12VDC Fan - 4 Pin

[Sadlercomfort]

Simple question.. Is it okay to assume I can connect the PWM pin of my fan directly to the 5V PWM output of my microcontroller? Maybe with a 100Ω resistor and a 5V Z diode?

https://www.arctic.ac/uk_en/downloads/dl/file/id/2233/f14_pwm_spec_sheet_english.pdf

 

[NMNeil]

The spec sheet you posted is a bit vague and doesn't mention 5 volts anywhere, but a 300mA 12 volt drive current would trash the uC. A 20 cent opto isolator may be the way to go to be 100% sure.
https://www.digikey.com/products/en...wproducts=0&quantity=&ptm=0&fid=0&pageSize=25

 

[Sadlercomfort]

The 300mA current will come directly from the +12V and Gnd pin right. I thought there might be an internal Mosfet inside the fan, switching the ground based on the PWM signal at the gate, which would be rated for 300mA.

 

[NMNeil]

Found this.
http://pcbheaven.com/wikipages/How_PC_Fans_Work/
But without knowing the gate threshold voltage, 5 or 12 volt it's impossible to tell which voltage would be correct. To be on the safe side contact the fan manufacturer.

 

[Sadlercomfort]

Right, after further investigation I believe its 5v. I'm currently using this module from ebay to control my fans:

https://www.ebay.co.uk/itm/12V-PWM-...782064&hash=item4671ad1164:g:ZN0AAOSwA4dWHvI4

But this uses a 8s003f3p6 STMicroelectronics 8-bit Microcontroller, which should have 5V pwm output. Also, I measured the PWM pin of the module while changing the speed of the fan and it never went above 5V.

 

[Sadlercomfort]

Just to update incase anyone else plans on doing something similar:

The 4-pin PWM 12VDC fan can be controlled using the PWM output of a microcontroller, which varies the PWM signal voltage from 0-5V by setting the duty cycle.

Here's the circuit I used:

However, the PWM frequency should be between 21-28kHz (Ideally 25kHz) and can be set in software using the uC registers.