AUTOMATIC ROOM IGHT CONTROLLER

AUTOMATIC ROOM LIGHT CONTROLLER

Usually when we enter in our room in darkness, we find it difficult to

locate the wall mounted switchboard to switch on the light, for a stranger, it

is tougher still as he has no knowledge of the correct switch to be turned on.

Here is a reliable circuit that takes over the task of switching on and

switching off of the lights automatically, when somebody enters or leaves

the room during darkness. This circuit has the following features.

The lights turns off only when the room is vaccent, or in other words, when

all the persons who entered the room have left.

A seven segment display shows the number of persons currently inside the

room.

In this project we use two infra red sensors. Both connected in the door. Two

photodiode’s are also connected to the receiver circuit to detect the infra red

signal. Both the infra red sensor is connected to the ic 555 as a monostable

timer. In attach with the sensor and 555 we use one up down counter circuit.

Up down counter increment and decrement the input pulses and display it

on the seven segment display. One logic circuit to compare the total number

of person in the room is also involved in this project. For this purpose we

use ic 7485 4 bit binary comparator to compare the total number of person

in the room.

One relay driver circuit to interface the main lights or fan with this unit.

Relay provide a high voltage to the fan and lights for proper working.

In this monostable timer we use ic 555 . Pin no 8 of this ic is connected to

the positive supply. Pin no 1 is connected to the negative supply. Pin no 2 Is

connected to the photodiode. In this project we use two

555 ic. Working of this project is just like this when When any body enter in

the room then one infra red sensor is active and one ic is enable and at this

time second 555 is disable. When any person came out from the room then

other 555 is on and disable first ic and enable this second one. Note that only

one sensor is on at a time. With the help of this ic we give a up and down

pulse to the up – down counter.

Photodiode is connected to the pin no2 via 22 k ohm reistor. 22 k ohm is

grounded from the . In normal way when we switch on the circuit both the

infra red sensor is on and light is fall on the photodiode. Now when any

body enter in the room then circuit sense the intruption and at this time 555

gives its output. Output from the this 555 is connected to the up-down

counter through npn transistor. Here we get this output from the collector

of the transistor. This collector point is also connected to the pin no 4 of

second ic. Output available on the collector point is negative and due to this

pin no 4 of the next ic is become negative and hence this 555 is off. With the

help of this logic at a time we switch on one ic and off the second one by

controlling a pin no 4 by giving a negative voltage on pin no4.

Our next circuit is ic 74192. Ic 74192 is a up down counter. Pin no 16 and

11 is connected to the positive supply. Pin no 1,8,9 is connected to the

ground voltage… Pin no 4 and 5 is clock input for up and down pulses. This

up and down pulse is from the two ic 555. Pin no 14 of this circuit is

connected to the master reset pin 14. . Pin no 2,6,7,3 is output pin of this ic.

These output are in bcd output and in flip flop mode. Pin no 15 and 10 of

this ic is connected to the ground pin.

Output of this up/down counter is further connected to the 4 bit binay

comparator circuit. BCD output from the up down counter is connected to

the ic 7485 and ic 7447. IC 77485 compare the magnitutde of this output

and compare this output to the ground pin 9.11.14.1. when there is any

single output on the 7485 then pin no 5 of this comparator is high and and

switch on the relay coil.relay further switch on the output bulb to on. When

BCD is connected to the 7485 and at the same time this bcd is connected to

the ic 7447 to display the seven segment code.

Now when any body enter in the room then ic 555 sense the signal through

photodiode and then this signal is further connected to the ic 74192 for

clock up signal . this ic gives its output in BCD form and then this output is

now connected to the two ic no 1 ic 7485 and ic 7447. Output of the ic

7447 is connected to the common anode segment display. IC 7485 compare

the bcd signal to the ground potential when all the bcd is zero then there is

no output on the pin no 5. If single bcd is high then pin no 5 become high

and output bulb is on.

CIRCUIT DIAGRAM.

SENSOR LOGIC.

In this project we show that how we save the valuable

energy. Not only save the valuable energy but for security

reason we use this project in many audiotoriam . Where we

want to check the total person to be entered or exit.

First part of this project is Infra red sensor. Here we use infra

red sensor as a transmitter and photodiode as a receiver.

When any body cross the infra red beam then circuit provide

a sharp pulse and circuit recognize the pulse for counting.

In this project we use two beams of lights. Every person

cross this two beams. By crossing these beams in steps we

check the interruption of entery in the room or exit from the

room.

Photodiode in this sensor is connected to the ic 555. here ic

555 work as a monostablke timer. Here we use two 555

timer.

