what is the PWM frequency FOR CONTROLLING THE CEILING FAN (230 VAC,50Hz)

Discussion in 'Embedded Systems and Microcontrollers' started by Nanda Kumar 1, Sep 7, 2016.

  1. Nanda Kumar 1

    Thread Starter Member

    Aug 25, 2016
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    I every one today iam planning to do simple project ,fan speed controlling with pwm. I am little bit confused when i am choosing the PWM frequency. how to choose the pwm frequency?
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Pick one.

    Preferably one that is high enough for the human ear to be deaf to, and one that is not interfering with any important radio freq.

    That would put it above 20 kHz and below 800 khz. Although some PWM freq. are in the megahertz region, beginners find it easier to build oscillators working at lower freqs. I suggest you start in the kilohertz range.
     
  3. hp1729

    Well-Known Member

    Nov 23, 2015
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    Just a fan? AC fan? Just runs on 50 Hz. Do you find electronics and PWM chip in it?

    https://www.barnesian.com/arduino-powered-smart-fan-controller/
    Does Proportional Integral Derivative count as PWM?

    https://e2e.ti.com/blogs_/b/motordr...an-energy-efficient-bldc-ceiling-fan-solution
    How about BLDC?


    https://www.maximintegrated.com/en/app-notes/index.mvp/id/1784 talks about fan control by PWM but doesn't specify ceiling fans. Suggests 20 Hz to 160 Hz.

    (begin quote)
    Direct PWM

    Pulse-width modulating (PWM) the fan directly involves turning the fan's power supply on and off at a fixed frequency. Duty-cycle adjustments are made to control the speed of the fan. The larger the duty cycle, the faster the fan spins. Choosing the appropriate frequency for this method can be somewhat tricky. If the frequency of the PWM signal is too slow, the fan's speed will noticeably oscillate within a PWM cycle. To illustrate this point, take the ridiculous extreme of a 50% duty-cycle, 0.01Hz drive signal. The fan will spin to full speed during the first 50 seconds and then stop within the next 50 seconds. The frequency can also be too high, as commutation is done electronically using circuits that are powered off the fan's plus and minus terminals. Using PWM with the fan and therefore the internal commutation electronics too quickly can cause the internal commutation electronics to cease functioning correctly. Remember that these electronics were not designed to run on anything but DC supplies. Thus, useful frequencies range from 20Hz to 160Hz. In addition, the PWM rise and fall times must be sufficiently slow to ensure long-term reliability of the fan.
    (end quote)

    Interesting subject. Good topic!!! Thanks for bringing this up.

    So start with 100 Hz and see if it makes too much noise. Kermit's suggestion makes some sense.

     
    Last edited: Sep 7, 2016
    Nanda Kumar 1 likes this.
  4. Nanda Kumar 1

    Thread Starter Member

    Aug 25, 2016
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    Thank you @hp1729 .I will check today
     
  5. Nanda Kumar 1

    Thread Starter Member

    Aug 25, 2016
    37
    0
    Thank you for u r replay @Kermit2 .Iam using crystal frequency of 24MHz.But just i want to know is what is the pwm frequency i want to set when i am controlling the ceiling fan.
     
  6. Sensacell

    Well-Known Member

    Jun 19, 2012
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    You need to understand the technology of the motor you intend to control.
    Depending on the type of motor, PWM may not work at all.
     
  7. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    AC induction motors do not like to be controlled. It is probably the most difficult type of motor to control by any method.

    DC motors respond very well to PWM control schemes.

    Triac control is the easiest and most common way to control AC induction motors. You would know them as a "dimmer" switch.
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Maybe qualify that by 1PHASE induction motors, ;).
    3ph motors have been controlled by VFD's for decades now even used on elevator control.
    Max.
     
  9. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Devil in the details...
     
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The only real way to use PWM to control a single phase motor is to use a Triac and detect the zero crossing point and then sync the PWM pulse/frequency to the incomming AC crossing point.
    Seems a rather obtuse way of doing it?
    Did you get any clues from the Fairchild AN-3006?
    See the wave forms in post#19
    http://forum.allaboutcircuits.com/threads/ac-cycles-for-clock.120596/
    Max.
     
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