MOD NOTE: New thread started from this post split from this thread.

Appreciate it thank you. Addin the updated schematic just to make sure I've done it right.
View attachment 254086
Also if there is a better solution based on whatever circuit, happy to explore that. Cheers

Hello,

I'm looking a schema with usage of pwm pin, with low number of component without potentiometer, It's for my 1989 computer
the temp is from 25°, in 3 or 4 step to max speed of the 12v fan.

Best regard

 

Do You want a 12-Volt PWM Power-Controller ?,
or does your Fan have a PWM-Input-Pin ?

Do You already have a Temperature-Sensor ?,
if not, what type of device do You want to sense the Temperature of ?

Do You have a Spec-Sheet for your Fan ? ( please attach it )
.
.
.

 

I used a LM35 temperature sensor and an Lm358 op amp for temperature control.