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    With this sound activated switch, control by sound may be very useful, not just on a robot but also for a bit of home automation, for example a sound-activated light responding to a knock on the door or a hand clap. The light will be automatically switched off after a few seconds. An alternative use is burglar protection — if someone wants to open the door or break something the light will come on, suggesting that someone’s at home.

    The circuit can work from any 5–12 VDC regulated power supply provided a relay with the suitable coil voltage is used.

    Schematic of the sound activated switch circuit

    When you first connect the supply voltage to the sound activated switch circuit, the relay will be energised because of the effect of capacitor C2. Allow a few seconds for the relay to be switched off. You can increase or decrease the ‘on’ period by changing the value of C2. A higher value results in a longer ‘on’ period, and vice versa. Do not use a value greater than 47 μ F.

    Biasing resistor R1 determines to a large extent the microphone sensitivity. An electret microphone usually has one internal FET inside which requires a bias voltage to operate. The optimum bias level for response to sound has to be found by trial and error. All relevant electrical safety precautions should be observed when connecting mains powered loads to the relay contacts.

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    87 Responses to "Sound Activated Switch Circuit"

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    1. hey man,

      we are doing a project for a circuits class and i was wondering if you had further information on this circuit because it seems really interesting. do you have any specifics of the mic or the other components. thanks,

      logan

      Like or Dislike: Thumb up 0 Thumb down 0

      • Hello,Mr.logan.I can tell you all detailes about that circuit;
        [“Sound Activated Switch circuit”]and analize it.

        Bye,

        [bah9mh@yahoo.com].

        Like or Dislike: Thumb up 0 Thumb down 1

    2. I just have a few questions about what kind of michrophone and info on the relay.

      Like or Dislike: Thumb up 0 Thumb down 0

    3. maybe you can help me . how can i .. used this circuit in my pc i want the pc sound output to trigger the relay ..thanks

      Like or Dislike: Thumb up 0 Thumb down 0

      • You can disconnect the microphone and connect the audio cable directly between PC and this sound activated switch. Then adjust the volume of the sound until the relay is triggered.

        Like or Dislike: Thumb up 0 Thumb down 0

    4. i just wanna ask
      1. how to change the circuit to make the circuit can “ON” when the first sound then “off” when the second sound
      thanks

      Like or Dislike: Thumb up 0 Thumb down 0

      • Hello,Mr.dhaesa pramana,

        I can make the circuit that you asked for
        and also some nice projects,too.
        Here are my mail;[bah9mh@yahoo.com].

        Bye,

        Like or Dislike: Thumb up 0 Thumb down 0

      • it can do using pic programmed.if you want to it mail me.

        Like or Dislike: Thumb up 0 Thumb down 0

    5. Hi, I have built this circuit, but it doesn’t work! Only change i made was instead use electrolytic C1, I used tantalum, which I don’t think it will make any different, I don’t know what is wrong with it, can someone please help me! Thanks…

      Like or Dislike: Thumb up 0 Thumb down 0

    6. lorellie bintad says: on September 25, 2009 at 6:32 pm

      thank you so much for the information! it helps me a lot!

      Like or Dislike: Thumb up 0 Thumb down 0

    7. Oppong Akwasi says: on November 20, 2009 at 6:47 pm

      i just wanna ask
      how to change the circuit to make the circuit can “ON” when the first sound then “off” when the second sound
      thanks

      Like or Dislike: Thumb up 0 Thumb down 0

      • Hello,Mr.Oppong Akwasi,

        I can make the circuit that you asked for
        and also some nice projects,too.
        Here are my mail;[bah9mh@yahoo.com].

        Bye,

        Like or Dislike: Thumb up 0 Thumb down 0

    8. the project is really interesting. we would lie to know more about the project. details. specifications…

      Like or Dislike: Thumb up 0 Thumb down 0

    9. Have you experimented with specific sound recognition, something like a whistle or bell that will cut through other noise and give a clean signal. Most of the “clap lights”I have experienced lack definition.

      Thanks

      Like or Dislike: Thumb up 0 Thumb down 0

    10. chanderbhan says: on January 6, 2010 at 2:31 pm

      good cirkit have you experimented with specific sound recogniting ;something like awhistle

      Like or Dislike: Thumb up 0 Thumb down 0

    11. We would like to know more about this project sound activated switch.So please send us more information along with the circuit diagram.We have planned to do a project on it.

