AUTOMATIC EMERGENCY LIGHT USING LED

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 at 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.

BLOCK DIAGRAM

HARDWARE EQUIPMENTS

• Transformer(230V-12V AC)• Rectifier(1N4007 Diodes)• Filter(1mF capacitor)• Voltage Regulator(LM317)• Transistors(BC547,BD140)• Diodes(1N4007)• Resistors(16,100,180,1K,1.2K)• Zener Diode• LED(5mm white LED)• Rechargeable Battery

CIRCUIT DIAGRAM

WORKING

The charger power supply section

It is built around 3-terminal adjustable regulator IC LM317 (IC1). In the charger power supply section, input AC mains is stepped down by transformer X1 to deliver 9V, 500 mA to the bridge rectifier, which comprises diodes D1 through D4. Filter capacitor C1 eliminates ripples. Unregulated DC voltage is fed to input pin 3 of IC1 and provides charging current through diode D5 and limiting resistor R16. By adjusting preset VR1, the output voltage can be adjusted to deliver the required charging current. When the battery gets charged to 6.8V, zener diode ZD1 conducts and charging current from regulator IC1 finds a path through transistor T1 to ground and it stops charging of the battery.

LED Driver section

The LED driver section uses a total of twelve 5mm white LEDs. All the LEDs are connected in parallel with a 100-ohm resistor in series with each. The common-anode junction of all the twelve LEDs is connected to the collector of pnp transistor T2 and the emitter of transistor T2 is directly connected to the positive terminal of 6V battery. The unregulated DC voltage, produced at the cathode junction of diodes D1 and D3, is fed to the base of transistor T2 through a 1K ohm resistor. When mains power is available, the base of transistor T2 remains high andT2 does not conduct. Thus LEDs are off. On the other hand, when mains fails, the base of transistor T2 becomes low and it conducts. This makes all the LEDs glow. The mains power supply, when available , charges the battery and keeps the LEDs off astransistor T2 remains cut-off. During mains failure, the charging section stops working & the battery supply makes the LEDs glow. You can use more LEDs provided the total current consumption does not exceed 1.5A. Driver transistor T2 can deliver up to 1.5A with proper heat-sink arrangement.

COMPONENTS• TRANSFORMER- It step downs the voltage from

230v-9v AC .• BRIDGE RECTIFIER- It converts 9v AC to 9v DC. There

are four 1N4007 diodes used to form a bridge.• RECHARGEABLE BATTERY- A 6v 4.5Ah lead acid

battery is used to give as o/p.

• TRANSISTOR- 1) BC547 is an NPN bi-polar junction transistor. Its mainly used for amplification and switching purposes. It has a maximum current gain of 800. 2) BD140 is a PNP bi-polar transistor. Its mainly used for medium power linear switching.

• VOLTAGE REGULATOR- LM317 device is an adjustable three-terminal positive-voltage regulator capable of supplying more than 1.5 A over an output-voltage range of 1.25 V to 37 V.

• ZENER DIODE- Zener diodes are widely used in electronic equipment of all kinds. They are used to generate low power stabilized supply rails from a higher voltage and to provide reference voltages for circuits, especially stabilized power supplies.

• FILTER- Capacitor c1 is used as a filter because capacitors easily pass AC (changing) signals but they block DC (constant) signals. Here it is used to eleiminate ripples.

• DIODE- a diode is a two-terminal device that conducts primarily in one direction. Diode 1N4007 has lower voltage drop & high surge current capability.

• LED- Twelve 5mm high luminous intensity white LED lights are used having forward voltage(Vf)=3-3.6v & forward current of 30mA.

• RESISTORS- Various resistors of value 16,180,100,1k,2.2k are used to reduce current flow & voltage levels at various points in the circuit.

PCB LAYOUT

PCB LAYOUT WITH COMPONENTS

ADVANTAGES

Ø Saves fuel.Ø Pollution free.Ø Easy to use.Ø Very low cost Ø Easy to install anywhere Ø ON/OFF time is quick.

DISADVANTAGES

• It can be used only for short period.• Delectated circuit• Cool white LEDs can cause problems to eyes.

FUTURE SCOPE

• Uses at conference room, exhibition hall lighting.

• Uses at Direction arrow board for bathroom.• Long lasting battery that works for approx. 8

hrs.• Automatic LED can be used for mass

production as cheap & efficient method.