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  • 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

    gas leak detector schematic

    SEN1327 gas sensor pin details and picture

    sen 1327 gas sensor

    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.

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    72 Responses to "Gas Leak Detector Circuit"

    1. Jai Sudan says: on March 4, 2012 at 6:34 am

      very nice project. Thanks for posting.

      with regards,

      Jai Sudan.

    2. will i get this 4 – pin gas sensor in my local area??
      or i should take it from net???

    3. sir very important project,,,,,,,,thanks for shearing…………

    4. sir please tell me out of the 6 pins of mq-6,which 4 do i need to use??

      • rehanul dhan says: on March 25, 2012 at 8:34 pm

        Mq-6 is the material name of this sensor.mq-6 material is semicircle shaped material..you need SEN1437 to use the gas leakage circuit…
        SEN1437 has four pin component.first pin is OUTPUT,second pin is ANG,third pin is VCC,last one is GND…

      • rehanul dhan says: on March 25, 2012 at 8:41 pm

        Sorry,i mistake on this post..sensor is SEN1327..

    5. rehanul dhan says: on March 25, 2012 at 8:16 pm

      Its very important project.,very nice…
      I have prepared this detector…its most useful in home..

    6. chandra.d says: on March 26, 2012 at 3:52 pm

      sir,could this gas leakage detector detect the type of gas N.G.V ? , FOR CAR USES.

    7. sir i’ve used MQ-6 gas sensor.but no 4 pin sip header.so i soldered the sensor & take the pins.as soon as switch is closed alarm sounds.whats the problem? kindly reply me.

    8. but sir this sen-1327 is not available in market….only 6 pin sensor is available..so what do i do??

    9. praneeth says: on April 18, 2012 at 1:13 pm

      Where can I found SEN-1327? Pls reply..

    10. if gas leaks and when the ckt gets triggered,there is possibility of spark.!!

    11. Ur's Mani says: on April 29, 2012 at 2:59 pm

      nice and useful project & i want many project…….

    12. HOW MUCH IT(SEN1327) COSTS???

    13. can i use this circuit with gsm sms sending circuit

    14. morteza says: on June 6, 2012 at 4:04 pm

      this project is very good.
      a have an answer.dose this circut detect a cng gas????(cng=home usable gas)

    15. hi pls i bought an mq-2 gas sensor could you pls email me how to connect it with this circuit

    16. RK Murthy Challa says: on June 8, 2012 at 7:20 pm

      It is an excellent project in view of security. Please let know shall I get the Sensor MQ-6 freely or let me inform where can I purchase.

      Than Q

    17. sudheer says: on June 8, 2012 at 7:54 pm

      i didn’nt get sen 1327 gas sensor in warangal(A.P).from wer i can get it?

    18. where i can get mq-6 & 1327 sensor.. how much is the cost of entire circuit… pls pls pls reply…

    19. Naveed Shahzad says: on June 10, 2012 at 10:14 am

      very nice project thanks for posting

    20. can u plz tell the approx price of SEN1327

    21. i already have this gas sensor how to connect this circuit is it need gas cylinder to get the output of this ckt

    22. sir ,Gas leakage alarm praticaly implement which type problem faced,plz gives the solution.thanks

    23. a.loganathan says: on August 16, 2012 at 9:30 am

      nice projecttttttttt…….

    24. hellow!! can i replace mq 6 to mq 7???is that okay?

    25. sir is this a multi gas detector,. ist can detect methane, carbon dioxide, and nitrogen???

    26. gas sensor has 6 terminal so tell me how can i connect this in circuit ? becoz in circuit their is only give 4 terminal

    27. sir i want to get the circuit diagram with proper specification of lpg sen-1327 or mq-6 gas sensor.
      please help me;;;

    28. Priyadarsan says: on October 2, 2012 at 8:22 am

      Does anyone know how the values of the resistors and capacitors were designed? Can you post the calculation please.

