How does a single speed controller differ from an on-off and a proportional controller?

Discussion in 'General Electronics Chat' started by rudha13, Mar 29, 2016.

  1. rudha13

    Thread Starter New Member

    Sep 6, 2015
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    Hello everyone...
    In process control systems, I recently came across this topic and wasn't quite clear about the difference between a single speed controller and the two controllers mentioned above. How do they differ and what are the characteristics of an error encountered in such a system?
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    ON/OFF is exactly that, no in between.
    Proportional can take several forms, the common popular one is PWM, Pulse Width Modulated DC.
    Max.
     
  3. rudha13

    Thread Starter New Member

    Sep 6, 2015
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    oh, ok... thank you for your answer, but with all due respect, can you tell me a bit more regarding this topic. This has definitely got me piqued ... thank you..!
     
  4. mcasale

    Member

    Jul 18, 2011
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    12
    To clarify a bit - on/off control, or bang/bang, is when the plant (the thing you are controlling) is driven by a full-on or a full-off signal. For example, in an oven controller the heater would be full on or off, depending on the error signal. If the oven was too cold, the heater would turn full on. If the oven was too hot, the heater would turn off.

    A "proportional controller", or more accurately a PID (Proportional/Integral/Derivative) drives the plant with a signal that can be anywhere between full-on and full-off. Nowadays, the calculations are done with an MCU, which usually generates a PWM output signal.

    The toughest part about any controller is modeling the plant. You need to (at least) approximate the plant's poles and zeros to ensure it is stable under expected conditions. This is NOT trivial.
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
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    rudha13 likes this.
  6. rudha13

    Thread Starter New Member

    Sep 6, 2015
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