Today, I'm planning on starting a new test with a low temperature oven.
Yesterday I went into Charleston to Home Depot in order to buy the parts necessary for the test oven construction.
First, I'm going to modify the existing code I wrote for the temperature controller. This controller is using a thermocouple and a microcontroller. The temperature controller will drive an LED using inverse logic; when it doesn't want heat, it will turn the LED on; when it does want heat, it will turn the LED off.
The LED will shine into a 'dusk-to-dawn' photocell switch I bought at Home Depot for less then $10. When the 'dusk-to-dawn' switch sees light, it switches off its electrical output; when no light is present, it switches on its electrical output, and thus the reason for the reverse LED output above.
I plan on driving a simple 100 watt bulb for the heat generation. This may not be enough, so I can add additional bulbs if necessary, up to 600 watts, before I start hitting the first of the current limits.
While here on vacation, I'm limited to what I can use or build for an oven. At home I have a large clay pot (ala Alton Brown) that I use for an oven, but I didn't bring that with us on our vacation trip. So I've been scrounging around to figure out something cheap and safe to use. Since my temperatures are so low (it won't exceed 200 dF), anything can be used, even a cardboard box. However, we are so cramped in this little studio condo, I don't want to put anything else in here. I can't do it outside because the dang raccoons are getting into everything! I did buy a small cooler for the task, but on the drive back home, I realized I could just use the oven in the condo's stove and be done with it. I'll just place the bulb in the bottom of the oven, and control the heat in the oven this way.
My test will consist of a large piece of beef round tip, 6.1 pounds.
I plan on cooking it for at least 2 days, possibly 3.
I'm going to modify my controller so it will maintain a 200 dF temperature for the first 4 - 6 hours, until the internal temperature of the meat comes up to 130 dF, then switch to a lower temperature of 140 dF for the oven, which I will maintain for the next 2 - 3 days.
I'll post an update later today on the oven construction and software mods. My wife needs the oven through lunch today, so it will be early afternoon before launch.