RADAR System Using Arduino UNO & Ultrasonic Sensor
Build a fully functional 180° scanning RADAR that sweeps an HC-SR04 ultrasonic sensor on a servo motor, measures distances at every angle, and streams live data to the Serial Monitor — a perfect STEM and science fair project.
What You'll Build
The servo rotates the HC-SR04 sensor in 1° steps from 0° to 180°. At every angle the sensor fires an ultrasonic pulse, times the echo, and calculates the distance. The Arduino prints both the angle and distance to the Serial Monitor — simulating the sweep of a real RADAR system. Optional: pipe the Serial output into the Processing IDE to render a graphical RADAR display.
Scan Range
0° – 180°
Max Distance
~400 cm
Difficulty
Intermediate
Build Time
1 – 2 Hours
How It Works
5-Step Scan Cycle
- Step 1 — Servo writes angle (0–180°) and waits 15ms to settle
- Step 2 — Arduino pulses TRIG pin HIGH for 10µs
- Step 3 — Ultrasound travels out, hits object, returns
- Step 4 —
pulseIn(ECHO)captures echo duration in µs - Step 5 — Distance calculated and printed with angle to Serial
Servo sweeps 0° → 180°
The for loop increments the servo angle by 1° each iteration, then waits 15ms for the servo to physically reach the position before taking a reading.
Ultrasonic ping fired
TRIG is pulled LOW (2µs), then HIGH (10µs), then LOW again. This generates a precise 40kHz ultrasonic burst from the HC-SR04's transmitter.
Echo timed with pulseIn()
pulseIn(echoPin, HIGH) returns the microsecond duration of the echo pulse — the time taken for the sound wave to reach an object and return.
Distance calculated
Distance (cm) = duration × 0.0343 ÷ 2. The ÷2 accounts for the round trip — the pulse travels to the object and back, so only half the total time equals the one-way distance.
Angle + Distance printed to Serial Monitor
The Arduino streams "Angle: X | Distance: Y cm" at 9600 baud for every degree, creating a complete map of the scanned environment.
Distance Formula
Components Required
| Component | Qty | Purpose |
|---|---|---|
| Arduino UNO (R3) | ×1 | Main controller — runs servo sweep and distance logic |
| HC-SR04 Ultrasonic Sensor | ×1 | Measures distance via sound echo (2–400 cm range) |
| SG90 Servo Motor | ×1 | Rotates the HC-SR04 through 0–180° |
| Breadboard | ×1 | Prototyping power rails for clean wiring |
| Jumper Wires (M-M, M-F) | ×15+ | All signal and power connections |
| USB Cable / 5V Power Supply | ×1 | Powers Arduino and servo |
Servo.h is built into the Arduino IDE — no extra installation required. The HC-SR04 is read using built-in pulseIn() — no library needed.
Circuit Diagram
Wiring Diagram
● radar_arduino.json — Circuit Overview
Pin Connection Map
HC-SR04 Ultrasonic
VCC→ Arduino 5V
GND→ Arduino GND
TRIG→ Arduino D9
ECHO→ Arduino D10
SG90 Servo Motor
Red→ Arduino 5V
Brown / Black→ Arduino GND
Orange / Yellow→ Arduino D6 (Signal)
Simulation File
diagram.json (Wokwi)
📁 How to use: Go to wokwi.com, click the diagram.json tab and replace all contents with the JSON below. Create a sketch.ino file and paste the code from the next section. Press ▶ to run.
diagram.json
{
"version": 1,
"author": "MakeMindz",
"editor": "wokwi",
"parts": [
{
"type": "wokwi-arduino-uno",
"id": "uno",
"top": 130,
"left": 295,
"attrs": {}
},
{
"type": "wokwi-hc-sr04",
"id": "sonar",
"top": 80,
"left": 30,
"attrs": { "distance": "25" }
},
{
"type": "wokwi-servo",
"id": "servo1",
"top": 280,
"left": 30,
"attrs": { "angle": "90", "horn": "single" }
}
],
"connections": [
["sonar:VCC", "uno:5V", "red", []],
["sonar:GND", "uno:GND", "black", []],
["sonar:TRIG", "uno:9", "orange", []],
["sonar:ECHO", "uno:10", "purple", []],
["servo1:V+", "uno:5V", "red", []],
["servo1:GND", "uno:GND", "black", []],
["servo1:PWM", "uno:6", "orange", []]
]
}
💡
Wokwi tip: Click the HC-SR04 in the simulation and drag its Distance slider to simulate objects at different ranges. Watch the Serial Monitor update in real time as the servo sweeps and distance changes.
