Wireless Music Level Indicator Circuit

A wireless music level indicator is an electronic device built for sensing the varying levels of a music signal and convert it into corresponding levels of illumination over an LED array bar.

This simple circuit will create dazzling LED light effect by detecting any music frequency in the atmosphere and by illuminating a 10 LED bar graph meter, indicating the level of music.

The proposed circuit is suitable for applications where music and entertainment are involved, such as in parties, festivals, get to togethers etc.

Since the circuit is designed to operate without wires, no physical contact becomes necessary making the unit easy to handle and very portable.

The circuit can be powered with a 3V battery or even with your cellphone charger and could be plugged in anywhere in the music hall for getting the intended dazzling music operated light effects.

How it Works

Referring to the circuit diagram below, we can understand the design with the help of the following points:

The circuit is basically built around two stages: 1) a microphone amplifier, 2) a LM3915 based digital LED display processor.

The T1, T2, T3 forms a simple transistorized mic amplifier circuit, which amplifies weak atmospheric music or audio levels to relatively stronger voltage amplitudes at the collector of T3.

The LM3915 is configured as a voltage detector and an LED driver. Any voltage rise and fall pattern at its pin#5 is transformed into a correspondingly sequencing 10 LED display bar graph display connected across the 10 outputs of the IC.

Meaning, at the minimum voltage range, LED#1 will illuminate and as the voltage rises, the corresponding LEDs will begin illuminating in an incrementing sequential manner. At the maximum range the 10th LED will illuminate.

The process will reverse as the voltage drops at this pin, creating a continuous to and fro movement on the LED illumination witha wonderful music enriched light effect.

This maximum detection range can be set or adjusted with the shown 10K preset attached on the same pinout of the IC.

In the proposed design, the amplified audio output from the MIC stage is applied to pin#5 of LM3915. The IC sense the varying amplitudes of the music signals and accordingly causes the LEDs to dance in the intended reverse forward pattern.

The values of C2 and R2 together for individually could be tweaked for adjusting the time response of the sequencing. Higher values will allow slower movement of the LEDs, while lower values will allow the LEDs to sequence at a faster rate.

Video Demonstration:

Parts List

• R1 = 4k7
• R2, R6, R9 = 1K
• R3 = 2M2
• R4 = 33K
• R5 = 470 ohms
• R7 = 10K
• R8 = 10k preset
• C1 = 0.22uF ceramic
• C2 = 100uF/16V or 25V
• C3, C4 = 1uF/16V or 25V
• T1, T2 = BC547
• T3 = BC557
• MIC = electret MIC
• LEDs = all are red LEDs, 5mm, 20mA type, or as desired.

How to Connect with a 3.5mm jack Audio Input

For users who do not wish to have a wireless music level detection functionality can easily modify the design accordingly by eliminating the MIC amplifier stage entirely.

The schematic for a 10 LED music level indcicator for USB connection or for a 3.5mm mobile phone connection is shown below. The circuit input can be also be directly connected with a loudspeaker terminals for achieving the required high quality music level indication.