Bluetooth Controlled Robot Using 8051 Microcontroller

Introduction

A Bluetooth controlled robot is a versatile project that combines wireless communication and robotics. Using the 8051 microcontroller, this project demonstrates how to control a robot's movement via Bluetooth commands sent from a smartphone. The robot can move forward, backward, left, and right based on the received commands. This project is ideal for learning about wireless communication, motor control, and microcontroller programming.

Components Required

• 8051 Microcontroller (e.g., AT89S52)

• HC-05 Bluetooth Module

• L293D Motor Driver IC

• DC Motors (2 units)

• Robot Chassis

• Wheels and Castor Wheel

• Power Supply (Battery Pack, 12V for motors, 5V for 8051 and Bluetooth module)

• Resistors (10kΩ, 1kΩ)

• Capacitors (33pF, 100μF)

• Crystal Oscillator (11.0592 MHz)

• Breadboard and Connecting Wires

Circuit Diagram

The 8051 microcontroller interfaces with the HC-05 Bluetooth module for wireless communication and the L293D motor driver to control the DC motors.

+5V ----- +5V

          |

          |

        HC-05

        +---+

    +5V |VCC| 

    GND |GND|

    TX  |TXD|------- RXD (P3.0 of 8051)

    RX  |RXD|------- TXD (P3.1 of 8051)

         +---+

L293D Motor Driver

      +---+

1,9  | VCC2 | ----- 12V (Motor Power Supply)

8,16 | VCC1 | ----- +5V

    4,5,12,13 | GND | ----- Ground

  2 | IN1 | ----- P2.0 (8051)

  7 | IN2 | ----- P2.1 (8051)

10 | IN3 | ----- P2.2 (8051)

15 | IN4 | ----- P2.3 (8051)

  3 | OUT1| ----- Motor 1

  6 | OUT2| ----- Motor 1

11 | OUT3| ----- Motor 2

14 | OUT4| ----- Motor 2

      +---+

DC Motors

Motor 1 - Connected to OUT1 and OUT2 of L293D

Motor 2 - Connected to OUT3 and OUT4 of L293D

Pin Connections

• HC-05 Bluetooth Module:

• VCC to +5V

• GND to Ground

• TXD to RXD (P3.0 of 8051)

• RXD to TXD (P3.1 of 8051)

• L293D Motor Driver IC:

• VCC2 to 12V (Motor Power Supply)

• VCC1 to +5V

• GND to Ground

• IN1 to P2.0 of 8051

• IN2 to P2.1 of 8051

• IN3 to P2.2 of 8051

• IN4 to P2.3 of 8051

• OUT1 and OUT2 to Motor 1

• OUT3 and OUT4 to Motor 2

Software Implementation

The code is written in C using Keil uVision IDE. It involves initializing the UART for Bluetooth communication, reading commands from the Bluetooth module, and controlling the motors based on these commands.

#include <reg51.h>

sbit IN1 = P2^0; // Motor 1 IN1

sbit IN2 = P2^1; // Motor 1 IN2

sbit IN3 = P2^2; // Motor 2 IN3

sbit IN4 = P2^3; // Motor 2 IN4

void delay(unsigned int count) {

    int i, j;

    for(i=0; i<count; i++)

        for(j=0; j<1275; j++);

}

void uart_init(void) {

    TMOD = 0x20; // Timer1 in mode 2

    TH1 = 0xFD; // Baud rate 9600

    SCON = 0x50; // 8-bit data, 1 stop bit, REN enabled

    TR1 = 1; // Start Timer1

}

char uart_receive(void) {

    while(RI == 0); // Wait for reception to complete

    RI = 0; // Clear reception interrupt flag

    return SBUF; // Return received character

}

void move_forward() {

    IN1 = 1; IN2 = 0;

    IN3 = 1; IN4 = 0;

}

void move_backward() {

    IN1 = 0; IN2 = 1;

    IN3 = 0; IN4 = 1;

}

void turn_left() {

    IN1 = 0; IN2 = 1;

    IN3 = 1; IN4 = 0;

}

void turn_right() {

    IN1 = 1; IN2 = 0;

    IN3 = 0; IN4 = 1;

}

void stop() {

    IN1 = 0; IN2 = 0;

    IN3 = 0; IN4 = 0;

}

void main() {

    char command;

    uart_init(); // Initialize UART

    while(1) {

        command = uart_receive(); // Receive command from Bluetooth

        switch(command) {

            case 'F': // Forward

                move_forward();

                break;

            case 'B': // Backward

                move_backward();

                break;

            case 'L': // Left

                turn_left();

                break;

            case 'R': // Right

                turn_right();

                break;

            case 'S': // Stop

                stop();

                break;

            default:

                stop();

                break;

        }

        delay(100); // Small delay for motor control

    }

}

Explanation

1. Initialization:

2. UART Initialization: The uart_init() function configures the UART for Bluetooth communication at a baud rate of 9600.

3. Receiving Commands:

4. The uart_receive() function waits for and reads a character from the Bluetooth module via UART.

5. Motor Control:

6. Functions like move_forward(), move_backward(), turn_left(), turn_right(), and stop() control the direction of the motors based on the received commands.

7. Command Processing:

8. The main loop continuously receives commands and uses a switch-case structure to call the appropriate motor control function based on the command received.

Conclusion

This project demonstrates the use of the 8051 microcontroller to create a Bluetooth controlled robot. The system can receive commands from a smartphone via a Bluetooth module and control the robot's movement accordingly. This project is a great way to learn about wireless communication, motor control, and using microcontrollers in robotics applications.

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