Fermentation Controller Part 3

Well, I finally got around to finishing this off and testing it. It seems to work like a charm.
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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.

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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.
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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.
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DIY Hop Torpedo

So, after having ruined several batches of beer with dry hopping and having hop particles fall out of the bag, making the beer bitter and grassy, I decided it was time to make a change. I had always been curious about recirculating while dry hopping, and the benefits I would think could be made from this. Sierra Nevada has perfected the system using their “Torpedo.” This is more like a Hop espresso machine-- they compress hops together and force the beer through it at 50 PSI. While my DIY hopback could handle the pressure, I don’t have the technology to compress the hops, nor to generate that kind of pressure gradient across the hops without having to do a LOT of work. So, rather than do this, I thought it would be much easier to just make a recirculation dry hopper. I already had my hopback, which is designed to work perfectly in this situation, as well, and so I just needed a very slow pump and some connectors to make this work. I figured the easiest way to do this was to dry hop straight from a cornelius keg, so I could keep things sterile, and it already has a dip tube and a return tube (the gas inlet), making construction MUCH easier.
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Here’s what I did. I bought a single speed peristaltic pump (Anco 907-058 pump) that was rated for continuous use (very important that it is rated for continuous use). At 58 RPM using 1/4” ID tubing, it pumps about 3.5 ml per second, or about a gallon every 18 minutes. I attached this to some 3/16” beer line on both ends of the peristaltic tubing with a 1/4” stainless hose splice, then to a black (liquid out) ball lock quick disconnect. On the other side of the pump’s peristaltic tubing, I connected 3/16” beer line to a 1/4” to 1/2” hose adapter into a 1/2” female stainless disconnect. Another cord was made with 3/16 beer line with a gray (gas in) ball lock quick disconnect, and on the other end another 1/4” to 1/2 inch hose adapter to a 1/2” female stainless quick disconnect. My Hopback has been fitted with male 1/2” stainless disconnects, so it can clip between the two cords.

Here is how it is used:
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Sanitation:
I fill a Cornelius keg with at least a gallon of Starsan. I then plug both of the quick disconnects onto the keg, place a hopback bypass connector in place of the hopback, and start circulating the Starsan through the tubing. In the meantime, I place the stainless hopback into the oven at 350 to sterilize it, and I let it cool, and fill it with hops (up to 5 ounces).

Flushing lines with CO
2:
After recirculating Starsan for a while, I remove the quick disconnects from the keg, and place the “gas flush input” on the liquid out quick disconnect, and the “gas flush valve” on the gas in quick disconnect. The crummy thing about this setup (with my pump, at least) is that in order to force the stars an out, the peristaltic tubing needs to be removed from the machine. This means I have to unscrew the cover, and screw it back in once the tubing is replaced, making it more of a pain to use. I close off the gas flush valve, set the CO
2 pressure on my regulator to 5 mmHG, then plug the gas flush input into the CO2 quick connector. I then slowly open the needle valve and slowly drain the liquid out of the lines until CO2 flows out, then I close the valve and disconnect the CO2.

Flushing hops with CO
2:
Once all the lines are clear of Starsan, I replace the hopback bypass with the sterilized and filled hopback, and reconnect to CO
2. I open the gas flush valve a bit more and let CO2 vent to the atmosphere for a few minutes. This purges all the air from the hops and hopback.

Recirculating:
When air is purged from the hopback, I spray Starsan over the gas in and liquid out posts of the keg to dry hop to sanitize it. I disconnect the gas flush input and place the quick disconnect gas flush valve on the keg. I also remove the gas flush valve and place the gas in quick disconnect onto the keg’s gas in port. I replace the peristaltic tubing into the pump, and then turn it on. My plan is to recirculate for a total of 3 days, and no more.

I am running a test right now, with the first sample running. I have a Bavarian Hefeweizen that I brewed 2 years ago, is not very good and has been filling a keg. I’ll probably never drink it but don’t have the heart to throw it away. Instead, I will sacrifice it to science! I am currently dry hopping it with 4 ounces of citra… not the most normal choice for a bavarian hefeweizen, but something that will definitely be noticeable, and with the light flavor of the hefeweizen I think this will be a good test of what the process does. I’ll let it run for a few days, and report back.

