VU Meter Circuit: Build Your 7.8V Level Indicator

Description

This circuit represents a measurement system for level, utilizing a standard configuration around National components. The circuit encompassing IC1 performs input adaptation and amplification, facilitated by the adjustable trimmer TR1 [GAIN]. The circuit incorporating IC2 manages the half-wave rectification of the acoustic signal. Through switch S1, the type of indication displayed by LED D10-11 can be selected. Considering the values of resistors R6 and R7 within the circuit, the initial signal level at the input is 7.8V (the gain of the first stage, IC1, is one), and the voltage difference across the LED D10-11 should be approximately 3 db. The positive supply rail possesses the capability to provide increased current, and it’s safeguarded against overload by the LED current.

IC1 - TL072

The TL072 is a versatile operational amplifier commonly employed in analog circuit design. It’s known for its low noise, high open-loop gain, and differential input architecture, making it suitable for a variety of applications including amplification, filtering, and instrumentation. Its single supply operation capability simplifies power supply design. This particular IC is used here to provide amplification within the initial stage of the level measurement circuit.

IC2 - LM3915

The LM3915 is a monolithic integrated circuit designed primarily for detecting and amplifying small AC signals. It’s frequently utilized in applications like light detectors, sound detectors, and proximity sensors. Its key feature is its high sensitivity and fast response time, allowing it to effectively process weak signals. In this circuit, the LM3915 is used for the half-wave rectification of the acoustic signal.

IC3 - LM3916

The LM3916 is an integrated circuit designed for detecting and amplifying small AC signals, similar to the LM3915. It is often used in applications where high sensitivity and low noise are critical, such as in light or sound detection circuits. Its key advantage is a wide bandwidth, enabling it to operate effectively over a broad range of frequencies. It’s implemented within this circuit as a component for rectification stage of signal.

Circuit diagram

Part list