PID tuning for mini gravity feed.


 

BDuggar

New member
Hello Everyone,

I have been looking for some guidance when it comes to adjusting the PID on my Heatermeter. I have found these instructions : https://github.com/CapnBry/HeaterMeter/wiki/PID-Tuning

I have made several adjustments, but I still cannot seem to get my pit to not overshoot after door opens. Currently I am over shooting anywhere from 15 to 30 degrees and it takes quite a while for it to come back to down to 225.

My Current settings are: PID Output Parameters
Proportional 2, Integral 0.001, Derivative 5


With that said after it settles down to 225 it is on rails. I just want as little overshoot as possible.

hf6a
 
Last edited:
What fan or Damper setup are you using? I use stock settings on my mini, and leave top stack fully open, and have very little overshoot (normally a few degrees).

I use a home designed 15CFM Fan/Damper. Fan speed 30% Max. I actually just used the fan (unplugged the servo) this weekend and the results were spectacular. No damper needed on my mini.
 
I think the issue I have is the heater meter isnt shutting down fast enough when it reaches set temp. It eventually shuts down completely, but the temperature continues to rise and then has to settle back down. If I set it to say 210 and then wait for it to over shoot to around 220-230 and then set it to 225 I works just fine.

Not sure what setting that equates too.


q7QY
 
Last edited:
From what is see on the last cook you did not have enough integral dialed in and the control just went crazy
Try the following
P=2.5
I=.0035
D= 6

as for fans you might try setting the %min to maybe 10 and play a little with the %max. Maybe lower it to 40

looking at your first post and graph, I would have raised P to 2.5 and I to 0.0035. Then I would work with fans setting to not overdrive or underdrive the smoker.
Check for leaks as well
 
Thanks for the observations. I am going to do some more testing and see if my current settings have the desired effects. I think I will just have to keep working at it. I will keep posting my results.
 
What type of gravity feed do you have? My gravity feed did not need any PID tuning. I use the stock PID just fine.

I think you may have other issues with you heatermeter. Your graph looks odd, looks like static or noise and is not stable.

Does you TC have exposed wires where the two wires come together. Reason I ask, it looks like it could be very sensitive.

Gravity feeds are usually insulated and their temperature gradually changes. If I set mine to let's say 250. It will slowly climb to between 250 and 255 and then it will settle down to 250 and stay there, barely moving a degree up or down. It basically a straight line for most of the cooking time.
 
I made the larger gravity feed from smokerbuilder.com and others on here have made the mini and I'm pretty sure they have had no issues with it. Not much needs to be done to them, and that's why I think your TC is likely the issue. I have a TC that the protective cover came of, although it still works fine, it's very sensitive and just air blowing on it causes it to freak out and is not usable for smoking.
 
i have/Built the same smoker, and can keep within 1 degree. i use the stock HM PID settings. I haven't tried my Adapt-a-Damper with it yet, but use a 15 CFM version that I set to 40% max and it never really gets over 5% of that 40% once up to temp. I'm currently using it with the damper portion (servo) unplugged and just use fan. If I do overshoot, it settles quite quickly, and that may be due to the fact that I keep the top damper on the smoke stack fully open all the time.

I agree with john. You probably need a less sensitive Pit Probe.

Here's one of my test burns. 13 hours straight line until it ran out of fuel.

By the way - You did a great job on the Smoker!

OwF2cHM.jpg
 
Last edited:
I also built a double pan gravity fed, using the same plans, and stock constants. While I might not (edit: where'd that word go....) have quite as flat of a curve as Will, it's pretty darned good. I use natural lump hardwood charcoal (Rockwood.) I find it burns cleaner, and leaves a lot less ash than compressed briquettes.
 
Last edited:
Ok. I was investigating and I think I had some Ash stop up from the fire box the cooking chamber. I'm gonna do a retest this weekend with stock settings and new probe.
 
I use any lump charcoal, I can buy at the time I'm at the store, mostly whatever Walmart has.

It definitely your prob, a new one that's less sensitive
 

 

Back
Top