I was expecting the fan to have 2 leads as opposed to 3. What is the function of the 3rd lead?

Question

I was expecting the fan to have 2 leads as opposed to 3.  What is the function of the 3rd lead?

Accepted Answer

The 3rd wire is digital pulse feedback to the board for measuring fan speed. The resulting output is a digital pulse train, of 5V peak, and 0V low. if you only need two wire application, simply don't use the third wire, black is usually in pin spot one, and is your ground, the next is V+ usually a nominal 5V to 24V input, it may be a 12V fan, but I have run these at 15V and 18V sustained for long durations. They may run on as low as 3.5V so long as the current is enough to get them started. the further wire from the black, pin 3, in this case, the yellow wire, is your feedback wire, unless you are using this in a computer, a programmable controller, you are replacing something that had 3 pins, or are very into electronics, most hobbyists will not use the feedback for their general purposes.

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