#MACS FAN CONTROL VIEW ONLY SERIES#

For continuous spinning motion, this minimum voltage needs to be supplied.ĭC voltage control is the method to vary DC fan speed and this can be implemented by incorporating resistances in the supply wire.

#MACS FAN CONTROL VIEW ONLY SERIES#

The voltage drop across the series resistor reduces the voltage reaching the fan supply pin, automatically slowing the speed of the fan. If the resistor connected is a variable one, the fan speed can be varied until it stalls at a minimum threshold voltage. Nowadays, standalone fan controllers with knobs are available for this type of DC fan speed control. Pulse width modulation (PWM) fans are DC fans with an extra wire for PWM. PWM fans are 4-pin fans where the fourth wire sends a PWM signal to the fan motor. The PWM signal is the control input of the PWM fan. The control input is usually an open-drain or open-collector output with a 5 V or 3.3 V pull-up. The PWM control signals are square waves of high frequency, usually 25kHz or above, to make the noise from the fan above the audible human range. The PWM signal can start or stop the motor, depending on the high and low state of it. When the PWM signal is high, the motor runs, otherwise, the motor is stationary.

The duty cycle of the PWM signal controls the speed of the fan motor. The motor will be supplied with 12 V throughout, however, the duty cycle of the PWM signal decides how long the fan should be running or not.

Macs fan control view only