RADAR stands for Radio Detection and Ranging. It’s a technology that detects the presence, distance, and sometimes speed of objects by sending out a signal (traditionally radio waves) and measuring how long it takes for that signal to bounce off an object and return.
The basic principle is simple:
This project uses the same core principle, but with ultrasonic sound waves instead of radio waves — technically this makes it a SONAR-style system (Sound Navigation And Ranging), though it mimics a radar’s sweeping display and behaviour. The physics of “send a wave, time the echo, calculate distance” is identical.
This is an Arduino-based radar system. An ultrasonic sensor mounted on a servo motor sweeps back and forth like a real radar, measuring the distance to nearby objects. The results are shown live on an OLED screen as a radar-style display, while LEDs and a buzzer warn you when something gets too close.
| Component | Quantity | Purpose |
|---|---|---|
| Arduino (Uno or similar) | 1 | Main controller / brain |
| HC-SR04 Ultrasonic Sensor | 1 | Measures distance using sound waves |
| SG90 Servo Motor | 1 | Rotates the sensor to scan side to side |
| SSD1306 OLED Display (0.96″, I²C) | 1 | Shows the radar screen |
| Green LED | 1 | Indicates “Safe” zone |
| Yellow LED | 1 | Indicates “Warning” zone |
| Red LED | 1 | Indicates “Danger” zone |
| Buzzer | 1 | Beeps as warning, faster when closer |
| 3.7V Li-ion Battery | 2 | Powers the circuit |
| Jumper wires & breadboard | As needed | Connections |
Arduino
HC-SR04 Ultrasonic Sensor
SG90 Servo Motor
SSD1306 OLED Display
Green LED
Yellow LED
Red LED
Buzzer
3.7V Li-ion Battery
Jumper Wires
Breadboard
I²C Address used in code: 0x3C
Open Arduino IDE → Sketch → Include Library → Manage Libraries, then search and install:
• Adafruit GFX Library
• Adafruit SSD1306
• Servo (usually pre-installed with Arduino IDE)
• Check the correct board and port are selected.
• Make sure no other program (like Serial Monitor) is holding the port open during upload.
• Try a different USB cable/port if the Arduino isn’t detected.
1. Setup: On power-up, the Arduino initializes the OLED, attaches the servo, and shows a “RADAR” start screen for 1.5 seconds.
2. Sweep: The servo moves in 2° steps from 0° to 180° and back, continuously, like a real radar dish.
3. Distance Measurement: At each angle, the Arduino sends a short ultrasonic pulse from the Trig pin, listens for the echo on the Echo pin, and converts the time taken into a distance in centimetres using distance = duration / 58.0.
4. Display Update: The OLED redraws the radar screen each cycle — range rings and a sweeping line show the current scan angle, a dot marks any detected object within 30 cm, and the angle, distance, and status are printed as text.
5. Warning System: Above 30 cm the green LED is on (Safe); between 10–30 cm the yellow LED is on with a slow beep (Warning); below 10 cm the red LED is on with a fast beep (Danger).
6. Serial Output: The current angle and distance are also printed to the Serial Monitor for debugging.
7. Loop: All of this repeats continuously, giving a live, constantly updating radar display.
Output indication using LED
Object detection using OLED
Scan the QR code below to download the full Arduino sketch for this project.
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