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Barbecue Tech

So, I’d owned a Weber barrel-style smoker for years. It was great, but it just didn’t have enough grill space for me to cook for a crowd.  So, my lovely wife got me an offset smoker with a larger grill:

And thus, it was decreed that our house would host the family Thanksgiving this year. Now, I could have sat around and tended the smoker for 8 hours like our barbecue ancestors would have, but we have the benefit of modern technology… so a few modifications were in order:

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The first modifications were some simple ones to improve airflow — namely, extending the chimney down to grill level and sealing some of the air gaps with JB weld.

The next problem I looked had to do with the byproduct of charcoal cooking — the ash. The side fire box comes  with a pull-out ash tray, but the problem is that the grill which holds the coals sits on top of the ash tray — so there’s no way to remove ashes while you’re cooking. (Also, the metal in the OEM charcoal grill had warped due to heat after a single cook.) So, I bought a replacement grill from Lowe’s and had my brother-in-law cut it down to size (about 17″x30″). Now, it sits nicely above the ash tray, and I can dump the ash while cooking, without affecting the coals:

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You can also see in that picture part of the electronics setup: the stoking fan, a 10cfm fan which can be turned on and off electronically to control the rate at which the charcoal burns (and thus, the smoker temperature). Normal smokers depend completely on the chimney effect, which works well, but the only way to control airflow is by adjusting the intake and outflow openings, which is inexact and can also be greatly affected by wind conditions.

The fan is controlled by the brains of the operation:
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This is a Stoker, from Rock’s Barbque. Based on a TINI board, it has 5 inputs and outputs for temperature sensors and fans, as well as the user interface you can see here for controlling the fans and configuring temperature setpoints. It also has an ethernet port, which I have connected to a wireless bridge (you can see it hiding above the controller in the picture above) so that it can connect both to my local network and the Internet as well.

Through the buttons on the controller itself, or the built-in web interface, you can see what the current temperature readings are, and also control it:
smoker

Here, I have Sensors 1 and 3 set up in different locations in the smoker, pulling the ambient (‘cooking’) temperature. Sensor 1 is controlling Blower 1 (the fan), and if the temperature goes past the target, the fan will turn on or off (some hysteresis is introduced to keep the fan from turning on and off rapidly when near the target temp).

Now, you might think, temperature over time… that would be a great thing to see on a graph. With the assistance of AmirM’s StokerLog, we can! Here’s the chart from my Thanksgiving turkey cook:
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As you can see, I started the smoker around 9:30, added the bird at around 10, and proceeded to cook it for about 5 hours. Here, the purple line is the temperature according to a temperature probe inserted into the deepest part of the breast, and the blue line moving at right angles is the fan output, either on or off.

One of the best things about the smoker setup is that I no longer have to watch it like a nervous mother hen — I wasn’t even at the house between 10:30 and 12, but I never worried because I’d forwarded a port on my router to the stoker’s web interface and could check on it as much as I wanted.

How did the turkey turn out? Awesomely moist, and with a great smoke flavor:
Turkey

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