• Connect the individual lines of positive power to the corresponding digital output pins on the Arduino Nano (e.g., pins 2 to 6).
• We highly recommend using resistors but we didn't as the LEDs weren't on for long

• Connect the Arduino Nano to your computer via USB.
• Open the Arduino IDE, copy over the provided code, and upload it to the Arduino Nano.

/*
 * Ultrasonic radar
 *
 * https://zaitronics.com.au/blogs/main/led-radar-using-ultrasonic-distance-measuring-sensor-servo
 *
 * by Ethan - Zaitronics
 */
#include <Servo.h>

// Define pins for HC-SR04
const int trigPin = 9;
const int echoPin = 10;

// Define pins for LEDs
const int ledPins[] = {2, 3, 4, 5, 6};

// Define pin for servo motor
const int servoPin = 8;

Servo myServo;
long previousMillis = 0;
const long interval = 500; // Interval for distance measurement
int pos = 45; // Initial position of the servo
int step = 1; // Step size for the servo movement
bool objectDetected = false;

void setup() {
  // Initialize serial communication for debugging
  Serial.begin(9600);

  // Initialize pins for HC-SR04
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);

  // Initialize LED pins as outputs
  for (int i = 0; i < 5; i++) {
    pinMode(ledPins[i], OUTPUT);
    digitalWrite(ledPins[i], LOW); // Ensure all LEDs are off initially
  }

  // Attach the servo motor to the servo pin
  myServo.attach(servoPin);

  // Initialize the servo position to 45 degrees
  myServo.write(45);
}

void loop() {
  // Get the current time
  unsigned long currentMillis = millis();

  // Check if it's time to measure the distance
  if (currentMillis - previousMillis >= interval) {
    // Save the last time a measurement was taken
    previousMillis = currentMillis;

    // Measure distance
    long duration, distance;
    digitalWrite(trigPin, LOW);
    delayMicroseconds(2);
    digitalWrite(trigPin, HIGH);
    delayMicroseconds(10);
    digitalWrite(trigPin, LOW);
    duration = pulseIn(echoPin, HIGH);

    // Calculate the distance in cm
    distance = duration * 0.034 / 2;

    // Print the distance and servo position for debugging
    Serial.print("Distance: ");
    Serial.print(distance);
    Serial.print(" cm, Servo Position: ");
    Serial.println(pos);

    // Determine if an object is detected within 20 cm
    objectDetected = (distance <= 20);
  }

  // Turn off all LEDs initially
  for (int i = 0; i < 5; i++) {
    digitalWrite(ledPins[i], LOW);
  }

  // Determine which LED to turn on based on the servo position and distance
  if (objectDetected) {
    if (pos >= 45 && pos < 63) {
      digitalWrite(ledPins[0], HIGH);
    } else if (pos >= 63 && pos < 81) {
      digitalWrite(ledPins[1], HIGH);
    } else if (pos >= 81 && pos < 99) {
      digitalWrite(ledPins[2], HIGH);
    } else if (pos >= 99 && pos < 117) {
      digitalWrite(ledPins[3], HIGH);
    } else if (pos >= 117 && pos <= 135) {
      digitalWrite(ledPins[4], HIGH);
    }
  }

  // Move the servo from 45 to 135 degrees and back
  myServo.write(pos);
  pos += step;
  if (pos >= 135 || pos <= 45) {
    step = -step; // Reverse the direction
  }

  delay(20); // Adjust the delay to control the servo speed
}

Congratulations! You've successfully built an LED radar system using an Arduino Nano, HC-SR04 ultrasonic sensor, SG90 servo motor, and LEDs. Experiment with different positions and angles to optimize the detection range and LED indicators. This project serves as a great foundation for further exploration into robotics and sensor-based applications.