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Four pin fan simulator for a water-cooled server


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I only have some working knowledge of electronics. 

I took a project to turn an HP DL585 G5 server into a water-cooled system for myself and remove all the Nidec VA450DC fans. I was greeted with a fan missing bios shutdown. I then followed some solutions posted in other forums for different hp servers by making a fan tach simulator using the 555 timer. I set it to 5300rpm, the fans high rated rpm. It didn't work. I also noted the fan is reported failed if the blue PWM line is disconnected (though the fan still spins) but it it is reported ok even if the tach yellow line is disconnected. This fan has a LED indicator attached to the connector. Whenever the PWM line is interrupted the LED turns orange (failed) otherwise, it is green. 


So, I thought if the fan simulator, which I made now is only 3 pin, can be made to also take the PWM blue line as a fourth pin, there is a good chance that it will work. I did check the blue and yellow lines with oscilloscope. Pictures below. 


I used ArduinoScope (https://github.com/iroth/simplearduinoscope) and I have some pictures. 
First, when the pc is turned on, the fan goes at full rpm and the yellow and blue lines show these images:




Preview by Yaho







Preview by Yahoo


When rmp is reduced by the bios after startup:

yellow pin (some wave I don't understand):

Yellow_reduced_rpm.jpgPreview by Yahoo



Blue pin: (almost 1/2 slower)


Preview by Yahooblue_reduced_rpm.jpg




Would there be a circuit that will make a four pin fan simulator with a 555 or 556 timer? My search so far is not successful. 



Here is the three pin circuit I am made (curtesy of ACalcutt http://www.techidiots.net/notes/fake-fan-sensor ):


Preview by Yahoo


And here is the 8 pin fan connector (removed from one of the fans and I placed a standard three pin connector)







And here is the water-cooled server AT A POINT OF NO RETURN:




Does anyone know a working circuit for a four pin fan simulator?


Thank you!

Edited by andrewk
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You might want to look here for a related post applied to a Gen8 Microserver: http://homeservershow.com/forums/index.php?/topic/7294-faking-the-fan-signal/

Thank you! 

I actually saw that and tried the solution, the G5 connector is different and has 7 wires in it. The solution of shorting the tach with the ground didn't work. I need a fan simulator that takes four pins (+, GND, PWM, and Tach). 


Thanks again.

Edited by andrewk
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Ok. It happens the yellow and blue lines are reversed. The blue is actually the tachometer - speed sensor line and the yellow is a PWM line. Unfortunate perfect reversing of a standard feature made me hunt a non existing error. 

After reconnecting the blue line to the fake fan, the server now recognizes it as a functioning fan and all is working well.


Thank you all that helped!!


Problem solved. I can happily move to the next step!

Edited by andrewk
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