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CPU fan functioning principe

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tedson

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cpu fan hall sensor

Searching to increase the speed of an CPU cooler Fan, and don'n KNOW how it works.
It has 4 coils on stator and magnetical band on rotor.
The PCB has 2 transistors, 1 hall sensor and a diode.
It is impossible to see the circuits on the PCB without dammage.
At least if I know the principe, the order/connections of the coils and the succesion of pulses....
How to rebuild the PCB to have variable speed ?
 

cpu fan hall sensor

The speed is really controlled by the voltage the fan is given. The sensor switches on power to the coils at the appropriate moment based on the magnets position - it is a *very* simple brushless DC motor.

The voltage (really the current caused by the voltage) causes a certain strength of magnetic field in the coils. The stronger this is, the quicker the rotor is moved, and the quicker the next pulse is given to the coils. Lower the voltage and the weaker magnetic field causes slower running.

There is a minimum voltage required to start the fan - to overcome friction, inertia, whatever.

Hope this helps you,
FoxyRick.
 

cpu fan rebuild

To slow down, it works.
To speed up, the voltage can burn the components.
Or, I wish to increase the speed of the fan.
Please light me !
What are the sequence/sense of the current in the coils?
Are they rotated by one(1,2,3,4) or 1+3,2+4?
Can you draw a schematic ?
 

how cpu is functioning

CPU Fan normally is driven by a FAN motor driver..

Please check the datasheet of common Fan motor drivers made by ROHM.

Basically it is 2 Phase, seldom that they use 3 phase to control.

The speed control is made by PWM controller only. with input coming from thermistor, for temperature.. and it has a lock detect function... If you will try to lock the fan blade with your hand and stop it. after 5~6 sec. it will try to auto -
start again.

the auto-start is now implemented digitally, before it takes the delay from the charging and discharging of capacitors.
 

try this site:
**broken link removed**
 

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