      Like or Dislike: Thumb up 0 Thumb down 0

    12. a i would like to know what is RE1 i new in this field

      Like or Dislike: Thumb up 0 Thumb down 0

    13. dhananjai gupta says: on September 5, 2010 at 2:20 am

      can u help me too by elaborating on relay n microphone , as before fabricating to pcb i will try it out on a software “capture cis” and then i will fabricate so quickly help me

      Like or Dislike: Thumb up 0 Thumb down 0

    14. do this circuit works on the principle of bistable multivibrator

      Like or Dislike: Thumb up 0 Thumb down 0

    15. how to change the circuit to make the circuit can “ON” when the first sound then “off” when the second sound

      Like or Dislike: Thumb up 0 Thumb down 0

      • Adnan Rafiq says: on November 30, 2011 at 11:58 am

        i am also need this circuit.if you have please share it with me.you can contact me.i am a electrical engineer.my phone number is +923327929262.

        Like or Dislike: Thumb up 0 Thumb down 0

      • Hello,Mr.asif ali,

        I can make the circuit that you asked for
        and also some nice projects,too.
        Here are my mail;[bah9mh@yahoo.com].

        Bye,

        Like or Dislike: Thumb up 0 Thumb down 0

    16. can any1 tell me what sort of mic should i use??

      Like or Dislike: Thumb up 0 Thumb down 0

    17. we can use mic from regular microphone, or you can use from mic of cellphone.

      Like or Dislike: Thumb up 0 Thumb down 0

    18. onome sheriff says: on April 3, 2011 at 6:41 pm

      how can we prevent other sound from activating the switch

      Like or Dislike: Thumb up 0 Thumb down 0

    19. kolio says: on May 2, 2011 at 9:09 pm

      what kind of capacitors i need to use? please show me the pictures of this capacitors

      i have not 4.7 mF no-polarity capacitors!!! i need use 475 capacitor?

      i think 104 = 1n0 ? is this capacitors used in scheme?

      please tell me mans

      Like or Dislike: Thumb up 0 Thumb down 0

    20. I made scheme but i have trouble

      on RE1 contacts with no sounds i have 0.05 V
      with very big sounds around i have 0.10 V
      and i can view increase volts with increase sound around

      my microphone from mobilephone and have 1.2 kOhm

      sorry. with no sounds i have 0.15 V
      when i increase sounds i have 0.18 V

      with connected parallel resistor 57 ohm i not see reaction or increasing Volts

      it is my scheme with volts
      http://i20.fastpic.ru/big/2011/0508/01/88e546c05bb39eee88add77cc49e0301.jpg

      i need replace R1 to small Ohms? 4k7, 3k3, 1k8 ? to increase sensity

      Like or Dislike: Thumb up 0 Thumb down 0

    21. kolio says: on May 8, 2011 at 3:14 pm

      all works
      super

      just microphone very sensitive

      Like or Dislike: Thumb up 0 Thumb down 0

      • plss give me the required items you use in this project.because it didn’t work in the breadboard and also the specified mic you use

        Like or Dislike: Thumb up 0 Thumb down 0

      • To dadx.
        Please read the my posting(comments).
        I will be assist the making it.

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    22. Chester says: on June 18, 2011 at 11:09 pm

      Hey kolio since you have completed the circuit could you give me the list of items required for this diagram to work? Thanks alot!

      From: Chester

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    23. IT’s working. perfect! I made this 1hours ago. I have using the T1(T2) – BC547 instead of 2SC945 part. It has no problem. Thax.

      Like or Dislike: Thumb up 0 Thumb down 0

      • Hi, can you send me the scheme and a part list. Im here in the Dominican Republic and I have to order it in the Staates. So it should be right. Thanks a lot.
        Detlef

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      • You’ve got a mail-!. Please check ur eMail box.

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      • nhel romano says: on October 15, 2011 at 1:39 am

        could you pls. send me the scheme and the parts list, i quite couldn’t understand the diagram. I’m hoping for your positive response regarding this matter. thanks.

        Like or Dislike: Thumb up 0 Thumb down 0

      • To nhel romano.

        OK. I will do it but…

        Please, let me know that your homepage, weblog or email if you like to receive it.
        The posting on this comment area not allowed a long part list.
        So, you should have a email at least.

        Thanks.

        Like or Dislike: Thumb up 0 Thumb down 0

      • rekha says: on August 24, 2012 at 6:23 pm
          member

        hi..could you please mail me the scheme & parts list pls…
        my mail id is “lightray.rekha@gmail.com”
        waiting for your responce..
        thanx.. rekha

        Like or Dislike: Thumb up 0 Thumb down 0

      • HI..
        could you please mail me the scheme & parts list pls…
        my mail id is “pirate_king113918@yahoo.com”
        waiting for your responce..
        thanx.. AZ

        Like or Dislike: Thumb up 0 Thumb down 0

      • could you please mail me the scheme & parts list pls…..my mail id is “nsm_bahary@yahoo.com”
        thanx

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      • maheshjshetty says: on August 22, 2013 at 2:53 pm
          member

        yong please send me the right circuit diagram and my email:jaysunrasmah@gmail.com.

