Gas Leakage Sensor Alarm Circuit Engineering Project using 555 Timer and MQ6 SEN 1327 Gas Sensor Module

In this article we will be discussing about a home security alarm circuit. This is a LPG gas leakage sensor circuit that detects the outflow of LPG gas and alerts the user via audio and visual indications. The heart of this simple engineering project is a gas sensor module SEN 1327. QM 6 gas sensor is used in this SEN 1327 module. The output signal from this gas sensor module is used to drive a 555 timer astable multivibrator. Here 555 timer works as a tone generator, the frequency of tone can be altered by varying the preset VR1.

Gas leakage detector circuit diagram

Click on the image for enlarged view

Components Required

Resistors (22Ω, 4.7k Ω, 10k Ω, 1k Ω, 56 Ω)
Preset (VR1=10k Ω)
Zener diode (5V)
Capacitors (100nF x 2)
Gas sensor module SEN 1327
555 timer IC
Transistor (SL 100)
Loudspeaker (8 Ω, 0.5W)
LED

Working of gas leakage alarm

Zener diode Z1 is used to regulate the Vcc to 5V DC to drive the gas sensor module. See Voltage regulator using zener diode.

The sen-1327 gas sensor module from Rhydolabz is used in this circuit. Its output goes high when the gas level exceeds definite point.

A preset employed in the module is used to set the threshold or reference level. Interfacing with the SEN 1327 sensor module is done through a 4 pin SIP header.

A MQ-6 gas sensor is used in the module. As per its datasheet, it has high sensitivity to propane, butane, isobutene, LPG and natural gas.

Each time there is LPG concentration of 1000 ppm (parts per million) in the area, the OUTPUT pin of the sensor module goes high.

High voltage at the 4th pin (Reset pin) enables timer IC 555, which is wired as an astable multivibrator. The multivibrator essentially works as a tone originator.

Without the high voltage at 4th pin (Reset pin) the IC remain in the Reset state.

Output pin 3 of IC 555 is connected to LED1 and speaker driver transistor SL100. LED1 glows and the alarm sounds to aware the user of gas leakage.

The pitch of the tone can be changed by varying preset VR1.

Provide a suitable heat sink for transistor SL100.

Pin out of SEN 1327 gas sensor module & 555 timer

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