Nerding out with SmoBoT: Part I

I just finished up my first cook with my SmoBoT damper controller. I mentioned in the post on Friday that I’d used two early units in the process of shooting the video I’d posted. There were some firmware issues with the Beta unit I used to shoot the video. There was nothing so wrong with it that it couldn’t be dealt with, but it was just touchy enough that I didn’t want to do an overnight cook with it. The unit I’m keeping came in over the weekend while we were in Gibson City. When we got back I got it out of the mailbox and then went up to Kroger to get a pork butt. I wound up with an eight-pounder. I figured that would be a good first overnight run. Pork butts are the most forgiving piece of meat there is. It’s not impossible to mess them up, but you have to work at it.

It’s been a long time since I’ve been able to write a post like this. Longtime readers — both of you — might remember that I restarted this blog a couple of years ago when I bought the Egg. Several posts from back then were basically running commentary on how my cook was going. I honestly thought that’s what I was going to do today. It didn’t turn out that way, though. It turns out the blog posts I wrote a couple a years ago were my running notes of the cook. I mostly wrote them so I’d have a record later to refer to. I also found that if I was writing I was doing less screwing around with the Egg. Less screwing around with the Egg meant fewer chances to screw something up.

I don’t need to do that when I’m using the SmoBot for one simple reason. This:


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One of the many tricks SmoBoT can play is that it reports data in near-realtime over the Internet. That graph actually builds out as the day goes on. This graphic is just a screenshot from the cloud service that the controller talks to. All the arrows and annotations in red are things I’ve added to the screenshot myself for your amusement. The point here is that I don’t have to write running commentary to remember what happened because SmoBoT remembers for me.


Click to embiggen.

I lit the Egg in what’s become my standard routine. It’s probably overkill, but it involves a blowtorch, so I like it. I get these “fat wood” fire starters and push one vertically through the lump charcoal down to the grate at the bottom of the fuel bowl. I’ve made a change here: I got rid of the stock metal-plate-with-very-small-holes that-will-eventually-get-plugged-up-with-ash. I replaced it with a 9-inch grill grid I got on Amazon. Anyway, I start the fat wood stick with a blowtorch. So much more satisfying than one of those oversized Bic lighters. I lit the fire just about 7 PM and it got up to the target temperature of 220 in about 40 minutes. That drop in the blue line shows when I opened the lid to put on the butt.

SmoBoT measures three temperatures. The most important is the grate temperature because it’s what will dictate how much the damper opens and closes. Since precision makes a real difference, that sensor is n industrial-grade K-type thermocouple you can see clipped at the back of the cooking grid. I placed it in such a way that one “arm” of the plate setter blocked it from direct heat. There are two thermistor-type food temperature probes. The one dead center of the butt is “Food 1 Temp” on the graph.  The probe on the left is “Food 2.” These are pretty much the same type of probes you find on most inexpensive food temperature measurement devices. They’re accurate to within a degree or two, and that’s actually good enough. It’s a little hard to see on the graph, but you’ll see that “Food 2” ran several degrees higher the whole cook. That’s because it wound up being placed nearer the surface of the meat than “Food 1.”

Everything proceeded normally through the night. Mostly because I was asleep.  It’s a little more obvious if you zoom in on the graphic, but you’ll notice that there was an oscillation pattern all night.  It ran a couple of degrees high, then it it dropped below for a while. Never more than a few degrees. I didn’t think anything of it, but then I heard from Eric the Developer this morning. Part of what the web service is for is to be able to gather data from multiple units to see if improvements can be made to the algorithm. It turns out those oscillations are an indication that SmoBoT is thinking too much. It’s too sensitive. It’s reacting too fast. Perhaps it loves too much. Maybe there are anger issues. Whatever it is, a firmware update is going to come down mid-week.

The context of today’s cook is that Carla has a long day at school. The menu tonight is sliced smoked pork sandwiches. Remember my kimmelweck buns from last week?  Well, I did another near-batch of them this afternoon. I say “near” because they don’t have the salt-pumpernickel-caraway mixture baked on the top. I figured they’d be ready to go in the oven around 4:30 PM and I really wanted to wait until then to pull the butt off. I like a temperature between 180 and 190 for sliced pork, so when I saw the Food 1 temperature hit 173 around 10 AM I decided it was time to drop the pit temperature down.

Well, that was stupid.

I’ve talked at length about The Stall. Never in a million years did I ever think I’d manage to cause one to happen. I woke up briefly at 4:30 AM and decided to check my phone to see what the temperature was. It was around 160, which is pretty much a prime stall point. But in reality I don’t think I was ever in a stall until I dropped the temperature. Remember that a stall is the evaporative cooling effect of water boiling off balancing (or overcoming) the increase in meat temperature. My increase was slow, but it was always positive.  Until I dropped the temperature down to 190. As you can see on the graph, my food temps actually dropped a few degrees. I kicked the pit temperature up to 225, then down to 190 again, but then changed my mind and settled at an even 200.

That’s the danger of being able to set your smoker temperature using a smart phone. With great power comes the ability to be profoundly dumb. In hindsight I should have waited for Food 1 to hit 181 or so and then drop the temperature to 210. If the food was still rising, I could drop it another 10. I seriously doubt I would have had to go any further.

Anyway, once the buns were out of the oven (not a euphemism) I want ahead and pulled the meat off the Egg at 4:20 PM. Here was the final reading on the SmoBot controller

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And here is the lid thermometer


It may be a little hard to see, but even after 20+ hours of cooking, the lid thermometer read a good 10 degrees cooler than the thermocouple. It was much more pronounced early on.

But here’s the star of the show:


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Pretty, isn’t it?

As I write this I’m still waiting for Carla to get home, so the butt is triple-wrapped in heavy-duty foil and safely stowed in a foam cooler stuffed with towels. Even though it will have been several hours since I pulled it off, I’ll still need to use gloves when I handle it to slice it. Otherwise I’ll burn my hands.

Part II will detail how it turned out and lessons learned. Stay tuned.