        Like or Dislike: Thumb up 0 Thumb down 0

      • could you please send me the scheme and the parts list, i quite couldn’t understand the diagram. Im hoping for your positive responce regarding this metter.

        Like or Dislike: Thumb up 0 Thumb down 0

    24. khushboo says: on July 3, 2011 at 2:22 pm

      i made this circuit. but its not working..!!
      the relay operates as soon as the supply is switched ON. The transistor t1 is not saturated. can anyone tell what could be the problem?

      Like or Dislike: Thumb up 0 Thumb down 0

      • Adnan Rafiq says: on November 30, 2011 at 11:55 am

        Please contact me i will give you information.i have also need infomation.my phone number is +923327929262.i am a electrical engineer

        Like or Dislike: Thumb up 0 Thumb down 0

    25. khushboo says: on July 3, 2011 at 2:26 pm

      I made the circuit. but its not working!
      the relay operates as soon as i connect the supply. the supply is of 12 volts & relay too.
      the transistor t1 is not saturated.
      please tell what could be the problem.

      Like or Dislike: Thumb up 0 Thumb down 0

    26. Hi
      i am making this project but the circuit is not working the changes made i used for C1=47uF electrolytic and for C2 the same value until now i did not get solution
      can you help me i need detailed explanation
      about capacitors
      regards

      Like or Dislike: Thumb up 0 Thumb down 0

      • It’s working with C1=C2=47uF.
        I have tested it with breadboard.
        In your case, It very high sensitive, so it work by even breath sound.
        I do not recommend it out of range capacitors.

        Like or Dislike: Thumb up 0 Thumb down 0

      • Hello,

        You can replace certain components to reduce the sensitivity of the circuit.

        Like or Dislike: Thumb up 0 Thumb down 0

    27. Hello,
      can u please let me know with the present design,what is the time it take for the circuit to go “OFF” after a sound activated “ON”

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    28. I will introduce how to choose good MIC.
      Good choosing a MIC: for making “SOUND ACTIVATED SWITCH CIRCUIT”.
      Good Condition:
      - category: Microphones
      - Type: Electret Condenser
      - Size / Dimension: Circular – 10mm Dia x 5mm H
      - Sensitivity: -38dB ±2dB
      - Voltage Rated: 4.5V
      - Impedance: 2.2K Ohm
      - Frequency: 38Hz ~ 16kHz

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    29. Announce to making failed outsider.
      I had not designed this circuit. I am person who making succeed just.

      I will let you know making tip:
      - You should not supply over the total DC 6volt.(because : the MIC is DC 4.5 volt).
      - The 0uf condenser: You should use the Tantal 0uf1(=0.1uF=100nf) type. This has positive and negative Polarity. Do never use ceramic, film or electric types. It relative the frequency.
      - The 4u7 condenser: You can use electric type 4.7uF only. It is general.
      - I have using the T1(T2) – BC547 instead of 2SC945 part. Sure, you can use 2SC945 too.
      - The resistor: do not over 5 % but I recommend 1 % resistor.
      - In addition: you need 3M tape for a adjusting the MIC’s sensitive.

      Good Luck.
      From: Yong.

      Like or Dislike: Thumb up 0 Thumb down 0

    30. Additional comment:
      If you follow my guide line, then you never supply over 6 volt. It under condition the MIC’s Max voltage.
      I recommend the 5 volt regulator. (example: IC-7805 regulator)
      Thanks.

      Like or Dislike: Thumb up 0 Thumb down 0

    31. nhel romano says: on November 28, 2011 at 8:28 am

      this circuit was big help, I used it as a project on my subject in control system. It really works. Aside from an encountered problem during lay outing.. but as soon as i finished i was amazed. :)

      Like or Dislike: Thumb up 0 Thumb down 0

      • rekha says: on August 24, 2012 at 6:19 pm
          member

        hi..could you please mail me the scheme & parts list pls…
        my mail id is “lightray.rekha@gmail.com”
        waiting for your responce..
        thanx.. rekha

        Like or Dislike: Thumb up 0 Thumb down 0

    32. what electrical components do u need to make a voice activatedswitch

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    33. Guys, im really interested in building this miracle.
      If it is not hard for you, would u mind sending me the list of items required for building.
      Thanks!

      Like or Dislike: Thumb up 0 Thumb down 0

    34. Guys, i am really interested in building this miracle.
      If it is not hard for you, would u mind sending me the list of items required for building.
      Thanks!

