Clap Switch Controller by using IC555 Timer

 

Circuit Diagram

 · Here circuit diagram for clap switch using 555 – timer is shown above. It means that the switch turns on whenever there is a clap (or a sound) made and will make LED to lit up. But LED will turn off after sometimes.

· Components and their use:

1. Condenser Mic: To identify the sound and turn it into electrical energy for further process.

2. Transistor: Common base configuration of NPN BJT Transistor to use it as a switch, and to trigger the 555 IC.

3. Battery: For power supply.

4. Resistors and Capacitors

5. LED: To verify whether the circuit is properly working or not.

6. 555 – timer IC

Pin Diagram

 

· 555 – timer IC is used to generate time delay, pulse generation, oscillator application.

· 555 – timer is used in monostable Mode for this application.                                         

Monostable Mode of 555 IC:                                                                                                   

1. Monostable vibrator is made by adding an extra resistor and capacitor to 555 timer. Here these resistor and capacitor are R₁ and C₁ respectively as shown in the circuit diagram.               

  2.   In Monostable Mode 555 IC will generate a pulse whenever a trigger signal is given to the pin  (2)                                                                                                                                         

3. The length of the pulse is determined by the value of R₁ and C₁.

 · Through a low voltage trigger 555 – timer is used to turn the LED ON.

· It is to be noticed that in circuit diagram point – A is joined to the trigger pin of 555 – timer, and for 555 – timer to trigger, the trigger pin must be below voltage level of V_cc / 3

Working of the circuit:

· Initially there is not enough base-emitter voltage to turn ON the transistor and hence 555 IC is not triggered and hence LED remains OFF.

· Now, whenever the sound is made near condenser mic, it turns it into the electrical energy and it will increase the base-emitter voltage and hence BJT will turn on. And this will also cause the potential at point A to become low and as we talked earlier it will trigger the 555 – timer to trigger and the LED will turn ON.

· The output pin of 555 IC is pin 3 which is connected to 20Ω resistor which is connected to the LED to verify our output.

· As we are using 555 IC in Monostable mode, so it will turn off after some time which is theoretically given as 1.1 × R₁ × C₁ (Here value of R₁ = 10kΩ and C₁ = 10mF). By changing value of R₁ and C₁ we can change the duration for which LED will remain ON.