Extractor Fan and Reed Switch Project

This is my first Arduino project so please let me know if I am approaching anything incorrectly.

The project description:
Monitor the rotations of an extractor fan (wind powered). When the fan drops below a certain rotation frequency (ie there is no wind that day) turn on an electric fan.

This is a simple project and I want it to be reliable as it will be installed outside on a chimney, the extraction fan is for a waterless toilet.

Input sensor
through my research online i have found that a reed switch is the best option to monitor the rotations of the extractor.

the rest of the project should be fairly straight forward,
below is my processing code in sudoish code:

check rotation frequency();
if (frequency < 1/per second && fan == FALSE){
fan = TRUE;
} else {
fan = FALSE;

my questions are:

  1. do you think that a reed switch is the best option?
  2. how should i chose a reed switch, there are may different types, any help here would be much appreciated?
  3. do you think the sudo code is correct, can you suggest a better algorithm?
  4. im using a arduino uno as my micro controller, is this viable to turn on a 12V electric fan, with a motor rating of 1 amp and power consumption of 7.2 Watts? how does the arduino handle 12v as apposed to the normal 5V?

again any help would be most appreciated, i hope i given enough information

A reed switch would work, but having moving parts will eventually fail - consider a hall sensor and a magnet instead.

I'd suggest that you keep track of when the wind powered fan last ran - no need to run the electric fan if there's a temporary lull. You might want to cap the time that the electric fan runs too to save power - is it necessary to have a fan running all the time?

The arduino can't power a motor directly - you will need a transistor to switch the 12V supply - check out the circuit in the playground for controlling a solenoid - a motor is much the same.

Hi Wildbill,
thanks for enlightening me to the reed switch, after a little research i understand the difference between the two sensors and it seems the more reliable of the two because of its solid state as you mentioned.

thanks for the tips on about storing some more info and also on transformers. i know what to look into, perfect.

Hi Jowell,

Old post, just wondering how did you go with your project? I'm totally newbie to Arduino but would like to create a extractor fan for my toilet. Would be great to see your final results!