Sound Activated Switch Circuit

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.


Join the conversation!

Error! Please fill all fields.
  • moch-rizal25gmail-com

    Dear Bahman,

    Can you please send me the simulation project, the scheme, part list, or pcb layout?

    When i try it in breadboard, it is failed. I dont know why, im still new in electrical. So please can you help me? Or anyone that has already succeed with this circuit.

    Im already send you an email. It is

    Thank You

  • otskaurgmail-com


    Can anybody tell me what 060379 – 11 stands for? I can’t seem to find any information about this part.

    Thank you

  • yyyy

    Ughhm… I have this project. We have to make a toy car which is clap-activated. Can u guys help me?

  • Ehtisham Akbar

    I’ve made a clap switch circuit using a relay. But it is too sensitive, for ex a click of ball point is enough to glow a light.
    how can i make it less sensitive. i want it to operate only on a sound of clap…..

  • Justine Sanz

    I’m just wondering, how much sound would it cost for this circuit to activate.. Coz i need a minimum of 70dB as the input sound.. can you help me at this? thanks a lot bro :))

  • dave

    Hello, I have a driveway alarm, it beeps twice whenever a car or being passes through it. It consists of the sensor outside and the alarm signal box located indoors. I need a sound activated relay to activate when this alarm goes off. Then a relay would power a security light directed to the driveway area. I have searched the Net but haven’t found anything that would work. Any Ideas ? Thank You in advance

  • John

    And another question I have is would it be safe to use a potentiometer for resistor one?

  • John

    I am creating a suit for my shows and I am using around 22 feet of EL wire running off a 9V battery and an inverter. Could I use this circuit to control the input of the inverter? Meaning, can I put the battery into this circuit, and run the circuit output into the inverter?

    And also, will changing the value of capacitor 1 change anything?

  • manish

    1.what sound should i give to mic so to get required proper output….?
    2.for relay what is exactly used either a coil or a no/nc connection ??

    please give the reply as soon as possible.

    • boby


      The answer to your questions are;

      1.Just sound of clapping[the sound of striking your palms together].

      2.Use coil pins of relay,a transistor and a diode.

      [I also, designed a very practical sound switch with a relay that work very good.].

      Have a nice day,

  • James Wang

    can i ask how specific that C2 and C1,how many volts?electrolytic or SMD,tantalum??..thank you

    • Bahman M.


      Those C1 & C2 because of their values and ranges are
      polarized type,so,they can be electrolytic or tantalum types.
      Also, you should be noted that in sound wave,for our ears there is not difference between a negative half cycle or positive one.

Looking for the latest from TI?