# If  you have a PID controller.  What are your PID settings?  Heres mine.



## handymanstan (Jan 15, 2013)

I have read many posts here and elsewhere about Pids and I still don’t understand all the settings.

This seems to be a tool with growing interest and if we all can understand it better.  Great.

Maybe if everyone who has a Pid here puts up there settings we can come to a consensus and fine tune our settings for best Q.

I have a mypin ta series

My Pid came with the default settings of                                    The settings I use

AL1-90.00                                                                              AL1-350.00

AL2-90.00                                                                              AL2-180.00 When I cold smoke I change this to 50.00

PVF-00                                                                                  PVF-5

PUF-0.0                                                                                 PUF- this changes with every smoke but my average is +10

P-3.00                                                                                   P-30.0

I-240                                                                                      I-240

D-off                                                                                      D-60

I am not sure if the settings I have are the best but my pid works and keeps the smoker within 1-2 degrees.  I have found that if I change from hot to cold smoke or cold to hot I have to re auto tune to keep that range.  I don’t auto tune from the start but let the heat come up to like 220 when I want 225 and then hit AT.  It goes through the learning curve a lot faster  this way.

And I got these setting off the internet so I just don’t know.

Stan


----------



## roger shoaf (Jan 15, 2013)

Stan,

Let me preface this by admitting that I am not an expert, nor have I ever set a PID.

It seems to me that if the settings you use give results you are getting then are you there yet?  By this I mean if you have a target point of 225F and your control maintains the box between 223F and 227F  and you get consistently good results, then what are you going to gain by going from a +-2 to a +-1?

I suspect that factors like the insulation of your smoker, ambient conditions like wind,air temp and humidity are bigger variables at this point.

Another thing to consider is the quality of your data.  So for example if the thermocouple you are using will give you only a certain repeatability then this is going to have an effect on the result.  then there is the thermal stratification that may exist the condition of the meat in areas like moisture and fat content, what the critter had been dining on.


----------



## handymanstan (Jan 17, 2013)

Roger Shoaf said:


> Stan,
> 
> Let me preface this by admitting that I am not an expert, nor have I ever set a PID.
> 
> ...


----------



## roger shoaf (Jan 17, 2013)

This might help: http://www.omega.com/temperature/z/pdf/z115-117.pdf

I still think you need to ask yourself several questions:

1 What are you trying to accomplish?

For example if you want to gain constant results on a particular process, understanding your goal is the first step.

Lets say you want to cook a 1" thick piece of fresh beef to an internal temperature of  140 F in an oven that is maintained at 225 F.

Now in the above specification you need to understand that to maintain the desired environment you have to define your terms.  Does it mean that you can crank it up to 300 F and then let it coast to 125 F?  or does it mean that the environment will go as high as 225.1 and no lower than 224.9 F?

My suspicion is that as far as the quality of food your plate is concerned, +- 5 F probably would work just as well as +- .01 F

The next question is why you want to narrow the window.  For instance let's say you were an engineer that worked at a plant that had a vat of liquid that had to be maintained at a temperature for a long period of time.  If the process was critical that the vat of stuff  could not get warmer than X degrees or it would not work right but if it was too cool then the process would take too long then getting it nailed to a very narrow window might be critical.

Alternatively the engineer might get the acceptable results if the vat had a wider window.  here he might want to reduce the wear on the  equipment that switches the heaters on and off so there he might want to widen the window to the widest point so that the machinery would last longer.

Another goal might be to be more energy efficient, so therefore he would not want to expend any unnecessary power heating the vat up more than was needed.

As a practical point in a home smoker If you had a large thermal mass like a brick oven and it had gobs of insulation you are going to get a real consistent rate of heat loss but a lot of extra energy is going to go into warming the sucker up, but if you had a tin box with no insulation on your patio then you are going to be pumping out a lot of heat to play catch up with the changing rates of heat loss.

The next question is how much effort are you going to have to go to to find the optimal setting for your equipment?  Are you going to take a reading every 3 minutes and plot a graph with a piece of paper?  Are you going to get a thermometer that will print a chart?

