What is an Emergency Light : Circuit Diagram & Its Working

Emergency lighting is used in an urgent situation like when the main supply is disconnected or regular electrical light fails. So the sudden electricity loss could result in a fire otherwise a power cut. This lighting system is used in buildings and it includes a battery to activate the light automatically once the power failure occurs. In the emergency situation, these lights play a key role to provide safety for residents. If the power failure occurs, an emergency light can activate with the help of batteries to visually show the route safely for residents to leave from the building. This article discusses an overview of emergency light and its working.

What is an Emergency Light & How it Works?

Definition: An emergency light is used to automatically turn ON a lamp which is operated by a battery. It stops the user from being into a difficult situation because of unexpected darkness and helps the user to get access to make an instantaneous emergency light. This circuit uses light-emitting diodes in its place of the incandescent lamps; therefore making the circuit is very power efficient as well as brighter with its light o/p. In addition, the circuit uses an innovative theory to enhance the economical characteristic of the unit.

Emergency lights are connected to the electrical supply of the building. Each light has its own circuit. These lights include a battery so that it works like a backup power supply once the building loses its power supply. Here, the lifespan of a battery is short when we compare it with other kinds of lighting systems. So all the emergency lights must be checked to make sure the battery can give emergency light for a minimum of 90 minutes. These tests are necessary to check the performance of the battery every six months with professionals.

How do Emergency Lights Appear?

There are different kinds of lights available in the market in different sizes and shapes. Each light is designed based on the application. There are some common emergency lighting systems used in buildings are

  • Exit Lights
  • Batten Lights
  • Oyster Lights
  • Spotfire Lights

How to Make an Emergency Light / DIY Emergency Light

The DIY emergency light can be designed in a step by step process like the following. The required components of the 12v emergency light circuit diagram mainly include LDR, 50K VR, 10K Resistor, BD139 & BD140 transistor, 33ohm resistor, and white LED and 12V battery.

Connect the circuit on the breadboard as per the diagram shown below using the above components.
In this circuit, the LDR based light will activate a high watt white LED once there is dark in the room. It can be used as a simple lamp in the children’s room to keep away from the panic condition once the power gets fail. This circuit gives sufficient light in the room.


Emergency Light Circuit using 12v Battery
Emergency Light Circuit using 12v Battery

The design of this circuit is very easy so that it can be arranged in a little box. As a power source, a 12 V small battery is used to provide the supply to the circuit. The transistors like T1 & T2 are used as electronic switches for switching ON/OFF the white LEDs.

When there is enough light within the room, then LDR activates so that the base terminal of the T1 transistor will become high. The remaining transistor-like T2 also Turns off as its base terminal is grounded. In this condition, the white LED will turn off. Once the light dropping over the LDR decreases, then the T1 transistor in forwarding bias will provide base current to transistor ‘T2’. This ‘T2’ transistor will turn on to make the white LED ON.

Here, the LED is 1 watt high bright Luxeon diode. It uses approximately 300 mA current. So it is better to turn off the lamp to save the power in a battery after a few minutes

Emergency Light Circuit Diagram

An emergency light system is used to turn ON a lamp automatically where a regular AC supply stops working and turns OFF once the main power supply gets back.

This light is essential where the power cut occurs frequently, so it can avoid the user from a difficult situation while going through when unexpectedly mains power supply turns off. It permits the user to access an alternative like turn ON an inverter or a generator until the main supply is restored.

Circuit Explanation & Working

Here there are two circuits that work on using a 6V battery and 12v battery. The construction of these circuits is shown below. These circuits can be built with LEDs in place of incandescent lamp, therefore this is extremely power efficient & clear with its output.

6V Emergency Light Circuit Diagram

The circuit diagram of 6V emergency light is shown below. The required components of this circuit mainly include resistors 10K & 470 ohms, capacitor (C1) -100uF/25V, Bridge diodes like D1, D2 (1N4007), D3 to D5 (1N5408), T1 (BD140), Tr1( 0 to 6V & 500mA), LEDs and S1 switch including change over contacts with the help of a 6V battery.

Emergency Light Circuit using 6v Battery
Emergency Light Circuit using 6v Battery

In the above circuit, a standard power supply mainly includes the transformer, a capacitor, and a bridge circuit. The essential component used in this circuit is a PNP transistor. Here, this transistor is used as a switch.

Once the main supply is ON, then the positive supply gets the base terminal of the ‘T1’transistor, so it will be switched off.

Thus the voltage from the battery is not able to reach the LED bank, keeping it switched off. In the meantime, the battery is charged by the power supply voltage and it’s charged through the system of trickle charging.

However, as soon as the main supply interrupts, then the +ve at the base terminal of the transistor will disappear & it will be in forwarding bias through the resistor-10K.

If the transistor ‘T1’ turns ON, immediately the LEDs will blink. At first, all the diodes are connected in the voltage lane and are slowly go around one by one when the LED gets dimmer.

Applications of Emergency Light

The applications of these lights include the following.

  • Emergency lights are used where the light turns on automatically when the power supply gets off.
  • These are used as emergency lamps in buildings, homes, workplaces, study rooms in order to keep away from unexpected power failures.
  • These lights are used in several industries


1). What are the best emergency lightings?

They are Wipro coral & amber, Philips ujjwal, pigeon lamp, etc.

2) How do emergency lights work?

These lights are connected through wires to the power supply of building for nonstop charging of inside batteries to supply backup power used for the lighting.

3). What is the capacity of emergency light?

These lights can last upto 90 minutes.

4). When should we test emergency lights?

These lights must be tested once a month.

5). Do these lights include a battery?

Yes, it includes a rechargeable battery.

Thus, this is all about an overview of emergency light with a circuit diagram and its working. Here is a question for you. What are the types of emergency lights?

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