Things that are necessary for doing work anywhere, like workplaces, homes, or streets; safety matters the most. A safe workplace reduces injury and illness expenses and increases productivity and quality. Safety comes with precautions that’s why people are installing alarms on every level of the home, industries, etc. The fire alarm is one of those alarms, to immediately protect surroundings from fire. Here we design a simple “Fire Alarm Project” by using a 10K NTC (Negative Temperature Coefficient) thermistor and LM368 Operational Amplifier IC.
This Simple Fire Alarm Project can be used as an indicator or warning circuit for excessive fire and temperature, to connect or disconnect the target device you can connect a relay at the output. Moreover, it prevents the machines and environment from any hazardous or physical harm
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Hardware Components
The following components are required to make Fire Alarm Circuit
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | NTC Thermistor | 10K | 1 |
| 2. | Op-Amp IC | LM358 | 1 |
| 3. | IC Jacket | 8 – pin | 1 |
| 4. | Fire Alarm Circuit PCB | PCBWAY | 1 |
| 5. | Buzzer | 5V | 1 |
| 6. | Potentiometer | 10K | 1 |
| 7. | Resistor | 10K | 1 |
| 8. | Soldering Iron | 45W – 65W | 1 |
| 9. | Soldering Wire with flux | – | 1 |
| 10. | DC Battery | 9V | 1 |
| 11. | Battery Clip | – | 1 |
LM358 Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of LM358
Fire Alarm Circuit
Working Explanation
The working of this circuit is pretty simple. On powering up the circuit and bringing a heating element close to it, the temperature around the thermistor begins to increase. Subsequently, the resistance of the thermistor decreases Due to which the output voltage of the voltage divider increases.
The output from the voltage divider then goes to the non-inverting of the LM358 Op-Amp. Since the voltage divider output is given to the non-inverting input of the IC, its value will become more than that of the inverting input. The amplifier output is then taken to a 5V buzzer which goes off. Indicating the presence of an ongoing fire. You can adjust the sensitivity of this fire alarm circuit by tuning the 10K preset pot. Alternatively, you can combine this configuration with various fire suppression systems such as automatic water sprinklers or foam extinguishing systems.
Applications
- A Fire alarm system plays an important role in industrial fire protection SOPs in order to preserve & sustain human life.
- They are used in homes in order to detect and timely alert the residents about the presence of a fire. So that the evacuation process can be initiated in a timely manner.
- They are also used in places such as criminal detention centers to keep the inmates from starting a fire that might hurt the prison guard personnel.
