Posts: 18
Joined: Sat Mar 07, 2015 12:58 pm

Re: Raspberry Pi fan speed

Sat Mar 14, 2015 9:57 pm

rurwin wrote:Did you measure it with an oscilloscope? because a meter will just tell you lies.

It's almost certainly a short pulse every revolution. A meter will just give you the average voltage, whereas what you need is the peak voltage.
I was hoping someone would mention that. It is indeed a pulse train, related to the rotation speed. Some fans seem to have a transistor pulling the line to ground, with a pull-up resistor to the 5V rail, so you will see an "average" voltage of between 0v and 5v if you are reading it with a Digital/Analog volt meter. It is most certainly NOT the voltage you are reading!

Posts: 1
Joined: Tue Jan 05, 2016 8:12 am

Re: Raspberry Pi fan speed

Sat Jan 16, 2016 6:15 am

Has anyone successfully used the code that kupus4000 posted?

Posts: 1
Joined: Wed Sep 13, 2017 10:36 pm

Re: Raspberry Pi fan speed

Wed Sep 13, 2017 10:39 pm

After much of the reading, I found what I am looking for. Sample code.
Thanks, I will give that a try soon. Please post more if anyone else tried.

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