Fan speed controlling

[Hayee]

Hi Everyone,
I am using FAN with microcontroller and it is working fine. microcontroller just Turn ON and OFF the FAN at particular conditions. Following is the FAN model and circuit diagram.

In the circuit there is a signal coming from FAN which will be go into the circuit and the output of it goes to microcontroller. This signal tell weather the FAN is ON or OFF. basically this signal is used to check if the FAN is in working condition or not.

I am just wondering can I give the PWM signal to the FAN to vary the speed of FAN. Uptill now FAN is running on its MAX speed. By giving the PWM I can change the speed of the FAN according to the certain conditions.

Thanks

 

[KlausST]

Hi,

I am just wondering can I give the PWM signal to the FAN to vary the speed of FAN.

I don´t know either. But if I wanted to know .. I´d read the datasheet. The most reliable source of such information.

***

To the circuit:
* some part values look odd. But in detail it depends on the operation conditions. (we don´t know)
* usually FAN_SIG gives a pulse signal, where the pulse frequency tells about the RPM. If you use the circuit above .. you lose the RPM information, you just get an ON/OFF information. I don´t see a benefit in using this additional circuit. Any microcontroller should be happy to get the raw signal. The circuit just increases effort, cost and limits the use of the signal.

Klaus

 

[D.A.(Tony)Stewart]

No you cannot use PWM on a FAN with internal BLDC with caps.

But you can find an analog solution I posted a while ago.

 

[Hayee]

@KlausST
No datasheet is available for this FAN. I tried to search the internet but I didn't found. Can you help me out to get the datasheet of it.
The reason for using this circuit is that I only need a logic level to check if FAN is running or not. I don't want to measure the RPM of the FAN.

@D.A.(Tony)Stewart can you share the link of that post?

 

[KlausST]

Hi,

If you did a search for the datasheet .. there is no need for me to do the same.

there are fans with internal speed control, using temperature sensor.
there are fans with PWM input for speed control
there are fans made for speed control by varying the input voltage

For sure you may use a fan with unknown function and no datasheet ... but then the result is unpredictable.

I´d use a suitable fan which comes with a datasheet.
This does not mean one needs to buy an expensive one ... look for a used one, maybe form a device you don´t need anymore.

Klaus

 

[FvM]

Yellow wire is typically used for pulse output at DC fans.