Working of infra red transmitter and

receiver circuit.

Photo Transistor

A phototransistor is in essence nothing more than a normal bipolar

transistor that is encased in a transparent case so that light can reach

the Base-Collector diode. The phototransistor works like a photodiode,

but with a much higher sensitivity for light, because the electrons that

tunnel through the Base-Collector diode are amplified by the transistor

function.

Phototransistors are specially designed transistors with the base region

exposed. These transistors are light sensitive, especially when infrared

source of light is used. They have only two leads (collector and

emitter). When there is no light the phototransistor is closed and does

not allow a collector-emitter current to go through. The phototransistor

opens only with the presence of sufficient light

An opto electronic device that conducts current when exposed to light

is the PHOTOTRANSISTOR. A phototransistor, however, is much more

sensitive to light and produces more output current for a given light

intensity that does a photodiode. Figure 3-32 shows one type of

phototransistor, which is made by placing a photodiode in the base

circuit of an NPN transistor. Light falling on the photodiode changes the

base current of the transistor, causing the collector current to be

amplified. Phototransistors may also be of the PNP type, with the

photodiode placed in the base-collector circuit.

Figure 3-33 illustrates the schematic symbols for the various types of

phototransistors. Phototransistors may be of the two-terminal type, in

which the light intensity on the photodiode alone determines the

amount of conduction. They may also be of the three-terminal type,

which have an added base lead that allows an electrical bias to be

applied to the base. The bias allows an optimum transistor conduction

level, and thus compensates for ambient (normal room) light intensity.

Figure 3-33. - 2-terminal and 3-terminal phototransistors.

Applications

Infrared

Infrared (IR) radiation is electromagnetic radiation of a wavelength

longer than visible light, but shorter than microwave radiation. The

name means "below red" (from the Latin infra, "below"), red being the

color of visible light of longest wavelength. Infrared radiation has

wavelengths between 700 nm and 1 mm.

IR is often subdivided into near-IR (NIR, 0.7-5 µm in wavelength), mid-

IR (MIR (also intermediate-IR (IIR)), 5 - 30 µm) and far-IR (FIR, 30 -

1000 µm). However, these terms are not precise, and are used

differently in the various study. Infrared radiation is often linked to

heat, since objects at room temperature or above will emit radiation

mostly concentrated in the mid-infrared band

Uses

Infrared is used in night-vision equipment, when there is insufficient

visible light to see an object. The radiation is detected and turned into

an image on a screen, hotter objects showing up brighter, enabling the

police and military to chase targets.

Smoke is more transparent to infrared than to visible light, so fire

fighters apply infrared imaging equipment when working in smoke-

filled areas.

A more common use of IR is in television remote controls. In this case it is used in

preference to radio waves because it does not interfere with the television signal. IR data

transmission is also employed in short-range communication among computer

peripherals and personal digital assistants. These devices usually conform to standards

published by IrDA, the Infrared Data Association. Remote controls and IrDA devices use

infrared light-emitting diodes (LEDs) to emit infrared radiation which is focused by a

plastic lens into a narrow beam. The beam is modulated, i.e. switched on and off, to

encode the data. The receiver uses a silicon photodiode to convert the infrared radiation

to an electric current. It responds only to the rapidly pulsing signal created by the

transmitter, and filters out slowly changing infrared radiation from sunlight, people and

other warm objects.

The light used in fiber optic communication is typically infrared.

Diode

A diode functions as the electronic version of a one-way valve. By

restricting the direction of movement of charge carriers, it allows an

electric current to flow in one direction, but blocks it in the opposite

direction.

A diode's current-voltage, or I-V, characteristic can be approximated by

two regions of operation. Below a certain difference in potential

between the two leads, the diode can be thought of as an open (non-

conductive) circuit. As the potential difference is increased, at some

stage the diode will become conductive and allow current to flow, at

which point it can be thought of as a connection with zero (or at least

very low) resistance

Light-emitting diode

A light-emitting diode (LED) is a semiconductor device that emits

incoherent monochromatic light when electrically biased in the forward

direction. This effect is a form of electroluminescence. The color

depends on the semiconducting material used, and can be near-

ultraviolet, visible or infrared. Nick Holonyak Jr. (1928 - ) developed the

first practical visible-spectrum LED in 1962.

Light-emitting diodes

(various)

LED Technology

A LED is a special type of semiconductor diode. Like a normal diode, it

consists of a chip of semiconducting material impregnated, or doped,

with impurities to create a structure called a pn junction. Charge-

carriers (electrons and holes) are created by an electric current

passing through the junction, and release energy in the form of

photons as they recombine. The wavelength of the light, and therefore

its colour, depends on the bandgap energy of the materials forming

the pn junction. A normal diode, typically made of silicon or

germanium, emits invisible far-infrared light, but the materials used for

a LED have bandgap energies corresponding to near-infrared, visible or

near-ultraviolet light.

