How to read PC fan speed using Arduino

Arduino tutorial on reading the speed of a 3 pin PC Fan, we're reading the PWM value. I also have a LCD display showing the fan RPM.

0:00 Intro
0:10 Required Materials
1:16 Assembly
3:48 Coding
5:23 Outro

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[DD-jknf]

Just an FYI. That's not a PWM signal, 3 pin PC fans are DC controlled. On a 4 pin PC fan the blue wire is the PWM signal (to control the speed). The yellow is common to both types and carries the tach signal from the hall sensor (for reading the speed). This is more for anyone watching this, who is wanting to try this out. 👍

[aleksandrbmelnikov]

How does resistor affect RPM signal when tapping CPU, GPU, or case fan(s) already connected to headers on motherboard? If these wires are removed from fan headers, motherboard will report that fans have failed. I don't want to feed power into sensor pins.

[MrCIA]

I want to turn an old PC fan into a wind speed measuring device. This means that I only want to read the Yellow wire, without RED and BLACK from the fan connected to a power source. Practically the wind will turn the fan, it will have an RPM which I will translate to m/s wind speed. Would only having yellow wire connected work or you also need ground? If anyone has done this, could you try disconnecting the fan from the positive and turn it by hand, see if you get a reading?

[fyras]

great video, thank you .btw will it be drisky if I don't use the resistor?

[merus]

Hello. Does it work with multiple fans?