Obstacle Avoiding Robot

The main task of this robot here is to avoid any sort of obstacle, which can be done using Infrared waves or the ultrasonic waves. The only difference between the two, is the sensing range. In this project, we have used Infrared sensors module, which reflects the infrared waves depending upon the reflectance characteristic of the object and accordingly senses the accurate distance. The industries where automated supervision is required, this type of robot is used.

PIC Microcontroller:

The micro-controller used in this project is PIC16f877A, which is a 16f series 40 pin device and has got 33 IO (input/output) pins and the program memory is of 14.3K bytes. The PIC USB ICSP Programmer is used to burn the Hex file of the program from the PC to the RAM memory of the IC. The other details of the PIC 16f877A can be accessed from the data sheet which is attached with this article.

IR Sensors:

Infrared sensors, widely known as IR Sensors, have got one transmitter and a receiver, where the transmitter transmits the IR waves of the range 700 nm-1 mm, invisible to human eye and in the presence of an opaque object, the waves will be reflected back and it will be sensed by a receiver and hence, the output of the IR sensor will be high. Whereas, in the absence of an object the waves are transmitted to the infinite region and are not received by the receiver, hence the output will be low. On the IR sensor module, there is a LM 358 IC, which is a comparator IC which will compare the threshold voltage with the output of the IR receiver, the threshold voltage can be changed by the user by changing the value of the resistance via a Potentiometer. In this way the sensitivity of the IR Sensor can be changed. The only limitation of the IR Sensor is it's range, the maximum distance it can sense can be varied from 10-12 cm and it works on 3.3-5 Volts power supply.

In this project, the IR sensors are placed on the Left, Center and Right side of the robot, such that it can detect the obstacle on either of the sides and can respond to it accordingly.

DC Motor:

The DC motor used in this project is a 1000 RPM DC motor, which is used to facilitate the required forward or reverse motion to avoid the obstacle. This motor will not run solely on the current provided by the microcontroller because the current provided by the board is about 20mA and the DC motor works smoothly only on 500-600mA current, hence, the current amplifier is used to amplify the current obtained from the board pins. The motor driver IC used in this project is L293D, which will drive the motor smoothly without any vibrations or jerks, facilitating smooth motion.

• L293D:

This is an motor driver IC, where the 'D' stands for the free-wheeling diode, which will not hamper the motor in the absence of any current, as the motor consists of a coil acting as an inductor hence, the energy will be dissipated across the diode and hence, it will not damage the other circuitry. The IC has inbuilt 3 NPN transistors and 1 PNP transistors, the pair of 1PNP-1NPN transistor makes up the pseudo-darlington pair. 2 motors can be driven individually from this motor driver IC and the direction as well as the speed can be controlled via the input and the enable pin. Each motor, is supplied with the enable pin to make the L293D IC function. Other details of this IC can be found out on the datasheet, attached with this article.

• Conditions:

Since, 3 IR sensors are being used there will be  conditions, here n=3 as there are 3 IR sensors, hence, the conditions will be obeyed as follows:

IR Centre	IR Left	IR Right	Condition
0	0	0	Motor runs in forward direction, moving straight.
0	0	1	Motor runs in forward direction, moving straight.
0	1	0	Motor runs in forward direction, moving straight.
0	1	1	Motor runs in forward direction, moving straight.
1	0	0	Motor reverses it's direction, moves backward, and then right motor stops and the robot takes a right turn.
1	0	1	Motor reverses it's direction, moves backward, and then left motor stops and the robot takes a left turn.
1	1	0	Motor reverses it's direction, moves backward, and then right motor stops and the robot takes a right turn.
1	1	1	Both motor stops.

• Robot Model:

figure 1.1: Placement of IR Sensors for detecting obstacle

figure 1.2: Obstacle Avoiding Robot

Demonstration:
1. Here is the video link to the demonstration of the robot :  https://youtu.be/OK4ojAxdBIQ 

Datasheets:
1. http://akizukidenshi.com/download/PIC16F877A.pdf

2. http://www.ti.com/lit/ds/symlink/l293.pdf


The code will be available to blog followers upon request. :)