AUTOMATIC EMERGENCY LIGHT WITH LED SUBMITTED BY

ABSTRACT This automatic emergency led light used in night at emergency time when the power cut or off by some region. This emergency light takes 230V AC and it converts it in 12V DC and charge the battery which is used in this circuit. The power of the battery is used that time when the power is cut off or we need to use it. This light is used mostly in villages because there is the lack of electricity is provided.

BLOCK DIAGRAM

HARD WARE EQUIPMENTS TRANSFORMER (230 – 12 V AC) RECTIFIER FILTER LED BC557 1N4007 RESISTOR CAPACITOR

BC557 The BC557 transistor is an PNP Epitaxial Silicon Transistor The BC557 transistor is a general-purpose transistor in small plastic packages. It is used in general-purpose switching and amplification BC847/BC547 series 45 V, 100 mA PNP general-purpose transistors.

The arrow in the PNP transistor symbol is on the emitter leg and points in the direction of the conventional current flow when the device is in forward active mode.

SCHEMATIC DIAGRAM

The consumer unit (or ‘electricity meter’) or the fuse in some houses is a badly lit place. If a 12 volt transformer is also located in this place, with a circuit it may be used to provide emergency lighting by two high-current LEDs. These diodes are powered via a small circuit that switches over to four NiCd batteries when the mains fail. The output voltage of the transformer is rectified by bridge rectifier D1to D4 and filtered by capacitor C1. The batteries are charged continuously with a current of about 7.5 mA via diode D5 and resistor R2. The base of transistor T1 is high via R3, so that the transistor is cut off. When the mains voltage fails say by SW2, C1 is discharged via R1; when the potential across it has dropped to a given value, the battery voltage switches on Q1 via R3 and R1, provided switch S1 is closed. When Q1 is on, a current of some 20 mA flows through diodes D7 and D8 LEDs. The light from these LEDs are sufficient to enable the defect fuse or the tripped circuit breaker to be located.

1N4007 Diodes are used to convert AC into DC these are used as half wave rectifier or full wave rectifier. Three points must he kept in mind while using any type of diode.

LED LEDs are semiconductor devices are made out of silicon When current passes through the LED, it emits photons as a byproduct. Normal light bulbs produce light by heating a metal filament until its white hot LEDs present many advantages over traditional light sources including lower energy consumption, longer lifetime, improved robustness, smaller size and faster switching

Resistor Resistor is a two terminal passive electrical component that implements electrical resistance as a circuit element. Resistors limits or regulate the flow of electrical current in an electronic circuit. Resistors are available in a range of different resistance values which are used as per the requirement.

Capacitor capacitor is a two terminal passive electrical component used to store the electrical energy electrostatically in an electrical field Capacitors are two types electrolytic and ceramic. Ceramic capacitors are unpolarized. These capacitors have negligible internal inductance or resistance. Electrolytic capacitors are polarized and if connected backwards are likely to explode.

BIBILOGRAPHY The 8051 Microcontroller and Embedded systems” by Muhammad Ali Mazidi and Janice Gillispie Mazidi , Pearson Education. ATMEL 89S52 Data Sheets. www.atmel.com www.beyondlogic.org www.wikipedia.org www.howstuffworks.com www.alldatasheets.com

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