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  • #76
    Re: PID Silvia Sydney

    Hi there Mal,

    Thanks for the link, has proven very useful.

    I started again with the auto tune process, and this time its proven to be alot more stable. I think my problem before was starting the auto-tune feature before the temperature was reasonably stable, therefore skewing the settings.

    Parameters as follows:-

    p = 4.7
    i = 187
    d = 46
    tv = .40 ( target value, this is the default btw, auto tune doesnt appear to modify this parameter )

    With the new settings, while idle the setpoint is kept almost perfectly, every 30 seconds or so it might drop 0.1C but only for a brief moment. Recovery times after a shot will need a fair amount of tweeking though, as I observed the following (approximate times) :-

    * initial overshoot of +0.5C (1 minute)
    * slow decrease to +0.3C (1 minute)
    * slow increase to +2.3C (4 minutes)
    * this is where things leveled out (1 minute)
    * slow decrease to setpoint (5 minutes)


    Overall recovery of over 12 minutes. Which is actually fine for my usage, but Id like to rain that in to around 3 minutes if possible. Next step is to follow the guidelines in your link, onto round three


    christian

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    • #77
      Re: PID Silvia Sydney

      Good news Christian ,

      Those new parameters look a lot more healthy than before, so thats a good start. Yes, the AutoTune feature doesnt affect anything other than the PID parameters, all other functions have to be adjusted manually.

      The best way to approach tuning your current settings now, to achieve less overshoot, is use the guide from the link I provided earlier as you mention, and once you have it operating as tight as you can get it from this perspective, then you can start upping the Function at Line 1-7. The only detriment that increasing this Function causes, is to delay the arrival at Setpoint from cold by a small margin, the higher the value of this parameter. Its no big deal though, just a matter of tweaking it so that the all round performance of the controller is to your satisfaction.

      All the best,
      Mal.

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      • #78
        Re: PID Silvia Sydney

        Hi Christian,

        Good to hear you have the same setup with a Silvia. My experiences with the overshoot are exactly the same as yours.

        I havent had a play with it lately, its too frustrating for me!!!

        Autotune also came up with roughly the same figures.

        Ive tried altering 1-7 but its still quite random.

        I rarely pull consecutive shots unless theres guests over so it doesnt bother me so much, but still Id like to improve on it. Ill have a play tomorrow and let you know the outcome.

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        • #79
          Re: PID Silvia Sydney

          Originally posted by bloop link=1143536728/75#77 date=1145885925
          Ive tried altering 1-7 but its still quite random.
          Hi Bloop,

          Playing around with the Overshoot function is not very useful really, until youve managed to fine tune the PID settings to their optimum for your particular requirements. Once you have achieved that, the Overshoot function will prove to be more effective,

          Cheers,
          Mal.

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