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Fire Alarm Circuit Diagram and Connection Using IC 555

Last Updated on: 2023-04-30T05:31:47Z , , ,


In this article, we are going to see a very simple fire alarm circuit diagram with IC 555. Fire Alarm Circuit is built with some sensors, electronic components, and a buzzer. While it detects any fire it activates the buzzer or siren. The fire alarm is a very important safety device that notifies us when a fire happens so we can take the right action at the right time. The circuit diagram shown here is a very simple electronic circuit built with very few electronic components. This circuit can be operated with a 9V DC power supply so you can use it with a 9V battery also. This type of mini fire alarm circuit is used in homes, small offices, farms, etc. Of course, you can build this circuit for your electronic project also.

Component Required

  • IC 555 Chip - 1 PCs
  • BC547 Transistor - 1 PCs
  • 1 Mega Ohm Preset - 1 PCs
  • 10uF Electrolytic Capacitor - 1 PCs
  • 10K Thermistor - 1 PCs
  • Resistor 100 Kilo Ohm - 2 PCs, 1 Kilo Ohm - 1 PCs, 4.7 Kilo Ohm - 1 PCs
  • 9V Buzzer
  • 9V DC Power Source

Circuit Diagram


Here, you can see the Fire Alarm Circuit Diagram using IC 555 and the connection between each component.

Fire Alarm Circuit Diagram and Connection

Connection Procedure

  1. Connect Pin No 1(Ground) of the IC 555 to the negative terminal of the power source.
  2. Connect Pin No 8(Vcc) of the IC 555 to the positive terminal of the power source.
  3. Connect the negative terminal of the buzzer to the negative terminal of the power source.
  4. Connect the positive terminal of the buzzer to Pin No 3(output) of the IC 555.
  5. Connect  Pin No 6(Threshold) and Pin No 7(Discharge) of the IC 555 together and then connect to the positive terminal of the power source in series with a 1 Kilo Ohm Resistor.
  6. Connect Pin No 2(Trigger) of IC 555 to the joint of Pin No 6 and 7 in series with a 100 Kilo Ohm resistor.
  7. Also, connect Pin No 2(Trigger) of IC 555 to the negative terminal of the power source in series with a 10uF Electrolytic Capacitor.
  8. Connect Pin No 4(Reset) of the IC 555 to the positive terminal of the power source in series with a 4.7 Kilo Ohm Resistor.
  9. Also, connect Pin No 4(Reset) of the IC 555 to the collector terminal of the Transistor BC547.
  10. Connect the emitter terminal of the Transistor BC547 to the negative terminal of the power source.
  11. Connect the Base terminal of the Transistor BC547 to the positive terminal of the power source in series with a 100 Kilo Ohm Resistor.
  12. Connect the Base terminal of the Transistor BC547 to the Poweer terminal of the 1 Mega Ohm Preset.
  13. Connect the Output and Ground terminal of the Preset together and then connect it to the negative terminal of the power source in series with a 10K Thermistor.


Operation and Working Principle


Here, the thermistor acts as a heat sensor. We know that when the temperature around the thermistor varies the resistance of the thermistor also varies. So in normal conditions when there is no fire the temperature around the thermistor is constant. But when the fire happens the temperature around the thermistor increases so it activates the IC 555 to generate the output signal so the Buzzer will activate. By varying the preset we can vary the temperature sensitivity of the circuit.



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Fire Alarm Circuit Diagram and Connection Using IC 555 Fire Alarm Circuit Diagram and Connection Using IC 555 Reviewed by Author on April 25, 2023 Rating: 5
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