Gas Leak Detection & Alarm using 555 Timer IC

Overview

In this project, we will build a Gas Leak Detection & Alarm System using IC 555 Timer and MQ-2 Gas Sensor. It works as a Home Security Alarm during Gas Leakage. Whenever the sensor detects gas, the LED & Buzzer goes high indication the audio visual alarming.

We will use MQ-2 Gas Sensor which is one of the low cost and popular gas sensor in the market. The MQ-2 gas sensor is sensitive to LPG, i-butane, propane, methane, alcohol, Hydrogen and smoke. In the circuit, the 555 Timer IC is configured in astable mode. The output signal from this gas sensor module is used to drive a 555 timer astable multivibrator.

Components Required

Following are the components required to build a Gas Leak Detection & Alarm using 555 Timer IC.

1. Resistors (22Ω, 4.7k Ω, 10k Ω, 1k Ω, 560 Ω)
2. Variable Resistor 10k Ω
3. 1N4148 Zener diode
4. Capacitors 100nF – 2
5. MQ-2 Gas Sensor Module
6. 555 timer IC
7. Transistor BC547
8. 5V Buzzer
9. LED 5V Red
10. 5-9V DC Power Supply

MQ2 Gas/Smoke Sensor Module

The MQ-2 gas sensor is a versatile and cost-effective solution for detecting a variety of gases.

The MQ-2 sensor stands out as a multifunctional gas detector that can identify various gases such as alcohol, carbon monoxide, hydrogen, isobutene, liquefied petroleum gas, methane, propane, and smoke. Its affordability and user-friendly attributes make it a favorite choice for beginners in the field.

Technical Specifications

• Target Gases: LPG, Propane, Methane, Alcohol, Hydrogen, Smoke
• Operating Voltage: Typically 5V (with a preheat time of over 24 hours for initial use)
• Load Resistance: 20 KΩ
• Heater Resistance: 33Ω ± 5%
• Sensing Resistance: 10 KΩ – 60 KΩ
• Heating consumption: <800mw
• Sensitivity: High to gases in the scope of detection
• Concentration Range: 200 – 10000ppm
• Preheat Duration: 20 seconds (minimum)
• Operating Temperature: -10 to 50 degrees Celsius

Circuit: Gas Leak Detection & Alarm using 555 Timer

Here is the circuit diagram for Gas Leak Detection & Alarm based on 555 Timer IC and MQ-2 Gas Sensor. In this circuit the IC 555 Timer is configured in astable multivibrator mode.

The 555 timer IC (NE555P) is the core of the alarm system. It’s connected as follows: pin 1 to GND, pin 8 to VCC, pin 4 to VCC for resetting, and pins 2, 6, and threshold (THR) through a capacitor C2 (104 or 0.1 µF). The timing components R3 (1k ohm) and C2 determine the frequency of the output oscillation on pin 3. This output drives a transistor Q1 (BC547) which in turn switches the load consisting of a red LED (LED1) and a buzzer (BZ1) in series with a resistor R4 (560 ohm) to limit the current.

The analog output of the sensor, is connected through a 22-ohm resistor to a voltage divider circuit formed by R1 (4.7K ohm) and the potentiometer VR1 (10k ohm). The sensor’s output is also connected to a diode (D1, 1N4148) for protection, and this node is tied to pin 2 (Trigger) of the 555 timer IC through capacitor C1 (0.1 µF).

The circuit can be assembled on a Vero Board or Zero PCB. You can use a 9V Battery to Supply the power to the entire system.

Working of the Circuit

In this circuit, the purpose of the potentiometer is to set the threshold level for gas concentration. The LPG concentration of 1000 ppm (parts per million) in the area is enough to trigger the circuit. When the gas concentration exceeds this threshold, the output voltage increases to a level that triggers the 555 timer. This output drives a transistor Q1 which in turn switches the load consisting of a red LED and a buzzer.

The High output causes the LED to light up and the buzzer to sound, thus signaling the presence of gas. The LED and the buzzer will continue to alert until the gas concentration drops below the set threshold, at which point the 555 timer will reset, turning off the alarm indicators.

You may checkout some Gas Level Detection related projects:

• Gas Leak Alarm System using Arduino
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