Electronics Club: June 2012

LPG gas is supplied in pressurised steel cylinders. As this gas is heavier than air, when it leaks from a cylinder it flows along floor and tends to settle in low spots such as a basement. This can cause fire or suffocation if not dealt with.

Here is a gas leak detector circuit that detects the leakage of LPG gas and alerts the user through audio-visual indications. The circuit operates off a 9V PP3 battery. Zener diode ZD1 is used to convert 9V into 5V DC to drive the gas sensor module.
The gas leakage circuit uses the SEN-1327 gas sensor module from RhydoLABZ. Its output goes high when the gas level reaches or exceeds certain point. A preset in the module is used to set the threshold. Interfacing with the sensor module is done through a 4-pin SIP header.

Pin details of the gas sensor module are shown in Fig. 2. An MQ-6 gas sensor is used in the gas sensor module. The sensor can also be used to detect combustible gases, especially methane.

Gas leak detector schematic

Fig. 1: Circuit for gas leakage alarm

SEN - 1327 gas sensor pin details and picture

Fig. 2: Pin details of gas sensor module

Fig. 3: SEN-1327 gas sensor module

Whenever there is LPG concentration of 1000 ppm (parts per million) in the area, the OUT pin of the sensor module goes high. This signal drives timer IC 555, which is wired as an astable multivibrator. The multivibrator basically works as a tone generator.

Output pin 3 of IC 555 is connected to LED1 and speaker-driver transistor SL100 through current-limiting resistors R5 and R4, respectively. LED1 glows and the alarm sounds to alert the user of gas leakage. The pitch of the tone can be changed by varying preset VR1. Use a suitable heat-sink for transistor SL100.

What is SEN Gas Sensor module and how it works?

Here is the answer >-->>

The SEN-1327 LPG Gas Sensor Module is designed to enable LPG detection interface to Microcontroller without ADC Channels. It allows to determine when a preset LPG gas level has been reached or exceeded. Interfacing with the sensor module is done through a 4-pin SIP header and requires One I/O pin from the host microcontroller.
The onboard microcontroller provide initial heating interval after powerup and then starts to meassure LPG sensor output.If it found the LPG contents above setted value, it will inform the Host controller by pulling the Output Pin to High and Starts to blink a onboard status LED. The sensor module is mainly intended to provide a means of comparing LPG sources and being able to set an alarm limit when the source becomes excessive.

SEN-1327 module features