@noskillzengineer said in Fans and stuff improvements…:
In my experience, 4 wire fans have physical switches, likely because of control on the fan itself, that is responsible for the speed control of the fan.
I have never used a 4-wire fan with a physical switch. I have 2 of them in the PC that I am using, and some more on the bench that I have tested with various Duet-based controller electronics.
PWM is PWM whether it is controlled by hardware alone (which would be very unusual these days) or by software.
Why support 4? If your response means 4 pin headers like PC fan headers that will also run two and three fans/motors, then no issues here.
There are two problems with controlling the a speed of 3-wire fans:
Most of them were never designed to have PWM applied to the power feed to them. You won't find any PCs using PWM to control the power feed to a 3-wire fan. It's remarkable that so many 2- and 3-wire fans tolerate PWM at all.
If you PWM the supply to a 3-wire fan then the output from the tacho wire is no longer reliable, because the tacho sensor depends on receiving continuous power. So the tacho reading would be wrong except at full speed.
4-wire fans are designed to work with PWM, so they are a much better choice if you want variable speed and RPM sensing. OTOH we could provide a 3-wire always-on (or just on/off) fan connector if users want that.