Can i not simply add a resister value to drop the 5v from the arduino down to 0v without all the needed hardware?

I will be powering 84 leds with RGB in an array.

```
Solution 1: 4 x 21 array uses 84 LEDs exactly
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
+----|>|----|>|----|>|----|>|---/\/\/----+ R = 180 ohms
The wizard says: In solution 1:
each 180 ohm resistor dissipates 72 mW
the wizard thinks ¼W resistors are fine for your application
together, all resistors dissipate 1512 mW
together, the diodes dissipate 3696 mW
total power dissipated by the array is 5208 mW
the array draws current of 420 mA from the source.
```

and this is what it looks like:

Its an array and once an object gets close enough it turns into an "X"

David