8051 Micro Controller based Line follower Autonomous robot using IR sensor, Driver IC (L293D) & 8051 board

Introduction:

This article presents the design and implementation of line follower robot using 8051 Microcontroller. It is programmed to follow a dark line on the white background and detect turns (or) deviations and modify the motors appropriately. The path is sensed by the IR (Infra Red) sensors. The microcontroller controls two DC motors of robot to navigate through its path.

Basic Principle:

The basic principle involved in this is it captures the line position with IR sensors mounted at front end of the robot.  Below is the block diagram of the line follower robot, when the sensor sense the path, analog signal is given to the op-amp to produce 0s and 1s which are then fed to the microcontroller, then the microcontroller decides the next move according to the program. When both the sensors are indicating low (0) then robot start moving on the black path, for white if it indicates high (1) then it moves along the path. Microcontroller and driver circuit are used for the control of motors.

Line Follower Robot Block Diagram

Mechanical parts:

Chassis - Buy this component from muincept Technologies

 

Castor Wheel - Buy this component from muincept Technologies

L-Clamp - Buy this component from muincept Technologies

Motor - Buy this component from muincept Technologies

Wheel- Buy this component from muincept Technologies

Chassis:

Chassis is the base frame of a car, carriage, or other wheeled vehicle. The rectangular, usually steel frame that holds the body and motor of an automotive vehicle.

               

Figure: Chassis

Caster Wheel:

A Caster wheel is an undriven, single wheel that is designed to be mounted to the bottom of a larger object so as to enable that object to be easily moved. They are available in various sizes, and are commonly made of rubber, plastic, nylon, aluminum, or stainless steel, etc.

      

L-Clamp:

            

Figure: L-Clamp

Wheel:

Wheel is a circular object that revolves on an axle and is fixed below a vehicle or other object to enable it to move over the ground.

        

Figure: Wheel

DC Motor:

DC Motors convert electrical energy (voltage or power source) to mechanical energy (produce rotational motion). They run on direct current. 

                                                      Figure: DC Motor

Input and Output devices

Battery Source - Buy this component from muincept Technologies

Voltage regulator - Buy this component from muincept Technologies

Sensor - Buy this component from muincept Technologies

Driver IC - Buy this component from muincept Technologies

Microcontroller unit - Buy this component from muincept Technologies

Serial Cable - Buy this component from muincept Technologies

Source:

An ideal voltage source is a voltage source that maintains the same voltage across the source's terminals no matter what current is drawn from the terminals of the source or what current flows into the terminals.

DC source:

Direct current (DC) is the unidirectional flow of electric charge. Direct current is produced by sources such as batteries, solar cells, and commutator-type electric machines of the dynamo type, etc.

Voltage Regulator:

Voltage regulator, any electrical or electronic device that maintains the voltage of a power source within acceptable limits.

IC7805

IC 7805 is a 5V Voltage Regulator that restricts the voltage output to 5V and draws 5V regulated power supply.

                                                    Figure: Pin diagram of IC7805

Sensor

IR reflective sensors have one emitter (IR LED) and one receiver (Phototransistor or photo diode. If we have white surface it reflects the light and it will sensed by the receiver, similarly if we have black surface it absorbs the light and receiver can not sense light.

Photo diode has property that if IR light fall on it its electrical resistance comes down (i.e. it comes down from 150kΩ to 10kΩ if no noise present).

 

                                 Figure:IRSensor                                                      

Sample Calculation:                                                             
Say Receiver has resistance
Rs=150kΩ without light (on black surface)
Rs=10kΩ with light (on white surface)

The voltage that goes to comparator Without light: (on black surface)
Vp=(Rs÷(Rs+R))Vcc=150÷(150+10))*5=4.6875V
With light: (on white surface)
Vp=(Rs÷(Rs+R))Vcc=10÷(10+10))*5=2.5000V

Thus we get variation of voltage that is sensed by comparator IC (LM324).
This gives logical high or low according to input.

