Edge Detector Robot (Free wheel Robot)


Edge Detector Robot

To design & test Edge Detector Robot (Free wheel Robo) and its application.


Autonomous robots are robots that can perform with a high degree of autonomy, which is particularly desirable in fields such as space exploration, cleaning floors, mowing lawns, and waste water treatment. A semiautonomous robot is controlled by its programming and is restricted to what its programming tells it. It can not learn further than a certain point. Edge avoider is a robot which never falls of a edge of a table. It has protruding sensors which can detect beforehand, what lies ahead, whether it is surface or an end. The distance between the sensors is also maintained greater that the width of the robot considering the turning radius of the wheels. When the surface is detected the IR module give a high pulse to the controller and when the edge is detected the IR module does not reflect light thus giving a low pulse to the controller. This results in a mechanism which turns the robot into the appropriate direction whenever the limit of the table ends thus never falling from it.

The purpose of this robot is to keep moving on a platform without falling from it. For this it detects the edge of the platform and avoid the edge by turning.

Robot will be move forward as long as the sensor detects an surface under it. As soon as edge detector sensor goes out of the table, the robot will make an in-place rotation greater than 90 degree and then continue as per sensor value.


Robotics is a currently growing field with various studies going all over the world. Robots are of various types ranging from remote controlled robots to gesture control robots, from wireless robots to humanoid robot. A part of robotics is the study of autonomous robots which are mainly made by the use of microcontrollers to control them automatically and instantly. Edge avoider robot is an example of semi-autonomous robot which when placed on a desk doesn’t fall from it. This paper focuses on the use of logic gates to make edge avoider robot thus reducing its manufacturing cost and increasing speed.


In recent years a great deal of time and effort has been spent of developing systems to enable an autonomous robot to follow a marked path using a vision system. Not surprisingly, the majority of this research has been towards modifying, or designing from scratch, a full-sized road vehicle so that it can drive on ordinary roads without human supervision. Due to the large amount of space available in an ordinary road vehicle, high performance computers can be used to perform complex image processing and, typically, to maintain a mathematical model of the vehicle and the environment. Research into autonomous driving using smaller robots typically follows one of two approaches. In the first approach a mathematical model of the vehicle and its surroundings is generated, tested in simulation, and then applied to a robot built specifically for the purpose. In the second approach a combination of a visual serving system and a kinematic model is used, again the robot is typically designed around the solution technique. Due to the size of these robots, the processing resources available are quite limited so simpler models and techniques, such as visual serving, are used to reduce the processing load.


• To study the IR Sensor
• To design the circuit.
• To study Robotics.
• To design circuit for Edge Detector robot.
• To study motor driver IC.
• Study of op-amp.

List of Components:

 Geared DC Motors
 IR sensor
 Comparator
 IC 7805
 LED’s
 MOTOR driver IC (L293D)
 Resistor & Capacitor
 Connecting Wires
 Power Supply / Batteries



Fig. Block Diagram of Edge Detector Robot

Concept of Edge Avoider Robot:

Concept of Edge Avoider robot is same as line follower. In these types of robots, we generally use behaviour of light at black and white surface. When light fall on a white surface it will almost full reflects and in case of black surface light is absorbed by black surface. This behaviour of light is used in an line follower robot as well as edge avoider robot.

Here we have used IR transmitter and receiver also called photo diodes are used for sending and receiving light. IR transmits infrared lights. When infrared rays falls on any surface except black or much dark surfaces, it’s reflected back and catched by photodiode and generates some voltage changes. When IR light falls on black surface, light is absorbed by the black surface and no rays reflect back, resultantly photo diode doesn’t receive any light or rays.
Circuit Diagram and Explanation:

In this Edge Detector Robot circuit we have used an IR sensor for detecting the Edge and a Comparator IC for comparing voltages. Comparator configured in non-inverting mode and 10 K potentiometer is connected at its inverting terminal for adjusting reference voltage and IR receiver’s output is directly connected at non-inverting pins of all comparators. One Red LED is connected at output of in the sensor board when this led blinks then it means our sensor is working. The first step is the block diagram which gives an overview of the interconnection among various components. The components are comparator IC (LM358), IR Sensors and Motor Driver IC (L293D).

