I want to install 2 x 120mm fans in the fresh air vent in my room to take air out of the room so to reduce stale damp air building up and causing mould.
I have seen a company who sell commercial versions www.envirofan.net.au and wanted to build a DIY version.
At the simplest level I would just want the fans running all the time but would love to add functionality to be able to run them on a timer, from a hyrometer or web interface.
But to start is there a way to run a 120mm PC case fan directly from an Arduino board?
The PWM signal that modulates its speed is TTL, so a TTL output from the Arduino is okay. But the required frequency range is in the 25KHz range, which is much higher frequency than the default Arduino config and is a little tricky to obtain. Google "arduino PWM frequency" for pointers. You can easily get 31KHz which will likely work.
very interesting topic. I thought about something very similar. I wanted to read the PWM output from my mainboard's fan output. Because I wanted to control a CPU fan. Because for a CPU fan you need some kind CPU-Temp input for arduino. But I think is a little dangerous to rely on software input from a daemon for temp Input. The PWM output of the mainboard should be much better. Anyway didn't want to get off-topic