Parts List: Number
Cornelius Gas In Post 2
Cornelius Liquid Out Post 1
Cornelius Gas in post to 1/4” NPT female adapter 1
Cornelius Gas in Post to 1/4” NPT male adapter 1
Cornelius Liquid Out Post to 1/4” NPT female adapter 1
Noshok 1/4” Male NPT Needle bleeder valve 1
1/2” NPT stainless mail to male quick disconnect 4 (2 for hopback bypass, 2 for hopback)
1/2” FPT stainless female quick disconnect 2
3/16” beer line 10 feet
Ball lock gas in quick disconnect (w/ swivel adapter) 1
Ball lock liquid out quick disconnect (w/ swivel adapter) 1
1/4” stainless steel hose splicer 2
Hose Clamps 8
Peristaltic pump with rate of approx 2-3 ml/sec 1
Hopback 1



Update 2/18/13: The hefeweizen took on a huge flavor and aroma of Citra. The project is a success!



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Prius problems with Invisicord

So, the other day I was driving home from work on highway 518, and this black mustang pulls in behind me. I was traveling at the exact speed limit (or maybe up to 10 mph over!) and this guy was riding my tail the whole way until the I-5 turnoff. When I say he was on my tail, I mean I couldn’t see his grill in my rear view mirror-- he couldn’t have been more than 10 feet away at 70 mph…. scary incompetent. A few minutes later, a guy cuts in front of me, again at full speed, and I had to slam on my breaks to avoid hitting him. Given this, I decided that I was going to bite the bullet and buy a dash cam… that way if they did this again and we crashed, I would have video footage. Also, I have a tendency to report people who are assholes in traffic, and this will allow me to record the license plate number without my having to search for a pen and write on my leg at 70 mph.

So, I bought a dash cam… a Lukas LK-9700, with a Lukas lk-270-12vt power interruptor, with the intention of hooking it up the way it says in the manual. Well, it turns out I would need to find an “always on” fuse in the prius, then someplace to bolt the ground to the chassis. It turns out that in a Prius, the fuse box is in a ridiculously inaccessible location, such that you have to turn upside down and put your head on the drivers side floor, to look up at the fuses. And these are tiny little fuses that are extremely difficult to get out (there is a tool in the front fuse box-- rather there is SUPPOSED to be a tool there, but mine was missing), and I don’t have any way of tapping a fuse if I could find one that was always on, anyway. So, I did some research and found a simple and elegant solution, that turned out to be the start of a major nightmare… the Invisicord.

You see, the Prius comes with a special mirror, which senses daylight and automatically dims the mirror, and includes “homelink,” which allows you to program your garage door opener into the mirror, so you just press a button in the mirror instead of having to grab a different device. And it runs on a 12 volt feed! The invisicord product allows you to plug any 12 volt device directly into the mirror, but splicing off the electricity that powers this mirror. So I checked voltage and polarity to the 3 wires (red, black and black and white) going to the mirror, and confirmed that black was neutral, red was always on if the car was or not, and the white/black appeared to be 12 volt switched power, only coming on when the car was on. So, I cut the cable for the power interruptor, affixed in the invisicord ends to the cable, and plugged them in. The camera did nothing. It should have turned on as soon as the power was connected, as I connected to the always on power. I pressed the start button on the power interruptor, and the camera immediately powered up. After a few seconds, however, it started displaying LoPo, which is its signal indicating it has low power. I set the interruptor to 12v output and to stop supplying power when the battery reached 11.8 volts. I confirmed that the power coming through the homelink mirror was about 12 volts. The power coming through the other end, even though output voltage was set at 12 volts, was measured at 5 volts. I tried every combination of output voltage setting and it always stayed at 5 volts. Somehow, the power interruptor was dropping the voltage when it should have been passing it directly through. After dealing with this for a long time, I decided to just skip the power interruptor, as it was apparently malfunctioning.

