The circuit diagram of sound detector circuit using op-amp 741 is shown in figure 1. The heart of the circuit is op-amp 741 which is used in order to sense the vibrations of sound waves condenser microphones.
Sometimes due to lack of concentration and our ignorance, we are unable to hear anything around us. And, that could lead to unfortunate misfortunes which could have been avoided with appropriate precautions. This circuit called ‘Sound Scanner’ is what detects vibrations of the sound waves and amplifies it to be heard distinctly by human ears. As per the design of the scanner, it works efficiently within the 6 meters limit around the vicinity where it is fixed. This set up can be done in any desirable places like car porches and at the corners of house. As soon as a microphone incorporated in the project detects sound wave vibration, the sound detector circuit using op-amp 741 produces beep sounds to alert people around that area.
Circuit Description of sound detector circuit using op-amp 741
The circuit diagram of sound detector circuit using op-amp 741 is shown in figure 1. The heart of the circuit is op-amp 741 which is used in order to sense the vibrations of sound waves condenser microphones. The sensitivity of the condenser microphone is adjusted by the value of resistor R1 used in the circuit. Once the microphone detects sound vibrations, it picks them up and converts into electrical signals. The output of microphone is fed as input to the pin 2 of IC1 via coupling capacitor C1. Then the signal undergoes amplification and it is forwarded to IC2(IC 741C) which in this project serves as a comparator device.
The non-inverting pin 3 of IC2 receives input from amplified output signal of IC1 through another capacitor C2. In the same way, an inverting pin 2 of IC2 fetches input signal from a reference voltage passed via voltage controller VR2.
At the final stage, IC2 output is fed as triggering input pulse to Darlington pair transistors T1 and T2. A piezo-buzzer which is connected at the end of transistor T2 i.e. at the emitter terminal is that component responsible to produce beeping sound at the end of operations followed throughout the entire circuit.
The fascinating fact about the project sound detector circuit using op-amp 741 is that it can be designed within a small area on a PCB or Veroboard as well. To attain maximum possible gain of IC1 and sensitivity of IC2, adjust the respective values of potentiometer VR1 and VR2 as stated in the earlier paragraphs.
During practical implementations of the project, if the beeping sound from piezo-buzzer goes on and on and doesn’t stop, set the wiper of VR2 towards the ground line. For faultless circuit, follow the instructions given below:
Fix the piezo-buzzer at a place where people can hear and sensor at appropriate place where you need continuous monitoring.
So as to extend the sensitivity of the microphone, connect it using two-core shielded wire and enclose it in a small case.
To avoid noises from AC mains, battery supplies are highly recommended for this particular project.
PARTS LIST OF SOUND DETECTOR CIRCUIT USING OP-AMP 741
|Resistors (all ¼-watt, ± 5% Carbon)|
|R1 = 2.8 KΩ|
R2 = 4.7 KΩ
R3, R4, R6 = 10 KΩ
R5 = 1 KΩ
VR1 = 1 MΩ
VR2 = 100 KΩ
|C1 = 0.47 µF|
C2 = 10 µF/16V
|IC1, IC2 = LM741C|
T1, T2 = BC548
|MIC1 = Condenser Microphone|
PZ1 = Piezo Buzzer
SW1 = On/Off Switch