The circuit for an LPG leakage detector is easily accessible on the market; nevertheless, it is rather pricey and is often based on a microcontroller (MCU). This article will provide you with a simple, low-cost, and straightforward circuit for an LPG detector that you may build. The primary purpose of the circuit is to identify any location where there is an LPG leak. It is constructed of a step-down transformer known as X1, two rectifier diodes known as 1N4007 (D1 and D2), a 1000F capacitor known as C1, a dual comparator known as LM393 (IC2), a darlington transistor known as TIP122 (T2), a 12V high-gain siren/buzzer known as PZ1, and a few additional components. In order to maintain a constant 5V DC output, which is delivered to the circuit, the mains supply is stepped down by transformer X1, rectified by a full-wave rectifier consisting of diodes D1 and D2, filtered by capacitor C1, and then fed to regulator 7805 (IC1). The dual comparator IC LM393 is the most important component of the circuit (IC2). It is utilized for the purpose of comparing two distinct voltages, specifically the reference voltage and the output voltage of the MQ-6 gas sensor. The potmeter VR1 is used to establish the reference voltage at the non-inverting pin 3 of IC2 in order to modify the voltage levels according to the sensitivity requirements. The output voltage from the LPG sensor (MQ-6) is connected to the inverting pin 2 of IC2. In the event when the reference voltage at pin 3 of IC2 is lower than the sensor voltage at pin 2 of IC2, the output will drop, indicating that there is no LPG leakage. As long as there is a low output, T1 will remain turned off, and there will be no passage of current through

the buzzer. As a result, the buzzer will not sound and will remain in silence mode. In the event that the reference voltage is higher than the sensor voltage, the output will go high, which indicates that there is a loss of LPG. The high output activates transistor T1, and a loud buzzer begins to sound in order to draw the attention of those who are nearby. This circuit, which combines low-cost components and an interactive manner to alter different sensitivity levels based on client needs with the use of a potmeter called VR1, makes it very simple to locate gas leakages. The low-cost components used in this circuit include: After the circuit has been assembled on a PCB, it should be encased in a box that has a hole in it so that the gas may enter. Within a distance of one meter, position the unit so that it is adjacent to the LPG cylinder or the gas burner. Adjusting the sensitivity of the sensor can be done by adjusting the setting VR1. Before utilizing the circuit, you need to make sure the voltages are where they should be according to the test points table. Now, spray the gas from the bottle toward the MQ-6 gas sensor (as illustrated on the left side of the author's prototype), and measure the voltage at TP3; it should be high. If you do not have a gas bottle with gas in it, you can position the LPG leakage detector close to the gas stove burner and turn it on for a few seconds without it igniting. This will detect any leaks. After that, flip the switch to turn off the burner, then adjust VR1 until the buzzer sounds.