This gets input from the sensor, compare it with predefined voltage and send to Motor Driver IC.
Comparator is a device which compares two input voltages and gives output high/low. In circuit diagram it is normally represented by a triangle having-Inverting (negative) Input (-) Non-Inverting (Positive) Input (+),Vcc , Ground, Output.

IR Sensors:
An Infra-Red sensor detects Infra-Red light/white light from a particular object/line and then converts light energy to electrical energy. An IR sensor pair consists of an emitter and a detector. The emitter is blue in color and the detector can be grey, black or white in color.

IR Sensor
IR Sensor

IR Emitter:

An infra-red emitter is a Light Emitting Diode (LED) made from Gallium Arsenide. It detects IR energy at a wavelength of 880nm and emits the same. The infrared phototransistor acts as a transistor with the base voltage determined by the amount of light hitting the transistor. Hence it acts as a variable current source. Greater amount of IR light cause greater currents to flow through the collector-emitter leads. The variable current traveling through the resistor causes a voltage drop in the pull-up resistor. This voltage is measured as the output of the device.

IR Detector:
An infra-red detector is a photo detector. It detects IR energy emitted by the emitter and converts it into electrical energy. The main principle involved in the conversion of light energy to electrical energy is photoelectric effect. The output is taken at negative terminal of IR detector. The output can be taken to a microcontroller either to its ADC (Analog to Digital Converter) or LM 358 can be used as a comparator

Voltage Regulator:
A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. It converts a positive voltage (7-29V) to +5 volts. Heat sink provided in the center to release heat generated due to drop across the IC. Input volt age of about 5 to 18 V is given, Ground is 0 V and regulated output of +5V. It may use an electromechanical mechanism, or passive or active electronic components. Depending on the design, it may be used to regulate one or more AC or DC voltages. There are two types of regulator:

• Positive Voltage Series (78xx)

• Negative Voltage Series (79xx) 78xx: ’78’ indicate the positive series and ‘xx’ indicates the voltage rating. Suppose 7805 produces the maximum 5V. ’05’ indicates the regulator output is 5V. 79xx: ’78’ indicate the negative series and ‘xx’ indicates the voltage rating. Suppose 7905 produces the maximum -5V. ’05’ indicates the regulator output is -5V.

Circuit for 7805 voltage Regulator
Circuit for 7805 voltage Regulator

Comparator IC:

The LM358 IC is a great, low power and easy to use dual channel op-amp IC. It is designed and introduced by national semiconductor. It consists of two internally frequency compensated, high gain, and independent op-amps. This IC is designed for specially to operate from a single power supply over a wide range of voltages. The LM358 IC is available in a chip sized package and applications of this op amp include conventional op-amp circuits, DC gain blocks and transducer amplifiers. LM358 IC is a good, standard Dual operational amplifier and it is suitable for your needs. It can handle 3-32V DC supply & source up to 20mA per channel. This op-amp is apt, if you want to operate two separate op-amps for a single power supply. It’s available in an 8-pin DIP package.

Comparator IC_LM358
Comparator IC_LM358

Motor Driver IC:

