How do I control the speed of this fan? Red Yellow Blue wires? (RC hobbiests may be interested!!)

Discussion in 'The Projects Forum' started by RogueRose, Jun 5, 2015.

  1. RogueRose

    Thread Starter Member

    Oct 10, 2014
    I am trying to get this fan working. It is attached to a pretty complex circuit board that has a 12v input. the fan is rated at 12v @ 16.5a and has a red yellow and blue wire. I have tried red as positive and blue and yellow as negative. I get the fan to make an initial jerk but after that it just stops. IDK if yellow goes opposite of blue (meaning direction) when I hook it up.

    I found a video of a guy with this working. Unfortunately it is in German but I see that he is running it from a 3 cell LiPo pack with a volt/am meter in-line and then some kind of speed controller (contacting him wasn't helpful..).

    Can anyone help me figure oue what I need to control this fan the way he does?
  2. MaxHeadRoom


    Jul 18, 2013
    That is a standard RC 3 phase BLDC prop motor.
    You can get them from and RC supplier, you need a PWM source to run it however.
  3. korchoi


    Jun 5, 2015
    MaxHead is right, this is a three-phase brushless motor.It is internally made out of three coils in series forming a closed triangle.
    Each of the 3 coil junctions(ends) is then soldered to its respective wire, which is exposed outside.
    The initial jerk you saw and felt was the initial alignment of the internal axis of the coils.
    The motor in a nutshell:
    This motor takes 3 Pulsed DC voltages, one 180º out of phase with the other.
    easy way out:
    Lucky you, there are ESC's(Electronic Speed Controllers) easily available that will control any brushless motor inside its driving limits.
    Electronic Speed controllers take a PWM input and drive a Brushless Motor according to the pulse width.
    The pulse width will determine the speed and direction of rotation.How exactly it translates will vary according to Motor and ESC models.
    You can buy ESC's from most RC hobbyist sellers. Just make sure it can handle 16.5A.
    hard mode:
    You can build yourself three High-current switches out of MOSFET's and assign each one to a coil junction.
    Then you make a driver circuit that enables one switch at a time, changing switches at a variable rate(n Hz)
    this rate multiplied by 3 will give you the rotation of the motor in Hz. Multiply it by 60 to get the RPM.

    will you go easy mode or hard mode?
  4. JWHassler


    Sep 25, 2013
    Not to detract from a very readable and (AFAIK) correct rundown, isn't that 120 degrees?
  5. korchoi


    Jun 5, 2015
    it's been a while, and i don't quite remember these things so well.
    Yes, it is 360/3 = 120º dephased between each junction.
    With so much automation these days, we end up making these silly mistakes...