Line Following Obstacle Avoiding Maze solving Robot part3 (Arduino project)

Line Following Obstacle Avoiding Maze solving Robot part 2

PART1 System Design

PART2 Mechanical design

PART3 Motor control

PART4 Electronic integration

PART5 Software development

PART6 Final Code

Continue from Part 2

L293D DC Motor Driver & Pin Configuration

“The L293D is a monolithic integrated, high voltage, high current, 4-channel driver.” Basically this means using this chip you can use DC motors and power supplies of up to 36 Volts, thats some pretty big motors and the chip can supply a maximum current of 600mA per channel, the L293D chip is also what’s known as a type of H-Bridge. The H-Bridge is typically an electrical circuit that enables a voltage to be applied across a load in either direction to an output, e.g. motor.

This means you can essentially reverse the direction of current and thus reverse the direction of the motor. It works by having 4 elements in the circuit commonly known as corners: high side left, high side right, low side right, and low side left. By using combinations of these you are able to start, stop and reverse the current. You could make this circuit out of relays but its easier to use an IC – The L293D chip is pretty much 2 H-Bridge circuits, 1 per side of the chip or 1 per motor.

The bit we really care about in all of this is the 2 input pins per motor that do this logic and these, more importantly for our needs, can be controlled from the Arduino board.

You also don’t have to worry about voltage regulation so much because it allows for 2 power sources – 1 direct source, upto 36V for the motors and the other, 5V, to control the IC which can be supplied from the Arduino power supply or since my motor power supply is only 6V I’m going to use this (if the motor supply was higher I would consider using a transistor or voltage regulator). The only thing to remember is that the grounding connection must be shared/ common for both supplies. Below you can see the pin layout for the chip and the truth table showing the output logic.

Motor driver pins:

RIGHT MOTOR	LEFT MOTOR
Black B1=13pin Brown B2=12pin	Blue A1=11pin Green A2=10pi

Arduino L293D Circuit Components

10 K Ohm resistors (Brown, Black, Orange, Gold)

50V 10uF Capacitor

6V DC motor

L293D motor controller/ driver chip (IC)

A switch (push, toggle etc..)

Arduino Deumilanove w/ ATMEGA328

Breadboard / Prototyping board

Jumper/ Connector wires

4x AA battery holder

4x AA batteries

Optional 220nF multilayer ceramic capacitor (Y5V)

Optional 9V DC power supply or use the USB power for the Arduino

Building the L293D motor driver circuit

First let’s start with the 16 pins on the L293D chip and what we need to wire these to. You’ll see that it’s basically got 2 sides, 1 for each motor.

1- Enables and disables the motor whether it is on or off (high or low) comes from the Arduino digital PWM pin 9

2- Logic pin for the motor (input is either high or low) goes to Arduino digital pin 4

3- Is for one of the motor terminals can be either +/-

4- Ground

5- Ground

6- Is for the other motor terminal

7- Logic pin for our motor (input is either high or low) goes to Arduino digital PWM pin 3

8- Power supply for the motor, this should be given the rated voltage of your motor, so mine is from a 6V supply

9- Enables and disables the 2nd motor on or off (high or low)

10- Logic pin for the 2nd motor (input is either high or low)

11- Is for one of the 2nd motor terminals can be either +/-

12- Ground

13- Ground

Datasheet of Sensors and characteristics of sensors:

ENCODERS: QRB 1134 Sensor

Orange: Power supply

White : Signal pin

Blue,green: Ground

DESCRIPTION

The QRB1133/1134 consists of an infrared emitting diode and an NPN silicon phototransistor mounted side by side on a converging

optical axis in a black plastic housing. The phototransistor responds to radiation from the emitting diode only when a reflective

object passes within its field of view. The area of the optimum response approximates a circle .200” in diameter.

Interfacing QRB 1134 Sensor To Arduino :

Pin:

Sensor analog pin A1and A5

Code wheel: Encoder generated from Code wheel generator software. This gives the exact number of tracks of black and white stripes.

QRB Sensors reading:

	White	Black
Right wheel	800	220
Left wheel	800	220

Analog values of QRB