Introduction: Arduino Vu Meter With Amplifier

Your four main parts for this project are an Arduino, a LoLshield, and an amplifier

The LoLshield is a circuit board that comes with a library that enables one to individually control a matrix of LEDs.  Once you have the correct library installed you can use the code LedSign::Set(x,y,1); to individually choose one led to turn on with your limited number of pins on the arduino. 

Instructions on how to construct the LoLshield can be found here ( 

For our amplifier we choose to use the O2 NwavGuy amp.  For information on ordering and/or constructing follow this link,

Step 1: Connections

Now that you have your two main components you need to start connecting them.  You music signal need to go both to the amplifier. Solder two wires to the input jack of the circuit bored like so.

Step 2: Power Control

In order to ensure that you don’t over power the arduino you will have to solder in a 330 Ω   resistor and a .01 μF capactor in series with the gray wire.

Then just connect the capacitor to pin A4 on the LoLshield and the black wire to the GND pin.

Step 3: Code

This is the code we used for the visualizer, just upload it to you arduino

FFT for LoL Shield v0.9
by Andy Doro

based on FFT library and code from the Arduino forums and
the Charlieplexing library for the LoL Shield.

#include <Charliplexing.h>
#include <fix_fft.h>

#define AUDIOPIN 4

char im[128], data[128];

char data_avgs[14];

int i=0,val;

void setup() {
  LedSign::Init();            //Initilizes the LoL Shield

void loop() {

  for (i=0; i < 128; i++){                                    
    val = analogRead(AUDIOPIN);                                   
    data[i] = val;                                      
    im[i] = 0;                                                    


  for (i=0; i< 64;i++){                                     
    data[i] = sqrt(data[i] * data[i] + im[i] * im[i]);  // this gets the absolute value of the values in the array, so we're only dealing with positive numbers

  // average bars together
  for (i=0; i<14; i++) {
    data_avgs[i] = (data[i*4] + data[i*4 + 1] + data[i*4 + 2] + data[i*4 + 3]);   // average together
    data_avgs[i] = map(data_avgs[i], 0, 30, 0, 9);                              // remap values for LoL

  // set LoLShield

  for (int x=0; x < 14; x++) {
   for (int y=0; y < 9; y++) {
     if (y < data_avgs[13-x]) { // 13-x reverses the bars so low to high frequences are represented from left to right.
      LedSign::Set(x,y,1);        // set the LED on
     } else {
       LedSign::Set(x,y,0);       // set the LED off
  delay (30);

Step 4: Power

Now to power the arduino you will need a 9V battery adapter.  Just plug a 9 v into the arduino and your visualizer is ready.

If your creative side demands you can make an interesting box to house the whole set up in.