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PID using OPAMPS or transistors

Discussion in 'Electronic Basics' started by Vipin Nair, Mar 9, 2006.

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  1. Vipin Nair

    Vipin Nair Guest

    Hello,
    Does anyone has circuits of PID controller implementation with OP-Amps or
    Transistors.
    Any sample configuration is OK.

    Regards
    Vipin
     
  2. PI is very simple. you feed PV (process variable, or measured value)
    or SP (setpoint) into the - input through a resistor, and the SP or PV
    into the + input. The feedback from output to - input is a capacitor
    in series with a resistor. This configuration produces both integral
    and proportional effects on error (integral effect always takes place
    on error, since its job is to bring average error to zero,
    eventually). If you want to be able to move the setpoint, and have
    only integral response take you to the new setpoint, you can't put
    both effects in the same feedback path.

    Adding derivative also involves some choices. Do you want the
    derivative to act on error (setpoint and process changes) or just on
    process change?

    Then you start adding things like anti-windup prevention on the
    integral, etc.
     
  3. Ban

    Ban Guest


    1 opamp implementation:
    ||Cd ___ ||Ci
    .--------||-o--|___|--||-.
    | || | R2 || |
    in | ___ | |\ |
    o--o-|___|-----o--|-\ | out
    R1 | >------o--o
    .-|+/
    | |/
    ===
    GND
    (created by AACircuit v1.28 beta 10/06/04 www.tech-chat.de)

    If you know the corner frequencies fd and fi and the required gain Ap.
    Ap= - R2/R1

    fi= 1/(2pi*Ci*R2)

    fd=1/(2pi*Cd*R1)

    This is valid for Cd/Ci<<R2/R1. It is advisable to limit the max. diff. gain
    with a small resistor in series with Cd.
    I can also draw an independently adjustable circuit with 4opamps if needed.
     
  4. Yes. Typically equal to or greater than R1/10.
     
  5. Vipin Nair

    Vipin Nair Guest

    Hi,
    Thanx for the solutions
    Il build upon it.

    Rgds
    Vipin
     
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