AUTOMATIC EMERGENCY LED LIGHT 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. In this circuit we use PNP transistor the advantage of this emergency light is that if we use this emergency light in a room no other light source is required but in other emergency light we use another light source when the power is available.

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.

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.

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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