This is a Motor driver IC that can drive two motors simultaneously. Motors are arranged in a fashion called H-Bridge. An H-bridge is an electronic circuit which enables DC electric motors to be run forwards or backwards. These circuits are often used in robotics. H-bridges are available as integrated circuits, or can be built from discrete components. The two basic states of an H-bridge. The term “H-bridge” is derived from the typical graphical representation of such a circuit. An H-bridge is built with four switches (solid-state or mechanical). When the switches S1 and S4 are closed (and S2 and S3 are open) a positive voltage will be applied across the motor. By opening S1 and S4 switches and closing S2 and S3 switches, this volt age is reversed, allowing reverse operation of the motor. Using the nomenclature above, the switches S1 and S2 should never be closed at the same time, as this would cause a short circuit on the input voltage source. The same applies to the switches S3 and S4. This condition is known as shoot-through. The switching property of this H-Bridge can be replaced by a Transistor or a Relay or a MOSFET or even by an IC. Here we are replacing this with an IC named L293D as the driver whose description is as given below. The Device is a monolithic integrated high voltage, high current four channel driver designed to accept standard DTL or TTL logic levels and drive inductive loads as and switching power transistors. To simplify use as two bridges each pair of channels is equipped with an enable input. A separate supply input is provided for the logic, allowing operation at a lower voltage and internal clamp diodes are included. This device is suitable for use in switching applications at frequencies up to 5 kHz. The L293D is assembled in a 16 lead plastic package which has 4 center pins connected together and used for h eat sinking The L293D is assembled in a 20 lead surface mount which has 8 center pins connected together and used for heat sinking.

Geared DC Motor with driver IC
Geared DC Motor with driver IC

Fig. Geared DC Motor with driver IC


A DC motor is any of a class of electrical machines that converts direct current electrical power into mechanical power. The most common types rely on the forces produced by magnetic fields. Nearly all types of DC motors have some internal mechanism, either electromechanical or electronic, to periodically change the direction of current flow in part of the motor. Most types produce rotary motion; a linear motor directly produces force and motion in a straight line.
DC motors were the first type widely used, since they could be powered from existing direct-current lighting power distribution systems. A DC motor’s speed can be controlled over a wide range, using either a variable supply voltage or by changing the strength of current in its field winding. Small DC motors are used in tools, toys, and appliances. The universal motor can operate on direct current but is a lightweight motor used for portable power tools and appliances. Larger DC motors are used in propulsion of electric vehicles, elevator and hoists, or in drives for steel rolling mills. The advent of power electronics has made replacement of DC motors with AC motors possible in many applications.


Geared DC motors can be defined as an extension of DC motor which already had its Insight details demystified here. A geared DC Motor has a gear assembly attached to the motor. The speed of motor is counted in terms of rotations of the shaft per minute and is termed as RPM .The gear assembly helps in increasing the torque and reducing the speed. Using the correct combination of gears in a gear motor, its speed can be reduced to any desirable figure. This concept where gears reduce the speed of the vehicle but increase its torque is known as gear reduction. This Insight will explore all the minor and major details that make the gear head and hence the working of geared DC motor.

Operation of Motor Driver IC:

The H-Bridge arrangement is generally used to reverse the polarity of the motor, but can also be used to ‘brake’ the motor, where the motor comes to a sudden stop, a s the motors terminals are shorted, or to let the motor ‘free run’ to a stop, as the mot or is effectively disconnected from the circuit. The following table summarizes operation. S1 S2 S3 S4 Result 1 0 0 1 Motor moves right 0 1 1 0 Motor moves left 0 0 0 0 Motor free runs 0 1 0 1 Motor brakes.

S1 S2 S3 S4 Result
1 0 0 1 Motor moves right
0 1 1 0 Motor moves left
0 0 0 0 Motor free runs
0 1 0 1 Motor brakes

• 600ma output current capability per channel
• 1.2A peak output current (non repetitive)
• Enable facility over temperature protection
• High noise immunity
• Internal clamp diodes


Potentiometer is a variable resistor which is used to vary the resistance by rotating the shaft. Potentiometers are available from 100 ohm to 470Kohm (or more).Potentiometer is a voltage divider. If we connect lead A to Vcc and lead B to ground then you get voltages from 0 to Vcc at lead W. Mainly Potentiometer are used to generate reference voltage for LM358.

PCB Designing:

Fourth step is designing the PCB layout using PCB Express software. In the PCB express software, choose the different IC’s and other components from the component manager and draw a clean PCB layout. The PCB layout of line follower robot is given as

Schematic Diagram:

After Simulation schematic diagram is drawn on proteus 8 professional or Express PCB and the schematic diagram is shown below. Using proteus or Express PCB we will simulate the project and check if it works properly. So that we can perform the hardware implementation of the project.

