That is great input Sigmo!
I just received confirmation from
Masterbuilt that my new controller unit is on the way so I will have that to toy with myself. I also bought a flexible ducting hose to try and "duct" the exhaust from the opposite side of where the vent/damper is currently located. This would have the air flow across the smoker rather than straight up from element to vent/damper.
Lots of experiments on the list lol.
I think the experimenting is half of the fun for me! I suspect the same is true for a lot of us.
The duct to collect the exhaust air over at the opposite corner from where the factory vent is located would be good for me, too. The vent is directly above the heater in mine, too.
I've put some of those cheesy disposable aluminum-pan bits in various places to help direct the airflow. If I'm not using the top rack, I usually put a sheet of that thin aluminum on the top rack such that it blocks off all but the leftmost four inches or so. Thus, the air has to go over to the left before it can get to the vent. But of course, that monopolizes that top rack.
I don't remember who it is on here, but they posted a photo showing how they mounted a piece to do that same thing, but they mounted it to the "ceiling" of the smoker, creating that same sort of plenum, but without wasting so much of the smoker's space. I may have to do that or use your hose idea.
Thanks Bear. You confirmed what I suspected. Now to figure out a way to get the heat to distribute. I fan inside the unit stirring the air up would probably be best, but I couldn't imagine it lasting very long. LOL
My wife bakes fancy cakes for weddings and the like. And years ago, I installed a small stirring fan in our home oven to even the temperatures out in that unit. But here's the secret:
I used a fan that I took out of an old gas chromatograph's column oven. The way they work is simply to have a very long shaft between the motor and the little squirrel cage. The motor mounts outside of the oven, and that long shaft pokes through a hole that goes all the way from the outside of the oven, through the insulation, and into the interior. So the motor and bearings do not experience the heat of the oven.
And the little convection oven fan I got works the same way. It has a very long shaft, and it even has a second small set of fan blades back near the motor. I've seen these referred to as a "heat slinger" in the description of some "draft inducers" which have the same kind of task. The idea is to act as a heat sink to cool the shaft before it goes into the front bearing.
One downside of this design is that you need to come up with some sort of enclosure to surround the motor which, of course, is mounted to the outside of the smoker.
The idea of putting a fan entirely inside of the smoker is not good if you're using high temperatures because most would not be designed to handle such temperatures and might give off some nasty fumes when they are heated, not to mention the fact that they'd likely not last very long.
I admit, though, that I have used a little computer fan to stir the smoke up when cold smoking, but even at that, I suspect the smoke might eventually gum up the bearings. But since the little fans are so cheap, I was willing to risk it for cold smoking.
I've fooled the stock sensor... but in the opposite way you need. Same info applies though. You just need the proper resistor in parallel. ohms law.
http://www.smokingmeatforums.com/t/238214/350-in-a-mes30-yep-heres-my-mod
-J
Pardon this long story, but:
I was looking for a way to find very cheap meat probes to use with a fancy industrial controller, and after looking around, found that I could buy entire temperature meters with meat probes on EBAY, from China, for about $8 each. So even if I throw the meter away, I've got a meat probe for $8.
Being too impatient to wait for the cheap meter/probe units to arrive, I took the probe from one of my existing electronic oven thermometers, and characterized the probe at a variety of temperatures. It turns out that they used a thermistor type probe, and that's no surprise since they're inexpensive.
The problem is that these thermistors are very non-linear. So you need to implement a conversion to linearize the thermistor. The one I tested was a negative temperature coefficient, and probably what they'd call a 400K Ohm thermistor. The fancy PLC I plan to use has special input modules for resistances, and the "brains" actually implement some standard thermistor linearizations that you can tweak. But these input modules are not cheap, and the only ones I could find used, were for 40K thermistors. I'm still waiting to get a few of the $8 units, but I fear they'll be the same.
I also found a few articles about how to implement the math to linearize such probes or how to approximate a linearization with a very simple two-resistor circuit. Just do a web search for "thermistor linearization", and you'll get a lot of interesting hits.
I wonder if
Masterbuilt uses the two-resistor approximate linearization circuit. And if so, I wonder if we couldn't actually do a pretty good job of tweaking one in, over a rather wide range, by changing the values of those two resistors (assuming that's what they use, and further assuming they're accessible on the PCB of their controller).
I could also very well imagine them directly reading the resistance, and then implementing the linearization in the firmware of the microcontroller. If that's the case, the best you can probably do is exactly what you folks are doing. Either put a resistor in series or one in parallel depending on which direction you want to "push" the readings. But the problem, as you folks have already noted, is that you can only achieve perfect adjustment at one temperature.
But then again, that might well be good enough!
As Bear mentioned, you probably don't want to set things up to heat these units up beyond their original design limits. And as I've talked about before, you want to make sure that you're really comparing temperatures right at the smoker's sensor before adjusting things. The temperatures can vary so widely from one place to another in the smoker that you must take that into account before assuming that the smoker's sensor/controller is really off.
I would hope that the snap-disk would prevent things from overheating too badly in any case. And if I found that the snap disk was tripping prematurely, I'd likely replace it rather than jumper around it, defeating that safety system. As Bear pointed out, I don't know what sort of insulation they use, but if it's the foam stuff, it probably can't handle temperatures too far above what the factory controller is supposed to give us.
If I was making my own smoker from scratch, I'd use some mineral insulation of some sort so that I could run it up to "oven" temperatures if I wanted to. But I'm not sure what these MESs use.