This project is clap sound operated timer switch.  You can put ON the garage light, toy for the children, TV or deck for a set period through this project.  After the set time the load connected with the relay automatically gets OFF.  You can use this project for stairs light.




Most popular timer IC NE555 is used in this project.  The condenser mice in the circuit receives the clapping sound and gives it to the base of transistor Q1 [BC549C] through resistance R8 [3K9] and condenser C4 [0.01mfd].  The amplified signal from the collector of transistor is given to the pin no. 2 of IC through condenser C2 [0.01mfd].  The variable control VR1 [2M2] in the circuit can be used to set the ON time.  The condenser C2 [100mfd/16v] is used between pin no. 7 of IC and ground.  Through which the minimum ON time is four minutes and maximum ON time 10 minutes can be adjusted.

By changing the value of condenser you can increase or decrease the ON time of the project.  The pin no. 4 and 8 of the IC are the positive supply pin.  Whereas pin no. 1 is the ground pin.  When clap sound is produce the output is available from the pin no. 3.  Which is given to the relay coil through diode D1 and D2.  It activates the relay.  With the operation of relay the load connected with the contacts of the relay to gets ON for the set period.


When this project is used to put ON the garage light then first of all, put ON the horn of your vehicle in front of gate of the garage.  The relay operates when the sound of horn is picked up by the condenser mice.  The garage light gets ON through the contacts of the relays.  It gets OFF after some time as per the time set by the preset.  The project is run by 6V – 9V DC supply.




  1. Use IC base for the IC.
  2. Take care that there is no shorting on PCB while soldering the components.
  3. First of all, check all components so that they are OK as per the circuit.
  4. Take care of positive and negative terminals of the diode.
  5. Check the collector, base and emittor terminals of the transistor before soldering on PCB.
  6. Clean all the terminals of the components before soldering.


  1. Use relay 6V/100E for DC 6V supply.