So, I switched the invisicord tips to the power cable from the camera, bypassing the power interruptor. It came on right away and stayed on. Or at least it looked that way. In fact, it never appeared to turn off, but about every 30 seconds, the display very briefly went blank, then it immediately started the startup sequence again. We had to go to a party, and so I tested it out while driving, and if I recall, it stopped doing this as I was driving. Great, I thought. When I got there… strange things started to occur. When I powered the car off…. the car wouldn’t turn off. I initially thought it did as the engine went silent, but then AC kept blowing at me and the dashboard was still lit up, or at least parts were. I turned the car off and on again… same thing. So, I decided that I should just disable the thing by unplugging it… the car immediately shut down. After the party I had to go to work (8pm to 3 am shift… ugh). I plugged the camera in for driving and it seemed to work well. Got to Burien, where I work, and was in line at Starbucks, and I got to thinking… the Prius has a tiny 12 volt battery, and I don’t really want to finish a shift at 3 am and then find my battery dead. So I figured that i could just move the positive plug from the always on wire to the wire that was active only when the engine was running.

This, it turns out, was a big, HUGE mistake.

Immediately after this, I didn’t notice anything odd. There were no sounds, there was no indication of anything going wrong. Then I looked down at my dashboard… it was displaying a blinking “no gas” icon. Now, I had filled it less than 50 miles before, so there was no way it was out of gas. I stared at it, blinking a few times. Hmmm. So I decided to turnoff the car and back on again to see what was going on. On restart, everything looked ok except the gas was still flashing. Then, after about 5 seconds, all hell broke loose. All of the indicators on the dashboard went into full frenzied failure mode. The multifunction display (MFD) said P/S on it, and the touch screen wasn’t active anymore to change settings, the radio wasn’t working. It said my tires were flat, it said the parking brake was engaged. Like the HAL-2000, it was going insane. And the air conditioning system lost its mind. It started blasting hot air into the cabin. The indicator for what gear the car was in was going nuts, as well… park was indicated all the time, but every second it flashed so that the background behind all of the letters, D, N, R, B, P etc (apparently called the “running mode indicator”) were lighting up. This kept going no matter what gear I moved the indicator into. I quickly unplugged the camera. The motor did turn on, and I was relieved to find out that despite the flashing running mode indicator, it did continue to respond to the stick shift and did move forward when I pressed the gas. I was even more pleased to find that the brakes still worked fine.

Unfortunately, I found out fairly quickly that the steering had become an issue. I was able to turn the wheels with a great amount of effort-- it seems that the p/s warning on the info panel means that power steering is deactivated. Man how I now appreciate power steering in the prius… making a sharp corner is VERY hard without power steering. Anyway, I managed to make the crippled car hobble to work without an explosion or fire, but it was less than a mile. Let me just tell you that I was pretty distracted during my shift at work. Fortunately it was not busy, and I got to spend quite a bit of time on the internet trying to find out what was going on. I thought I might have friend the car’s computer.

It is hard to find any information on similar problems as this, it turns out. What is the proper search term for “my prius has P,D,R,N,B all blinking, power steering doesn’t work, and p/s indicator light is on after trying to tap power from a home link mirror.” That particular search turned up nothing. Nothing else really did either, untilI found one where someone tried to tap power from their home link mirror for a radar detector. He also had some problems, but not as extensive as mine, and it turned out he had fried a fuse.

So, I was hoping that was the case, and at the end of my shift, I went out to face the car. My intention was to pull a bunch of fuses and see how they all were, but it turned out the tool to pull the fuses was not where it was supposed to be, so I was stuck driving home this crippled car. To be sure-- I expected it to fail at some point on the trip and I would be stuck at the side of the road. All I wanted to do to feel successful was to get in range where I could call AAA and have them tow it to my location (I think they tow up to 20 miles, and work is 26 miles from home). So, my plan was to drive until it broke down, then to call AAA. Remember, every error that could be was displaying. I had the hot air blasting against me and had no control. If I had no control of that, then what is the cooling system inside the car doing? I couldn’t even see how fast the car was going, and I was driving slower than everyone else, as I was never sure the steering wouldn’t fail completely. Moreover, I had no idea if the battery was being charged normally, if it was draining to empty or if it was being overcharged… any of these things could be disastrous for my trip. But, somehow, it managed to limp back home.