Build Guide
Step-by-Step Instructions
1
Mount HC-SR04 on Servo Horn
Fix the HC-SR04 sensor onto the SG90 servo horn using double-sided tape or a cable tie. Ensure both transmitter (T) and receiver (R) cylinders face forward and the sensor is centred on the horn so it rotates evenly.
2
Wire the HC-SR04 Sensor
- VCC → Arduino 5V
- GND → Arduino GND
- TRIG → Arduino D9
- ECHO → Arduino D10
Use male-to-female jumper wires from the sensor to the Arduino headers directly, or via a breadboard power rail.
3
Wire the SG90 Servo Motor
- Red wire → Arduino 5V
- Brown / Black wire → Arduino GND
- Orange / Yellow signal wire → Arduino D6
⚠️
Powering the servo directly from the Arduino 5V pin works for a single SG90 in simulation. For real hardware with multiple servos or longer sweep times, use an external 5V supply shared with the Arduino GND to avoid voltage drops.
4
Manage the Rotating Wires
Route the HC-SR04 wires loosely alongside the servo so they don't pull tight at 0° or 180°. Coil any extra wire and secure with a small cable tie — leave enough slack for full 180° rotation without snagging.
5
Open Arduino IDE and Include Servo Library
Download the Arduino IDE from arduino.cc. The Servo.h library is built in — no extra installation needed. Select Board → Arduino UNO and your USB port.
6
Upload the Sketch
Copy the full code from the section below, paste it into a new Arduino IDE sketch, and click the Upload arrow. Wait for "Done uploading" before opening the Serial Monitor.
7
Open Serial Monitor & Observe
Go to Tools → Serial Monitor. Set baud rate to 9600. You should see lines like Angle: 45 | Distance: 22 cm streaming as the servo sweeps. Place objects at different distances and angles to see readings change.
8
(Optional) Add Processing IDE Graphical Display
Download the Processing sketch and run it alongside the Arduino sketch. It reads the Serial port and renders a live green-on-black RADAR sweep with object blips — just like a real RADAR display.
Arduino Sketch
Full Source Code
radar_system.ino
// ─────────────────────────────────────────────────────
// RADAR System — Arduino UNO + HC-SR04 + SG90 Servo
// MakeMindz.com | roboticsandcircuits.blogspot.com
// Sweeps 0–180°, measures distance at each angle,
// streams Angle + Distance to Serial Monitor (9600 baud)
// ─────────────────────────────────────────────────────
#include <Servo.h>
// ── Pin Definitions ──────────────────────────────────
#define trigPin 9 // HC-SR04 trigger output
#define echoPin 10 // HC-SR04 echo input
#define servoPin 6 // SG90 PWM signal
// ── Object Declaration ───────────────────────────────
Servo radarServo;
// ── Global Variables ─────────────────────────────────
long duration; // Echo pulse duration in microseconds
int distance; // Calculated distance in cm
// ── setup() ──────────────────────────────────────────
void setup() {
Serial.begin(9600);
pinMode(trigPin, OUTPUT);
pinMode(echoPin, INPUT);
radarServo.attach(servoPin);
Serial.println("RADAR System — MakeMindz.com");
Serial.println("──────────────────────────────");
}
// ── loop() ───────────────────────────────────────────
// Sweeps servo 0° → 180° taking a distance reading every 1°
void loop() {
for (int angle = 0; angle <= 180; angle++) {
// Step 1: Rotate servo to current angle
radarServo.write(angle);
delay(15); // Wait for servo to reach position
// Step 2: Send ultrasonic pulse
// Pull TRIG low first to ensure clean pulse
digitalWrite(trigPin, LOW);
delayMicroseconds(2);
// HIGH pulse for exactly 10µs fires the sonic burst
digitalWrite(trigPin, HIGH);
delayMicroseconds(10);
digitalWrite(trigPin, LOW);
// Step 3: Measure echo duration
duration = pulseIn(echoPin, HIGH);
// Step 4: Calculate distance
// distance = duration × speed_of_sound ÷ 2
// speed of sound = 0.0343 cm/µs at 20°C
distance = duration * 0.0343 / 2;
// Step 5: Print angle and distance to Serial Monitor
Serial.print("Angle: ");
Serial.print(angle);
Serial.print(" | Distance: ");
Serial.print(distance);
Serial.println(" cm");
}
// After full 180° sweep, loop() restarts automatically
// Add a reverse sweep here if you want a back-and-forth motion:
// for (int angle = 180; angle >= 0; angle--) { ... }
}
Example Serial Monitor Output
// Serial Monitor — 9600 baud
RADAR System — MakeMindz.com
──────────────────────────────
Angle: 30 | Distance: 25 cm
Angle: 60 | Distance: 18 cm
Angle: 90 | Distance: 10 cm ← close object detected
Angle: 120 | Distance: 33 cm
Angle: 150 | Distance: 47 cm
Angle: 180 | Distance: 52 cm
Online Simulation
Test Without Hardware
Live simulation — pre-built on Tinkercad
The complete RADAR circuit is already set up on Tinkercad. Click the Tinkercad link below to open it, press Simulate, open the Serial Monitor, and watch angle + distance data stream live. Drag the HC-SR04 distance slider to place virtual objects.
