30-08-2017, 04:49 PM
The circuit for a LPG leak detector is readily available on the market, but is extremely expensive and generally based on a microcontroller (MCU). Here is presented an inexpensive circuit for an LPG detector that can be easily constructed.
The main purpose of the circuit is to detect LPG leaks anywhere. Fig. 1 shows the prototype of the author.
LPG Leak Detector Circuit and Operation
The circuit diagram of the low-cost LPG detector is shown in Figure 2. A capacitor of 1000μF (C1), a voltage regulator 7805 (built-in voltage regulator) IC1) MQ-6 LPG gas sensor (GS1), dual comparator LM393 (IC2), darlington transistor TIP122 (T2), 12V high gain siren / buzzer (PZ1) and some other components.
Parts List Transformer X1 rectifies the mains supply through a full-wave rectifier comprising the diodes D1 and D2, filtered by the capacitor C1 and fed to the regulator 7805 (IC1) to maintain a constant output of 5V DC which is fed to the circuit .
At the heart of the circuit is the dual comparator IC LM393 (IC2). It is used to compare two different voltages, namely reference voltage and output voltage of the MQ-6 gas sensor.
The reference voltage on the non-inverting pin 3 of IC2 is set using the VR1 potentiometer to adjust the voltage levels according to the sensitivity requirements. The output voltage of the LPG sensor (MQ-6) is fed to the inverter pin 2 of IC2.
If the reference voltage (pin 3 of IC2) is less than the voltage of the sensor (pin 2 of IC2), the output goes down, which means there are no LPG leaks. With a low output, T1 remains cut off and there is no current flow through the buzzer; does not ring and remains in silent mode.
If the reference voltage is greater than the voltage of the sensor, the output is high, which means there are LPG leaks. The high output switches on the T1 transistor and the buzzer sound loudly to alert the people around.
It is very easy to find gas leaks with this circuit, which uses low cost components and an interactive way to adjust different levels of sensitivity, based on the needs of the customer, with the help of the VR1 potmeter.
Construction and testing
A true-size PCB pattern of the LPG leak detector is shown in Figure 3 and its arrangement of components in Figure 4.
After mounting the circuit on a PCB, enclose it in a box with an opening for the gas to enter. Place the unit near the LPG cylinder or gas stove, at a distance of one meter. Vary the VR1 preset to adjust the sensitivity of the sensor.
Check that the voltages are according to the table of test points before using the circuit. Now, spray gas from the bottle (as shown on the left side of the author's prototype) to the MQ-6 gas sensor and measure the voltage at TP3; must be high.
If you do not have a full bottle of gas, place the LPG leak detector near the gas burner burner and turn it on for a few seconds without turning on the burner. Then turn off the burner and set VR1 until the buzzer sounds.
The main purpose of the circuit is to detect LPG leaks anywhere. Fig. 1 shows the prototype of the author.
LPG Leak Detector Circuit and Operation
The circuit diagram of the low-cost LPG detector is shown in Figure 2. A capacitor of 1000μF (C1), a voltage regulator 7805 (built-in voltage regulator) IC1) MQ-6 LPG gas sensor (GS1), dual comparator LM393 (IC2), darlington transistor TIP122 (T2), 12V high gain siren / buzzer (PZ1) and some other components.
Parts List Transformer X1 rectifies the mains supply through a full-wave rectifier comprising the diodes D1 and D2, filtered by the capacitor C1 and fed to the regulator 7805 (IC1) to maintain a constant output of 5V DC which is fed to the circuit .
At the heart of the circuit is the dual comparator IC LM393 (IC2). It is used to compare two different voltages, namely reference voltage and output voltage of the MQ-6 gas sensor.
The reference voltage on the non-inverting pin 3 of IC2 is set using the VR1 potentiometer to adjust the voltage levels according to the sensitivity requirements. The output voltage of the LPG sensor (MQ-6) is fed to the inverter pin 2 of IC2.
If the reference voltage (pin 3 of IC2) is less than the voltage of the sensor (pin 2 of IC2), the output goes down, which means there are no LPG leaks. With a low output, T1 remains cut off and there is no current flow through the buzzer; does not ring and remains in silent mode.
If the reference voltage is greater than the voltage of the sensor, the output is high, which means there are LPG leaks. The high output switches on the T1 transistor and the buzzer sound loudly to alert the people around.
It is very easy to find gas leaks with this circuit, which uses low cost components and an interactive way to adjust different levels of sensitivity, based on the needs of the customer, with the help of the VR1 potmeter.
Construction and testing
A true-size PCB pattern of the LPG leak detector is shown in Figure 3 and its arrangement of components in Figure 4.
After mounting the circuit on a PCB, enclose it in a box with an opening for the gas to enter. Place the unit near the LPG cylinder or gas stove, at a distance of one meter. Vary the VR1 preset to adjust the sensitivity of the sensor.
Check that the voltages are according to the table of test points before using the circuit. Now, spray gas from the bottle (as shown on the left side of the author's prototype) to the MQ-6 gas sensor and measure the voltage at TP3; must be high.
If you do not have a full bottle of gas, place the LPG leak detector near the gas burner burner and turn it on for a few seconds without turning on the burner. Then turn off the burner and set VR1 until the buzzer sounds.