Ultrasonic Scanner

What You'll Build

You will build a miniature radar station. A servo slowly sweeps an ultrasonic sensor from 15° to 165° and back, and at every angle the sensor measures how far away the nearest object is. The angle and distance pair gets printed to the Serial Monitor so you can watch objects appear and disappear as the beam passes over them.

What You Need

• ✓Arduino Uno
• ✓HC-SR04 ultrasonic sensor
• ✓SG90 servo
• ✓Breadboard
• ✓Jumper wires

How It Works

The HC-SR04 works like a bat. It sends out a burst of sound too high for humans to hear, then measures how long the echo takes to come back. Because sound travels about 0.034 cm per microsecond, distance equals time divided by two, multiplied by that speed. The servo simply rotates the sensor so you can scan a whole area instead of one direction.

Wiring

Step-by-Step Instructions

1. 1

   Mount the sensor

   Tape or glue the ultrasonic sensor onto the servo horn so the two 'eyes' face forward. Keep the wires loose enough to turn.

2. 2

   Power the servo properly

   Use a regulated 5V supply for the servo when possible. An SG90 can pull 600–700 mA when it stalls, which is more than the Arduino's 5V pin can supply safely. Give the servo its own regulated 5V source and connect servo GND and Arduino GND together. Do not connect an unknown-voltage battery directly to the servo.

3. 3

   Test distance alone

   Before adding movement, upload a short sketch that just prints the distance. Wave your hand and check the numbers make sense.

4. 4

   Add the sweep

   Now let the servo step one degree at a time. A short delay after each step gives the servo time to actually arrive before you measure.

5. 5

   Read the output

   Open the Serial Monitor and watch pairs like 90,42 — angle 90 degrees, 42 centimetres away.

Arduino Code

#include <Servo.h>

Servo radar;
const int TRIG = 10;
const int ECHO = 9;

void setup() {
  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);
  radar.attach(11);
  Serial.begin(9600);
}

int readDistance() {
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);
  long duration = pulseIn(ECHO, HIGH);
  return duration * 0.034 / 2;
}

void loop() {
  for (int angle = 15; angle <= 165; angle++) {
    radar.write(angle);
    delay(30);
    Serial.print(angle);
    Serial.print(",");
    Serial.println(readDistance());
  }
  for (int angle = 165; angle > 15; angle--) {
    radar.write(angle);
    delay(30);
    Serial.print(angle);
    Serial.print(",");
    Serial.println(readDistance());
  }
}

Understanding the Code

Challenges & Upgrades

Troubleshooting