I'm going to make a fan control , for moving hot air from my fireplace in the summerhouse living room , to the bedroom.
The fan is a : Papst 8412 N/2GLE (12v dc / 37ma)
As i would like to read the tacho signal , i need a highside driver , and was thinking about using this one (i have some home) , as i see it i can just connect it to the AVR OCR pin , maybe via a 470 ohm just for protection.
What frequency should i run the pwm at ??
I can see that a high frequency might be better (22khz outside the audible range) , but can a 3 wire fan do that ??
The fet has a 100us turn on , and a 150us turn off time.
I'd prob be using a M8 , and have 2 NTC's (one in each room , no need to move air if the temp is the same) + IR control for the fan
Edit: Saw some hints in here
And it also gave me the hint with the pullup on the tacho line :oops: ... At first there was no signal , but after a 10K pullup to 12v "It's Alive" :lol: :lol:
Also some tips about PWM and Tacho readings , as the tacho doesn't get power all the time , when pwm'ing.
But i'm not sure if it's a problem if i use a highside driver , and a pullup on the tacho line.
Any hints/tips are welcome ....