Hii friend,

Today I am going to make a circuit of Fire Alarm which is very sensitive.Today I will make this circuit using Relay and Transistor BC547.

Let's get started,

Step 1: Components Required -

(2.) Buzzer x1

(3.) Relay - 6V x1

(5.) Battery clipper x2

(6.) Battery - 9V x2

Step 2: Transistor - BC547

This is the pins of this transistor.

C - Collector,

B - Base and

E - Emmiter.

Firstly we have to connect transistor to the relay.

Solder Collector pin of transistor to coil-1 pin of the Relay as you can see in the picture.

Next we have to connect Photodiode to the relay.

Solder Cathode leg of Photodiode to Coil-2 pin of Relay and

Anode leg of Photodiode to Base pin of the Relay as solder in the picture.

Next solder +ve wire of battery clipper to Coil-2 of Relay and

Solder -ve wire of battery clipper to emmiter pin of the transistor as you can see in the picture.

Solder -ve pin of buzzer to common pin of the Relay.

Now we have to connect second battery clipper wire to the circuit.

Solder +ve wire of battery clipper to +ve pin of buzzer and

solder -ve wire of battery clipper to NO (Normally Open) pin of the Relay as you can see in the picture.

When fire will burn around this circuit with distance approx 5Cm then Buzzer will give sound automatically.

NOTE : We can also connect 3V LED to this circuit.Connect 3V LED with 220 ohm resistor in the parallel of Buzzer.

Thank you