Are you going to get software and have your PC make the graphs for you?

If you had good solid data that would show you performance, then you could probably tweak your PID to give a very flat line on your chart, but if you got the thing dialed in for a given set of variables such as the amount of meat in the smoker, the ambient conditions, and the particular equipment that you had, and then tried to use those particular settings on another smoker in a different climate you probably will get a different result.

Is this helpful?


----------



## smokeybass (Jan 30, 2013)

Roger,

It sounds like you are some sort of controls engineer! I utilize a lot of PID loops and do a lot of loop tuning in my line of work. I do utilize computers and those graphs you speak of.

So Stan,

when it comes to BBQ I do not use PID Controllers however I can give some of my insight to tuning PI Loops (i have never in my life utilized the D) Depending on how the Controller calculates and samples where you set the proportional gain can vary. So for example when I am utilizing some of my older controls equipment the Higher a number I set the slower reacting the PID loop raises its output. SO moving on the way that I tune PI Loops.

First I would utilize the factory setting of 30 in P with no Integral or Derivative. Adjusting this number up or down to get the output of the controller as steady as possible. With the output fluctuating a lot this means your P is not where it needs to be. Your temperature may not be anywhere near your setpoint, but it does not matter at this point. This is where the Integral comes in.

Once you have achieved this. And maybe your number really is 3. Then you start bringing in the I. Everything that I have used always ends up being a number less than 1. So start with .01 from there the integral will typically start bringing your temperature closer to your setpoint. You may not reach it with a .01 but your loops should react smoothly without any overshoot and bring you closer. This will take some time but as you bring in more integral your loop will react and will achieve your setpoint. Now once you have done this its time to start the process over again. IE turn everything off. Start from a cold smoker or a smoker with a temperature that you would normally begin using your PI controller. Let it react with your P and I settings and see if it overshoots/hunts/ or even reaches your ideal temperature.

Derivative ....well D i have never had a reason to use. I have seen D used in any application other than say clean rooms with variable speed and pitch fans. Super techy stuff.

What i am normally controlling is the temperature of a heat exchanger that utilizes 350 degree water to make 110-180 degree water. I think that this application would be very close to controlling a smoker. I have also used PI loops to control the speed of Fans to maintain a pressure range from 1 to 2" of w/c. There are alot of things that also can affect the outcome of your Loops. Not all settings can be the same for everything. The size of the damper/valve you are using. The rate of change in temperature of whatever it is you are using to heat/cool the space. All of these can change the numbers you utilize for P&I control. I have looked at the mypin TA series and unless I knew what exactly you were controlling and how, I cant give to much more advice. So is everything as clear as mud now?  Hopefully I gave you a little bit of useful information.

-Evan


----------



## roger shoaf (Jan 31, 2013)

SmokeyBass said:


> Roger,
> 
> It sounds like you are some sort of controls engineer! I utilize a lot of PID loops and do a lot of loop tuning in my line of work. I do utilize computers and those graphs you speak of.


No engineer.  Just a locksmith.  My interest is to be able to get the device to do what I want it to do with out luck and chance being a factor.

I want to build my own because buying something off the shelf means you get what someone else designs and builds and their decisions are usually compromises to production costs or marketing ideas.


----------



## smokeybass (Jan 31, 2013)

Luck and chance are not a factor when you are dealing with these Loops controllers. Some of the variables you pointed out are valid points but there are many variables that come into play when utilizing a PID controller. The first person that guided me on loop tuning assimilated PID loops to the process you use when you are getting the temperature of your shower right. P is being able to tell how close you are to the temperature you want, I is being able to tell wow this is getting hot or cold quick i better turn it back the other way. And D is, well, D is kind of like I remember it being hot or cold yesterday maybe i should act like this. However thats where variables like heat load changing from smoke to smoke would come in and possibly screw up your loop, again im not 100% familiar with how these smoker systems work. ANYWAY something of your own could be built with 3 or 4 different pieces of equipment. These of course would be all off the shelf items put into some fashion that would resemble a controller. I would have to look into these systems more to really give a "what would I do" sort of reply. I can only guess at what is being controlled at this point. Basically all you would need is

An actuator of some sort. Belimo, Bray, Honeywell, anything that accepts a 4-20ma or 2-10vdc input.

