Question about power

I just want to start off by saying am still very new to playing with this kind of stuff so sorry for any stupid questions.

I have setup 3 TLC5940NT with my arduino to control 48 leds (16 RGB leds) and everything works but i didn’t think i would be able to use just the 5v power on the arduino because i thought it would be to much for it but tonight i just tested it and it works with 16 of the led’s all on at the same time (haven’t tried more just because i didn’t think that would even work). So my question is this okay or am i just asking for trouble later on with running it like this and what would i need to do to get power for all 48 led’s?

Just some things i did while testing this

first i used my multimeter and checked what voltage i was getting out of the 5v on the arduino board pin, i got 6v

next i had my multimeter attached to where all the led’s got power from and with 16 red led’s the voltage never dropped below 4.7v and with the 16 green or the 16 blue it never dropped below 4.8v

the code i ran turning on the led’s for each color one at a time

#include "Tlc5940.h"

void setup()
{
  Tlc.init();
}

void loop()
{
  //All Red
  Tlc.clear();
  for(int c = 0; c < NUM_TLCS * 16; c += 3) {
    Tlc.set(c,4095);
    Tlc.update();
    delay(1000);
  } 
  //All Green
  Tlc.clear();
  for(int c = 1; c < NUM_TLCS * 16; c += 3) {
    Tlc.set(c,4095);
    Tlc.update();
    delay(1000);
  } 
  //All Blue
  Tlc.clear();
  for(int c = 2; c < NUM_TLCS * 16; c += 3) {
    Tlc.set(c,4095);
    Tlc.update();
    delay(1000);
  }
}

Thanks

Add up the current, 20mA per LED for 48 LEDs is 0.96A, this is too much for the USB power and for the 5V regulators on the board.
You need an external regulated supply for the LEDs.
A discussion of the power you can take from the regulators on an arduino is here:-
http://www.thebox.myzen.co.uk/Tutorial/Power_Examples.html

The reason it works with 16 LEDs is that you'll only need about 320mA of current to drive those. In theory you could drive 25 LEDs requiring 20mA but that doesn't take into account the current that the rest of the stuff you have plugged in will draw.

Once you go over the ~500mA of current USB can provide (coupled with the limitations of the regulator on the Arduino), you'll have some serious problems from the voltage drop.

LEDs are power hogs!