Ok, lets get some stuff ready.
1. Soldering Iron, Solder.
2. Arduino Nano
3. USB chord
4. Sharp IR sensor.
current awesome meter reading: [ ===
--------------] not looking too good...
Go ahead and heat up your solding iron.
While that is heating lets make a stencil for where your sensor will go. What I did was first traced the outside of the IR sensor, then you find where the LEDs are and make the most amazing circles you have ever made in all of everdom. I eyeballed this but you could do some measuring or check out the datasheet to get exact measurements. I'm a pro circle drawer though so... don't feel bad if yours aren't as good as mine.
Connect it up!
make sure you have the correct length by putting the arduino inside the mouse and see if it reaches where you would like to put the sensor.
Now solder the RED
wire of the IR sensor to the 5v pin
to A3 (analog in 3)
(check diagram above if you aren't sure what ones these are)
Now, get your mirror out.
Look at how smart and amazing you are. d'awwwe.
Ok, your IR sensor is now connected to your arduino board, 10 points. Plug that USB in and lets get programming.
disclaimer: I know this code is nasty and hacked together. I was tired and me and "for loops" were getting in a fight, soooooo. yeah. if you want to suggest improvements--have at it.
awesome meter: [ ====
----------] getting better!