Automatic Emergency Light Circuit Using 5V Relay

An Automatic Emergency light is essentially a backup light that goes off in case of a power outage or an emergency. Nowadays, they are mandatory in new commercial and high occupancy residential buildings such as offices, night schools, colleges & hotels, etc. Usually, Emergency lights are powered by a backup DC battery and are not connected to the main power supply which is why it works in a power blackout. So, in this project, we are going to build an Automatic Emergency Light Circuit Using 5V SPDT Relay.

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2$ PCB Prototype

Hardware Components

The following components are required to make an Automatic Emergency Light Circuit

S.no	Component	Value	Qty
1.	Relays	5V/SPDT	1
2.	AC/DC Adapter	5V	1
3.	LED light array	12V/5mm	1
4.	DC Rechargeable Battery	12V	1
5.	Soldering Iron	45W – 60W	1
6.	Soldering Wire with Flux	–	1
7.	Press Switch
8.	Resistors	1K	As per need
9.	Alligator Clips	–	2
10.	AC outlet	220V	1
11.	Jumper wires	–	As per need

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5V Relay Pinout

Useful Steps

Follow the steps as shown in the video above.

1) Strip the lead of the adapter and then solder the live & neutral wire of the AC adapter with the coil pins (1 & 2) of the SPDT relay.

2) Solder the COM pin of the SPDT relay with the +ve terminal of the 12V LED array.

3) Connect a jumper wire to the -ve pin of the LED Array & another to the NC pin of the SPDT relay.

4) Connect the clip attached to the -ve terminal of the LED to the -ve terminal of the DC battery.

5) Plugin the Adapter into the 220V wall outlet & the NC terminal of the SPDT relay to the +ve terminal of the battery & turn on the switch. The DC battery will begin to charge.

6) Now, on turning off the 220V supply, the relay energizes & makes the coil, switching ON the 12V LED array.

Working Explanation

The working of this circuit is pretty simple. A 12V DC battery is connected to an Array of LEDs, through a 5V SPDT Relay. In normal conditions, the coil of the relay remains energized and the switch is attracted towards the NO terminal and the NC terminal remains open. During this the LED array remains closed off from the battery supply and is turned off, also the DC battery gets charged during this condition.

Now, on turning off the AC supply, the coil de-energizes & the relay switch reverts back to the normally closed (NC) condition, making the circuit of the relay to the array of LEDs, thus turning them ON.

Applications

• This circuit is used in case of power outages & in places with low visibility such as store rooms, dark rooms, etc.