✅
Tinkercad advantage: This simulation is pre-wired — just click Simulate and Start Simulation. No setup required. Use it to test your understanding of the code before building the physical circuit.
Learning Outcomes
What You'll Learn
Ultrasonic Distance Measurement
Understand how sound pulses, echo timing, and the pulseIn() function work together.
Servo Motor Control
Use the Servo library to precisely position the SG90 at any angle between 0° and 180°.
Angle-Based Scanning
Learn how iterating servo angles creates a spatial map of objects around the sensor.
Serial Communication
Stream structured data from Arduino to the Serial Monitor for real-time analysis.
Physics — Speed of Sound
Apply the distance = speed × time formula and understand why we divide by 2.
Sensor + Actuator Integration
Combine an input sensor and output actuator into a single coordinated embedded system.
Next Steps
Advanced Improvements
🖥️Processing IDE graphical RADAR display
📺OLED display for live distance output
🔔Buzzer alert when object is within 20 cm
💡LED bar graph for proximity indication
💾SD card data logging with timestamps
🔄360° continuous rotation servo scanning
Real-World Use Cases
Applications
Obstacle Detection
Foundation for autonomous robot navigation — detect and map surrounding obstacles.
Parking Sensor Prototype
Scan a parking area and alert when a vehicle enters the detection zone.
Surveillance Simulation
Sweep-scan a room boundary and log any object positions detected during the scan.
STEM Exhibition
Impressive science fair project that demonstrates real engineering radar concepts.
More from MakeMindz
Explore More Projects
⭐ Beginner Projects
🔧 Intermediate Projects
🚀 Advanced Projects
Wiring Diagram
Pin Connection Map
HC-SR04 Ultrasonic
SG90 Servo Motor
diagram.json (Wokwi)
sketch.ino file and paste the code from the next section. Press ▶ to run.
{
"version": 1,
"author": "MakeMindz",
"editor": "wokwi",
"parts": [
{
"type": "wokwi-arduino-uno",
"id": "uno",
"top": 130,
"left": 295,
"attrs": {}
},
{
"type": "wokwi-hc-sr04",
"id": "sonar",
"top": 80,
"left": 30,
"attrs": { "distance": "25" }
},
{
"type": "wokwi-servo",
"id": "servo1",
"top": 280,
"left": 30,
"attrs": { "angle": "90", "horn": "single" }
}
],
"connections": [
["sonar:VCC", "uno:5V", "red", []],
["sonar:GND", "uno:GND", "black", []],
["sonar:TRIG", "uno:9", "orange", []],
["sonar:ECHO", "uno:10", "purple", []],
["servo1:V+", "uno:5V", "red", []],
["servo1:GND", "uno:GND", "black", []],
["servo1:PWM", "uno:6", "orange", []]
]
}
Step-by-Step Instructions
Mount HC-SR04 on Servo Horn
Fix the HC-SR04 sensor onto the SG90 servo horn using double-sided tape or a cable tie. Ensure both transmitter (T) and receiver (R) cylinders face forward and the sensor is centred on the horn so it rotates evenly.
Wire the HC-SR04 Sensor
- VCC → Arduino 5V
- GND → Arduino GND
- TRIG → Arduino D9
- ECHO → Arduino D10
Use male-to-female jumper wires from the sensor to the Arduino headers directly, or via a breadboard power rail.
Wire the SG90 Servo Motor
- Red wire → Arduino 5V
- Brown / Black wire → Arduino GND
- Orange / Yellow signal wire → Arduino D6
Manage the Rotating Wires
Route the HC-SR04 wires loosely alongside the servo so they don't pull tight at 0° or 180°. Coil any extra wire and secure with a small cable tie — leave enough slack for full 180° rotation without snagging.
Open Arduino IDE and Include Servo Library
Download the Arduino IDE from arduino.cc. The Servo.h library is built in — no extra installation needed. Select Board → Arduino UNO and your USB port.
