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Best way to connect 3 x 120mm fans? MOBO or PSU?

So, I bought 3 new 120mm fans. They have each a 3-pin connector and a molex.

I have one pwm slot available on my mobo, and I don't know how many molex are available.

 

I also bought a 3 way splitter.


What I was planning to do is to ignore the molex and PSU connection, and simply connect all of them to the splitter into the mobo. Will that work? Can it draw power directly and solely from the mobo?

 

In case I need to connect them to the PSU, can I interconnect the 3 fans by their molexes, and only one going into the PSU?

 

 

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yes connect them to mobo should be fine, mobo can handle 1A output, most fans are 0.1-0.2A. If you connect to PSU fans will run full speed all the time
E: Also yes you could connect the 3 fans molex and plug them all in on 1 plug

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You could also buy a fan controller, if you ever want to add more fans. The Y cable should be fine, though.

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4 minutes ago, Cyracus said:

yes connect them to mobo should be fine, mobo can handle 1A output, most fans are 0.1-0.2A. If you connect to PSU fans will run full speed all the time
E: Also yes you could connect the 3 fans molex and plug them all in on 1 plug

Thanks! Like this, you mean?

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3 minutes ago, startrek03 said:

You could also buy a fan controller, if you ever want to add more fans. The Y cable should be fine, though.

Thanks! Will do in the future, for sure.

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2 minutes ago, takk said:

Thanks! Like this, you mean?

Untitled.png

If you just want to run them max speed anytime your computer is on.

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2 minutes ago, startrek03 said:

This would also work according to @Cyracus

image.png.8e7d31a75350597c28775f675f860e54.png

Ohhh, using the molex and then the pwm on the mobo?
 

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2 minutes ago, takk said:

Ohhh, using the molex and then the pwm on the mobo?
 

No, just plugging the splitter cable into the motherboard fan header and the fans into the splitter cable.

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One more question, btw thanks a lot for the help from you both! :)

Would this work, to draw power from the PSU and be able to control it?

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No, that won't work

 

The PWM wires from all fans would have to be joined together and go to motherboard header. This way the pwm signal from the motherboard can go to all fans and the fans will adjust speed according to pwm signal.

 

In your last picture, only one fan gets the signal from the motherboard, the other two would continue to run at 100%

 

A motherboard header should be powerful enough to power 3 fans at the same time, if they're regular computer fans, not those monster 4000+ rpm 20-50w fans.

A header is good for at least 1A of current and most fans are 0.1..0.25A , so 3 fans won't be a problem.

 

In order for fans to be controlled through PWM, they need to have a 4 pin connector, and you say your fans have only 3 pin connector. First two pins are voltage and ground, third pin is rpm sensor, 4th pin is pwm signal

So your fans can't be controlled through pwm, but may still be controllable by adjusting the voltage.

 

Some motherboards are smart enough to determine that the fan in a header doesn't change its rpm speed when a pwm signal is sent (therefore the fan probably has only a 3pin connector) and the the motherboard switches to adjusting voltage to control speed.

 

So if you're lucky and your motherboard does this, then you could simply use that 4pin pwm cable in your first post to connect your fans to a single header on the motherboard.

If you're not lucky, the fans will simply run at 100% and your best option would be to get a fan controller that can adjust speed on 3pin fans.

 

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31 minutes ago, mariushm said:

No, that won't work

 

The PWM wires from all fans would have to be joined together and go to motherboard header. This way the pwm signal from the motherboard can go to all fans and the fans will adjust speed according to pwm signal.

 

In your last picture, only one fan gets the signal from the motherboard, the other two would continue to run at 100%

 

A motherboard header should be powerful enough to power 3 fans at the same time, if they're regular computer fans, not those monster 4000+ rpm 20-50w fans.

A header is good for at least 1A of current and most fans are 0.1..0.25A , so 3 fans won't be a problem.

 

In order for fans to be controlled through PWM, they need to have a 4 pin connector, and you say your fans have only 3 pin connector. First two pins are voltage and ground, third pin is rpm sensor, 4th pin is pwm signal

So your fans can't be controlled through pwm, but may still be controllable by adjusting the voltage.

 

Some motherboards are smart enough to determine that the fan in a header doesn't change its rpm speed when a pwm signal is sent (therefore the fan probably has only a 3pin connector) and the the motherboard switches to adjusting voltage to control speed.

 

So if you're lucky and your motherboard does this, then you could simply use that 4pin pwm cable in your first post to connect your fans to a single header on the motherboard.

If you're not lucky, the fans will simply run at 100% and your best option would be to get a fan controller that can adjust speed on 3pin fans.

 

 

Thank you! Apparently, my mobo (A320M-K) has an option for DC control, so I hope that helps!

 

I don't think I'll mind them at full speed, tho. When they arrive I'll see if they're too noisy and decide what to do.

 

For now I think I'll just try to use the splitter cable and connect all of them into the mobo, with no molex/PSU connection.

 

I can still connect all 3 3-pin connectors into the splitter into the pwm, and then the molex interconnected to the PSU, right? Just in case I want to do DC control but take power from the PSU instead. (sorry if it looks confusing)

 

 

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4 minutes ago, narrdarr said:

i like the pictures. thumbs up

Haha thanks!

 

Anyway, I think I figured out. I was worried if my mobo would handle 3 fans. The new ones I bought are a bit heavy on load, they use 0.28a, but as there is 1a free it should be fine.

 

I just checked and the current 3 fans I have on my case are directly connected to the PSU, that is why I have a "free" pwm slot. As I don't mind the noise from the 3 front fans at full speed, I won't change anything for now.

 

But if I decide to change case/get better fans I'll get a fan controller/hub!


Thanks a lot guys.

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I use a powered splitter just like that. But got pwm fans. The dc fans I just use a regular splitter. But I have a large selection of fan headers so I don’t do more than 2 per. 

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