Can Micro based Triac speed control damage Ceiling fan?

Discussion in 'General Electronics Chat' started by SHARANYADAS, Mar 27, 2018.

  1. SHARANYADAS

    Thread Starter Member

    Apr 13, 2017
    53
    2
    Hi experts,
    I have developed a Atmega328p based(IR+ Bluetooth controlled) home automation system.The circuit has 6 relays to turn on/off 6 no of loads.It also has a snubberless triac & a zero cross detector circuit for controlling the fan speed(From 0 to full in 5 steps).The ZCD circuit detects the zero cross and let the atmega328p knows (using external interrupt of the atmega) & the atmega delay some time(depending on the Fan speed chosen) & sends out a 100uS High to Low pulse to MOC3021.
    I previously built the same circuit(The zero cross detector circuit was a little bit different then & the Triac was BT136 with external snubber consists of 39R + .01uF) and attached to a fan.Now the fan got a permanent noise while it rotates(The previous circuit was disconnected later from the Fan but the sound is still present after moreover 1 year.It sounds like something Mechanical).
    Now my question is,did the Triac dimmer damage the fan permanently(Like I got a permanent "Grrrr" sound from the fan while it rotates)?Or the fan was already faulty(Although it didn't have any noise before I added the dimmer circuit)?

    Today I attached my 2nd circuit to another fan and it is working perfectly.
    Please tell me as I don't want to ruin my 2nd fan(Currently the circuit is attached to).The Triac dimmer part & the ZCD circuits are attached.I found the ZCD part in "all about circuits"!!The Microcontroller control & the relay driver circuit is not shown here.

    The parts value are as follows for the Triac dimmer part:
    Triac - BTB16-600BW.(snubberless triac from ST)
    R2 - 390R.
    R3 - 330R.
    R1 - 470R.
    C1 - .047uF.

    Triac_dimmer.png ZCD.jpg
     
    Last edited: Mar 27, 2018
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    17,911
    5,477
    The MOC3021 is a random phase opto, not zero crossing type.
    If operating random phase then the zero crossing has to be detected first for sync.
    See Fairchild AN-3006.
    Max..
     
  3. SHARANYADAS

    Thread Starter Member

    Apr 13, 2017
    53
    2
    Yes,as far as i am concerned,these circuits requires triac firing without the zero cross as the zero cross part is already taken care of by the ZCD circuit which lets the Microcontroller know when to fire.
     
  4. SHARANYADAS

    Thread Starter Member

    Apr 13, 2017
    53
    2
    The ZCD circuit is used for sync.
     
  5. MisterBill2

    Distinguished Member

    Jan 23, 2018
    3,205
    626
    A fan motor may develop some mechanical looseness as it ages and that will allow it to make some noise. That will happen with age and use. Using a solid state speed controller of any kind results in a non-sine-wave ac drive which will often produce noise since it has lots of harmonic energy. It is possible to reduce the vibration noise in most motors but it is seldom worth the effort.
     
    SHARANYADAS likes this.
  6. DickCappels

    Moderator

    Aug 21, 2008
    5,458
    1,698
    Yes. I have blown the thermal fuses on two floor fan motors. Check the true power going into the fan motor with and without the speed control. If the power with the speed control is higher than without it then there is a good chance you will have problems.
     
  7. SHARANYADAS

    Thread Starter Member

    Apr 13, 2017
    53
    2
    One thing i would like to know.The stepless Electronic regulators (image attached) available in the market also works on the same procedure(zero cross detection & triac firing.Delay is determined by the variable Resistor & fixed Capacitor ).That regulators should also damage the ceiling fans on the long run.Right?

    Dimmer.jpg
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
    17,911
    5,477
    I have been using this type in my present home for both ceiling fans and air exchanger for ~30yrs, still working.
    Max.
     
    SHARANYADAS likes this.
  9. MisterBill2

    Distinguished Member

    Jan 23, 2018
    3,205
    626

    I suspect that some of the poor quality products can be damaged simply by looking at them funny, as it were. Those fans with anything free to vibrate may start making noise when they are powered with a waveform having a lot of harmonics. Better quality fans will have no problems at all.
     
    SHARANYADAS likes this.
  10. MrAl

    AAC Fanatic!

    Jun 17, 2014
    5,935
    1,276
    Hi,

    True AC motors are supposed to be driven by variable frequency drives. That means the frequency has to be lowered as the voltage is lowered and that means you can cut back on the speed, which after all is what you do with a speed control because you dont want it to run at top speed. The reason for the frequency change is so that there is no slip, which occurs if the frequency is not right for the voltage it is getting. What this in turn means is that you will be applying voltage when the shaft is not in the right position for the right torque and possibly the right current if the frequency is too high. So it goes out of phase with the intended mechanical timing.

    Just what are the effects of a frequency that is too high then. Well one is a slower motor, we know that. Does any damage occur, that's the most important point.

    I have known success cases and failure cases, so i have to come to the conclusion that it does depend on quality of the motor. How you can tell in advance, before it fails, might not be possible unless you know of a case with a given product had failed.

    For the VFD there is a relationship for F and V for AC motors. I dont remember offhand what it was offhand. I dont think it was proportional but it was long ago when i had to do one of these VFD's at a place i worked.
    [LATER] I just looked it up on WiPe, and they are claiming a proportional relationship.
     
    Last edited: Mar 28, 2018
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