Smoke detectors are very useful in the detection of smoke or fire in buildings, and so are the important parameters of safety. So today In this project, we will make a Simple Smoke Detector Alarm Circuit without using any Microcontroller. This circuit triggers the buzzer whenever it detects smoke or fire near it.
Hardware Components
The following components are required to make a Smoke Detector Alarm Circuit
| S.No | Component | Value | Qty |
|---|---|---|---|
| 1. | Breadboard | – | 1 |
| 2. | Connecting Wires | – | 1 |
| 3. | Battery | 9v | 1 |
| 4. | Smoke Sensor | MQ2/MQ6 | 1 |
| 5. | NPN Transistor | BC547 | 1 |
| 6. | Potentiometer | 10k | 1 |
| 7. | Resistors | 1k | 1 |
| 8. | Electrolytic Capacitor | 10uF | 1 |
| 9. | Regulator IC | LM7805 | 1 |
| 10. | LwwwED | 5mm | 1 |
| 11. | Buzzer | – | 1 |
LM7805 Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of LM7805
BC547 Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of BC547
Smoke Detector Circuit
Working Explanation
Working on this smoke detector alarm circuit is easy. In this article, we used the transistor operating properties to work with this circuit as a smoke detector. BC547 NPN transistor will turn on whenever it gets at least 0.70v at its base terminal. We, therefore, applied a voltage divider circuit at its base.
But before using this circuit, we must calibrate it by using a pot. During calibration, we applied a voltage just below 0.70v at the base of the transistor. Whenever the sensor detects smoke, it reduces its strength, because of this reduction in resistance, the voltage across the base of the transistor rises. Now when the voltage at the terminal of a transistor becomes greater than or equal to 0.70v, then the transistor turns on, the LED lights up, and the buzzer also starts beeping. And when we do not find smoke, both the indicator components turn off as the voltage across the base terminal of the transistor falls below 0.70v.
Application
- This circuit triggers the buzzer whenever it finds smoke or fire nearby it.
- This circuit mainly uses the MQ6 smoke/gas sensor for detecting the level of smoke. MQ6 gas sensor is also sensible to the LPG, alcohol, methane, etc.
