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Automatic LED Emergency Light

Automatic LED Emergency Light

Submitted By :- JACKSON GEORGE.JIPSON GEORGE.DHIRAJ VISHWAKARMA.ROHIT TIWARI.

Introduction:-

This is the cost effective automatic emergency light circuit with light sensing. This system charges from main supply and gets activated when main supply is turned OFF. This emergency light will work for more than 4 hours. When power supply is turned OFF, the circuit senses the day light and according to the light it turns on the LEDs. If the light is present even though power fails the circuit turns OFF the LEDs. Here LDR (Light dependent Resistor) is used to sense the light.

Objective:-

This automatic emergency led light used in night time when the power is cut or off by some reason. 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 fromthe battery is used that time when the power is cut off or we need to use it.

In this circuit we use NPN transistor. The advantage of this emergency light is that if we use this light in a room with LED light source for high energy conversion efficiency. Re- chargeable batteries (Nickel-Metal Hydride) for getting high usable life.

Circuit diagram:-

Circuit description:-

Here step down transformer is used to reduce input AC voltage to low AC voltage. Diode Bridge is used to convert input AC voltage to pulsating DC. Here capacitor C1 is used to remove the ripples from the rectified DC. LED indicates the main supply and resistor R1 is used to protect the LED from high voltage. In this circuit transistor switches states white LEDs based on the supply as well as light conditions. The output of LDR is connected to the base of transistor to switch the transistor based on the light conditions. The collector terminal of the transistor is connected is connected to the gate of MOSFET to switch white LEDs according to the conditions. In this circuit voltage regulator 7812 is used to regulate voltage and current. This voltage regulator has built in current limiting circuit. The output of this voltage regulator is positive 11.15 V.

Circuit photos:-

Circuit components:-

9V step down transformer. Diode Bridge 1A. 7812 Voltage regulator. Light dependent resistor 2 M ohm. IRF540 MOSFET transistor. BC 558B DC battery 9V 250mAh Pot-10k 6 LED Panel Red LED 1k resistor Ceramic capacitor-0.1 F 1N4007 diodes-2 Electrolytic capacitor-470 F

Need of Automatic LED Emergency Light.

Provides light when the ordinary lighting falls due to a power cut. Required especially in villages where there are long power cuts. Important to install it near stairs. Near safety signs it should be installed. Used in childs room to avoid sudden power failure.

Working principle:-

Deep discharge is taken care by the LED characteristic and over charge protection is taken care by the fixed voltage regulator. This uses a simple 3pin fixed regulator which has a built in current limiting circuit. The only required adjustment is the present which has to be set to ensure the LEDs just light up.

Automatic emergency light has a light sensor installed in it know as (Light Dependent Resistor) LDR. When the intensity of light falling on it decreases, its resistance decreases. As the circuit is completed the LED panels glows. The 5mm LDR is just mounted on the Emergency light as shown in the circuit .LDR is used to avoid it lighting up during day time or when the room lights are ON.

When power supply is available, battery charges though the diode D2. At the same time white LEDs will glow based on the light conditions. When power fails, the white LEDs which are connected MOSFET will glow based on the light condition till the battery shuts down. When LDR (light dependent resistor) is in light, the resistance of LDR is very low. As a result base of the transistor becomes high. As a result white LEDs which are connected to MOSFET turns OFF. When the circuit is in dark, the resistance of mega ohms. Now the base of the transistor becomes low as a result transistor switches the white LEDs to ON state.

Testing procedure:-

Give the connections according to the circuit diagram. While giving the connections, take care in such a way that there is no common connection between AC and DC supplies. Apply the main supply to the circuit, now you can observe that LEDs will not glow and battery will charge. Remove the AC supply and place circuit in dark, now LEDs will glow. If you place the circuit in light the LEDs turns OFF.

Observation :-

When the plug is connected to power supply battery charges at the same time the red LED glows it indicates that the battery is charging. When the power supply is cut down the white LEDs which are connected to the MOSFET will glow based on the light condition till the battery shut down But when the light is falling on the LDR the resistance of LDR is low and thus the LED does not glows.

Block diagram:-

Block description:-

First the powersupplyis given 230V through thestep downtransformer, thetransformerconvert it into 12V 1A but it is not gives dc so bridge rectifier is used in it to convert it into dc. For filter the signals in the circuit a capacitor is used on it which filter the signals and convert it into pure DC. It also charged the battery when the power is given in the circuit. Atransistoris used to maintain the and the control units diode it maintain the voltage and also used it as a switch in reverse biased condition after that battery is the second power supplier which charged first and give backup power when the main power iscut off.

Conclusion:-

Automatic LED Emergency light circuit is studied and tested, hence it is working.

Bibliography:-

http://www.electronicshub.org/automatic-led-emergency-light-circuit/ Applications of Electronics by R.D.SUPEKAR Applied and Digital Electronics Electronics Projects Vol.18 http://en.wikipedia.org/wiki/Emergency_light http://www.candlepowerforums.com http://www.radiolocman.com http:www.electronicsforu.com