PID temperature controller question..

Discussion in 'The Projects Forum' started by robindog, Feb 14, 2011.

  1. robindog

    Thread Starter New Member

    Feb 13, 2011
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    I installed a TCG-6131P controller to regulate temperature on silicone rubber heating strip installed on my solvent printer to provide heat to help the ink dry fester as I print on vinyl. My problem is the the controller is over and under shooting quite a bit. I noticed if I unhook the heating wire from the controller first then start up the unit its seems stable, however as soon as I put the heater wire back on the controller terminal it starts over and under shooting. I uploaded here the wiring diagram and the spec for the controller showing default settings and also my settings. I am trying to achieve a setting of 33°C setting. All help welcome!!!
     
  2. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    Sounds like you need to adjust the P/I/D settings. But first, turn on the Auto-tune function and see if that establishes good control operation.

    Ken
     
  3. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    Why would you have the target set at 60° if you want 33°? (I never saw one of these before, so there may be a logical reason.)

    ETA: I think I would try setting the target at 33° and the target limit at slightly above that. It seems logical that the target limit is simply a way to ensure that it's impossible to set a target above the limit (prevents user input error.) The one thing that's not logical about my suggestion is that the default parameters have the target at 150° and the upper limit at 20°.

    I would try it per the attached, but I'm just guessing.
     
    Last edited: Feb 14, 2011
  4. robindog

    Thread Starter New Member

    Feb 13, 2011
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    The documentation is very poor on this PID controller from lightobject.com all I know not much of it make much sense to me. Tried the auto tuning, nothing happened" Thought maybe something to do with the ambient which I have at 75°F....well I have lots of hair..maybe I'll start pulling them out one by one..."
     
  5. robindog

    Thread Starter New Member

    Feb 13, 2011
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  6. robindog

    Thread Starter New Member

    Feb 13, 2011
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    well... I got nothing...
     
  7. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    My next guess would be that the Integration Time has to be set to some value, say 20 seconds.

    When you say nothing, does that mean the heater doesn't come on at all?
    I think you installed a relay between the PID and the heater; does the relay operate?

    Where do you have the thermocouple mounted? Is it a type K thermocouple?
     
  8. hgmjr

    Moderator

    Jan 28, 2005
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    Robindog,

    It sounds like the thermal time constant of your wire heater is too responsive for the controller to accommodate within its control range.

    I wonder if it would be possible to attach the thermal wire to a thermal mass like a large piece of metal. This would slow down the time rate of change of the temperature and permit the controller to better regulate the temperature overall.

    hgmjr
     
  9. robindog

    Thread Starter New Member

    Feb 13, 2011
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    What I meant by nothing" is nothing chaged, still over heating! just wondering if maybe I should install a solid state external relay between the heater and the PID. The TCG-6131P is good for 3amps and the heater consumes 240watts it might be cutting int a bit close..."just a thought" I may add the thermocouple is type K and is attached to the Silicone Rubber heater. I tried just about every different way to tune the PID. I got it to the point where it starts to put out heat with the relay clicking on and off but in a short time the Pv. value numbers are dropping down to zero then back up to higher while still heating, this time I usually shut it off to prevent way over heating.
     
  10. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    Work first with your proportional only. if the controller cannot respond and maintain a steady state with P only, you won't get any further with the I or D.

    If you have severe overshoot with P only, then you should be looking at the hysteresis within your thermal mass as suggested, substantially reducing your power, or dramatically increasing the sensitivity of your senor.
     
  11. bertus

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    Apr 5, 2008
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  12. robindog

    Thread Starter New Member

    Feb 13, 2011
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    I cam to the conclusion that possibly the thermocouple wire at the heat maybe connected in reverse, or the connection is possibly bad... Will post it if I get it right. Thanks for all of you for your help!!
     
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