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Faking the fan signal


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I bought a CORSAIR SP120 as it was going cheap, ended up removing the cable from the HP fan and soldering it direct to the corsair but it doesn't work. It spins up but surges and reports constant fan fails.

This can be added to the does not work list!

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Let me first of all say "hi" to everyone, since I've been following this forum for quite a while now but haven't found the time to actively contribute.. yet :). So here is my first contribution:



In my realisation, a custom Arduino board, the teensy++ 2.0 (https://www.pjrc.com/teensy/), is used. Works well, I am quite happy with it. The PWM decoding is fluctuating a bit though, but post-processing in form of averaging does a good job there. Besides the connection to the motherboard pin header, to the fan and power supply connection for the Arduino, external components in addition to the Arduino board are not needed. The teensy also has a USB connector (like almost any Arduino, I guess), so you could connect it to the Microserver's internal USB port to supply power to the Arduino and for serial communication.


Hope you find the approach interesting and useful. If you are interested in more details just let me know.





Hi Tom,


I am too trying something with the Arduino board for fan control, with a dedicated thermal sensor, movement detector, buzzer  and  even an override from external LCD with buttons for the fan speed.. work in progress..

ThPWM  control of the main fan would be a good addition !  did you get it working ? do you have some code/schema to share ?

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  • 1 month later...

I did the bridge 4-5-6 method with just some bare pins wired together, is there a better / more secure way to terminate those pins?


This fan is keeping my system cool and is pretty much dead silent, the PSU fan is much louder.




which are the right cable colors for this fan to connect to the HP G8 G1610T??


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  • 5 months later...

I also considered higher TDP chips but this would require modding / making some sort of fan set up which I've not done before. I think that it would be pointless too as the 16gb ram would then be the bottleneck, hence why I wonder if a different platform all together might be the best bet.


Sent from my Nexus 6 using Tapatalk

Please ignore/delete my post here as it was in error!


Sent from my Nexus 6 using Tapatalk

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  • 5 months later...

Hi, sorry but I am still not entirely sure what to do to reduce the noise of my microserver which constantly spins at 50% due to a pci raidcard.

I understood that if I connect pins 4 5 6 together, this will fake the rotation signal and the microserver believe a fan is running.
I then take a new fan and connect 12v to pin 1. Ground of the fan to ground of microserver (so the tied together pins 4 5 6) and pwm to pin 3.
I understood that then the fan will constantly run at 100%. But why do I need to connect pwm to pin 3 even tough the microserver doesn't control the speed.
Furthermore. Isn't it possible to not connect pin 3 and only use pin 1 (12v) and ground, so that I can use a fan without pwm? In that case, one could easily put a potentiometer in between to control the fan manually between 0v and 12v.
Could somebody please enlighten me. :-)

Gesendet von meinem E6653 mit Tapatalk

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  • 7 months later...


On 12.03.2014 at 10:46 AM, MihaiT said:

Attach a more silent FAN with rotation detect/ locked rotor signal :



(right click, open in new tab)


Personally I'd go replacing the FAN with a silent one which has ~ 75% of the original fan's airflow. I don't use the server for heavy tasks and I think it will be enough. 


Whatever you do, pay attention and leave the thermal protection enabled in the BIOS. If you have add-on cards or high env. temp., try to install some smaller fans inside.


The original disclaimer still applies.


I am sorry to bother you with so stupid question, but with all respect to your research I couldn't get what you have written. Can you help me with getting the point?


You state there are 5 pins used - VCC (1), GND (6), PWM control (3), GND loop (5), RD (4). As far as I  know pin 4 uses trip-point rotation detection. How can you place pulse output there and get a some sort of result? As far as I know pulse detection should be on pin 2, but Microserver doesn't utilise this pin...


What does exactly ground loop pin do? Is it just used to equate the potentials of the fan circuit or this pin plays another role here?


How does MS act when 4-5-6 pins are short-circuited? Does it see the fan anyway? Or it just rotates at 100% speed?


How does it act with the connector I left in quote above? Does it see the rotation %? Or system does only show it's ouput PWM value?

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On 21.07.2014 at 5:16 PM, MihaiT said:


I was referring to the PWM signal level which can be 5 or 3.3 volts. The motherboard didn't supplied more than 3.3V during my tests. 



Motherboard produces 3.3v of 5.25v due to new specs requrements. Low-level should not exceed 0.8V.

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