Fine tuning PID

[Tiny Tim]

I think it's the latter.  ;D

[carnie1]

Thanks for all the help, I didn't get a chance to test Maverick yet, I talked to BBQ Guru and they are gonna check my setup out
NePa I was makin fun of the "Dutchie" talk about the school colors

[NePaSmoKer]

oh ok i gotcha now.
becareful amongst the english.

nepas

[Mr Walleye]

Just for the heck of it I ran my altitude and the current barometric pressure on the link and it show 208.9 degrees. I didn't realize it would make that much difference.  :o

Mike

[Tiny Tim]

Ran mine and came up with 209.3.  Now I just gotta build a PID so I can put this knowledge to use.  Anybody know where I can get a thermocouple cheaper than $30?

[Habanero Smoker]

BigSmoker provided that link some time ago. It is very helpful. As a general rule, for my elevation, the boiling point is 110.9°F.

What the heck are you doing 10+ miles above sea level? ;) :D

Sometimes I need to get clear of all the smoke, and the other stuff floating around down there ;)

Iceman is correct it should have been 210.9°F, depending on the barometric pressure.

[carnie1]

OK I finally decided to put some food in and try out the PID, I'm doing bacon wrapped chicken and a small turkey breast. During testing the heat went right up and stayed within a few degrees now I have the PID set at 220 but it wont go above 199 and it went right to 220 on the pre heat, it's about 80 outside with a little breeze, Any Ideas?  Thank You

[carnie1]

Hmmm, It's right on the money now at 220 and it cooled down to 74 outside but of course I'm done now.

[West Coast Kansan]

Not sure how much food you had in the smoker but the food will absorb heat and keep the temps down until it starts to warm up. Moisture (Chicken / Bacon) also absorbs heat so if the vent was pretty nearly shut that may have had an effect as well. Thinking it may not be your PID - Other PID user will know better.

[Mr Walleye]

Carnie1

Did you get it working correctly?

I've been away for a couple of days and just saw your post. When you ran the auto tune did you have any kind of load in the tower?

Mike

[Sabre]

P= Proportiomal, I- Intergral, and D= Derivative, these are all functions of the PID>  Math stuff, anyway the most important one to tweak would be the derivative, most controllers have zero set for derivative.  this is a function of how fast the controller reacts to change in temp. so when you open the door the pid ramps way up and swings around set point. or if there is a slight over shoot, the pid ramps way down. Try to dial the d all the way down and see what happens, however remember the setting you are currently at just in case

[Mr Walleye]

Thanks Sabre.

What I think would help everybody, especially me, is to have more of a "laymans" description of what spacifically the Auber P, I & D settings do in this exact installation, ie the Bradley Smoker. Here is what the Auber manual says regarding the settings:

6.6.1 PID
Please not that because this controller uses fuzzy logic enhanced PID control software, the definition of the control constants (P, I & D) are different than that od traditional proportional, integral, and derivative parameters. For the first time user, we strongly suggest you use the Auto Tuning function to set the PID parameters first (see 6.3). If the auto tuning result is not satisfactory, you can manually fine-tune the PID constant for improved performance.

(1) Proportional constant "P"
Proportional action is the action that the control output varies in proportion to the deviation between the set value and the measured temperature. Larger proportional constant means quick and larger action. However, if the proportional constant in increased too much, even slight distubances may cause variation in the processing temperature. Control action starts to behave like ON/OFF action and the hunting phenomenon occurs. Please note the P is not defined as Proportional Band as in the traditional model. Its unit is not in degrees. The Larger the constant results in larger and quicker action, which is the opposite of the traditional proportional band value. It also funtions in the entire control range rather then a limited band.

(2) Integral time "I"
Integral action is used to eliminate offset. Larger number means slower action. When temperature fluctuations regularly (system oscillations), increase the integral time. Decrease it if the controler is taking too long to eliminate the temperature offset. When I=0, the system becomes a PD controller.

(3) Derivative time "D"
Derivative action can be used to minimize the temperature over-shoot by responding to its rate of change. The larger the number the faster the action.



So, based on this wealth of information  ::) does this mean...

The higher you set P the faster and more power it applies to the heating element based on the temp difference. Does this setting affect anything when the tower temp is higher than the target temp?

The "I" setting, hmmmmm. Lets see, first off is "offset" described as a temp swing both above and below the target temp? If it does apply to both I'm really confused. Larger number means slower action. What action?

The "D" setting controls over-shoot. The larger the number the faster the action. I am assuming over-shoot is when the tower temp is higher than the terget temp.

Everytime I read through this and think I have it, I just get further confused. Man this is so far over my head and I'm even standing on a chair!  ;D

[West Coast Kansan]

 :D

[Sabre]

Mr Walleye,
     Your startig to sound like an instrument technician!!! Yes over shoot is the amount above and bellow setpoint yuor process varries, Derivative is not allways your friend. Good luck with the tuning, Im sticking to the slider on the OBS, if I have to spend more time fooling around with the temp, thats less time for the honey-doo list... plus it only takes one hand, the other is free for my favorite refreshment!

[Mr Walleye]

     Your startig to sound like an instrument technician!!!

::)  ::)  ;D

Actually I have mine working good. I was just trying to understand it better and mybe help anybody else trying to fine tune their's.

Mike