Comparator

Comparator is a device which compares two input voltages and gives output high/low. In circuit diagram it is normally represented by a triangle having- Inverting (negative) Input (-),Non Inverting (positive) Input(+), Vcc, Ground, Output.

Use of comparator in IR sensor

As above we see that two inputs are required for comparator. One input is from photo-receiver (like photo-diode), other is generated by us using potentiometer. The second voltage is also called as reference voltage for that sensor.

LM358

The LM358 is a great, easy-to-use dual-channel opamp. LM358 applications include transducer amplifiers, DC gain blocks and all the conventional opamp circuits.

                                                   Figure: Pin diagram of LM358

Driver IC:

L293D is a dual H-bridge motor driver integrated circuit (IC). Motor drivers act as current amplifiers since they take a low-current control signal and provide a higher-current signal. This higher current signal is used to drive the motors. L293D contains two inbuilt H-bridge driver circuits. In its common mode of operation, two DC motors can be driven simultaneously, both in forward and reverse direction. The motor operations of two motors can be controlled by input
logic at pins 2 & 7 and 10 & 15. Input logic 00 or 11 will stop the corresponding motor. Logic 01 and 10 will rotate it in clockwise and anticlockwise directions, respectively.

Enable pins 1 and 9 (corresponding to the two motors) must be high for motors to start operating. When an enable input is high, the associated driver gets enabled. Similarly, when the enable input is low, that driver is disabled, and their outputs are off and in the high-impedance state.

                                                        Figure: Driver IC L293D

Microcontroller:

Microcontroller acts as the Brain of robot, which generates desired output for corresponding inputs. In present days, there are several companies that manufacture microcontrollers, for example ATMEL, Microchip, Intel, Motorola, Philips etc. We will be using P89V51RD2 microcontroller in our robot. It is a PHILIPS product.

The NXP (founded by Philips) P89V51RD2 DIP is a 40MHz, 5 Volt 8051-based Microcontroller with 32 I/O lines is an extremely popular 8051 family of microcontroller available in standard 40-pin DIP package. The microcontroller comes with an on-chip boot loader which makes it easy to program using the serial port.

                                    Figure: Pin diagram of P89V51RD2 Microcontroller

Software Details:

The program code acts as the decision-maker embedded in the microcontroller i.e. it decides what will be the outputs for particular set of input combination. Programs for the P89V51RD2 series of microcontrollers can be written in assembly (ASM) and C. Keil, Flash magic etc. are some free development software’s for programming the P89V51RD2 Microcontrollers. We are using KEIL for programming. In KEIL we write our C code, after compilation it generates ‘.hex’ file that is hardware level code.

Keil uvision

Keil C51 is the industry-standard tool chain for all 8051-compatible devices, it supports classic 8051, Dallas 390, NXP MX, extended 8051 variants, and C251 devices. The µVision IDE/Debugger integrates complete device simulation, interfaces too many target debug adapters, and provides various monitor debug solutions.

Code for Line follower Robot:
#include<reg51.h>
sbit sensor1=P1^0;
sbit sensor2=P1^1;
sbit motor1=P0^0;
sbit motor2=P0^1;

void main()
{
sensor1=sensor2=0;
motor1=motor2=0;

while(1)
{
if((sensor1==1)&&(sensor2==0))

{
motor1=1;

motor2=0;

}

else if((sensor1==0)&&(sensor2==1))

{
motor1=0;

motor2=1;

}

else if((sensor1==0)&&(sensor2==0))

{
motor1=0;

motor2=0;

}

else if((sensor1==1)&&(sensor2==1))

{
motor1=1;

motor2=1;

}
}
}

Flash Magic:

The Flash Magic utility connects the PC's COM port to the serial port of the MCB2300 and provides In-System Flash Programming (ISP) support for Intel HEX files.

Serial Cable:

A serial cable is a cable used to transfer information between two devices using a serial communication protocol.

                                                                   Figure: Serial Cable

 Drop your comments it you need any clarification