Introduction to smoke detection system using MQ2 gas sensor
A smoke detection system is a critical component of fire safety measures, designed to swiftly identify the presence of smoke or potentially harmful gases in an environment. One commonly used sensor for this purpose is the MQ2 gas sensor. This sophisticated sensor utilizes a combination of advanced technologies to detect various gases, including smoke, methane, carbon monoxide, and LPG (liquefied petroleum gas).
In this project, we would design and construct a simple system that utilizes a few components to develop an advanced system that can detect smoke and alert the household for immediate action. This system is an analog system and does not need any programming.
This system is very portable and it can recharged such that you are covered even when there is no power supply.
Hardware components used in this project
| S/No | Component | Value | QTY |
| 1 | Transformer | 15 V | 1 |
| 2 | Diodes (D1,…,D5) | – | 5 |
| 3 | Capacitor (C1) | 1000uF | 1 |
| 5 | LM7812 | 12V | 1 |
| 6 | Resistor (R1) | 2.2ohms | 1 |
| 7 | Battery (BAT) | 3.7V | 2 |
| 8 | Switch (S1) | SPST | 1 |
| 9 | LM7805 | 5V | 1 |
| 10 | MQ2 | – | 1 |
| 11 | Resistor (R4) | 1k | 1 |
| 12 | Resistor (R2,R3) | 10K | 2 |
| 13 | Resistor (R5) | 33 | 1 |
| 14 | PNP transistor (T1) | BC357 | 1 |
| 15 | Buzzer (Buz) | – | 1 |
| 16 | LEDs | – | 2 |
Step-down Transformer: A step-down transformer with a 200V to 12V ratio is a valuable component in electronics projects, providing a safe and convenient way to convert high-voltage AC to a lower voltage suitable for powering various electronic devices and circuits. It plays a crucial role in ensuring the proper functioning and safety of your electronic projects.
PNP transistor: PNP transistors are often used in circuits where inverted logic is required. In other words, when a logical high voltage is applied to the base, the transistor is in the off state, and when a logical low voltage is applied, it turns on.
Diodes: The primary function of a diode is to allow the flow of electrical current in one direction while blocking it in the opposite direction. This property is due to the way the P-N junction behaves under different polarities.
MQ2 gas sensor: MQ2 gas sensor is a valuable tool for gas detection and monitoring applications. Its affordability, ease of use, and ability to detect a range of gases make it a popular choice in various industries and electronics projects where gas sensing is essential.
Voltage regulator LM7805: The LM7805 is part of the LM78xx series of voltage regulators, designed to take an unregulated DC input voltage, often ranging from 7V to 35V, and output a constant and precisely regulated +5V DC voltage.
Circuit Diagram for the smoke detection system using MQ2 gas sensor
How the smoke detection system works
This system has two parts which are the charging circuit and the gas detection circuit. The charging circuit performs the basic function of charging the rechargeable batteries to ensure that the batteries that are used in this system are always charged.
It is made up of a basic rectification circuit with a filter capacitor and a voltage regulator. The voltage regulator used in the charging circuit is a 12V voltage regulator. A power resistor is attached to the regulator to account for the voltage difference between the battery and the supply. A diode is placed between the battery and the resistor to prevent current from following from the battery to the regulator. An LED is added to indicate that the system is charging and a limiting resistor is placed before the LED to reduce the current that is entering the LED.
A switch (SPST) connects the two circuits and after the switch, an LED and a resistor are placed before the 5V voltage regulator to indicate that the system is ON. The reason why another voltage regulator is used is that the MQ2 gas sensor used in the smoke detection system utilizes just 5V to avoid the risk of destroying the sensor the right voltage has to be used.
The digital pin of the sensor is connected to the base of the PNP transistor through a resistor. By default the digital pin of the sensor is high and it turns low when it detects smoke or any gas. It is due to this fact that a PNP transistor is used to switch the buzzer on and off depending on when it senses smoke.
Immediately the sensor detects smoke the voltage on the digital pin turns low and switches the transistor on thereby making the buzzer make an audible sound which alerts people of the presence of smoke.
This smoke detection system is very compact and is very easy to design and implement. It provides room for people to make use of it to improve safety.
Images of the smoke detection system
Application and uses of Smoke detection system
This smoke detection system is most useful for domestic purposes due to its size. But it can also work well in industries as well. It should be placed in places with a high risk of fire accidents.
Video demonstration of the system
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