A circuit that responds to a clap sound to switch on or off is called a simple clap switch, and it uses a speaker as a microphone.
Because speakers and microphones have extremely similar constructions and may be used interchangeably for this purpose the speaker is employed as a microphone in this circuit.
Circuit Working:
Parts List:
| Component Type | Value | Quantity |
|---|---|---|
| Resistors (All resistors are 1/4 watt) | 3.3k | 1 |
| 470k | 1 | |
| 470Ω | 1 | |
| 2.2k | 2 | |
| Capacitors | Electrolytic 10μF | 2 |
| Electrolytic 100μF | 1 | |
| Semiconductors | IC 4017 | 1 |
| Transistors BC547 | 2 | |
| LED | Any 5mm 20mA | 1 |
| Speaker | 8Ω | 1 |
The circuit above is a 4017 decade counter integrated circuit IC in addition to being a clap switch that uses a speaker as a microphone.
With each clap this circuit will activate one LED, It will then cycle through LED with further claps.
The circuits working is mentioned below:
The microphone is the speaker, the sound wave from a clap causes a little voltage to appear across the speaker.
Transistor T1 BC547 receives this voltage from C1, and it amplifies the signal.
T1 is biased and the operational point is determined by resistor R2.
C2 prevents DC electricity from going to the circuits subsequent step.
Schmitt trigger function is provided by transistor T2 BC547.
When the input voltage reaches a particular threshold this circuit quickly flips between two stable states.
As a result the circuit is less susceptible to noise.
The schmitt triggers trigger points are determined by R3 and R4.
Pin 14 of the 4017 IC receives the output from T2 the clock input is for this.
The reset pin is located on pin 15 of the 4017 IC ,It resets the counter to output 0 pin 3 when it is low.
Resistor R5 connects the reset in this circuit to a positive voltage which keeps the integrated circuit operating.
The inhibit pin is located on pin 16 of the 4017 IC, this pins low signal stops the counting.
This circuit does not make use of it, it is a decade counter 4017 IC.
Pins 3 through 16 are its outputs, and each time a clock pulse is received on pin 14 they all go high sequentially, one after the other.
The 4017 ICs output in this circuit is connected to an LED via a resistor R5.
The LED illuminates when the counter output rises to a high level, both the T2 output and the 4017 ICs clock input pin 14 are low when there is no clapping.
The first LED in the circuit is lit because pin 3, the output is high and the counter is not timed.
A strong pulse on pin 14 of the 4017 integrated circuit is caused by a voltage spike that is created by a clap and travels via T1 and T2.
By clocking the counter and moving it to pin 4 the second LED in the circuit is turned on.
Formulas:
BC547 Biasing Resistors:
To guarantee appropriate operating points and gain, identify the biasing resistors for the BC547 transistors.
It is possible to compute the base current IB using ohms Law:
IB = Vin−VBE / RB
where,
- VBE is the base emitter voltage drop, which for silicon transistors is usually around 0.7V.
IC 4017 Timing Considerations:
If the outputs need to be triggered sequentially, use the resistors and capacitors in the circuit to adjust the length of the output pulse or the interval between claps.
T = 0.7 × RT × CT
For instance, the timing capacitor CT and resistor RT linked to the IC 4017 may be used to measure the length of the pulse.
Current Limiting Resistor for LEDs:
To restrict the current, calculate the resistor value in series with the LED.
RLED = Vcc−VLED / ILED
where,
- Vcc is the supply voltage, VLED is the LED forward voltage, and ILED is the required LED current.
When designing a clap switch circuit, one must be aware of how the various parts work and make the right calculations and selections of resistors, capacitors and other parts to provide the intended functionality.
These factors, albeit not precisely formulaic in the mathematical sense, direct the design process to guarantee the circuit functions consistently and successfully in recognizing claps and activating outputs appropriately.
How to Build:
To build a Simple Clap Switch using Speaker as a Microphone you need to follow the below mentioned connections process:
- Assemble all the components as shown in diagram.
- Connect pin 2 of IC 4017 to one ends of capacitors C2 and C3 and other end to ground.
- Connect pin 3 of IC 4017 through one end of a LED and a resistor R5 and other end to ground.
- Connect together pin 7 and pin 15 of IC 4017.
- Connect pin 8 and pin 13 together of IC 4017 to ground.
- Connect pin 16 of IC 4017 to positive supply of 6V.
- Connect pin 14 of IC 4017 between collector of transistor T2 and resistor R3.
- Connect collector of transistor T1 to one end of resistor R1 and other end to positive supply.
- Connect base of transistor T1 to capacitor C1 and one end of 8Ω speaker, and other end of speaker to ground.
- Connect emitter of transistor T1 to ground.
- Connect collector of transistor T2 to one end of resistor R3 and other of to positive supply.
- Connect base of transistor T2 to resistor R1 and collector of transistor T1.
- Connect emitter of transistor T2 to ground through resistor R4.
- Connect one end of resistor R2 to base of transistor T1 and other end between emitter of transistor T2 and resistor R4.
Additional Note:
- It is not optimal to use the speaker as a microphone.
- Condenser microphones are more sound sensitive, hence they make more sense for this circuit.
- Background noise may cause the circuit to become sensitive.
- To enhance noise rejection you might need to change the resistor values.
- The LED receives only a short pulse from the circuit.
- To keep the LED on for a longer period of time, you might need to connect an extra circuit.
Conclusion:
A clap switch operates an electrical equipment by means of sound.
For this job a condenser microphone is a more dependable and sensitive option, however a speaker can work in a hurry.
This is due to the fact that background noise might activate speakers, which are not designed with sound detection in mind.