Thanks I finally got it working ;D
I was missing the 10k resistor and I used the following as code:
volatile byte NbTopsFan;
int hallsensor = 2;void rpm()
{
NbTopsFan++;
}/***************************************/
void setup()
{
// pinMode(hallsensor, INPUT);
Serial.begin(9600);
attachInterrupt(0, rpm, RISING);
};void loop ()
{
NbTopsFan = 0;delay (1000);
NbTopsFan = NbTopsFan * 30;
Serial.print (" ");
Serial.print (NbTopsFan, DEC);
Serial.print (" rpm");};
It was a mix of yours and a mix of Benoit's, at least it works, now to get my character LCD to work. On a side note I couldn't get yours to work, in the terminal I would get random numbers regardless if my fan was running or not.