Why does my kit provide extruder fan wiring extension as a 2 pin, if the fan has 3 pins

So the Geeetech kit came with an extension for the extruder fan on an MK8, but its only two pins and the fan is 3 pins....


prob a noobie question. What does the third wire control?

In the case of a computer fan, I believe the third pin is for PWM control of the fan, so you can send a signal to only operate at 80% power or something similar. Otherwise I believe in a two wire setup the power is controlled by manipulating the power sent to the fan.

EDIT: I would assume just using the red and black wires would control the fan just fine. The absence of a signal on the white (?) wire would keep the fan fully on. But I am guessing.

Edited 1 time(s). Last edit at 05/07/2015 04:03PM by Kurzaa.

Awesome thanks. That is prob what it does.

The third wire is a tachometer signal coming back from the fan, used by motherboards to sense speed, so they can hit a given airflow. Motor is only on red/black, and all speed control is done on those same leads.

- Tim

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Kurzaa
In the case of a computer fan, I believe the third pin is for PWM control of the fan, so you can send a signal to only operate at 80% power or something similar. Otherwise I believe in a two wire setup the power is controlled by manipulating the power sent to the fan.

EDIT: I would assume just using the red and black wires would control the fan just fine. The absence of a signal on the white (?) wire would keep the fan fully on. But I am guessing.

As tadawson said, the 3rd wire is for a tach to monitor the fan's speed. It's only feedback so a computer for instance can monitor the fan speed and take appropriate action should a fan stop working or to provide some basic speed control feedback. 4-wire fans are available that have an additional wire that is a PWM signal for controlling fan speed when more control is desired than just varying the supply voltage. It also allows the fans to run at full voltage which can be damaging to some fans.

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tadawson
The third wire is a tachometer signal coming back from the fan, used by motherboards to sense speed, so they can hit a given airflow. Motor is only on red/black, and all speed control is done on those same leads.

- Tim

+1 on this. The pulse signal on the third wire is to make sure that the fan is turning on a computer motherboard. Not needed here so can be ignored.