Synchronous Motor Help Needed!

Discussion in 'General Electronics Chat' started by sjgallagher2, Dec 30, 2013.

  1. sjgallagher2

    Thread Starter Member

    Feb 6, 2013
    111
    7
    I just stripped my broken microwave and got this handy dandy SM16F BY36P1A3 synchronous motor out of it. Now that I have the motor, I would very much like to use it to control a door lock. The issue is, while I can get the motor to move in either direction, the way it switches is seemingly random. Just whenever I flip my on/off switch it could either go CW or CCW. My theory here is that the phase of the signal determines which way it'll go. But it could also be where the rotor stops and has to start from right? So my issue becomes A) determine, somehow, which of my theories may be correct, and B) find a way to time when the AC signal starts, or when the rotor stops.

    The input is from the outlet, stepped down to around 21VAC, so it's not like I can control when the incoming signal starts and stops too easily :p
    Does anyone have any prior experience with these motors? Can someone help me control this motor in either direction I want?
     
  2. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    How many leads?

    Was there a cap in the circuit?
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,009
    3,233
    sjgallagher2 likes this.
  4. sjgallagher2

    Thread Starter Member

    Feb 6, 2013
    111
    7
    There are two leads on the motor, which, in initial experiments, was connected directly to the transformer, which was connected directly to the outlet.
     
  5. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    They start in random directions.

    I have one on a piece of workshop equipment that I prefer to rotate clockwise. I just put a bit of torque on it in the clockwise direction with my fingers when switching it on, then it starts up and runs clockwise.
     
  6. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    For the turntable that wants random maybe?
    Built in alternate start?

    New one for me.

    A motor that does not have a bias for starting should not start at all.:confused: imo
     
  7. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,302
    1,988
    Observe your microwave closely...
     
  8. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    That's why I suggested the turn table.
    Is that how they work? Random? Alternate?
     
  9. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    How about a strategically placed PM to get it under control?
     
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,544
    2,369
    The same principle used in the older wall clock synchronous motors, they had a spring/kick start to make sure it started in the right direction, often the start mechanism would wear and the clock would run backwards.:(
    As RB says, you have to tension bias it at start up.
    Max.
     
    Last edited: Dec 30, 2013
    Metalmann likes this.
  11. inwo

    Well-Known Member

    Nov 7, 2013
    2,433
    315
    How does the MW motor start?
    Random or alternate?

    No I never looked!
     
  12. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    Then go and look. :)
     
  13. Metalmann

    Active Member

    Dec 8, 2012
    700
    223

    Yeah, every microwave I've ever had, started randomly like that.
     
Loading...