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I have an Asus P8H77-V LE Z77 motherbaord, FAN HELP 3 PIN

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October 17, 2012 6:40:14 PM

Hello, i brought a Asus P8H77-V LE Z77 and have fitted it into my HAF 912 Plus case, the case comes with a megaflow 200mm red LED fan and a normal 120mm fan at the back, with an slow for another 200mm LED at the top and another 120/140mm fan on the side. Both fans that come with the case are 3 pin, and i have read online that when plugged into the motherboard a 3pin fan can be controlled by the motherboard depending on tempretures and load, which is exactly what i want, for it to speed up and down when it needs to :) . but how would i do this with 4 3pin fans?? i have seen some 3pin splitters, but the only ones i have seen are ones that come directly off a molex connector and offer full speed which is not what i want, or are advising to buy a fan controller, and i dont see a point of trying to play a game while having to turn the fans up every time, i want each 3pin fan to be powered by a moulex and to be controlled (speed wise by the motherboard) i have heard that the 3rd pin sends a signal from the fan to the mb to tell it what speed its at, but then surely it uses the first two + and - pins to control it, surely you cannot split this without reducing voltage, so really what to do. i want both to be powered at the speed the motherboard powers them, and be able to add 2 more fans without changing the set up, note im guessing that the other 2 i buy will be 3 pin.

i had found this, http://www.pcworld.co.uk/gbuk/dynamode-fan-power-splitt... but i want to connect it to 4 fans, and because its for 4pin only the 3rd and 4th pin are connected to the motherboard, and in my case because i have a 3pin header, only the sense pin will be connected, which means the motherboard will only recive signal and do nothing else, a bit pointless ?

overall i want all 4 fans to be auto controlled by the motherboard, via the 3pin header, note i have lots of molex connectors free but i dont want them at full speed as the PC is meant to be silent.
a b Ĉ ASUS
a b V Motherboard
October 17, 2012 7:48:31 PM

Three-pin cables use two pins for power and one pin is a signal for a tachometer. The motherboard controls the fan speeds by lowering the voltage to the fan. Splitting the connector and/or using more than one fan doesn't lower the voltage. But understand that fans have a minimum start-up voltage which is the minimum voltage the fan needs to start spinning. If you feed a fan less than the minimum start-up voltage it will not spin but its motor will continually 'twitch' while it slowly burns out trying to start.

Computer fans run nominally at 12v. 120mm fans typically have a minimum start-up voltage of 5v or 7v. 200mm fans may or may not have higher start-up voltages (I'm not sure what yours are, others I have seen are 5v). Just make sure that whatever fan profile you use for all 4 of your fans doesn't dip the voltage so low that any of the fans don't spin - that will burn them out.

Something like this will allow you to hook up all those fans to a single motherboard header: http://www.amazon.co.uk/InLine-Molex-Female-Adapter-Y-C...

There is another consideration too: I can't find info on how much power the chassis fan connector can provide, but according to your manual the CPU fan connector can provide 2 amps @12v (24 watts). You need to make sure that if you connect your 4 fans to the chassis fan connector that it won't overload the chassis fan power circuit. This means finding out how much current that chassis fan connector can provide and adding up each fan's peak power draw that you plan to connect to it. Assuming the chassis fan connector provides the same, then you are probably fine - your 200mm CM fan only pulls about 3.5 watts, but you should be aware of such things.
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a b Ĉ ASUS
a b V Motherboard
October 17, 2012 8:12:16 PM

Yeah, you're probably ok, but like I said, I didn't see the exact specs on your motherboard's chassis fan connector, I'd expect it to be capable though. You can look at your other CM 120mm fan, somewhere on it should be its power demands.
a b Ĉ ASUS
a c 156 V Motherboard
October 17, 2012 9:37:14 PM

the 3 pins fan wont be pwm by the motherboard you need 4 pins fan for that buy yourself a fan controller plug the fan it power the controller with a molex and put senson where you want them in the system
October 18, 2012 1:06:40 PM

larkspur said:
Three-pin cables use two pins for power and one pin is a signal for a tachometer. The motherboard controls the fan speeds by lowering the voltage to the fan. Splitting the connector and/or using more than one fan doesn't lower the voltage. But understand that fans have a minimum start-up voltage which is the minimum voltage the fan needs to start spinning. If you feed a fan less than the minimum start-up voltage it will not spin but its motor will continually 'twitch' while it slowly burns out trying to start.

Computer fans run nominally at 12v. 120mm fans typically have a minimum start-up voltage of 5v or 7v. 200mm fans may or may not have higher start-up voltages (I'm not sure what yours are, others I have seen are 5v). Just make sure that whatever fan profile you use for all 4 of your fans doesn't dip the voltage so low that any of the fans don't spin - that will burn them out.

Something like this will allow you to hook up all those fans to a single motherboard header: http://www.amazon.co.uk/InLine-Molex-Female-Adapter-Y-C...

There is another consideration too: I can't find info on how much power the chassis fan connector can provide, but according to your manual the CPU fan connector can provide 2 amps @12v (24 watts). You need to make sure that if you connect your 4 fans to the chassis fan connector that it won't overload the chassis fan power circuit. This means finding out how much current that chassis fan connector can provide and adding up each fan's peak power draw that you plan to connect to it. Assuming the chassis fan connector provides the same, then you are probably fine - your 200mm CM fan only pulls about 3.5 watts, but you should be aware of such things.



cheers looks like youve found exactly what i was looking for:)  turns out the fans are bearly hearable when running off a molex so i dont even mind if i take them all of it:)  thanks i will buy the adapter you suggested this week.
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