PID controller using OP AMP: what components to use?

Discussion in 'The Projects Forum' started by Arnab Sarkar, Jul 24, 2016.

  1. Arnab Sarkar

    Thread Starter New Member

    Jul 24, 2016
    2
    0
    Hi all.

    I am trying to build a PID controller using Op Amps. A second order plant has been designed using OP amps. I have simulated the whole closed loop system in PSPICE and the step response is satisfactory. The schematic is attached below.

    Now my question is:
    1. What Op Amps I should use to implement this circuit? LM741 or TLO84 or LM324? For getting a step response the 'V5' in only 1V.
    2. What type of capacitors should I use? 1uF ceramic capacitors are not available, so should I use mylar or electrolytic ones? or should i use a 0.1 uF capacitor and change the variable resistances such that the gain remains constant?

    Any help would be appreciated.
     
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  2. DickCappels

    Moderator

    Aug 21, 2008
    2,654
    632
    What keeps U7 from saturating? Maybe a very large resistor actoss C2 would help.

    I would go with the TL084 over the
    741 and 324.

    You can use any unpolarized capacitor. X7R ceramic would be my first choice. Either that or scale up the impedances and resistances and use .01 uf NPO ceramics.
     
  3. Arnab Sarkar

    Thread Starter New Member

    Jul 24, 2016
    2
    0
    Thank you for your reply.

    If I use .01uf NPO ceramic capacitors and scale the resistances up, will there be any unwanted distortion in the output? What is the highest value of resistance you can use in the feedback path?
     
  4. #12

    Expert

    Nov 30, 2010
    16,298
    6,809
    I would keep it below 5 million ohms with a TL08x series chip.
     
  5. crutschow

    Expert

    Mar 14, 2008
    13,016
    3,235
    The closed loop DC feedback should do that, at least in steady-state.
     
  6. dannyf

    Well-Known Member

    Sep 13, 2015
    1,811
    362
    assuming dual-rail power supplies, and the component values specified, pretty much any of them will do.
     
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