lighting a tunnel

[system]

Hello,

I am constructing a tunnel and I wanted to employ my Arduino. I am new to this so some help would be greatly appreciated.
I have an Arduino Uno and a bunch of LEDs. When people enter into the tunnel, I want there to be blue LEDs to be on. Upon leaving the tunnel, I want the blue LEDs to turn off and white LEDs to turn on. I bought a ultrasonic motion sensor, but apparently the ultrasonic waves are absorbed into my viewers clothes?, so that won't work. Any suggestions? Also there is question as to whether or not my tiny Arduino can power enough lights to extend 12fton two different walls at the same time? :~

[system]

Yes, you'll need to use high powered leds, 10watts at least each, and mosfets/power transistors to drive them...

As for detection, maybe an infrared motion sensor .

[AnalysIR]

It might be a good idea to provide more information...

...eg the size of the tunnel (L x W x H), # of LEDs, ambient light, power source?

as per the previous post, using a PIR (Pasive infrared sensor ) might be a good idea......but it really depends on the physical details /scale etc.

[system]

I am constructing a tunnel

Is it between the US and Mexico ?

[system]

Also there is question as to whether or not my tiny Arduino can power enough lights to extend 12fton two different walls at the same time?

There are a number of different options here. The quickest , and easiest is to just purchase a 12V lantern battery from a hardware store and connect a 5V regulator circuit like the one attached (5V,5A).
Presumably the 12V battery is already part of your plan (to run the arduino)
I like rechargable Gel-Cels but you still need a regulator if you use them.