fanpwm
I currently using a 4pin fan in my project.
I need to drive the fan with a 120 Hz PWM signal. I read in all the documentation of the fan that the suitable PWM frequency is from 21 to 28 kHz.
I tested the fan using the 120Hz signal and it seems to work well.
Do you think that my configuration can be safe? Is there something that can go wrong driving the fan in that way?
You will need to have a higher input voltage to the FET to get it to the lowest RDS-ON. Right from the data sheet that you linked you can see the difference between having an input at 5V versus 10V.
One thing to note is that
if (pwmVal != 255) {
pwmVal += 10;
...
is not going to stop at 255, since pwmVal will be 250, then 260, e.t.c. One way to fix this would be write
if(pwmVal < 255)
{
pwmVal += 10;
}
else
{
pwmVal = 255;
}
By the way your code is written, if DEBUG is set to 0, nothing will happen (pwmVal will be set to 0). If DEBUG is set to 1, the fan speed will increase at a rate set by "wait" (which isn't defined in this code), until it gets to it's maximum. The value will also be printed to the serial port.
Best Answer
The manufacturer gives a suitable frequency range above 20 kHz to avoid a buzzing of the fan in the audible frequency range. As long as you don't mind this or your setup does not even produce any hum you will be fine.