I am not controlling a single fan though. It's wired to a fan hub, so the PWM signal is sent to all the fans in the system. I also wrote a companion windows app

I am not controlling a single fan though. It's wired to a fan hub, so the PWM signal is sent to all the fans in the system. I also wrote a companion windows application that reads CPU temps using PawnIO or HWiNFO which follow a curve that the user sets, and it sends the proper duty cycle to the arduino. It's not just a dumb fan controller that I could've bought off aliexpress.