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Gadgeteer and the Foodie - Sous-vide Gadgeteer style


#1

So I had these old cheap nasty pork chops in the freezer and no matter how I cooked them the vision and flavor of shoe leather came to mind, but of course being a true Scot, there was no way in hell I was chucking them out and being a Foodie I thought Sous-vide might be a way to cook these. Now Sous-vide cookers are rather expensive so once again my Scottish side kicked in so I thought I’ll make my own using Gadgeteer and a Crock Pot. The idea is rather simple as Sous-vide is French for ‘under vacuum’ and given the cooking temperature isn’t that hot (145 F is what I used), a freezer bag would be good enough and for the vacuum, well a straw and reverse lung power worked OK. A crock pot full of water and using Gadgeteer with a thermocouple and relay module for a controller and a sous-vide cooker I had. So into the crock pot they went and up to temperature and then after a couple of hours (wanted to be sure now), diner was served after I gave the cooked chops a quick sear.

Lessons learned

  1. no amount of cooking technique can save a crappy cut of meat, but the Sous-vide did the best job cooking these that we have tried. I’ll be doing this again with a better cut of meat (I did manage to use all the pork chops I have left in the freeze so big bonus there).
  2. check what happens when you power off the crock pot and then power it back on. The pot I used to test last night, powered back on, the pot I used tonight didn’t so I had to manually turn it on. Funny thing is I thought about this last night and included an alarm (Justin’s buzzer module) so once the set cooking temperature was reached if the temperature then fell below a set limit the alarm would go off, which alerted me to this limitation of the big crock pot in time to save diner.
  3. despite how much my wife tells me I suck, a vacuum sealer would be helpful.
  4. I was surprised at how well the crock pot held its heat and used less power then I thought it would.
  5. once again Gadgeteer Rocks!!!

#2

Hey bawe bag, you call yourself a Scot and you use deg F in your code!! Tut tut. :slight_smile:

This is pretty neat. I was thinking of the same idea after my friend used a Raspberry Pi to build his. I like the Gadgeteer way and I have a nice shiny new 5" TFT LCD sitting waiting for an excuse for a project (oh yeah, details of this Gadgeteer compatible display to be announced soon)

Did you write your own PID for this?


#3

I’ve never really figured out the resistive or inductive load differences that makes a pure relay switching of mains AC a good or a bad thing (versus a more complete zero-crossing detection, SSR solution).

I too would be interested to hear about how your control algorithm worked, and the tolerances you used. Personally I’m trying to find the right cooking device for a sous vide as strangely I don’t have something that will suffice (and the Scot in me says “don’t spend money on that, re-use something you have”)


#4

Are you talking about that Newhaven display? :slight_smile: Please give us more details! The funny thing I was also thinking of making this display gadgeteerable…


#5

It sure is. Got the PCB’s from DFRobot yesterday and just need time to solder the parts to it.

Drivers will need a bit of work. On the G120 it works fine with the I2C hardware bus but failed badly with G400 so I ended up with software I2C on there but the difference in graphics speed on the G400 compared to the G120 is big.

Have never gone about creating drivers before so will have to look at how the T43 etc are done.


#6

@ Dave McLaughlin funny you should mention deg F and PID as my original idea was to use a PID algorithm that we are working on as a missile guidance system for intercepting so called stealth aircraft by tracking their perturbations against various background radiations including natural atmospheric ‘temperature ribbons’ we call very small scale weather patterns (we use deg F for all the obvious reasons). Then I gave my head a smack and realized the crock pot has an ‘on’ and ‘off’ and the gadgeteer thermocouple module uses a MAX31855 chip and has a temperature resolution of about 0.25C giving a thermocouple accuracy of ±2°C, so I dumped the PID and went for a fast action/feedback loop after all I’m unleashing a Raptor on this so I’ve got speed to burn, puke, and generally waste like a drunken sailor on shore leave after a year long deployment on a sub. So control is simply is the temperature under my target, turn on the crock pot. If the temperature is over my target, then turn it off. Now the fact that this is a large water bath works out rather well as water has a lovely high thermal capacity so its happy to soak up heat and then slowly give it off so I can slog around a little on heat as long as I’m mindful as to the minimum temperature and duration times to cook/pasteurize the meat (I liked this site as he goes into some of the science of cooking http://www.douglasbaldwin.com/sous-vide.html ). I did check my thermocouple temperatures against a food thermometer a couple of times, but of course differences between the two leave you to guess which is right or at least closer to right, so you tend to err on the high side (its $5 cooking thermometer, remember I’m Scottish as I suspect you are as well).

Now all that said, there were some heating performance differences between my test crock pot and my cooking crock pot as the one I used for cooking seem to have a bit of a latent heating effect perhaps due to a difference in heating the stoneware liner so when I do this again with this pot I’ll adjust my control points a bit. I was perhaps a bit overstepping my newbie sous vide skillz by doing a bunch of chops in a large crock pot, so I think my next attempt will be a couple of chicken breasts in a rice cooker (after I ensure it handles a power cycle correctly) as I’m interested in how much of a difference the stoneware liners make in the crock pots, but I think ultimately the crock pots will be my sous vide cookers.

The funny part was my wife had thought I’d totally lost it (boy do I have her fooled as I totally lost it years ago) with trying sous vide and so anything less then killing us via food poisoning would be a win in her books, but she was pleasantly surprised how well this turned out. So I think I’ll pick up a vacuum sealer and give this another go.

The first version of my sous vide threw all its data etc onto Open.Sen.se but when I decide to crank the action/feedback loop I yanked the data upload code as I was worried I would exceed my upload rates for Open.Sen.se plus we really need to move to 4.3 to get around some of the network issues (ie my Great Network Shootout https://www.ghielectronics.com/community/forum/topic?id=14607 )

All in all a very successful Gadgeteer experiment and another example of me just having some good fun with Gadgeteer and learning about sous vide.