CRAZY L.O.L SPECTRUM ANALYZER

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Introduction: CRAZY L.O.L SPECTRUM ANALYZER

About: PLC, Arduino - Do it yourself project

Today I'd like to share how to make an audio spectrum analyzer - 36 bands by combining 4 LoL Shields together. This crazy project uses a FFT library to analyze a stereo audio signal, convert it to frequency bands, and display amplitude of these frequency bands on 4 x LoL Shields.

Before getting started, please watch the video below:

Step 1: THINGS WE NEED

      The main electronic components are as below:

        Step 2: SCHEMATIC

        The LoLShield is a 9x14 charlieplexing LED matrix for the Arduino and this design DOESN'T include any current limiting resistors. The LEDs are individually addressable, so we can use it to display information in a 9×14 led matrix.

        The LoL Shield leaves D0 (Rx), D1 (Tx) and analog pins A0 to A5 free for other applications. Picture below shows Arduino Uno pins usage for this project:

        My audio spectrum analyzer has 4 x (Arduino Uno + LoLShield). The power supply and stereo audio jack 3.5mm are connected as below schematic:

        Step 3: LOL SHIELD PCB & LED SOLDERING

        1. LoL SHIELD PCB

        Ѽ. You can refer to PCB design at: https://github.com/jprodgers/LoLshield by Jimmie P. Rodgers.

        Ѽ. PCBWay supported me these LoLShield printed circuit boards with fast delivery and high quality PCB.

        2. LED SOLDERING

        Ѽ. Each LoLShield needs 126 leds and I used different kind & colors for 4x LoLShields as follows:

        • 1 x LoLShield: diffused led, red color, 3mm.
        • 1 x LoLShield: diffused led, green color, 3mm.
        • 2 x LoLShield: non-diffused (clear) led, blue color, 3mm.

        Ѽ. Preparing LoLShield PCB and LED

        Ѽ. Soldering 126 LED onto LoLShield PCB. We should check the LEDs by battery after soldering every row - 14 LEDs

        • TOP LoLSHIELD

        • BOTTOM LoLSHIELD

        Ѽ. Finishing one LoLShield and continue to solder 3 remaining LoLShield.

        Step 4: CONNECTION AND ASSEMBLY

        Ѽ. Soldering power supply and audio signal to 4xLoLShield. A stereo signal uses two audio channels: left and right which are connected to Arduino Uno at analog pins A4 & A5.

        • A4: Left Audio Channel.
        • A5: Right Audio Channel.

        Ѽ. Aligning & mounting 4 x Arduino Uno on the acrylic plate.

        Ѽ. Plugging 4 x LoLShield on to 4 x Arduino Uno.

        Ѽ. Glue portable charger power bank and audio jack on acrylic plate

        Ѽ. Done!

        Step 5: PROGRAMMING

        You should refer to how LoLShield works based on the Charlieplexing method and Fast Fourier Transform (FFT) at:

        https://en.wikipedia.org/wiki/Charlieplexing

        https://github.com/kosme/fix_fft

        For Charlieplexing, we pay attention to the "three states" of the Arduino digital pins: "HIGH" (5V), "LOW" (0V) and "INPUT". The "INPUT" mode puts the Arduino pin in high-impedance state. Reference at:

        https://www.arduino.cc/en/Tutorial/DigitalPins

        In my project, the audio frequency bands are displayed on 4 x LoL Shield and they are described as shown below:

        Each Arduino reads audio signal at left/ right channel and perform the FFT.

          for (i=0; i < 64; i++)
          {                                     
            Audio_Input= analogRead(RIGHT_CHANNEL); // Read audio signal at right channel A5 - ARDUINO 1 & 2
            //Audio_Input = analogRead(LEFT_CHANNEL); // Read audio signal at left channel A4 - ARDUINO 3 & 4                                
        Real_Number[i] = Audio_Input;
        Imaginary_Number[i] = 0; } fix_fft(Real_Number, Imaginary_Number, 6, 0); // Perform Fast Fourier Transform with N_WAVE=6 (2^6=64) for (i=0; i< 32;i++) { Real_Number[i] = 2*sqrt(Real_Number[i] * Real_Number[i] + Imaginary_Number[i] * Imaginary_Number[i]); }

        Ѽ. Arduino 1 - Display amplitude frequency bands 01 ~ 09 of right channel (A5).

          for (int x=0; x < 14; x++)
          {
            for (int y=0; y < 9; y++)
            {
              if (x < Real_Number[y]) // Display frequency bands 01 to 09
            {
                LedSign::Set(13-x, 8-y, 1); // LED ON
              } 
              else
              {
                LedSign::Set(13-x, 8-y, 0); // LED OFF
              }
            } 
          }

        Ѽ. Arduino 2 - Display amplitude frequency bands 10 ~ 18 of right channel (A5).

          for (int x=0; x < 14; x++)
          {
            for (int y=0; y < 9; y++)
            {
              if (x < Real_Number[9 + y]) // Display frequency bands 10 to 18
            {
                LedSign::Set(13-x, 8-y, 1); // LED ON
              } 
              else
              {
                LedSign::Set(13-x, 8-y, 0); // LED OFF
              }
            } 
          }

        Ѽ. Arduino 3 - Display amplitude frequency bands 01 ~ 09 of left channel (A4).

        The code is as same as Arduino 1 and audio signal left channel connect to Arduino at analog pin A4.

        Ѽ. Arduino 4 - Display amplitude frequency bands 10 ~ 18 of left channel.

        The code is as same as Arduino 2 and audio signal left channel connect to Arduino at analog pin A4.

        Step 6: FINISH

        This portable spectrum analyzer can connect directly to a laptop/ desktop, mobile phone, tablet or other music players via the 3.5mm stereo audio jack. This project seems crazy, I hope you like it!

        Thank for your reading !!!

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          Comments

          0
          Palingenesis
          Palingenesis

          1 year ago

          Very nice.
          Do you know about the PCA 9685.
          Its advertised as a server controller on eBay, but it is actually an LED driver to drive 16 LED's.
          You can daisy-chain 64 of these enabling you to control 1024 LED's with 1 Arduino via I2C.