Design And Construction Of An IR-Based Obstacle Detection For Load Switching Using 8051 Microcontroller

ABSTRACT

The system attempts to actuate a load based system as soon as Infrared Rays collide with an object. In industries this system is used to take up an action as soon as an object is encountered on the conveyor belt. The system uses an IR receiver that receives an Infrared signal that is generated using an IR diode. These IR sensors are interfaced to a microcontroller of the 8051 family. The IR transmitter constantly transfers rays to the IR receiver which in turn constantly sends output to the microcontroller.

The microcontroller is then used to read the signal as soon as an object is encountered and then actuate the load. Here a simple lamp is used to demonstrate as a load. The lamp is actuated by microcontroller through a relay. As soon as the microcontroller receives the IR receiver signal, it switches on the relay which then turns on the lamp.

CHAPTER ONE

1.1                                                        INTRODUCTION

Wastage of electricity is one of the main problems which we are facing now-a-days. In our home, school, colleges or industry we see that fan/lights are kept on even if there are nobody in the room or area/passage. This happens due to negligence or because we forgot to turn lights off or when we are in hurry. To avoid all such situations we have designed this project called “ir based obstacle detection for load switching project”. The main concept behind this project is known as “Visitor counter” which measures the number of persons entering in any room like seminar hall, conference room, classroom. This function is implemented using a pair of Infrared sensors. LCD display placed outside the room displays this value of person count. This person count will be incremented if somebody enters in the room and at that time lights are turned on. And in a reverse way, person count will be decremented if somebody leaves the room. When the number of persons inside the room is zero,

1.2                                                   AIM OF THE PROJECT

The main aim of the project is to develop a system for the detection of obstacle and switching the load according to the detection using IR sensor.

1.3                                                 SCOPE OF THE PROJECT

The project uses 38 KHz IR signal generated feeding an IR diode which is received by tuned IR receiver. These IR sensors are interfaced to a microcontroller of 8051. The IR transmitter continuously transmits rays over the receiver and when these rays are blocked by any object an interrupt is sent to the microcontroller.

The microcontroller according to program written performs the desired action. A lamp is used as load in this project for demonstration purpose. This lamp is actuated by a relay which is interfaced to the microcontroller output. So when the interrupt is sent to the controller, it in turn switches ON the relay to actuate the load

1.4                                         SIGNIFICANCE OF THE PROJECT

This device is helpful in industries for sensing movement of material in a conveyor belt for any action to be taken.

APPLICATION OF THE PROJECT

This device is useful in the following places such as:

1. home,
2. school,

• colleges

1. or industry for conveyor belts, lifts and many industrial types of machinery.

 CHAPTER TWO

2.0                                                    LITERATURE REVIEW

2.1                                 OVERVIEW OF INFRARED TECHNOLOGY

Infrared technology addresses a wide variety of wireless applications. The main areas are sensing and remote controls. In the electromagnetic spectrum, the infrared portion is divided into three regions: near infrared region, mid infrared region and far infrared region.

The wavelengths of these regions and their applications are shown below.

• Near infrared region — 700 nm to 1400 nm — IR sensors, fiber optic
• Mid infrared region — 1400 nm to 3000 nm — Heat sensing
• Far infrared region — 3000 nm to 1 mm — Thermal imaging

The frequency range of infrared is higher than microwave and lesser than visible light.

For optical sensing and optical communication, photo optics technologies are used in the near infrared region as the light is less complex than RF when implemented as a source of signal. Optical wireless communication is done with IR data transmission for short range applications.

An infrared sensor emits and/or detects infrared radiation to sense its surroundings.

The working of any Infrared sensor is governed by three laws: Planck’s Radiation law, Stephen – Boltzmann law and Wien’s Displacement law.

Planck’s law states that “every object emits radiation at a temperature not equal to 0⁰K”. Stephen – Boltzmann law states that “at all wavelengths, the total energy emitted by a black body is proportional to the fourth power of the absolute temperature”. According to Wien’s Displacement law, “the radiation curve of a black body for different temperatures will reach its peak at a wavelength inversely proportional to the temperature”.

The basic concept of an Infrared Sensor which is used as Obstacle detector is to transmit an infrared signal, this infrared signal bounces from the surface of an object and the signal is received at the infrared receiver.