Upload the Sketch
Copy the full code from the section below, paste it into a new Arduino IDE sketch, and click the Upload arrow. Wait for "Done uploading" before opening the Serial Monitor.
Open Serial Monitor & Observe
Go to Tools → Serial Monitor. Set baud rate to 9600. You should see lines like Angle: 45 | Distance: 22 cm streaming as the servo sweeps. Place objects at different distances and angles to see readings change.
(Optional) Add Processing IDE Graphical Display
Download the Processing sketch and run it alongside the Arduino sketch. It reads the Serial port and renders a live green-on-black RADAR sweep with object blips — just like a real RADAR display.
Full Source Code
// ───────────────────────────────────────────────────── // RADAR System — Arduino UNO + HC-SR04 + SG90 Servo // MakeMindz.com | roboticsandcircuits.blogspot.com // Sweeps 0–180°, measures distance at each angle, // streams Angle + Distance to Serial Monitor (9600 baud) // ───────────────────────────────────────────────────── #include <Servo.h> // ── Pin Definitions ────────────────────────────────── #define trigPin 9 // HC-SR04 trigger output #define echoPin 10 // HC-SR04 echo input #define servoPin 6 // SG90 PWM signal // ── Object Declaration ─────────────────────────────── Servo radarServo; // ── Global Variables ───────────────────────────────── long duration; // Echo pulse duration in microseconds int distance; // Calculated distance in cm // ── setup() ────────────────────────────────────────── void setup() { Serial.begin(9600); pinMode(trigPin, OUTPUT); pinMode(echoPin, INPUT); radarServo.attach(servoPin); Serial.println("RADAR System — MakeMindz.com"); Serial.println("──────────────────────────────"); } // ── loop() ─────────────────────────────────────────── // Sweeps servo 0° → 180° taking a distance reading every 1° void loop() { for (int angle = 0; angle <= 180; angle++) { // Step 1: Rotate servo to current angle radarServo.write(angle); delay(15); // Wait for servo to reach position // Step 2: Send ultrasonic pulse // Pull TRIG low first to ensure clean pulse digitalWrite(trigPin, LOW); delayMicroseconds(2); // HIGH pulse for exactly 10µs fires the sonic burst digitalWrite(trigPin, HIGH); delayMicroseconds(10); digitalWrite(trigPin, LOW); // Step 3: Measure echo duration duration = pulseIn(echoPin, HIGH); // Step 4: Calculate distance // distance = duration × speed_of_sound ÷ 2 // speed of sound = 0.0343 cm/µs at 20°C distance = duration * 0.0343 / 2; // Step 5: Print angle and distance to Serial Monitor Serial.print("Angle: "); Serial.print(angle); Serial.print(" | Distance: "); Serial.print(distance); Serial.println(" cm"); } // After full 180° sweep, loop() restarts automatically // Add a reverse sweep here if you want a back-and-forth motion: // for (int angle = 180; angle >= 0; angle--) { ... } }
Example Serial Monitor Output
RADAR System — MakeMindz.com
──────────────────────────────
Angle: 30 | Distance: 25 cm
Angle: 60 | Distance: 18 cm
Angle: 90 | Distance: 10 cm ← close object detected
Angle: 120 | Distance: 33 cm
Angle: 150 | Distance: 47 cm
Angle: 180 | Distance: 52 cm
Test Without Hardware
Live simulation — pre-built on Tinkercad
The complete RADAR circuit is already set up on Tinkercad. Click the Tinkercad link below to open it, press Simulate, open the Serial Monitor, and watch angle + distance data stream live. Drag the HC-SR04 distance slider to place virtual objects.
What You'll Learn
Ultrasonic Distance Measurement
Understand how sound pulses, echo timing, and the pulseIn() function work together.
Servo Motor Control
Use the Servo library to precisely position the SG90 at any angle between 0° and 180°.
Angle-Based Scanning
Learn how iterating servo angles creates a spatial map of objects around the sensor.
Serial Communication
Stream structured data from Arduino to the Serial Monitor for real-time analysis.
Physics — Speed of Sound
Apply the distance = speed × time formula and understand why we divide by 2.
Sensor + Actuator Integration
Combine an input sensor and output actuator into a single coordinated embedded system.
Advanced Improvements
Applications
Obstacle Detection
Foundation for autonomous robot navigation — detect and map surrounding obstacles.
Parking Sensor Prototype
Scan a parking area and alert when a vehicle enters the detection zone.
Surveillance Simulation
Sweep-scan a room boundary and log any object positions detected during the scan.
STEM Exhibition
Impressive science fair project that demonstrates real engineering radar concepts.
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