Submitted by
P.BALACHANDRAN

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BLACK LINE FOLLOWER ROBOT USING MICROCONTROLLER
What is a line follower?
Line follower is a machine that can follow a path. The path can be visible like a black line on a white surface (or vice-versa) or it can be invisible like a magnetic field.
Why build a line follower?
Sensing a line and maneuvering the robot to stay on course, while constantly correcting wrong moves using feedback mechanism forms a simple yet effective closed loop system.
As a programmer you get an opportunity to ‘teach’ the robot how to follow the line thus giving it a human-like property of responding to stimuli.
INTRODUCTION
I designed my Robot, which use two motors control rear wheels and the single front wheel is free. It has 4-infrared sensors on the bottom for detect black tracking tape, when the sensors detected black color, output of comparator, LM324 is low logic and the other the output is high.
Microcontroller AT89C2051 and H-Bridge driver L293D were used to control direction and speed of motor.
HARDWARE DESCRIPTION
POWER SUPPLY
A simple DC powered Dual power supply (5v and 10V) usually uses two battery i.e. 6v -4.5A which is serially connected to get the output of 12v DC.
The given 12v output is decreased to 10v by connecting three 4A Diodes in series method. The drop across one diode is 0.7v because it is a silicon (Si) diode. So, the drop across the three diode is 2.1v. According to this, we get the required the voltage of approx. 10v. This voltage is given to the 8th pin of the comparator through the small capacitance of 330pf to grounded the unwanted signals.
Next, this voltage is again decreased and regulated by the regulator IC L7805. The input of 10v is given to the 1st pin of the 7805 and 2nd pin is grounded and the 3rd pin is used to get the output of the regulated 5v (approx.) the unwanted signals are grounded by the small capacitance value.
Finally, the required voltage is given to all sections by the regulated power supply.
SENSOR ARRAY
It consists of the four pairs of the sensors which sense the black path. The sensors are arranged by the several distances. The distance between the Transmitter and receiver is 2.5mm. The distance between the sensor sets and center point is 2cm. And the distance between the sensor array and black path is 15mm.
COMPARATOR SECTION
It is employed by the quad comparator LM324. The comparator compares the sensor output with the reference voltage which is varied by the manually through the 20K potential resistor controller. According to the output of the sensor section, It gives the output to the controller.
MICROCONTROLLER AT89C2051
Features
• Compatible with MCS®-51Products
• 2K Bytes of Reprogrammable Flash Memory
– Endurance: 10,000 Write/Erase Cycles
• 2.7V to 6V Operating Range
• Fully Static Operation: 0 Hz to 24 MHz
• Two-level Program Memory Lock
• 128 x 8-bit Internal RAM
• 15 Programmable I/O Lines
• Two 16-bit Timer/Counters
• Six Interrupt Sources
• Programmable Serial UART Channel
• Direct LED Drive Outputs
• On-chip Analog Comparator
• Low-power Idle and Power-down Modes
• Green (Pb/Halide-free) Packaging Option
Description
The AT89C2051 is a low-voltage, high-performance CMOS 8-bit microcomputer with 2K bytes of Flash programmable and erasable read-only memory (PEROM). The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry-standard MCS-51 instruction set. By combining a versatile 8-bit CPU with Flash on a monolithic chip, the Atmel AT89C2051 is a power-full microcomputer which provides a highly-flexible and cost-effective solution to many embedded control applications.
The AT89C2051 provides the following standard features: 2K bytes of Flash, 128 bytes of RAM, 15 I/O lines, two 16-bit timer/counters, a five vector two-level interrupt architecture, a full duplex serial port, a precision analog comparator, on-chip oscillator and clock circuitry. In addition, the AT89C2051 is designed with static logic for opera-tion down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port and interrupt system to continue functioning. The power-down mode saves the RAM contents but freezes the oscillator disabling all other chip functions until the next hardware reset.