Loudspeaker to Microphone converter circuit
#loudspeaker
#microphone
#transistor
#common base
#voltage gain
#signal converter
#sound waves
#voice coil
#impedance matching
#audio circuit
Description: This circuit utilizes a standard loudspeaker, enabling it to function as a microphone. It allows for the use of an inexpensive loudspeaker in this capacity. Sound waves impacting the speaker cone result in variations in the voice coil. The movement of the voice coil within the magnetic field of the speaker generates a small electrical signal. The circuit is designed to operate with a voltage range of 6 to 12 volts DC. The initial transistor operates in common base mode, which provides the benefits of matching the low input impedance of the speaker to the common base stage while also delivering a high voltage gain.
The second stage is directly coupled and operates in emitter follower mode. Although the voltage gain is slightly less than unity, the output impedance is low, allowing it to drive long cables effectively. While the audio quality may not match that of a standard or electret condenser microphone, reasonably acceptable results can still be achieved. Loudspeakers with cone diameters ranging from 1 inch to 3 inches are suitable, and speaker impedance can vary from 4 ohms to 64 ohms. The value of the 8.2-ohm resistor may be adjusted to correspond with the actual impedance of the speaker.
This circuit design effectively converts a loudspeaker into a makeshift microphone by capitalizing on the transduction properties of the speaker's cone and voice coil. The initial stage employs a common base transistor configuration, which is particularly advantageous for low-impedance sources such as loudspeakers. The common base stage facilitates a high voltage gain while maintaining a low input impedance, which is essential for efficient signal transfer from the speaker to the transistor.
In the second stage, the emitter follower configuration serves to buffer the signal, providing a low output impedance that is capable of driving longer cable runs without significant signal degradation. This characteristic is crucial in practical applications where the microphone may be positioned far from the processing equipment. Despite the limitations in audio fidelity compared to conventional microphones, this circuit can be employed in various applications where cost-effectiveness is prioritized, such as in DIY projects or educational demonstrations.
The versatility of the circuit allows for the use of a range of loudspeakers, accommodating different sizes and impedances. The ability to modify the resistor value to match the loudspeaker's impedance is an important feature, ensuring optimal performance and signal integrity. Overall, this circuit represents an innovative approach to audio signal capture, leveraging readily available components to achieve functional results in sound detection applications.This circuit takes an ordinary loudspeaker and allows it to be used in reverse, as a microphone. This circuits allows you to use a cheap loudspeaker as a microphone.Sound waves reaching the speaker cone cause fluctuations in the voice coil. The voice coil moving in the speakers magnetic field will produce a small electrical signal . The circuit is designed to be used with an operating voltage between 6 and 12 volts dc. The first transistor operates in common base mode. This has the advantage of matching the low input impedance of the speaker to the common base stage, and secondly has a high voltage gain.
The second stage is direct coupled and operates in emitter follower. Voltage gain is slightly less than unity, but output impedance is low, and will drive long cables. Speech quality is not as good compared to an ordinary or ECM microphone, but quite acceptable results can be obtained. Speaker cones with diameters of 1 inch to 3 inches may be used. Speaker impedance may be 4 ohm to 64 ohm. The 8.2 ohm resistor value may be changed to match the actual speakers own impedance.
The second stage is directly coupled and operates in emitter follower mode. Although the voltage gain is slightly less than unity, the output impedance is low, allowing it to drive long cables effectively. While the audio quality may not match that of a standard or electret condenser microphone, reasonably acceptable results can still be achieved. Loudspeakers with cone diameters ranging from 1 inch to 3 inches are suitable, and speaker impedance can vary from 4 ohms to 64 ohms. The value of the 8.2-ohm resistor may be adjusted to correspond with the actual impedance of the speaker.
This circuit design effectively converts a loudspeaker into a makeshift microphone by capitalizing on the transduction properties of the speaker's cone and voice coil. The initial stage employs a common base transistor configuration, which is particularly advantageous for low-impedance sources such as loudspeakers. The common base stage facilitates a high voltage gain while maintaining a low input impedance, which is essential for efficient signal transfer from the speaker to the transistor.
