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DESIGN AND CONSTRUCTION OF AUTOMATIC EMERGENCY LIGHT

Dept: ELECTRICAL ENGINEERING File: Word(doc) Chapters: 1-5 Views:

Abstract

As the name of the project implies “Automatic Emergency Light” is an electronic system that can provide light during emergency situations i.e when mains (NEPA) supply fails. This system can provide enough light with full brightness in a given room or office. The system makes use of white light emitting diodes for the lightings. It is automatic in operation, in the sense that it can switch itself off when the battery charges full. Automatic Emergency light comprises three sections: Rectifier section, charger section and the LED driver section. The rectifier section comprises the step down transformer and the bridge rectifier using four Diodes (IN4007x4), which converts the AC input to DC output (with some ac ripples). This DC voltage is feed into the charger circuit after filtration. The charger circuit is designed to charge the battery, which will power the LEDs when there is no mains supply. The LEDs driver section consists a number of white LEDs connected in parallel,

1.0  INTRODUCTION/BACKGROUND STUDY

What is Automatic Emergency Light?

An Emergency Light System is a LED (Light Emitting diode) base Electronics circuit, which is purposely designed to give light of enough or full brightness to a given room or office whenever the light from mains supply fails as a result of power outage.  This electronic circuit is deigned as an alternative source of light when the mains fails i.e for emergency situations.  It is a very simple circuit that makes use of Light Emitting diodes as light indicators or source.  The name “Automatic” implies that charging operation is not manual or mechanical but self operated.  It switches itself off once the battery charges full.

The circuit comprises majorly two sections; charger power supply and LED driver.  The charger power supply section is built around 3-terminal adjustable regulator (ICI) LM317, while the LED driver is built around a switching transistor BD140 (T

2

).  In the charger power supply section, input AC mains is stepped down by Transformer to deliver 9v, 500mA to a bridge rectifier which comprises (IN4007 x 4).  The output of the rectifier is filtered by a capacitor giving a pure DC o/p which is regulated by Ic regulator.

This regulated DC output is used to charge a 6V, 4.5Ah battery when there is mains supply.  When the battery charges fully, it automatically switches itself off.  That is to say, when the mains supply is ON, the LEDs are not ON.

When the mains supply fails, the already fully charged 6V battery powers the LED driver section and there will be full light depending on the number and the brightness of each LED.

 

1.1  Aim/Objective

The major aim of this project is to design and construct an Automatic Emergency Light System that is capable of providing light of adequate or full brightness when there is mains supply outage.  This circuit or system is purposely used during emergency situations for some periods of time.  It is aimed at providing enough light depending on its capacity, before the mains supply resumes.

1.2  Scope of Study

This circuit “Automatic Emergency Light” is designed only for lighting application and the bulbs are light emitting diodes (LED) only.  The system cannot power or lit filament bulbs, because filament bulbs use AC voltage.

In short, the circuit is not applicable to any AC load.  It doesn’t perform any work similar to an inverter system.  Inverter converts DC voltage to AC voltage, and can power AC loads, but Automatic Emergency Light doesn’t.

The lasting duration of service of this circuit is a function of the potential capacity of the battery.  When the battery completely discharges, (dies) the LEDs cannot give light again.  Therefore, in a situation where there is a long duration of power outage (say 2 or 3 days), without charging the system elsewhere, this system will not be useful, as the battery will drop to OV.

Therefore, the emergency light is used for an interim service of short duration.

 

1.2.1      Specification

1. AC input voltage to Transformer = 230V,
2. Frequency = 50HZ
3. Battery Voltage = 6V, 4.5Ah
4. Battery Output = 6V
5. Current Taking by each LED = 10mA – 20mA
6. Voltage Taking by LEDs section = 4V

 

1.3  LIMITATIONS

During the cause of this project execution, we envisaged some difficulties and set backs from power outage which hampered the smooth and easy execution of the project.  Other things encountered were: Lack of finance, Time factor, lack of some basic components.

We also combated with the marketers on inferior components, this was to ensure that we obtained a positive result at the end of the project.