First Build - Recommended PID Settings For Stumps Smoker?


 
R

Roy Dye

New member
I am very pleased with my first HM build. This has been a fun project and am very pleased that I have a replacement for my pitmasterIQ system that is very configurable and flexible.

Since I am new to this, I was wondering if anyone could recommend some initial PID settings based on my setup:

1) Stumps Prince Smoker...its no longer made but is bit smaller than their classic unit. It has a bit of mass, probably weighs in the 400-500 lb range. It takes about an hour to preheat to 225 with the pitmasterIQ system in the summer.
2) HM 4.24 with stock fan and Rotodamper 3

I typically don't go past 300 degF

Thanks,
Roy
 
I agree, start out with the default PID settings and see how she rolls then adjust from there.

I don't think you are going to get much detailed feedback because your Stumps smoker is not at all common.

Being larger than average I would start out with blower settings of Min=0 Max=100% and Startup Max=100%.

I am making an assumption that the opening required on your fire box vent to maintain 250F (without using the HM or any other blower system) is larger than the output of the RD3, so you probably need to let the blower run all the time (rather than "On at Max Only". If you have the latest Snapshot firmware you want to set "On Above 0%" to let the blower run the full range of operation)

I prefer to tune my systems so the HM is running about 35% or so to hold my setpoint, this gives the HM plenty of room to scale the fire up or down as needed during a long cook. So watch your system run with the stock settings and blower set to 100%, if you find the HM running really low then reduce the MAX setting for the blower. I really have no idea how much flow you are going to need for the stumps smoker so you will have to experiment a bit with it.
 
I am fairly pleased with the results of my trial run.

With stock PID settings, I had a bit of overshoot on the door opening and a smaller overshoot when I changed setpoint. If I had to guess, since the smoker has a bit of mass to it, the blower didn't need to stoke the fire that much to get back to temperature.

Should I change the derivative to correct the overshoot? What would be the amount?

Any suggestions welcome.

Here are some pics of my setup too.





Thanks,
Roy
 
Your graph looks pretty good for a first run...
The overshoot after the door opening was a bit much, next time click the HM button to the left to trigger lid mode before you open the door to prevent that spike of air from the blower, though with the door flung open the air wouldn't really go into the smoker anyways, unless it was opened and closed right away. At any rate, make sure the LID MODE is triggered when you open the door and let it continue a after you close the door to allow the pit a bit of time to stabilize before the HM starts stoking again.
 
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