AUTONOMOUS WORKSHOP

Basic Parts of a Mobile Robot

Flow Diagram of Working of Autonomous Robot

Analog Signal: An analog signal is a continuous wave denoted by a sine wave (pictured below) and may vary in signal strength (amplitude) or frequency (time).

Digital Signal: A digital signal - a must for computer processing - is described as using binary (0s and 1s), and therefore, cannot take on any fractional values

DC Motor Drivers

These are current amplifying circuits used to run motors. A low current control signal is converted into a proportionally higher current signal that can drive the motor Consists of H-bridges.

Motor Driver ICs are primarily used in autonomous robotics only. Most microprocessors operate at low voltages and require a small amount of current to operate while the motors require a relatively higher voltages and current . Thus current cannot be supplied to the motors directly from the microprocessor

Motor Driver IC

Connection of L293D with 2 DC Motors

H-Bridge

H-Bridge It is an electronic circuit which enables a voltage to be applied across a load in either direction. It allows a circuit full control over a standard electric DC motor. That is, with an H-bridge, a microcontroller, logic chip, or remote control can electronically command the motor to go forward, reverse, brake, and coast.

H-Bridge

H-bridges are available as integrated circuits, or can be built from discrete components. The term "H-bridge" is derived from the typical graphical representation of such a circuit, which is built with four switches, either solid-state (eg, L293/ L298) or mechanical (eg, relays).

H-Bridge Logic P1 P2 P3 P4 Current

Direction Effect

1 0 0 1 1 to 2 Motor Spins Forward

0 1 1 0 2 to 1 Motor Spins Backward

1 1 0 0 - Breakdown Occurs

0 0 0 0 - Free Spin

Need for a Motor Driver The current provided by the MCU is of the order of 5mA and that required by a motor is ~500mA. Hence, motor can’t be controlled directly by MCU and we need an interface between the MCU and the motor. This is the primary need for the motor driver IC. A Motor Driver IC like L293D or L298 is used for this purpose which has two H-bridge drivers. Hence, each IC can drive two motors

Need for a Motor Driver

Note that a motor driver does not amplify the current; it only acts as a switch (An H bridge is nothing but 4 switches).

Sensors Analogous to human sensory organs Eyes, ears, nose, tongue, skin Sensors help the robot knowing its surroundings better Improves its actions and decision making ability Provides feedback control

Sensors A device which provides information about the physical world to the microcontroller.

e.g. - • IR Sensor • Sound Sensor • Bump Sensor • Proximity Sensor • Ultrasonic Sensor

LDR - Light Dependent Resistor

LDR - Light Dependent Resistor

Made of cadmium sulphide The resistance of LDR varies with intensity of light. Resistance is inversely proportional to the intensity of light i.e. more the light, lesser the resistance. This property can be used to differentiate contrast colours

LED: Light Emitting Diode

LED: Light Emitting Diode LED acts as a source of light. This is used in combination with the LDR to form the sensor circuit. In the sensor circuit, LED and LDR are place side by side. The LED light reflected by the surface before falls on the LDR. If, it’s a white surface, LED light reflected will be more and hence, there’ll be more light intensity on the LDR. And when it’s dark, the LED light reflected by the surface will be lesser and hence lesser light intensity on the LDR. Hence and LED-LDR pair can be used to check whether it is on a black surface or white surface. Line following can be done with varying no. of sensors. In this tutorial, we’ll be working on a 3 sensor line follower.

IR SENSOR (DIGITAL)

PROXIMITY SENSOR (DIGITAL)

Arduino Uno

HOW TO INSTALL ARDUINO SOFTWARE

LINE FOLLOWING A line follower is a robot capable of tracking a line drawn on a surface Optical sensors capture the line position at the front end of the robot The robot is steered to keep it always over the line.

When you make the sensor circuit, the position of the sensors should be appropriate in accordance to the width of line you want to make it follow and the position of sensors accordingly.

Ensure that the light falling on the LDR is the reflected light only and not the side wise

scattered light

Line Following with two Pairs

How to Upload The Program

How to Upload The Program

PWM means Pulse Width Modulation. Micro-

controllers are digital devices. They cannot produce analog output. In order to

produce a range of voltage outputs it uses pwm. What basically happens is instead of giving a

continuous high output, it breaks the pulse into several pulse whose width can be varied Depending on the pulse width the average voltage is determined.

Using pwm the voltage range (0-5V) is divided into 256 levels in an arduino.

Speed control using PWM:

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