Unlike incandescent bulbs, which can operate with either AC or DC,

LEDs require a DC supply of the correct polarity. When the voltage

across the pn junction is in the correct direction, a significant current

flows and the device is said to be forward biased. The voltage across

the LED in this case is fixed for a given LED and is proportional to the

energy of the emitted photons. If the voltage is of the wrong polarity,

the device is said to be reverse biased, very little current flows, and no

light is emitted.

Conventional LEDs are made of inorganic minerals such as:

aluminium gallium arsenide (AlGaAs) - red and infrared

gallium arsenide/phosphide (GaAsP) - red, orange and yellow

gallium nitride (GaN) - green

gallium phosphide (GaP) - green

zinc selenide (ZnSe) - blue

indium gallium nitride (InGaN) - blue

silicon carbide (SiC) - blue

diamond (C) - ultraviolet

silicon (Si) - under development

LED development began with infrared and red devices, and

technological advances have made possible the production of devices

with ever shorter wavelengths.

The semiconducting chip is encased in a solid plastic lens, which is

much tougher than the glass envelope of a traditional light bulb or

tube. The plastic may be coloured, but this is only for cosmetic reasons

and does not affect the colour of the light emitted.

.

Typical Applications for

Phototransistors and IREDs

Why Use Phototransistors?

Phototransistors are solid-state light detectors that possess internal

gain. This makes them much more sensitive than photodiodes of

comparably sized area. These devices can be used to provide either an

analog or digital output signal. This family of detectors offers the

following general characteristics and features:

Low cost visible and near-IR photodetection

Available with gains from 100 to over 100,000

Moderately fast response times

Available in a wide range of packages including epoxy coated,

transfer molded, cast, hermetic packages and in chip form

Usable with almost any visible or near infrared light source such

as LEDs, neon, fluorescent, incandescent bulbs, laser, flame

sources, sunlight, etc....

Same general electrical characteristics as familiar signal

transistors (except that incident light replaces base drive

current)

Can be specially selected to meet the requirements of your

particular application

Why Use IREDs?

IRED's are solid state light sources which emit light in the near-IR part

of the spectrum. Because they emit at wavelengths which provide a

close match to the peak spectral response of silicon photodetectors

both GaAs and GaAlAs LEDs are often used with phototransistors and

photodarlingtons. Key characteristics and features of these light

sources include:

Long operating lifetimes

Low power consumption, compatible with solid state electronics

Narrow band of emitted wavelengths

Minimal generation of heat

Available in a wide range of packages including epoxy coated,

transfer molded, cast and hermetic packages

Low cost

Can be specially selected to meet the requirements of your

particular application

Applications

Phototransistors can be used as ambient light detectors. When used with a controllable

light source, typically and LED, they are often employed as the detector element for

optoisolators and transmissive or reflective optical switches. Typical configurations

include:

Optoisolator

The optoisolator is similar to a

transformer in that the output is

electrically isolated from the input.

Optical Switch

An object is detected when it

enters the gap of the optical switch

and blocks the light path between

the emitter and detector.

Retro Sensor

The retrosensor detects the

presence of an object by

generating light and then looking

for its reflectance off of the object

to be sensed.

Phototransistors and IREDs have been used in the following

applications.

Computer/Business Equipment

track zero detector - floppy

drive

margin controls - printers

read finger position - touch

Consumer

coin counters

position sensors - joysticks

remote controllers - toys,

screen

detect holes - computer card

monitor paper position -

copiers

Industrial

LED light source - light pens

security systems

safety shields

encoders - measure speed

and direction

photoelectric controls

appliances, audio/visual equipment

games - laser tag

Medical

provide electrical isolation between

patient and equipment

monitor intravenous injection rates

Basic of the ic 555 as a monostable timer.

  The 555 timer IC was first introduced around 1971 by the Signetics

Corporation as the SE555/NE555 and was called "The IC Time Machine"

and was also the very first and only commercial timer ic available. It

provided circuit designers and hobby tinkerers with a relatively cheap,

stable, and user-friendly integrated circuit for both monostable and astable

applications. Since this device was first made commercially available, a

myrad of novel and unique circuits have been developed and presented in

several trade, professional, and hobby publications. The past ten years some

manufacturers stopped making these timers because of competition or other

reasons. Yet other companies, like NTE (a subdivision of Philips) picked up

where some left off.