Music Intensity Display using LM3915

Music we listen is nothing but an electrical signal, whose amplitude varies with time. The stereo which is at the end of earphones, transmits these signals to the diaphragm of the earphones. The diaphragm moves the air, and that is what you listen. There are other parts inside the earphone bud that is not important for our topic.

Basically, we are trying to measure the intensity of the music signal which is nothing but the amplitude of the music. The amplitude of this signal is simply varying amplitude voltage signal.

So we used stereo to extract the signal from the source, which can be a laptop or a mobile phone.

Stereo pin has two terminals, one is the ground and other is the signal terminal.

• LM3915:

The LM3915 is a monolithic integrated circuit that senses analog voltage levels and drives ten LEDs, LCDs or vacuum fluorescent displays, providing a logarithmic 3 dB/step analog display.

Pin 9 is used for changing the display from a bar graph to a moving dot display.

The IC contains an adjustable voltage reference and an accurate ten-step voltage divider.

The LM3915's 3 dB/step display is suited for signals with wide dynamic range, such as audio level, power, light intensity or vibration.

The datasheet is attached with this article for more references to pin configurations and other applications.

• Circuit:

The ground and signal terminal of the stereo pin is connected to pin 2 and pin 5 respectively.

Pin 2 is the ground pin of IC which needs to be connected to the ground of the supply of IC which is 10V.

The reference is designed to be adjustable and develops a nominal 1.25V between the REF OUT (pin 7) and REF ADJ (pin 8) terminals. The reference voltage is impressed across program resistor R1 and, since the voltage is constant, a constant current I1 then flows through the output set resistor R2 giving an output voltage of:
If Pin 9 is kept open then the display is set to dot display, but when Pin 9 is connected to DC source as shown it will display in bar graph.

LED’s can be connected from pin 10 to pin 18 as per the requirement.

figure 1.1: The main setup of Music intensity display

figure 1.2 The proteus simulation of  Music Intensity Display

Demonstration:

Here is the video link to the demonstration of the setup: https://youtu.be/-Mr0V7SHw5Q

Attachments:

1. Datasheet of LM3915

2. Simulation of Circuit on Proteus

Attachment Link:

https://drive.google.com/folderview?id=0B7akLQ6hGFj2cVFzcGpleE9TdjA&usp=sharing


We have the simulation of our circuit on proteus, where we have used a sine source to substitute the music signal being applied to IC.

The code will be available to blog followers upon request.:)