This morning I managed to find an alternate tool to pull the fuses… sure enough, the ECU-IGN fuse was blown. It was a 7.5 amp fuse, and I cannot imagine how this could have been blown by a very low power camera… it should not have shorted anything.

Anyway, a quick trip to the auto store to buy a replacement fuse, and a brief 5 minute disconnection of the 12v battery, and the car acts like nothing ever happened.

So, for those of you who don;t want to read this whole diatribe, the motto of the story is this:

DON’T USE AN INVISICORD ON THE HOMELINK MIRROR OF A PRIUS!

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Fermentation controller part 1

I brew beer.

I’ve been doing it for the last 2 years, more seriously than I did in College. And I am going about it in an all out sort of way. I ferment in stainless steel conical fermentors, I have
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created temperature controlled heating belts to control temps in winter, so I can get them exact, and I have pursued consistency to a RIDICULOUS extent. As one home brewer pointed out- you can make great beer with a bucket and some parts from the toilet. The problem is getting it perfectly repeatable every time. So I have built an expensive and overly high tech brewng controller, multiple devices for various aspects of brewing. The one thing I have not done, and it is mostly because of size, is to convert a refrigerator or freezer into a fermentation temperature controller so I can brew all year round and be able to make repeatable beers. I live in a 1000 square foot house with a wife, 2 kids and a new puppy. There is NO space for anything. At the moment, I brew beer like a madman all winter and spring long, because once summer hits, I cannot keep the beer cool as it ferments, and as such, I get funky flavors and unrepeatable results.

I thought I was doomed to brew only in winter, until I saw a thread on homebrewtalk.com titled “conical fermentor heater/cooler.” This page showed a link to the manufacturer of my conical fermentor, and had a guy who had just built a cooling unit based on little 9 amp Peltier coolers for computer CPUs. The build was simple, not pretty and not refined, but it looked like a space saving and very effective way to cool a fermentor, without having to purchase a whole refrigerator, which I
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just don’t have room for. And it was cheap.

It became clear immediately that this would become my next big project. I would change the design a bit, but use exactly the same Peltier coolers, and the same general idea, which involves milling 2 pieces of aluminum to precisely fit the outside dimensions of the fermentor, so that I can attach the pelters and transfer as much heat as possible out of the fermentor and into the surrounding air. The original design uses a heating pad in addition to the chillers, and uses an aquarium thermostat which can control both heating and cooling. These controllers are “on-off” types… if the temp is lower than set point, it turns the heater on, and if above the set point it turns the heater off and the chiller on, etc, within a hysteresis band that is generally 1 degree wide. I am forgoing the heating pad, and using a PID controller to keep the temperature within 0.1 degree, and just reversing the polarity on the Peltier’s to provide heating. The big downside to my design is that in order to switch fem heating to cooling, I have to actually manually flip a switch. But, since I already had a PID and a high quality RTD temperature probe, I thought it better to just use this. Besides, I like the tighter control of temperature and I figure that in summer I am not going to have to do any heating, anyway, so most of the time I will just need to sweet it to heat or cool based on the season. OH--- and then after planning on doing it this way to save money, I decided to spend even more to buy a programmable pid that allows me to program a set of temperatures, times, and ramp times. Do I need it… nope. But it gives me a capability that I otherwise wouldn’t have had.

Now, form factor matters to me. I don’t want lots of stray wires all over the place, nor something very ugly to look at, and I do not want something that will be a hassle to set up and use. And I tend to like a little bling in my electronic devices to make them look good. So rather than follow this guys plans, I adapted them so I will have a simpler unit, with detachable heating units that can be unplugged for easy
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storage, and inst
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ead of 4 wires going to each side of the box, I will use a single 4 wire sheathed cable to control everything on the heating elements.

