Electronic – What do the green and yellow wires in a BLDC fan do

brushless-dc-motorfanwiring

I rescued a box of brand new 'Nidec UltraFlo V60E12BS1A7-09A032 12VDC 2.45A' fans from being thrown away and of course I haven't got the datasheet for them. The closest matching datasheet is here: http://www.nidecamerica.com/fanpdfs/c2008_1314.pdf but I suspect mine are custom made for HP.

It has four wires:

  1. black => GND
  2. red => +12VDC
  3. yellow => I thought this is tacho open collector to GND, but I can't measure any frequency on it both with and without a 10k pull up to +12V, it is near 0V all the time. On top of that the wire is as thick as both black and red, whereas the green wire is clearly thinner.
  4. green => Seems enable (0V) / disable (12V or anywhere in between)

Does anyone know the proper specs for the yellow and green wires on these fans?

Best Answer

EDIT: Thanks to fuggetaboudit, I did some more research, and the pinout, I'd guess, is:

Black = GND

Red = +12V

Yellow = Trip-Point Alarm (see option -04 in the document)

Green = PWM (option -06 in the document)

The document I'm referring to is here. In it, it says a suffix of -09 means:

PWM speed control circuit (option -06 or -56) terminated in a third lead wire (standard = blue) and an open-collector, non-latching, low-pass/high-fail, trip-point alarm circuit (option -04 or -54) terminated in a fourth lead wire (standard = yellow).

Given that your yellow wire acts like an open-collector output and your green wire controls the fan speed depending on an applied voltage, I'd bet this is the correct pinout.

Somewhat relevant: http://www.nidecamerica.com/apps_pwm.htm

I would be very certain that Mark is correct:

Black = GND

Red = +12V

Yellow = Tach Trip-Point Alarm (After checking the Nidec Datasheet)

Green = PWM

Every Nidec fan I've encountered has followed this color scheme, and most common 4-wire PWM fans in desktop computers also use the same color scheme. Empirical evidence, but given your measurements, I'd be willing to bet they're correct.

If you have access to a signal generator, try generating a 25kHz, square-wave, 0-5V signal to the green wire, and seeing how the duty cycle of that signal affects the fan speed.

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