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Abstract

The primary aim of the project is to learn about interfacing external peripherals such as sensors

and motors, to a microcontroller and program it to behave in an expected manner, based on the

information collected. This is done by designing a wall following robot which collects

information from its IR sensors and outputs information to the motors which drive the robot. Themain task of the robot is to move parallel to a wall and at the same time avoid any kind of

collision with the wall. It is however necessary to design some interfacing circuits to drive themotors and to receive data from the sensors in a way that the microcontroller would understand.

Project Description

The project may be divided into three main parts. Each of these parts will then be explained in

detail.

Robot Hardware (Body)

Interface Circuitry

Algorithm/Program

Robot Hardware:

The robot's body was constructed using two hard plastic sheets which were cut into circularplates. The two plates where then mounted on top of each other using stand-off's, creating gap in

between them, which was used to mount the battery. Two motors with gear box were used to

drive the robot using a differential wheel arrangement. The wheels were mounted on the gear

box and then entire assembly was fixed on the lower plate.

The HCS12 evaluation board was mounted on the top plate and all circuits were designed on the

prototype board provided along with the evaluation board. Three sensors were mounted on theright hand side of the top plate, which would help in following the right wall and one sensor was

mounted in the front to detect a wall in the front.

A picture of the robot is shown in Figure.

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Interface Circuitry:

The interface circuitry was required in order to control high current hardware (such as motor)using the microcontroller and to understand the signals given out by the IR sensor. The two main

circuits used are,

Motor Driver Circuit

IR Sensor Circuit

Motor Driver Circuit: The motor driver circuit was used to act as a buffer between the

microcontroller port and the high current motors. The IC used as a motor driver is L293D. Thepin diagram of the IC along with the connections is shown in Fig 3. The digital control signal

provided by HCS12 does not deliver sufficient current to drive the motor. Hence, a driver circuit,

which is capable of changing the direction of motor using the logic signals and is capable ofbeing driven at high current, is used. The IC is capable of driving motor with voltage up to 36V