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PWM and Actual current

  1. Apr 6, 2012 #1
    I am debugging a C code of a heating machine. I am so confused about real time current and programming control over all the parameters of the machine. The code was written by some one though, i understand it well until now.
    Problem is that the previous code works according to the actual current and the PWM cycles are purely depending on the actual current. I want to change this varying PWM cycles to constant PWM cycles even though the current changes. I noticed that the PWM cycle generation was depend on the actual current that generated from the transformer and because of that reason these cycles are always changing their period time.

    My doubt is that, if i make this to constant PWM cycles even though the actual current not same for all the working time. Is this to show only to customers or the current should also constant during this constant PWM cycles?
  2. jcsd
  3. Apr 6, 2012 #2


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    I guess I don't understand your post at all. The way I read it makes me believe that you have the cause and effect reversed. If the load doesn't change and the duty cycle of the PWM doesn't change, then how can the current change?
  4. Apr 7, 2012 #3


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    My take on this is that rama1001 is planning to change it from a variable period to a fixed period--and within that period vary the duty cycle. Such a major redesign falls outside my usual definition of "debugging".

    I suggest that rama1001 get his supervisor's approval to proceed on this course before investing time in it. Can we assume the program does not control the heating satisfactorily as it stands?
  5. Apr 7, 2012 #4
    mention of heaters and transformers suggests some form of AC power is being controlled.

    is it possible that the code senses the AC signal and implements phase angle modulation control? this may appear as variable period PWM to somebody who wasn't aware of this method.
  6. Apr 7, 2012 #5


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    My guess is that the OP understands less than we even think. Nowhere in the original post do I see the words "duty cycle". What exactly does this mean:
    I have never had a discussion of PWM without mentioning the words duty cycle.
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