Schematic of Edge Detector Robot
Schematic of Edge Detector Robot

Fig. Schematic of Edge Detector Robot



1. Copper Clad or Glass EPOXY Fiber PCB Board.
2. Glossy Photo Paper or Magazine Paper (I Used Glossy Photo Paper).
3. Copper Etching Chemical (Ferric Chloride or Hydrogen Peroxide) (I Used Ferric Chloride)
4. Iron.
5. 2 Containers (1 Small And 1 Big) (Make Sure That The Smaller One Gets Fitted Between The
Bigger One, There Must Be Space Between Them)
6. Hand Drill Machine (With 1mm Bit).
7. Laser Printer (If You Don’t Have Then Drawn the Designs with Permanent Marker on Board).
8. PCB Designs On Your Computer (Make Your Own In Proteus Software).
9. First make Schematic Diagram after that Layout.

Step 1: Design Your Schematics and Print Them

Make your circuit design on Proteus Software.
Print The Design On Glossy Photo Paper Or Magazine Paper Using Laser Printer Only.
If you don’t have a Laser Printer then you can draw the design with Permanent Marker on The COPPER CLAD or GLASS EPOXY FIBER Board.

Step 2: Prepare Your Copper Clad Board
To prepare the copper clad board:
1. Apply liquid soap or dishwasher liquid on the copper clad board.
2. Rub steel wool on it till it gets shiny.
3. Rub it with Scotch-Brite.
4. Soak it with water.
5. 5. Finally, clean it with a cloth.

Now Your Copper Clad Board Is Ready For Toner Transfer (Toner Onto The Board).

Step 3: Toner Transfer (Transfer of Toner onto the Board)
For the toner transfer:
1. Heat the iron to its maximum setting.
2. Cut the design and place it upside down on the board.
3. Slowly move and press the iron on the board with pressure for 20-25 minutes.

Step 4: Washing the Board and Completely Removing the Paper
After Heating, Wash the Board with Water Till the Paper Completely Gets Removed, Now Only Black Lines Are Left on the board do not remove those lines. After That IF There are any Non Transferred Lines Then Grab a Permanent marker and Draw the Lines.

Soldering Techniques:

1. Study the diagram and PCB layout.

2. Check all the components and study their pins and orientation.

3. Clean the leads of components if needed to remove rust or grease with a blade.

4. Place resistors first then IC base, capacitors etc.

5. Use little flux to the joints to increase the melting point of solder lead.

6. Place solder Lead to the joint and heat with soldering iron.

7. The solder joint should be firm, clean and shiny.

8. Poor and dry solder joints will make loose contacts and the circuit will not work properly.

9. After soldering, clean the solder side to remove excess solder or flux using Spirit or PCB cleaner.

10. Cut off the excess leads of components.

11. Careless handling may cause joint loosening and track breaks. So handle PCB carefully.

12. Check all the points before connecting to power supply.


• In hotels at big dinning table.
• This type of robot used in industries for given purpose.
• In Mining vehicle.
• This type of robot used in industries and MIDC/ Manufacturing companies.
• Guidance system for industrial robot.


Our project is an innovative idea of intelligent system which has basically line detection feature and will provide help in various fields like hospitals and service sectors. The sensors in this system are a type of infrared sensor that senses the Edge/Surface.

1. The battery activates the circuit.

2. The sensor transmitter transmits the frequency, which reflects from the surface. Sensor receiver receives the reflected frequency and gives it to Motor Driver IC.

3. Motor driver IC rotates the motors as per the signal receive and then the wheels rotates.

4. Result The objective of the Edge Detector robot is to detect an Edge or surface on its given path which is obtained for which it uses IR sensors which detects the Edge and sends the information to LM358 comparator and then to H bridge which controls the working of the wheels.

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