Temperature, mail, rpm... and stuff...

I started a new project, this time for my network equipment in a cabinet, where I want an arduino to control it by pwm, depending on the temperature... While making the sketch for the rpm counter, I then also decided I want to make a readout for it on a website, and want it to interface with my mailbox in the driveway to tell me when I get new mail, control lights, and so on...

First thing is to make an adapter for a fan that will go in the top of the cabinet.

And during the process I will try to describe and show every step of the process from start to end.

http://bld.is-a-geek.com/2010/12/12/from-drawing-to-reality/

So far the only real arduino based is how I connected the fan to an arduino, and how I read the rpm's.

#define fanPin 3    // FAN connected to digital pin 9

volatile byte rpmcount;
unsigned long timeold;

void setup()
{ 
  attachInterrupt(0, count, RISING); //0 = Digital pin 2
  analogWrite(fanPin, 25);
  Serial.begin(9600);

  rpmcount = 0;
  timeold = 0;
}

void loop()
{   
  if ((millis() - timeold) >= 1000)
  {
    Serial.println(30*1000/(millis() - timeold)*rpmcount, DEC);
    timeold = millis();
    rpmcount = 0;
  }
}

void count()
{
  rpmcount++;
}

And now some pictures from when I made the fan adabter