So, I bought the things needed and started going. On a previous project I bought an XY table for my drill press, so I could run it as a badly functional milling machine. This came in very handy for creation of this project, as the internals of the box have lots of grooves and structure that makes it difficult to get things to fit just right. I slowly had to mill away some of the protrusions on the enclosure so all of components would lie flat. I did this VERY slowly, taking no more that about 1/2 mm on each pass to make sure I wasn’t putting too much stress on the machine. It is a cheap (but still highly effective) Skil brand drill press, but even the best drill presses are really not intended to be used as mills. The chuck is held on entirely by friction and could pop off at any minute, flying through the air with a very sharp end mill on it. Yikes. And they are not built at all for lateral forces, which make the chuck even more likely to fly off, and can screw up the bearings. But a mill costs thousands of dollars, and my drill press cost about 129 bucks. So I just took it unbearably slow so I would’t put too much pressure on the bearings. And I said a little prayer before turning on the machine each time.
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I started with an 8x14x4 modular aluminum project box from ebay, planned the layout in illustrator, and then started drilling holes. The second picture above shows the areas that I milled on the inside. Initially I tried to just use my dremel, but it was taking approximately forever, so I abandoned that. Besides, I was doing it handheld and am sure I would have found a way to cut my finger off or something.

My biggest dread was making the holes for the top of the box. I needed to fit 2 components in that , according to my drawings would be an incredibly tight fit. Add to that that each component had only a 1.5mm lip on the outside to hold it in place-- if I made a cut too large by only 1.5mm, the component would just fall through. In previous projects I had just used a jigsaw to make the cuts, but I really didn’t want to screw this up. I marked the thing about as accurately as I could, went at it with a drill and a skill saw, cutting well within my margins. The IN got out the end mill again,as that would allow me to make perfectly straight cuts and trim off less than a mm at a time until I had it perfect. Thus worked very well, but at the end I still got out the hand file to make nice sharp corners, and to make a few bulges in places where the power supply bulged. I got the cutout PERFECT… not even the slightest wiggle. Thank god for my little “milling machine.”
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Homemade Sous Vide Immersion Circulator

One great thing about a parent at Evergreen, the school where my children go, is the number of parents with very intense hobbies and interests, that they pursue to the extreme, and enjoy talking about. Some of them, in particular, are foodies and pursue their efforts with almost ludicrous intensity.

These are people who read Charcuterie, then go out and build a sausage curing house, with temperature and humidity control, or spend hours at a time standing next to a Barbecue for a full 24 hours to make sure the brisket is just right. I have my own ridiculous foodie attributes as well, like making pizza dough that takes 5 days, maintaining 4 sourdough cultures, and going to ridiculous lengths to brew beer that could just as easily have been brewed with a bucket and a few parts from the toilet.

But, I have gone a step further into geekiness now. After making my complicated beer brewing setup, I started to feel very comfortable with electricity. I think it was one of my friends from Evergreen that taught me about Sous Vide cooking. Sous vice, for those who do not know what it is, is a method of cooking food in a temperature controlled water bath, vacuum sealed in a plastic bag. Sounds kind of gross, really. But with it, it is possible to do some things that are difficult or impossible to do in any other way. You can make amazing textured eggs with this, PERFECTLY cooked steaks from edge to edge, no matter how thick, and you can turn a piece of $2.99/lb chuck steak into essentially filet minon, but with FLAVOR. Pork Belly confit is unbelievable with this.

Originally, as my friend did, I built a sous vide machine based on plans from
Seattle Food Geek and was pretty happy with it. After building it, I became concerned about a few things-- first, it was not properly grounded, second, the holes I made were, shall we say, imperfect, so there was some condensation inside even after sealing with silicone, and the heaters stuck down a short distance only, so of any evaporation occurred, the elements would go dry and burn out. This was not a modular design in which components would be easily replaceable if they burned out. In addition, there had been several web accounts of the thing getting so hot that it melted the plastic housing. Finally, the small, yet cheap, pumps that run the device will melt if the temperature gets above 150 degrees. This is fine for most meat, but you can’t do vegetables and you can’t do confit.
sousvidedesign1

As I enjoy my life, and don’t want it to end too early, I decided I would try something new. I decided to design and build a modular, grounded immersion circulator, with easily and cheaply available replacement parts, with quality components and a higher maximum temperature. Since I wanted both the water and container (if metal) and the actual device itself grounded, and with GFCI on the cord so it will be safer anywhere it is plugged in, even a non-GFCI outlet.

