I'm aware that a very similar question has been asked here before: https://electronics.stackexchange.com/questions/91015/how-connect-a-4-wire-fan-to-arduino-and-control-the-speed
However, upon checking I have been getting mixed feedback and I have the impression most of it comes from the fact that most people do Fan Speed Control via 2 pins only and expect transistors. So I decided to ask here in hope for some further information.
I currently have my Arduino powered via USB and separately my 12dc Fan with it's own power supply. They share common ground and the PWM line from the fan is connected to the Arduino boars. Nothing else in between (no transistors, resistors or diodes).
It is working correctly, but I haven't had it running for long in fear it may be unsafe.
Should I be concerned about the PWM line connected as such? Can the 12v from the Fan's PSU damage the Arduino with this connection?
Upon research, it seems the PWM line has a 5.25V Max voltage. I'm not entirely sure, but am I right to guess that is the max Voltage that will go through that wire?
I do agree that a diode around the fan is a good idea and will definitelly add that.
*Edit: Thought I'd clarify that I'm using this setup to change the speed of my fan.