      Like or Dislike: Thumb up 0 Thumb down 0

    35. sorry for double posting.

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    36. sir , can i use bc547 (general purpose transistors instead of 2sc945 or c945 and will i use bc327 or bc557 instead of bd140
      send me information later

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    37. jaspreet saini says: on January 30, 2012 at 8:17 am

      sir i want to make a better major project for the sixth sem and i like this project very much give me the other better sugesstion

      Like or Dislike: Thumb up 0 Thumb down 0

    38. I want to connect a 5 point eagleman relay to circuit can u give me the pin description

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    39. Hello,everybody and ;Mr.asif ali,Mr. Adnan Rafiq,Mr.dhaesa pramana,Mr.Oppong Akwasi.

      I can make the circuit that you asked for
      and also some nice projects,too.
      Here are my mail;[bah9mh@yahoo.com].

      Bye,

      Like or Dislike: Thumb up 0 Thumb down 0

    40. Sir, i want the circuit to ”on” on 1st clap, n ”off” on the n3xt. Pls help me .
      I want the detailed list of components.

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      • boby says: on October 14, 2012 at 4:43 pm
          member

        Hello,Mr.rohit,
        Here I attached that circuit you asked
        for it.I tested it with Proteus and work
        correctly.So,please try it and let me know if it works correctly?

        Best Wishes,

        Like or Dislike: Thumb up 0 Thumb down 0

    41. Hello,Mr.rohit,
      I will design that circuit for you and
      test it by PROTEUS too for sure.
      And also I will send it to you,soonly.
      But,if that circuit have an extra detailes,please send all detailes to
      my mail;[bah9mh@yahoo.com].

      Like or Dislike: Thumb up 0 Thumb down 0

    42. This circuit is ♌φτ̲̅ coming on, do I have to increase or reduce the Mic biasing resistor? What should I do to make this circuit work. Every component have been connected in their right polarity according to the circuit diagram.

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    43. nice project.

      Like or Dislike: Thumb up 0 Thumb down 0

    44. mr logan i want switches which wear working on the voice control,for example in i robet movie…….
      reply me plz ………
      i searching for this type of project

      Like or Dislike: Thumb up 0 Thumb down 0

    45. khokon says: on February 21, 2013 at 5:55 pm
        member

      This circuit it doesn’t work, i am try 3 time but
      …actually i wasted my time…

      Like or Dislike: Thumb up 0 Thumb down 0

    46. Charles Logan says: on July 25, 2013 at 7:46 am

      Will someone please mail me the circuit diagram of project similar to the Sound activated Switch.. Only Difference is I Want the Switch to turn ON on 1st Sound and Turn OFF “ONLY when 2nd Sound is made” i.e the switch should remain ON unless sound is made to turn it off… plzzz mail me circuit diagram, components with specifications n please test it on “PROTEUS” or any other Simulation software n tell me the name of the software ..i want it for a mini project.. my email ID is clawssn@gmail.com

      Like or Dislike: Thumb up 0 Thumb down 0

      • Hello.Yes I have a design bymyself[a practical circuit]of sound[clap]activated
        switch to be turned ON for the first clap and turned
        OFF for the second one.You can send your request to
        my mail;[bah9mh@yahoo.com];I realized it and it works
        correctly also I tested in with PROTEUS.

        Have a nice day,

        Like or Dislike: Thumb up 0 Thumb down 0

    47. ‘Bahman Mohammadhoseini’>>>>sir i want that practical circuit of sound[clap]activated,and i built tht above circuit in proteus but i dnt get tht microphone there,

      Like or Dislike: Thumb up 0 Thumb down 0

    48. Bahman Mohammadhoseini says: on October 3, 2013 at 8:50 pm

      Dear Mr.Omkar,
      Hello.Please send your e-mail to my mail;[bah9mh@yahoo.com]so I can send you my clap switch design.
      Also,in older PROTEUS version there is not exist a
      microphone component and also you should give it an
      audio wave like a clapping sound as an input so you can simulate that circuit;and user should be a professional to work with it correctly.

      Have a nice day,

      Like or Dislike: Thumb up 0 Thumb down 0

    49. Sandpit Sandpit says: on February 12, 2014 at 9:15 am
        member

      HI..
      could you please mail me the scheme & parts list please …
      my mail ID is “dxcircuits@zoho.com”
      waiting for your response..
      thanks.. Sandpit

      Like or Dislike: Thumb up 0 Thumb down 0

    50. Could u plz send me the real list of this curcit

      Like or Dislike: Thumb up 1 Thumb down 0

    51. if there are too many switches in a room the how can we access the different switch as per our requirements

      Like or Dislike: Thumb up 0 Thumb down 0

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