case fan

[Cloudsy324r42344]

can i use a 3 pin case fan to a 4 pin motherboard header

 

[SpookyCitrus]

Yes, a 3 pin fan connector should still connect to a 4pin pwm fan header.

[Agall]

On 4/26/2023 at 2:38 PM, Cloudsy324r42344 said:

can i use a 3 pin case fan to a 4 pin motherboard header

 

3 pin fans are DC only fans, 4 pins are PWM capable fans. PWM gives proper speed control, otherwise you're using the DC voltage to control the fan. PWM fans generally use DC brushless motors which are overall better than DC motors since it doesn't require brushes to complete the circuit (which are a common wear point). PWM is pulse width modulation, which practically speaking converts DC to AC.

 

To answer your question, yes, a 3 pin fan in a 4 pin header just won't use the 4th pin, they're designed to be downwards compatible that way. So the blue connector in this case just isn't used to do PWM fan speed control.

 

 

 

Through filtering circuits, that step DC turns into a smooth AC wave.  

[ryd994]

On 4/26/2023 at 1:51 PM, Agall said:

Through filtering circuits, that step DC turns into a smooth AC wave.

Ugh, this is actually not how pwm fans work. The graph is how a inverter or a motor controller works. 

 

Case fans nowadays are mostly DC brushless motors. They have their own control board to connect the winding at the right timing. Timing is important because the magnetic field must be at the right place to pull the fan forward not backward. There are dedicated IC for that. Motherboard doesn't control the motor directly.

 

The pwm signal from MB to fan is a DC pwm signal. Aka, it doesn't change direction, and it takes more than a filtering circuit to drive the fan.

The duty cycle percentage is the percentage of max speed that the fan should run.

Then the fan control board will target that speed and control the motor accordingly. 

 

 

The advantage of pwm fan is two folds:

1. The speed control is linear. PWM cycle directly maps to a speed. For voltage control, the voltage doesn't map to the speep linearly. The control board may still keep the fan at rather high speed as the voltage lowers.

2. Wider range. PWM can go down to 30% or lower. Voltage control typically can't go that low or it might stop. Because the control board still need some decent voltage to work.

 

 

 

[filpo]

On 4/26/2023 at 9:38 PM, Cloudsy324r42344 said:

can i use a 3 pin case fan to a 4 pin motherboard header

 

yup but it won't be controllable

[NorKris]

8 minutes ago, filpo said:

yup but it won't be controllable

more wrong info,,, hmm 

[NorKris]

it wil be controllable 

[filpo]

4 minutes ago, NorKris said:

it wil be controllable 

well yes if you change the voltage but not in software (i.e. not pwm)

So TECHNICALLY yes

[NorKris]

2 minutes ago, filpo said:

well yes if you change the voltage but not in software (i.e. not pwm)

So TECHNICALLY yes

back in the day i used  Speedfan SOFTWARE   now i use armourycrap on one of my pcs to controll the speed of my 3pin's  and on the other pc i use icue

[filpo]

1 minute ago, NorKris said:

back in the day i used  Speedfan SOFTWARE   now i use armourycrap on one of my pcs to controll the speed of my 3pin's  and on the other pc i use icue

just cause I'm a teen doesn't mean to have to treat me like a baby. I didn't know about that 

[NorKris]

Just now, filpo said:

just cause I'm a teen doesn't mean to have to treat me like a baby. I didn't know about that 

i dont know ur age, i just know that giving adivce req that u have seen stuff, tested stuff and learned stuff 

Wait -> see -> learn -> then give   

 

keep in mind that stuff we share on the forums are googled just not tomorrow but in the feature, spreading wrong info makes ppl that googled somthing get that wrong info 

[Agall]

6 hours ago, ryd994 said:

Ugh, this is actually not how pwm fans work. The graph is how a inverter or a motor controller works. 

 

Case fans nowadays are mostly DC brushless motors. They have their own control board to connect the winding at the right timing. Timing is important because the magnetic field must be at the right place to pull the fan forward not backward. There are dedicated IC for that. Motherboard doesn't control the motor directly.

 

The pwm signal from MB to fan is a DC pwm signal. Aka, it doesn't change direction, and it takes more than a filtering circuit to drive the fan.

The duty cycle percentage is the percentage of max speed that the fan should run.

Then the fan control board will target that speed and control the motor accordingly. 

 

 

The advantage of pwm fan is two folds:

1. The speed control is linear. PWM cycle directly maps to a speed. For voltage control, the voltage doesn't map to the speep linearly. The control board may still keep the fan at rather high speed as the voltage lowers.

2. Wider range. PWM can go down to 30% or lower. Voltage control typically can't go that low or it might stop. Because the control board still need some decent voltage to work.

 

 

 

You're right, in context of the graph it was primarily to be a visualization of how PWM works as a concept. Historically this was something I'd have to teach to mechanics in the context of reactor control rod drive. Using AC circuitry was easier since they were already operating AC motor-generators and variable frequency generators, but I appreciate the correction.

 

I understand the difference, PWM in this scenario is independent of the motor's function unlike in an AC current, since otherwise a PWM fan (brushless DC motor) will just be unmodulated at maximum voltage.

 

PWM in this context is an inhibitor than a driver of the motor, which conceptually separates it from my previous scenarios where you're using PWM to modulate an AC signal's frequency sent to an AC motor. 

[thrasher_565]

theres also a pwm to dc convertor making 3pin fans pwm up to 1 amp.