There are five basic elements used in a typical infrared detection system: an infrared source, a transmission medium, optical component, infrared detectors or receivers and signal processing. Infrared lasers and Infrared LED’s of specific wavelength can be used as infrared sources. The three main types of media used for infrared transmission are vacuum, atmosphere and optical fibers. Optical components are used to focus the infrared radiation or to limit the spectral response.

Optical lenses made of Quartz, Germanium and Silicon are used to focus the infrared radiation. Infrared receivers can be photodiodes, phototransistors etc. some important specifications of infrared receivers are photosensitivity, detectivity and noise equivalent power. Signal processing is done by amplifiers as the output of infrared detector is very small.

Types of IR Sensors

Infrared sensors can be passive or active. Passive infrared sensors are basically Infrared detectors. Passive infrared sensors do not use any infrared source and detects energy emitted by obstacles in the field of view. They are of two types: quantum and thermal. Thermal infrared sensors use infrared energy as the source of heat and are independent of wavelength. Thermocouples, pyroelectric detectors and bolometers are the common types of thermal infrared detectors.

Quantum type infrared detectors offer higher detection performance and are faster than thermal type infrared detectors. The photosensitivity of quantum type detectors is wavelength dependent. Quantum type detectors are further classified into two types: intrinsic and extrinsic types. Intrinsic type quantum detectors are photoconductive cells and photovoltaic cells.

Active infrared sensors consist of two elements: infrared source and infrared detector. Infrared sources include an LED or infrared laser diode. Infrared detectors include photodiodes or phototransistors. The energy emitted by the infrared source is reflected by an object and falls on the infrared detector.

IR Transmitter

Infrared Transmitter is a light emitting diode (LED) which emits infrared radiations. Hence, they are called IR LED’s. Even though an IR LED looks like a normal LED, the radiation emitted by it is invisible to the human eye.

The picture of a typical Infrared LED is shown below.

There are different types of infrared transmitters depending on their wavelengths, output power and response time.

A simple infrared transmitter can be constructed using an infrared LED, a current limiting resistor and a power supply.

IR transmitters can be found in several applications. Some applications require infrared heat and the best infrared source is infrared transmitter. When infrared emitters are used with Quartz, solar cells can be made.

IR Receiver

Infrared receivers are also called as infrared sensors as they detect the radiation from an IR transmitter. IR receivers come in the form of photodiodes and phototransistors. Infrared Photodiodes are different from normal photo diodes as they detect only infrared radiation. The picture of a typical IR receiver or a photodiode is shown below.

Different types of IR receivers exist based on the wavelength, voltage, package, etc. When used in an infrared transmitter – receiver combination, the wavelength of the receiver should match with that of the transmitter.

2.2                                                PRINCIPLE OF WORKING

The principle of an IR sensor working as an Object Detection Sensor can be explained using the following figure. An IR sensor consists of an IR LED and an IR Photodiode; together they are called as Photo – Coupler or Opto – Coupler.

When the IR transmitter emits radiation, it reaches the object and some of the radiation reflects back to the IR receiver. Based on the intensity of the reception by the IR receiver, the output of the sensor is defined.

2.3                   DISTINGUISHING BETWEEN BLACK AND WHITE COLORS

It is universal that black color absorbs the entire radiation incident on it and white color reflects the entire radiation incident on it. Based on this principle, the second positioning of the sensor couple can be made. The IR LED and the photodiode are placed side by side. When the IR transmitter emits infrared radiation, since there is no direct line of contact between the transmitter and receiver, the emitted radiation must reflect back to the photodiode after hitting any object. The surface of the object can be divided into two types: reflective surface and non-reflective surface. If the surface of the object is reflective in nature i.e. it is white or other light color, most of the radiation incident on it will get reflected back and reaches the photodiode. Depending on the intensity of the radiation reflected back, current flows in the photodiode.

If the surface of the object is non-reflective in nature i.e. it is black or other dark color, it absorbs almost all the radiation incident on it. As there is no reflected radiation, there is no radiation incident on the photodiode and the resistance of the photodiode remains higher allowing no current to flow. This situation is similar to there being no object at all.