Can a PWM signal be sent to 3 pin fans? HELP

DarkDubzs · Sep 8, 2013

So basically i want to know if i can use the one available 4 pin fan connector on my motherboard to send a PWM to multiple non-PWM case fans. I was thinking if i could connect a 4 pin fan hub to the 4 pin header on the board and connecting 3 pin non-PWM fans to that hub. I want to have it so the single PWM signal is sent to all the fans so they can run at the same speeds, so basically it will be like they were PWM fans. The hub i mean is something like the DeepCool 4 Port PWM Fan Hub. The fans i would be using are the Cooler Master 120mm Silent Case Fan 4-in-1 Value Pack. Before i thought of this idea, i was going to get a fan controller, NZXT SENTRY 2 Accessories 5.25-Inch Touch Screen Fan Controller, but if this idea would work, i would rather do this because then the fans would control themselves via the PWM signal from the mobo. So would this idea work? Any help or feedback is greatly appreciated! Thanks!

Shaun o · Sep 8, 2013

Let me put it this way!

Does a square peg fit through a round hole ?
No.

Will a four pin Pwm work with a 3 pin case fan.
No i am sorry to say.

Because it is down to the circuit and Pwm chip fitted to the fan.
Three pin fans do not have a Pwm chip on the fans circuit board.

How a fan controller works is by reducing the voltage to a three pin fan.
By means of a variable resistor.

As three pin fans do not incorporate a Pwm chip.
You cannot modulate the amount of power to control the voltage to allow for reduced power so the fan spins slower.

They will just run at full belt even if you bought the deep cool thingy.

If you intend to use three pin fans in the setup then buy a fan controller.

lukecool · Jul 16, 2014

Speed Controls:
PWM control-
(Pulse-width modulation). This method requires a 4 pin PWM fan. The way PWM works is; the fan control modulates the width of the trigger pulse’s duty cycle that is sent to the fan plug’s pin 4. A duty cycle is the percentage of one pulse in which this square wave trigger is at an active (5 volt) level. The fan’s applied power (12 volts) mimics this (5 volt, 25 kHz) trigger. This means that If the square wave trigger’s 5 volt duty cycle is 40% of the pulse, 12 volts powers the motor for the duration of this duty cycle, then turns the motor off for 60% of this time because the trigger is at 0 volts. This causes the motor to run at 40% of its maximum speed. Simply put: pin 4’s trigger turns the fan’s motor on and off 25000 times per second (25 kHz); The longer the switch is on compared to the off time, the faster the fan goes. Because the full voltage, current, and torque is always available to the motor at any speed, the motor runs better, cooler, and quieter. If the power connections come directly from the power supply; one PWM control signal can simultaneously control several PWM fans, and there is no limit to the current it can control. PWM control is, by far, my preferred choice.

Voltage control-
The best feature of this control is, it works on any fan (2 , 3, and 4 pin fans). This system absorbs (with a variable load) part of the energy that is going to the motor in pins 1 and 2 by turning it into heat; the slower the motor, the more heat. It accomplishes this one of two ways, it uses a rheostat as a variable resistor OR a rectifier (with a heat sink) to short the unwanted part of the voltage to ground. This limits the voltage, current, and torque that is available to the motor. This control's current rating (amperage, wattage) is determined by the amount of heat that the system can safely dissipate with-out overheating. This type of control waste energy, limits current, and adds more heat inside your case.

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Can a PWM signal be sent to 3 pin fans? HELP

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