Fire went out during a long dip


 

MikeJK

New member
I cooked two shoulders and a brisket back to back in my ceramic cooker. The pork shoulders went first and this was my very first time with the Stoker.

I though the cook went well. The temp would drop when I open the lid to baste and then would over shoot after coming back to temp and then settle in. This was OK to me and it got a little better when I remembered to tell the Stoker to turn off for 5 min. Although this caused StokerLog to get a telnet error.

When I cooked the brisket I had a problem where after the overshoot, which was a big one, 20 deg, the dip lasted so long, over 30 degrees down, the fire went out. It was deprived of oxygen so long.

I had to take the brisket out and restart the charred wood. Then it almost happened again. The fan would not turn back on until it was more than 10 degrees below the set point. But because of the overshoot being so high, this was more than 30 degrees drop without any venting at the bottom.

To get out of this, I had to manually change the set points so the fan would turn off sooner (to decrease the overshoot) and on sooner (to decrease the undershoot). This seemed to get it back on track although the rest of the cook it the temp wasn't as stable.

What did I do wrong?

Thanks
 
Don't open it. Just kidding of course.

When I started using my Stoker on my ceramic (I also use it on my WSM) I experienced a similar thing. In my opinion its due to the nature of the cooker we're using. If you've ever done a dwell cook you know how well your ceramic will hold a temperature and for how long after you've cut off the oxygen; similar thing going on here with your Stoker cook. Once the overshoot stops and the fan turns off, it can take a very long time for the temp. to come down to the 10 degrees or so below your target temp. for the Stoker to kick back on, and yes, your fire may well go out during this period.

How do I combat this, I open my cooker as little as possible. I used to baste, spritz etc. but no longer do. Often times I'll close the cooker, turn Stoker on and open her back up in 18 hours to remove the butts.

My .02, hope it helps.
 
Thanks.

I am new to my ceramic cooker and I never basted the meet with my other cookers. Ironically, I basted with the pork shoulders, per a recipe I found, and the Stoker worked great. With the brisket, I never planned on opening the lid at all but I saw the food temperature rising more rapidly than I would have thought. I opened the lid this once to check out the probe position. I figured since I opened the lid quite a few times during the pork shoulder cook, it wouldn't hurt doing it once on the brisket. Was I wrong!

I don't mind the overshoot so much but I wish the fan would come on sooner to stop the rapid fall of temperature. It comes on too late. At least during that cook. I am not sure what was different with the brisket.

There is an example of this type of control using Fuzzy Logic with crate carriers. The kind they use to get the big crates off ships. You anticipate the swing of the crates as you are moving it. Pretty cool stuff. ...I think this would keep my fire from going out!
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That sounds too complicated so I think I will just keep the lid shut.
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Thanks for the feedback.
 
With the pork butts maybe you had more "cold mass" working as a heat sink and bringing your temps back down (at least early on in your cook) and it sounds like your brisket temp came-up pretty quickly. Just a couple ideas, I'm sure others will have thoughts too, I know several guys on here have Eggs too.

Another thing that has caused temp. swings in my ceramic is when I've used large pieces of wood vs. smaller chunks.
 
Can you post your graph?

When my stoker was new mine did the same thing. So I would watch as the temps came down and reset the temps to kick the fan on. Eventually the stoker settled in to my cooker. I think, dont know for fact, that there is an algorithm there that needs to be learned. Again I dont know if that is correct but mine seemed to get better every cook.
 
I have noticed the same thing on my ceramic smoker.

I wonder if I could work around it in stokerlog. I could have a parameter which measures how long the fan has been off, say 5 minutes, and the temp dropping. At that point, it could try to nudge the target up for a while to get the fire going.

I am concerned about the difficulty in testing the system. And the confusion it might cause for the novice that the target moves around by itself.

And of course, the state-machine like this is not fun to write
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Let me know what you think...
 
I would think it would be much better to fix this in the Stoker software.

When was the last update?

Do you know what type of algorithm they use? Is it an auto tuning PID?

If so, it would be nice to get access to the gains so a person could customize it to work better with their own cooker.

What would be really nice is if they gave us the source code. We could make it better and then they would probably sell more hardware!
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I asked for what you describe (i.e. the loop filter parameters). But I didn't get it. Instead, the developer gave control so that we can implement our own algorithm. But getting access to that new capability requires pretty large rewrite to use a new interface. So right now, it is at the end of the Todo list
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