In the second stage, the emitter follower configuration serves to buffer the signal, providing a low output impedance that is capable of driving longer cable runs without significant signal degradation. This characteristic is crucial in practical applications where the microphone may be positioned far from the processing equipment. Despite the limitations in audio fidelity compared to conventional microphones, this circuit can be employed in various applications where cost-effectiveness is prioritized, such as in DIY projects or educational demonstrations.
The versatility of the circuit allows for the use of a range of loudspeakers, accommodating different sizes and impedances. The ability to modify the resistor value to match the loudspeaker's impedance is an important feature, ensuring optimal performance and signal integrity. Overall, this circuit represents an innovative approach to audio signal capture, leveraging readily available components to achieve functional results in sound detection applications.This circuit takes an ordinary loudspeaker and allows it to be used in reverse, as a microphone. This circuits allows you to use a cheap loudspeaker as a microphone.Sound waves reaching the speaker cone cause fluctuations in the voice coil. The voice coil moving in the speakers magnetic field will produce a small electrical signal . The circuit is designed to be used with an operating voltage between 6 and 12 volts dc. The first transistor operates in common base mode. This has the advantage of matching the low input impedance of the speaker to the common base stage, and secondly has a high voltage gain.
The second stage is direct coupled and operates in emitter follower. Voltage gain is slightly less than unity, but output impedance is low, and will drive long cables. Speech quality is not as good compared to an ordinary or ECM microphone, but quite acceptable results can be obtained. Speaker cones with diameters of 1 inch to 3 inches may be used. Speaker impedance may be 4 ohm to 64 ohm. The 8.2 ohm resistor value may be changed to match the actual speakers own impedance.
Transistor current mirror circuit
The bases and emitters of the transistors are connected together, resulting in equal base-emitter voltages. Assuming the transistors are identical, equal Vbe leads to equal base currents, which in turn results in equal collector-emitter currents. By adjusting the voltage and...
Transistor Tutorial Power Amplifiers Part 4
An audio power amplifier can enhance weak signals from devices like tuners, CD players, or tape decks to fill a room with sound. This article emphasizes the operating principles and circuitry of low-frequency power amplifiers utilizing bipolar junction transistors (BJTs)....
Power Control
The circuit presented utilizes a two-transistor "flasher" to generate triggering pulses, replacing the traditional unijunction transistor design. This configuration allows for a broad range of control with minimal hysteresis and sensitivity to line voltage. Two diodes rectify the line voltage,...
TUNED-COLLECTOR ARMSTRONG OSCILLATOR
The DC path is established from the negative side (ground) of VCC through RE, Q1, T1, and returns to the positive side of VCC. The figure clearly illustrates that both the AC and DC components flow through the tank circuit....
Robot control circuit composed of transistor and NE555
Figure 2-33 (a) illustrates the schematic diagram of a robot approaching an object. When no objects are detected in front of the robot, it moves forward in a straight line. If an object is detected on the left or right...
Miniature Loop Alarm
Simple construction, reliable operation, very small power consumption, and, most of all, small size. I started with CMOS logic gates, but was soon forced to abandon the concept after a few unsuccessful (and far too complicated) attempts. Then I suddenly...
Transistor time relay circuit
This circuit consists of five transistor time relay circuits designed for time relay exchange. It utilizes two different power supplies, maintaining the same circuit configuration. The delay time can be adjusted by modifying a potentiometer. The parameters for the time...
Balanced Microphone Preamp
The design consists of differential compound pairs of transistors with a common mode (floating) gain control connecting the emitters of the pair. The compound pairs of 2N4403 and BC549s are far more linear than any single transistor. The circuit is...
Computer Microphone
This circuit was submitted by Lazar Pancic from Yugoslavia. The sound card for a PC typically includes a microphone input, speaker output, and sometimes line inputs and outputs. The microphone input is designed specifically for dynamic microphones, operating within an...