This first image shows the cooker.
Yes, that is an empty wine glass. Yes, I was celebrating. I'd just hit 130 F and the system was stable. In this image it is pretty easy to see the external access to the submersible heating element. As I mentioned in previous entries, I switched to a flat flange mounting element because it was much easier to get a watertight seal. The hole for the wiring is 1.25" diameter. My fraternity brothers will recognize the "AJ" on the cooler as the cooler I have had since 2001. Still finding it useful, obviously!
Here you can see the AC/DC relay.
The double white wires run to the heating element, the stereo cable runs to and from the Crydom relay, and the black and white pair are the wall plug. I use terminal blocks whenever I can, because they are so easy to connect to.
This next image shows the main electronics assembly.
The red and black twisted pair is the digital input line from the Crydom relay. The two sets of braided trios are the wire lines from the two LM34 temperature sensors I made. Each goes to a three-prong surface mount connector. You can see the two green wires running from those to the Arduino's A0 and A1 analogi inputs. Also, the 1.5V AA battery is used to power the submersible fan, and the black smudge in front of it is the Reed DC/DC relay that controls that. So far, the AA battery has lasted through all my testing etc. so I am not worried I need a larger battery. The four wires coming from the Arduino's digital line are:
D13: heating element relay (yellow)
D12: heating element indicator LED (blue)
D11: submersible fan relay (dark green)
D10: submersible fan indicator LED (light green)
The LEDs are currently programmed to turn on if the heating element and submersible fan run. You can see them on in this disappointingly blurry image.
I think I'll do another set of images when I cook a big fat roast, and I'll include a few more of the cooker then. Here's a shot inside the cooker. You can see the heating element and submersible fan (running) in this shot.
And here are the two LM34 relays. In a previous post I described how these are made.
That crap that is on the heatshrink is extra silicone caulk from when I installed it. I promise.
Here's a close up of the heating element connection. It was actually pretty easy, but I do use a GFI socket in case of an epic fail.
That image also shows the comparative thermometer I installed. The thing doesn't work. It kept giving me readings about 10 degrees colder than the LM34's were giving me, so I got a "second opinion" in the form of my daughter's digital thermometer. I ran the cooker up to 98 degrees, and while the comparative thermometer showed a brisk 88, the digital thermometer was less than half a degree off the LM34's. Soooo I'm going to believe them for now. I might bring home a thermocouple just to do some further verification later.
That's all for now. You can read the previous posts on the cooker here:
Part 1
Part 2
Part 3
Update
Also, if you make it to the update article where I switched to the Sharp S108T01 AC/DC relay, you must realize I am back to using a Crydom. The Sharp couldn't handle the 12.5 amps I was running across the heating element and started threatening to burn out. So I got a Crydom HD4825 which is rated for 480VAC and 25A of current. Works perfectly, every time, and never even warms up at my measly 120VAC, 12.5 A.
Next up: the software!
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