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Solved PID Tuning Whoa!

Discussion in 'General Questions' started by joea, Apr 3, 2022.

  1. joea

    joea Active Member

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    I've never done PID tuning. One of the things I missed/forgot to do when changing the hot end.

    So, while doing that, saw that bed needed (?) PID values as well. Found the Ki value in configuration.h that is in effect to be WAY different that what was computed

    What was reported:

    <- Classic PID
    <- Kp: 117.34
    <- Ki: 22.96
    <- Kd: 149.95

    What is there:

    #ifdef PIDTEMPBED
    //120v 250W silicone heater into 4mm borosilicate (MendelMax 1.5+)
    //from FOPDT model - kp=.39 Tp=405 Tdead=66, Tc set to 79.2, aggressive factor of .15 (vs .1, 1, 10)
    #define DEFAULT_bedKp 10.00
    #define DEFAULT_bedKi .023
    #define DEFAULT_bedKd 305.4

    Am I in the wrong place?

    EDIT:

    More poking about found this, which suggests Bed PID is not in effect at all?

    // Bed Temperature Control
    // Select PID or bang-bang with PIDTEMPBED. If bang-bang, BED_LIMIT_SWITCHING will enable hysteresis
    //
    // Uncomment this to enable PID on the bed. It uses the same frequency PWM as the extruder.
    // If your PID_dT above is the default, and correct for your hardware/configuration, that means 7.689Hz,
    // which is fine for driving a square wave into a resistive load and does not significantly impact you FET heating.
    // This also works fine on a Fotek SSR-10DA Solid State Relay into a 250W heater.
    // If your configuration is significantly different than this and you don't understand the issues involved, you probably
    // shouldn't use bed PID until someone else verifies your hardware works.
    // If this is enabled, find your own PID constants below.
    //#define PIDTEMPBED
    //
    //#define BED_LIMIT_SWITCHING
     
    #1 joea, Apr 3, 2022
    Last edited: Apr 3, 2022
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
    Staff Member

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    I was unable on the older R1s to PID tune the bed because the heater for it is quite slow to stabilize.
    Not as critical for the bed sao that is fine.
     

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