Speed controlling computer fans
For years I have been using the Silverstone fm121 as it comes with a remote mounted speed controlling potentiometer, goes as high as 110 CFM and 0.4 amps consumption. It is fairly quiet for this am...
Forum Discussion
The 4 wire fan is pretty easy to control, and shouldn't make any extra noise being controlled properly. Trying to pwm the power to such a fan will only result in headache, as the internal control chip will fight you the entire time.
4-wire "pwm" fan:
Connect just + and - the fan will run at minimum speed, which might be good enough?
The remaining two wires are a hall-effect output and pwm input. The pwm input connects to the controller chip inside the fan, and controls the speed within a range defined by the manufacturer. The hall effect output is "open drain" emits a series of pulses corresponding to the fan's rpm.
Connecting the pwm input to + through a 10k resistor will operate the fan at full speed. Connecting the hall-effect output to + through a 10k resistor will make it pulse low as the fan rotates. Without a "pull-up" resistor there is no output on this wire. This gives you a safe means to tell which wire is which.
The following website details a few simple circuits to generate the PWM signal needed to interface with the fan's internal control chip.
http://www.overclockers.com/pwm-fan-controller/
4-wire "pwm" fan:
Connect just + and - the fan will run at minimum speed, which might be good enough?
The remaining two wires are a hall-effect output and pwm input. The pwm input connects to the controller chip inside the fan, and controls the speed within a range defined by the manufacturer. The hall effect output is "open drain" emits a series of pulses corresponding to the fan's rpm.
Connecting the pwm input to + through a 10k resistor will operate the fan at full speed. Connecting the hall-effect output to + through a 10k resistor will make it pulse low as the fan rotates. Without a "pull-up" resistor there is no output on this wire. This gives you a safe means to tell which wire is which.
The following website details a few simple circuits to generate the PWM signal needed to interface with the fan's internal control chip.
http://www.overclockers.com/pwm-fan-controller/
