Fermentation controller part 2

DSC01222bannersmallSo, this project has been languishing because I have had difficulty locating a machinist willing to machine a part, and I am too lazy to make a perfect measurement not he outside of the conical fermentor, which is required to maximize the metal on metal contact required for this application. But lo and behold! Stout Tanks and Kettles once again comes to the rescue with a made to fit kit for my fermentor. Now, you have to buy the machined piece AND the fans together, so I am out money on the fan I already bought, but it is worth it just to have the thing finally made. I have finished the wiring tonight and begin testing in the morning.

Here is a bit more about how the thing is made. In the last part (part 1) I had managed to machine the case with my drill press and a sliding table. Now the electronics start!

I bought a few items: an Auber Instruments 2342-P and a Jetstream JTPS31MB variable power supply as well as a bunch of SSRs, relay switches, and other components to be mounted on a DIN rail. The jet stream unit is secured with some washers and screws. The PID has a plastic tab that secures it pretty well to the face, and can be better secured with some screws, as well. I decided to use the screws, which I normally don’t bother with, but I want it to be pretty rigid since the space inside is so tight. This secured everything very tightly. The enclosure is small considering the size of the components I am using, and it was a bit of effort to make sure everything was aligned properly so things didn’t bump together. The tightest part is the DIN rail mounted components. If there was a small DIN mounted DPDT contractor that could take 30 amps in both the open and closed position it would have made this much easier, but I couldn’t find one.
So instead, for the polarity switching I had to use two DPDT switches together. Unfortunately, with the one for the power relay, almost 2/3 of the space was filled with contractors and it didn’t leave much space for the terminal blocks. Out of absolutely pure luck, the needed components just fit to the point where not a single terminal block more could fit in there! In order to make sure it doesn’t overheat while running, I drilled holes in the side panels for ventilation, and installed a fan on the back wall with grooves where the fan blades are.

I wired it up and tested the internal components, and everything lit up like it was supposed to, but I was having a lot of trouble sourcing the business end of the thing... the part that heats and cools and attaches to my fermentor. As a matter of fact, I couldn’t find someone to machine the thing for a year (not that I tried that hard). And then, one day in February, I found that the company that makes my fermentor started to produce a kit with the machined part I need! I ordered one as soon as I saw it.

It came with 2 fans, as well, but I found that to make a tight fit, I had to file down the posts to lower the fans by a mm or 2. I decided to use switchcraft high power panel mount connectors so it would be easy to plug the heating elements in, and because they were pretty cheap. I covered the aluminum block with 1/4 inch closed cell foam tape to insulate it on the surfaces that don’t contact the fermentor, and drilled holes to connect a power block. I then cut out holes where the Peltier chillers were to go, and used goo gone to clean up the surface. I am using 9amp Peltier coolers, but can’t remember where I got them. A coat of thermal paste between both the Peltier and the block, and the Peltier and the fan, and I assembled the whole thing. I tested it for a few minutes.... everything powered on, the fans all turned, and a nice layer of ice built up on the chiller within a few minutes.

THE THING WORKS. The picture below shows ice building up on the metal.