I designed the immersion circulator out of aluminum tubes and plates, available at onlinemetals.com, and a few rubber mats to waterproof the connections. To the right are the schematics for the box construction and the general design. It is basically a 5x5x5 aluminum box (0.25” thick) with a 3x4x8 inch aluminum tube below it, and a plate welded into the tube to separate the wet side from the dry side. The most difficult part, I think, is the cutting of holes in 1/4” thick aluminum and trying to fit and braze a plate into the bottom, water containing tube. Ultimately, I gave up on brazing and just used JB weld. The heating element just needs a hole in the plate that is tapped for 1” NPT threads, and the other two holes in this plate are 1/4” NPT tapped holes to hold a RTD temperature sensor and a 1/4” NPT compression fitting, to waterproof the electrical cord going from the wet side to the dry side of the box. For a full sized PDF of the diagram, click on the picture and it will open a new window.

The pump I am using is a Rule il200p. It is good to 176˚F and rated for continuous duty, and pumps 200 gallons an hour, providing plenty of power. The heating element is a simple and cheap Camco 1500 watt water heater element. Inside the dry part I have two Auber instruments PIDs- one to control the water temperature, and another hooked to a detachable needle style k-type thermocouple for monitoring the temperature of what you cook. The thin probe can be inserted directly into the bag through a piece of closed cell foam tape, and it does not break the vacuum. Because I could not find an adequate pump that works on 120v, I had to buy a 5 amp 12 volt power supply through ebay that was incredibly tiny. This is the only power supply that could fit inside and still provide enough power for the pump and to drive the cooling fan. As a matter of fact, when I slightly scaled up the power of the fan, the whole thing crashed. Since it is all metal, and screwed together, there is no electrical resistance throughout the entire body, connecting the internals, the water, and the pot to which the unit is clipped to the ground wire, and the GFCI outlet makes it so if there is a current leak, it will shut off within milliseconds. For the outlet, I included a 1/2” NPT threaded hole, so that depending on how much water I want to circulate and with how much force, I can screw in various sized NPT hose barb adapters depending on the application it is being used for. And lastly, because of the design, the chamber containing the heating element will trap air above the outlet. As electric elements should never run dry, I included a push button air purge valve in the upper part of the box. When starting up the machine, it has to be purged of air before it starts firing the element. Also, as I may want to have notification if the temperature fluctuates more than 1 degree, or if the meat gets to its internal temperature, I placed an audible alarm on the unit as well.

Now, one thing I am not is an electrician, specifically, not an electrical engineer, and I am not very good at drawing electrical plans. So, I have made the below diagram to show how it all ties together, but it is pretty ugly.

SousVideElectrical

After cutting the holes and drilling and tapping holes necessary to hook the thing together, it worked PERFECTLY. That is until I tested the boundaries at 180 degrees for 36 hours. After about 24 the pump AND the fan had failed. I changed the design slightly afterwards to externalize the fan, which makes it much more spacious inside and allows it to be changed without having to open up the entire body. It is working flawlessness again, but I will now keep within the stated maximum temperature of the pump.

Here are a few shots of the finished project
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Lastly, I have a video of the machine running, but it is HUGE! I will place a link to it
HERE. Sorry, all I have is my iPhone for movies and I am not sure how to scale down, so this is a full 1080p HD quicktime movie.

If anyone has any questions, please feel free to contact me! I would love to help you build something like this. It is, I believe, as functional as the professional immersion circulators with a much lower cost ASSUMING YOU ALREADY HAVE THE TOOLS. It requires a drill press, a bunch of drills and taps, and a good quality metal file, as coarse as you can get. The total cost of the project was less than 200 dollars. Once built, it is very easy to replace anything that breaks, and it does not require sending the unit to a repairman, and therefore is quite inexpensive to fix if something goes wrong.
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