Arduino Based
Robotic Weeding Machine
A semi-autonomous weed-cutting robot combining ultrasonic obstacle avoidance, L298N motor control, and scalable AI integration for modern precision farming.
01 / Project Overview
The Arduino Based Robotic Weeding Machine is an intelligent agricultural automation system designed to remove unwanted weeds efficiently while avoiding obstacles in the field. It promotes eco-friendly weed management without excessive chemical herbicides.
This smart farming project combines an Arduino UNO, HC-SR04 ultrasonic sensor, L298N motor driver, and DC motors to create a capable robot that navigates farmland with minimal human intervention.
The system uses a high-speed DC motor attached to a rotating blade mechanism to cut weeds at ground level. An ultrasonic sensor mounted at the front continuously measures distance to nearby objects. If an obstacle is detected within a predefined range, the Arduino automatically stops or redirects the robot to prevent collision and damage.
A Raspberry Pi board can be optionally integrated for advanced processing, monitoring, or future AI-based weed detection, making the design scalable for smart agriculture.
02 / Working Principle
- The ultrasonic sensor continuously emits sound waves and measures the echo return time to determine obstacle distance.
- The Arduino UNO calculates the distance to obstacles in real time using the speed of sound formula.
- If the path is clear (distance > 20 cm), the robot moves forward while the blade motor rotates to cut weeds.
- When an obstacle is detected within the 20 cm threshold, the robot stops immediately and can reverse or change direction based on programmed logic.
- The L298N motor driver manages both wheel motors and blade motor operation safely with H-Bridge current control.
03 / Key Components
04 / Circuit Diagram
The interactive circuit diagram below shows all wiring connections. Scroll horizontally on mobile.
📋 Wiring Notes
- HC-SR04 VCC → Arduino 5V; GND → common GND
- L298N 12V → Battery+; GND → Battery–; 5V output can power Arduino
- Pins D5 & D6 are hardware PWM — use
analogWrite()for variable blade speed - Add 0.1 µF decoupling capacitors across motor terminals to reduce noise
- Optional: Raspberry Pi UART (TX→RX) to Arduino for AI commands
Rendered from JSON — Components
Rendered from JSON — Connections
| From | To | Label | Wire Colour |
|---|
06 / Arduino Code
Upload the sketch below via Arduino IDE. The robot will automatically begin navigating and cutting weeds, stopping whenever an obstacle enters the 20 cm safety zone.
/* * Robotic Weeding Machine * Controls a DC blade motor and drive motors via L298N. * HC-SR04 ultrasonic sensor provides obstacle detection. * Threshold: 20 cm — stops blade & drive motors on obstacle. */ // ── Pin Definitions ────────────────────────────────────── const int trigPin = 9; // HC-SR04 Trigger pin const int echoPin = 8; // HC-SR04 Echo pin const int motorIn1 = 5; // L298N IN1 (PWM capable) const int motorIn2 = 6; // L298N IN2 (PWM capable) // ── Variables ──────────────────────────────────────────── long duration; int distance; // ── Setup ──────────────────────────────────────────────── void setup() { Serial.begin(9600); pinMode(trigPin, OUTPUT); pinMode(echoPin, INPUT); pinMode(motorIn1, OUTPUT); pinMode(motorIn2, OUTPUT); } // ── Main Loop ──────────────────────────────────────────── void loop() { distance = measureDistance(); Serial.print("Distance: "); Serial.print(distance); Serial.println(" cm"); if (distance > 20) { runMotor(); // Path clear — run blade } else { stopMotor(); // Obstacle detected — stop } delay(100); // 10 Hz sensing loop } // ── Measure Distance (HC-SR04) ─────────────────────────── int measureDistance() { digitalWrite(trigPin, LOW); delayMicroseconds(2); digitalWrite(trigPin, HIGH); delayMicroseconds(10); digitalWrite(trigPin, LOW); duration = pulseIn(echoPin, HIGH); distance = duration * 0.034 / 2; return distance; } // ── Run Blade Motor (forward) ──────────────────────────── void runMotor() { digitalWrite(motorIn1, HIGH); digitalWrite(motorIn2, LOW); } // ── Stop Blade Motor ───────────────────────────────────── void stopMotor() { digitalWrite(motorIn1, LOW); digitalWrite(motorIn2, LOW); }
💡 Code Notes
- Obstacle threshold: Change
20on lineif (distance > 20)to adjust sensitivity. - PWM speed: Replace
digitalWrite(motorIn1, HIGH)withanalogWrite(motorIn1, 180)(0–255) for variable speed. - Sensing rate:
delay(100)gives 10 Hz — reduce to50for faster response. - Drive motors: Add separate IN3/IN4 pins and duplicate
runMotor()logic for wheel control.
07 / Technical Features
Real-Time Distance Sensing
HC-SR04 measures obstacles at 10 Hz with 2–400 cm range and ~3 mm accuracy.
Obstacle Avoidance
Programmable 20 cm threshold triggers instant motor stop and redirection logic.
PWM Speed Control
D5 and D6 are hardware PWM pins enabling precise blade and drive speed management.
H-Bridge Motor Control
L298N H-Bridge supports bidirectional control at up to 2A per channel, 12V supply.
Battery-Powered Mobile
12V rechargeable pack enables untethered field operation for extended sessions.
Scalable AI Integration
Optional Raspberry Pi UART bridge enables camera-based AI weed detection upgrades.
08 / Applications
This robotic weeding machine reduces manual labour, improves efficiency, and serves as a practical example of combining embedded systems, robotics, and agricultural automation into a single innovative solution.
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