A temperature sensor rated for what is being measured. For longevity I might even think about getting a Thermowell with a sensor. This would protect the sensing element.

And some sort of PID controller with scalable inputs and outputs.

Maybe visit Grainger.com or Kele.com or possibly Engenuity.com. Anything that I know of in my line of work may be more cost prohibitive than you think. Again I haven't done much research on this. It does sound interesting. But if i were to get this automated, I couldn't use the "But honey I can't leave the backyard I have to watch the smoker! You want delicious BBQ treats don't you!?!?"

-Evan


----------



## smokeybass (Jan 31, 2013)

Stan,

What are the other components you are using? or did this equipment come with your smoker?

-Evan


----------



## handymanstan (Jan 31, 2013)

Thank you Roger for the link.  I started this thread for people who like me buy, bought a PID and then found out the instructions were less then desirable.  I went on line for quite a while and found the settings I am using from someone who said this worked for his smoker.  I started this to benefit others and myself as my pid works but I don't really know why and I don't even know if when I auto tune.  Do the setting I put in even do anything or if the setting are just for manual control.


SmokeyBass said:


> Roger,
> 
> It sounds like you are some sort of controls engineer! I utilize a lot of PID loops and do a lot of loop tuning in my line of work. I do utilize computers and those graphs you speak of.
> 
> ...


Thank you Evan for the explanation even though I had to read it several times to get my head around it,  I am using the pid to control a SSR wired to the heating element of the smoker so when you say P makes the controller steady are you saying the SSR or the element is steady?  The I is at 240 and if I understand what you are saying is that the overshoot would be less with a number less then 1. and go to 0 for D.  I will try this and see.  Now normally when I start the smoker I set the temp to 200* then when it gets there I raise to 225 and auto tune the pid.  It usually will run up to about 228 then turn off and drop to about 223 then starts cycling to get to 225*.  If I auto tune from the start the temp will go up to about 232 or so then shut off and drop to about 222*  before cycling and it takes 10 15 mins more time doing it this way to get to 225. 


SmokeyBass said:


> Stan,
> 
> What are the other components you are using? or did this equipment come with your smoker?
> 
> -Evan


I bought the PID and SSR and therm on e-bay. I put them in a case with a outlet and just plug in the smoker.

Stan


----------



## smokeybass (Jan 31, 2013)

Quite honestly a 6 degree swing once the loops reached set point is in my opinion spectacular.  I will see what else I can come up with.


----------



## roger shoaf (Jan 31, 2013)

SmokeyBass said:


> Luck and chance are not a factor when you are dealing with these Loops controllers. Some of the variables you pointed out are valid points but there are many variables that come into play when utilizing a PID controller. The first person that guided me on loop tuning assimilated PID loops to the process you use when you are getting the temperature of your shower right. P is being able to tell how close you are to the temperature you want, I is being able to tell wow this is getting hot or cold quick i better turn it back the other way. And D is, well, D is kind of like I remember it being hot or cold yesterday maybe i should act like this. However thats where variables like heat load changing from smoke to smoke would come in and possibly screw up your loop, again im not 100% familiar with how these smoker systems work. ANYWAY something of your own could be built with 3 or 4 different pieces of equipment. These of course would be all off the shelf items put into some fashion that would resemble a controller. I would have to look into these systems more to really give a "what would I do" sort of reply. I can only guess at what is being controlled at this point. Basically all you would need is
> 
> An actuator of some sort. Belimo, Bray, Honeywell, anything that accepts a 4-20ma or 2-10vdc input.
> 
> ...


Perhaps I could have been clearer.  I don't want to build a PID I am going to build a smoker and use a PID to control the temps.  My reference to luck and chance more refers to my grilling experiences.


----------



## smokeybass (Feb 1, 2013)

Ah I gotcha. Ya, end of the day it's a delicious hobby


----------