    29. prasanta nayak says: on October 14, 2012 at 9:53 am

      sir plz send kv(low ampere) voltage tripler ckt diagrma

    30. nice project

    31. prashant manakar says: on October 22, 2012 at 10:12 am

      whats price for this leak detector

    32. may i know what is the use of zener diode in this circuit?

    33. may i know how the transistor is used in this circuit?

    34. Jim Keith Jim Keith says: on December 21, 2012 at 6:23 pm

      The transistor is simply an amplifier that drives the loudspeaker.

    35. hi sir,
      its the best project and i am using the same project now for my graduation project.. our teacher told us to add a display unit to see at which range the sensor will detect and gives alarm.. i have used MQ-6 instead of SEN1327 and its working very good.. but i have some difficulty in making the project report and getting out the spicifications of this circuit.. so please can you help me with that i have only 2 more weeks to submit my project and without these things i will fail

    36. Rajesh pandey says: on July 19, 2013 at 10:17 am

      sir please tell me the pin no.2 i.e. analog pin where it is connect

    37. Do any one know can I use mq9 instead of mq6?

    38. I want detect co, I found that mq9 is better than the other mq family do anyone help me?

    39. sai giridhar says: on August 23, 2013 at 2:38 pm

      Hello sir. I’m doing a mini project on this. Rather than using mq6 sen1327 ,can i use MQ5 sen-2060 ? will it work?
      why sl100 transistor is used ? is thr any specific purpose or any random transistor amplifier can be used?

      • There are a number of issues with this circuit–while it may work OK as shown, the power consumption is far too high (>1W) for battery operation. My suggestion is to power it via a regulated 5V from a wall wart and eliminate the 5V zener and R1. Or use an unregulated wall wart with a properly heat-sinked LM7805 voltage regulator.

        Also, pin 4 of the 555 makes a poor threshold detector –the TLC555 is better–see my post on the 555:

        To make the MQ5 sen-2060 work, R3 must be a pot wired as a variable resistor–I suggest 100K because it does not seem to specify the internal resistance range in the spec sheet.


        On the SL100 transistor, I would use any NPN transistor–if it runs too hot, go with a TO-220 power transistor. Run the speaker directly off the unregulated supply for more audionvolume.

    40. sir,plz tell me where to connect analog pin(pin-2)of the sensor.explain working of the circuit

    41. Hello ALL,
      Any one can help me to get PCB design layout and what all material I need to do this project. this seems interesting project and I want to do this for my project…. plz help me…

      THANKS in advance

    42. sir , i selected this as my mini project.
      so pls give me a complete working this circuit describing each and every component

    43. Sir i wish to know whether the analog pin of the module has any connection or it is left freely?

    44. how i collect the gas sansor sen1327 by net

    45. amit aman says: on August 14, 2014 at 6:18 pm

      Excellent n interesting project.

    46. Sir,can I use an MQ2 sensor for this project.If yes What are the modifications.please tell me.This is urgent

    47. sir,can I use MQ-2 instead of MQ-6?if possible which pins should be configured?please reply.

    48. can u send me pcb design layout any one plz

    49. Gas leakage how much dis cost

    50. This ckt s well working.tq frnds fr share D’s ckt

    51. Name *Munavir says: on July 6, 2015 at 3:04 pm

      sir could you please explain about the use of resistors used in the circuit??

    52. Mustafa says: on July 11, 2015 at 9:13 pm

      hello I want to know what is the results of this experment? thanks alot

    53. The project you shared was nice.can u explain a little more in detail…

    54. how this project do in arduino?if you know please send the program ……

    55. sir i want to know the procedure for this circuit.please send the procedure to my gmail.

    56. nisha ramesh says: on September 9, 2015 at 6:08 pm

      shall i use 4 pin mq4 gas leakage sensor instead of 4 pin sensor????

    57. divyabharathi says: on September 20, 2015 at 4:37 pm

      sir i want the procedure which how to make the gas leak detecter.

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