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ABSTRACT
Today, in industries and as well as in household applications an emergency light is employed
where there is frequent non uniform voltage distribution occurs. Many types of emergency lights
from rechargeable torches to systems like generators are available in market. All of them require
a switch to operate them when frequent power failure occurs. The present one deals with a model
which senses the mains as well as daylight to switch on the emergency light. This emergency
light holds requirements of domestic purposes also. There is no need to search the switch in the
dark as it switches on /off automatically.
There are some special features in this project which are as follows:
 When mains power is available, it senses and switches off the lamp instantly. This may be
a common feature in any of the emergency power systems.
 It incorporates an opto-eye which senses the ambient light and when the ambient light
reaches a present low level when there is no power, it switches on the emergency light
automatically. The switching is instantaneous.
 In most of the emergency lights there is a drawback. The discharge level of the battery is
not being controlled to a safe level. The batteries get discharged completely and lose their
life rapidly. This is a very serious complaint from the users. In this one, cut-off is
provided at predefined manufacturers minimum discharge level which gives the specified
life of the battery.
The opto-eye mentioned in the above features is a special one in this automatic emergency light
and opto-eye consists of a photo transistor and some specific arrangement of resistors. Here
instead of photo transistor a photo diode is also used and we can also increase the sensitivity of
Photo diode in reverse configuration. We also come across different operational amplifiers,
diodes, light emitting diode. In addition to these we also employ step down transformer and we
also make use of one switch for proper operation of the devise. For different batteries, charging
voltage and lamp can be choosen accordingly to be more illuminated.
INTRODUCTION:
The present mini project deals with the recent requirements of emergency light both for
industries and domestic purposes. Many types of emergency lights from rechargeable torches to
systems like generators are available in the market. When compared to all other emergency lights
this one is quite efficient one as we make use of integrated circuits, voltage regulator and an
excellent feature of opto eye is included in this present mini project. The present one deals with a
model which senses the mains as well as daylight to switch on the emergency light.
The circuit consists of an LM324 quad operational amplifier which
consists of fourteen pins. A logic function is performed by using this type of IC. There are four
ICs involved in this circuitry. Also photo device is also included which makes the use of light
intensity according to which voltage is produced across its terminals. When the wired AND logic
function is fulfilled from the three ICs which work as comparators and the remaining another IC
respond to it according to which the bulb will be glown . It also consists of a Darlington pair of
pnp transistors whose set is capable of delivering the fifteen amperes to the load.
This present one has one on/off switch on operating which the emergency
light glows. In most of the emergency light there exists a drawback. The discharge level of the
battery is not being controlled to a safe level. The batteries get discharged completely and lose
their life rapidly. This is a very serious aspect in order to overcome this a cutoff is provided and
there exists a minimum discharge level which ensures the long life of battery used in the circuit.