Simple SATA/PWM question - everybody is telling me something different, what is correct?!

[JackCarver]

If you connect your fans to a 12V Molex connection then they run at full speed. Where is the circuit which controls the power on/off in that case? That‘s in the mainboards PWM Controller, but it‘s connected to a constant 12V source of the PSU, so I say it‘s either or...

 

[newtekie1]

It‘s an either or....either you use the SATA plug or the pwm. For example if you have no free pwm at the MB then use SATA

But not together

Yeah, that isn't how it works at all.

PWM still works if you plug in the SATA/Molex connector on the good splitters.

It's real simple. Not sure why everyone is complicating this so much!

SATA, or Molex, is there to provide the power only. Nothing more, nothing less. The 4th pin, for PWM, will still allow the fan to operate under normal PWM circumstances. You just need to make sure that you get one with PWM capability, most of which will say very clearly in the description of the item.

Jeez, oh man...

Yes, exactly! The SATA/Molex connector provides power to the fans. PWM works independently of power going to the fans, in fact PWM fans always receive 12v(if it is a 12v fan).

You have to understand how PWM works. A PWM fan is always receiving 12v. It doesn't matter if it is coming from a SATA connector or from the motherboard, the fan is always getting 12v. The way PWM controls the fan speed is it pulses the ground. Without a ground, no current will flow and the fan won't spin. So how long the ground is pulsed controls how fast the fan spins. The 12v source to the fan doesn't matter with PWM.

This is how PWM works:

If you set the PWM duty cycle for a 12v to 25%, like the last line in that picture. Then the fan will receive a constant 12v from it's power source, but the PWM signal will only connect the ground 25% of the time, so current will only flow 25% of the time, and the fan will run at ~25% speed. But when the ground is connected by the PWM controller, 12v is always flowing through the fan.

 

[JackCarver]

PWM fans receive 12V with pulse width modulation, means 12V on/off all the time. That‘s the circuit which controls their speed. If you connect it to molex you have constant 12V means full speed the whole time and NO speed regulation. So keep that molex away if you want speed regulation.

Edit:
Fan controllers have also a molex connection to the PSU, but they have their own pwm Controller independent of the Mainboard. To connect the fans to a molex and to the pwm Connection of the mainboard makes so zero sense...

 

[newtekie1]

PWM fans receive 12V with pulse width modulation, means 12V on/off all the time. That‘s the circuit which controls their speed. If you connect it to molex you have constant 12V means full speed the whole time and NO speed regulation. So keep that molex away if you want speed regulation.

Nope, PWM pulses the ground. The fan motors are always connected to 12v, it's the ground that changes to adjust speed. You can plug in the SATA/Molex and still have PWM control. I know, I've got it connected that way right now.

 

[JackCarver]

Ok you’re right. My pump has the same connections I remember. One molex and one pwm for Tacho and Speed. Didn‘t see it on fans till now

 

[thesmokingman]

PWM fans receive 12V with pulse width modulation, means 12V on/off all the time. That‘s the circuit which controls their speed. If you connect it to molex you have constant 12V means full speed the whole time and NO speed regulation. So keep that molex away if you want speed regulation.

Edit:
Fan controllers have also a molex connection to the PSU, but they have their own pwm Controller independent of the Mainboard. To connect the fans to a molex and to the pwm Connection of the mainboard makes so zero sense...

You are wrong on all accounts.

 

[JackCarver]

You are wrong on all accounts.

Yes that's true, really thought it switches between 12/0V which controls the speed.

 

[TheMadDutchDude]

Are we SERIOUSLY still doing this? Bloody hell... honestly, you're just confusing the OP.

Yes, the fan will get the 12v constantly. However, the PWM controller resides within the fan to control this and will switch it on or off depending on the percentage requested.

It makes ABSOLUTELY NO DIFFERENCE if you get 12v from your motherboard, or 12v from your PSU. The PWM controller is on the fan itself and couldn't give two flying monkeys if it comes from your motherboard, your PSU, or your UFO in outer space.

I wonder why I bother sometimes...

 

[JackCarver]

Are we SERIOUSLY still doing this? Bloody hell... honestly, you're just confusing the OP.

Yes, the fan will get the 12v constantly. However, the PWM controller resides within the fan to control this and will switch it on or off depending on the percentage requested.

It makes ABSOLUTELY NO DIFFERENCE if you get 12v from your motherboard, or 12v from your PSU. The PWM controller is on the fan itself and couldn't give two flying monkeys if it comes from your motherboard, your PSU, or your UFO in outer space.

I wonder why I bother sometimes...

Yes as some explanations out there in space are a bit misleading. And if you don't dive a little deeper, then you get it wrong:

In short, PWM operates like a switch which constantly cycles on and off, thereby regulating the amount of power the fan or pump motor gains. The PWM system that is used for controlling fans and pumps works with the motor, either getting +12V (full power) or 0V (no power).

The fact, that there is a constant 12V but pulses the ground is not so clear in some explanations. So sorry for confusing the OP but I think if he reads his Thread then he get's it, as I too...

With the explanation above, you could mean there is a sort of voltage regulation within.

 

[Emiliano85]

Haha it almost ended up in another "this is correct, no this is correct, no 100% THIS is correct" discussion as always - luckily we got an answer.

Thanks @londiste, @TheMadDutchDude & @newtekie1 for finely solving this enigma.

 

[TheMadDutchDude]

Honestly, you'd be fine connecting three Noctua fans to your one motherboard header without the need for the additional SATA power. They draw 0.15A each, bringing you to 0.45A under full load. Most motherboards in recent years can distribute 1A per header, which you're just under half of with that load.

I'm glad to have been able to give you an answer. I'm sorry for all the confusion caused by people not understanding how PWM splitters such as the one you showed actually work.

 

[Emiliano85]

Honestly, you'd be fine connecting three Noctua fans to your one motherboard header without the need for the additional SATA power. They draw 0.15A each, bringing you to 0.45A under full load. Most motherboards in recent years can distribute 1A per header, which you're just under half of with that load.

I'm glad to have been able to give you an answer. I'm sorry for all the confusion caused by people not understanding how PWM splitters such as the one you showed actually work.

You’re a star! Really, i appreciate it - been looking for an answer for days. Unbelievable it had to be so hard.

I will go without plugin in the Molex, unless I manage to find a splitter without the power cable all together. Anyway nice to know how these things work regardless, might be I will not have the liberty to choose plan b in the future, which I am able to here by just utilizing the 4-pin parts of the cable as amps are lower than what header can provide.

Thanks again!

 

[JackCarver]

Your plugs only have two connectors and I assume these are Tach and PWM, so sorry but you have to use the Molex then.
Otherwise they should have 4 connectors.

 

[Emiliano85]

Your plugs only have two connectors and I assume these are Tach and Ground, so sorry but you have to use the Molex then.
Otherwise they should have 4 connectors.

Yes, but really what I just wanted to know was quite simple and more of a general information:

Will SATA always overrule PWM - deactivating the possibility to control fanspeed (when working with splitters - in general, not only this one).

Answer is no.

 

[JackCarver]

Tach and PWM, sorry for that, I corrected it above. You said you will go without the molex but that's not possible, then buy a 4 pin PWM splitter.
The splitter I posted with picture will be the one without molex ;-)

Edit:
It's the same arrangement as with my pump. The pwm plug only has Tach and PWM signal, to get power I had to plug it with molex.