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PID vs Non PID Controller

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    #16
    I had a Traeger Texas Model Pellet Grill from about 2004 until 2010 at which time I sold it and bought a Memphis Pro Pellet Grill. I have no idea what controller I have now or had before. The food has been good from both grills so I'm not sure if I am suppose to be concerned or not. From all the posts and reviews I've read over the years on pellet grills it sounds like most of the time AR Members are having good luck with several brands and models. For now I'm just going to get some more coffee. Have a good day!

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      #17
      Well if someone determines that the temp swing is actually beneficial as a rule, then we should open the control bandwidth or at least make a mode for this on the PID controllers everyone is using.

      some of the older modes on the fireboard are pretty wide.

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        #18
        To swing or not to swing, that is the question? I like Huskee thoughts on over time "energy in" is key, IT of finished cook, and staying away from scorch points......so I say swinging is ok on my pellet grill (I purposely avoided saying pooper there.....)

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          #19
          Total heat input is also explainable bbq magic. Why do we pull meat out around 200? Not because that’s the temp it is done at but at low and slow internal temp 200F determines how long it stays in the cooker and time x temp is what breaks down the collagen. Tender is what we are after, internal temp is a rough guide. Which is why you can tenderize at higher temps in less time, but surface drying (stall) effects will be different.


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            #20
            Ok, gotta put on my engineering hat for a minute here.

            v------ENGINEER HAT ON---------v

            A PID - short for Proportional-Integral-Derivative Controller - is a control mechanism used in all kinds of industrial control systems. You set a set point, and the controller monitors a measurement (the Process Variable or PV), and tries to maintain that PV based on - wait for it - the Proportial, Integral and Derivative terms of an equation.

            These type control systems are used for all manner of things. Maintaining a municipal reservoir levels by turning well pumps on and off based on tank level sensors and set points is one application I've used them in. Any brewery I've visited has PID's all over the place to control temperature based processes during the brewing and fermenting process.

            With a PID, compared to older control technologies, it is much easier to maintain a constant temperature/level/whatever. It is more precise, due to the use of the "derivative" portion of the equations, it can anticipate variations more accurately. With a non-PID controller it is common to overshoot the set point. Example - in going for 225F, the PID controller will anticipate the rate of rise, and probably slow the pellets moving to the burn pot before it reaches 225F. The non-PID controller will dump pellets at most likely a fixed rate until it hits 225F, then slow/stop, and overshoot the set point.

            ^--------- ENGINEER HAT OFF ----------^

            Ok, what this means for BBQ is this. A PID controller on a pellet smoker will maintain the temperature much more precisely than a non-PID controller. Most of them seem to claim to keep it within +/- 5F. A non-PID controller may maintain it within +/-20 degrees of the set point. Both will get your brisket/butt/ribs to the final doneness in the same amount of time, as both will average the set point temperature.

            What the original poster has come across is the Grilla Grills marketing speak as to why they use a cheaper NON-PID controller on their smokers. First, they fully admit that they do it to save cost. I figure they save $20 to $30 at the most in the cost of the grill by using a non-PID controller. Secondly, they argue that by using the non-PID controller, with its wider swings, that they produce more smoke. And I actually believe that argument. The PID controlled smoker will probably feed pellets at an almost constant rate throughout the cook. The non-PID controller will cycle between high smoke and low smoke, with high smoke as it climbs from below the set point back towards it, and low smoke as it overshoots and waits for things to come back down.

            Does it matter that your smoker is with 5 or within 20 degrees of the set point? Probably not. And without scientific comparison, can we say that a Grilla Silverbac produces more smoke with its 20 degree swings above/below 225 than say a Rec-tec with its PID controller? Probably not.

            I think this all comes back to marketing hype, and to be honest, think both types of controllers likely produce excellent BBQ.
            Last edited by jfmorris; October 30, 2019, 07:26 AM.

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            • Huskee
              Huskee commented
              Editing a comment
              I wish I had an engineer hat. My hat has a propeller.

            • Nate
              Nate commented
              Editing a comment
              Maybe docblonder could come put his mad scientist hat on and chime in.

            • jfmorris
              jfmorris commented
              Editing a comment
              Propeller hats are awesome Huskee ! It would be interesting to see what docblonder says. My suspicion is that Grilla and other non-PID based smokers have periods of heavier smoke followed by periods of lighter smoke, and that all in all it will average out the same as with a PID controller's smoke output, assuming the same number of pellets are burned.

            #21
            I have a bad visiting habit at contests. I'll say to everyone what my good friend told me:

            "Candy, just shut up and cook the meat!"

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              #22
              I coulda been an engineer....just had a little trouble with the math part of it....

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              • smokenoob
                smokenoob commented
                Editing a comment
                yeah, funny how I remember a lot of other stuff and not the calculus even though I aced years of it......never used it again. Guess they figured if you could get the math, you could get the other stuff.....
                remember all the earlier math though....more intuitive I guess???

              • jerrybell
                jerrybell commented
                Editing a comment
                Huskee Sometimes you have to settle for a marine biologist.

              • Huskee
                Huskee commented
                Editing a comment
                jerrybell Lol! Always a good time when someone else gets the Seinfeld references.

              #23
              Good discussion and explanation of the difference between a PID and a simple threshold controller. Now, most kitchen ovens are of the simple threshold type because a PID controller that can smoothly switch a 2KW heater is expensive. So the oven might swing by +-25F. Not an issue roasting chicken, but these wide swings can wreck havoc with some cookies and custards by overcooking during part of the cycle.

              Hey, one reason we BBQ is the huge window of time and temp where the results turn out just fine. Easier to be a backyard hero than a master chef. Most of the PID controllers I've tested on pellet cookers don't control the auger feeding pellets as much as they adjust the fan speed in the fire pot. That's the most direct way to maintain the temperature in a narrow range. But does that matter for 'Q? Hardly- some people cook brisket at 200F, others at 275F, and both do well. So the swings almost never matter.

              As to which creates "more or better" smoke, I don't really know. One issue with the PID controllers is they run the fan slowly during part of the cycle, starving the fuel of air, which makes for a darker and more bitter smoke. But without the PID, a threshold switch lets the fire burn out naturally, which can also be a problem.

              Unless I do the experiment, calling a "tie" for now...

              Comment


              • Nate
                Nate commented
                Editing a comment
                Doc, Thank you for jumping in! Appreciate the feedback and input.... sounds like a good experiment.... See if you can get Meathead to buy you a handful of pellet smokers to try it out on.... lol Thanks again!

              #24
              Thanks for the "Blonder Speak" input, that's always a good word from a knowledgeable expert. I do buy off on the fact that there may be an added smoke argument, my PID in the "smoke" mode modulates between 165F and 200F I suppose to let the burn pot smolder. The smoke that is produced is a thick white somewhat acrid smoke so I'm not sure that's good or bad (another discussion).

              But what I'm still hung up on is the constant temperature parameters. I haven't found anything yet that champions or debunks the benefits of even temperature in cooking versus swings in temperature during cooking. With my PID I get +-5F consistently and with my Fireboard/fan controller in my Webers I get very close to that as well. There has to be a correlation between consistent temperature and the cooking process, even if it means the rise in temperature internally is reached faster. Or are all these precise control devices nothing but over kill?

              Until I can determine that, my mind will remain........

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