Looking for wisdom from anyone... Long post warning!

I've owned my SM025 for going on 3 years now.  In general, all has been well except a problem at the beginning with not enough oxygen getting into the firebox and I would end up at the end of a smoke with charcoal bricks out of a wood piece instead of ash.  

On to a current issue that I cannot understand.   I do not like how it controls temperature some of the time.     

2 Examples:

1) A long pork butt smoke at 225 F - taking 14-16 hours - it seems that right about when I'm wondering why the meat isn't moving through the stall, the box temperature starts fluctuating / dropping.  I will be holding within a degree or two of 225 for the first 10-12 hours and then start dropping to 215 or 210 with no opening of the door or other changes.  Why would this happen and why wouldn't the controller kick on the element to a higher duty cycle to overcome whatever is going on inside?

2) This Easter I did something I'd never done before.  I smoked a few turkey breasts expecting it to take about 5 hours.  I added a precooked spiral sliced ham just to heat it when there was about 2 hours left.  Door was open for 30 sec to slide in the ham and close.  The temperature never recovered - it dropped down below the 225 set point and an hour later was at 208/209 and holding.  The element was still cycling on and off.  I know that adding this mass to the smoker was a heat sink, but the controller should have seen the temperature deviation from the set point and started increasing the duty cycle of the element to compensate.   

Avoiding issues such as these and resulting greater unpredictability are the whole reason I spent more $ to get a digital instead of simple rheostat controlled smoker!

I emailed with Cookshack and they offered to test my controller so I shipped it in.  Today I received a call telling me it is operating perfectly.  They loaded an SM025 with a pan of water and ran it for 16 hours using my controller.  They reported to me that the temp stayed consistent at the 225 set point and so all is well.   This didn't make me feel better - the problem I have will still be a problem.  In emails I was told that this is a PID style controller as I expected, but in the phone conversation I got a hint of a statement that the commercial controllers are PID, but this is "proportional" (didn't really get a clear answer).

Does anyone have insight?   Is this controller actually not a PID controller?   Do I need to scrap the stock controller and start hacking my own using something from Auber?  Has anyone done this?

Thanks for reading the long post and for any possible advice.  

Best Regards,

Jay

Original Post

Hello - yes - I have a Thermoworks K-type thermocouple setup and I find that the temp showed on the SMO25 display matches that measurement within a degree in testing.  Also - I am careful to ensure food is not touching or dripping on the probe coming in from the back.  Here is a chart from some testing I did and graphed results with empty box - yes, I'm a nerd.Capture

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Thanks for the data - nerd here too. I'd have expected that if the meat were touching the box probe, the result would be overheating, not under. It is very strange. If there were some way to monitor the current response of the heater compared to the temp reading, that would be good, but I can't think of a way outside of surgery on your unit. From your description of CS's test, they really didn't replicate the effect of changing temps (such as a short door opening) on controller response. That was an oversight on their part, IMO. I wonder if you replicate their test, with a pan of water and constant operation, does your controller behave?

I expect that repeating their test with constant "load" it would act perfectly - the issue is that when the rate of energy absorption inside the box changes, the controller cannot adapt.  This is evidenced in the stall change of energy absorption and the situation where I added mass.  It leads me to think that the controller is NOT a P.I.D. style.  This would be a travesty - Cookshack sells a digital controller that only needs a bit more programming built in to operate properly instead of acting "dumb".  I need to talk to the engineer that designed this controller - of course that's nigh on impossible.  So - I'm seeking anyone who may have cared about this before and did something about it.

I would doubt that the problem is one of the design of he controller, pid or otherwise, else many others of the thousands of people with your smoker would be having the same problem. Some component is malfunctioning. I hope you continue to communicate with CS on this.

Unfortunately - the phone call with CS proved that there was nothing further they felt they could do.  They are sending my controller back with no changes.    I'm going to try it with a pan of water - open after an hour and add a second pan and see what happens.   If I can reliably repeat the problem in that manner, I'll ask if anyone else could do the same test to compare results.    I wonder if I can adapt the controller from a Smokin-it Model 2D to my SM025 - their controllers are actually created by Auber.

Interesting.  If you want a PID controller, and don't mind hacking your smoker, Inkbird makes some very cool stuff at very affordable prices.

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