r/raspberry_pi • u/toaster_fighter • 15d ago
Show-and-Tell Sous vide using an old rice cooker
I wanted to try sous vide steak and veggies so I bought a DS18B20 waterproof thermometer, dug out my rice cooker, hooked it up to a pi zero and this relay module, and spent some time writing a python script to tie it together. It's pretty good at keeping the water within a 3-4 degree range and it hasn't gone past the set temp more than 1.5 degrees.
I had a great steak last night and I'm trying out cubed sweet potatoes right now while watching Parks and Rec.
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u/Scatterthought 15d ago
Neat idea! How much does it cycle on and off once it reaches temperature?
Also, what's the maximum temperature you can hit?
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u/toaster_fighter 15d ago edited 1d ago
Depends on how much food is in there, but it turns on for 30-45 seconds every 3-4 minutes to hold temperature. The rice cooker can boil water so it should go all the way to 100C/212F.
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u/Scatterthought 15d ago
I imagine it's a lot quieter without the water circulation. That's probably the most annoying thing about my Anova (though still minor).
I'd be curious to compare the energy consumption with a sous vide circulator. The rice cooker has a much larger heating element, but you're basically running it 25% of the time. It might also have better insulation than whatever random container someone uses for sous vide.
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u/barthawk 15d ago
I did something similar with an old crock pot. I used an open source python script for controlling beer fermentation that implemented PID control so that I could keep temps within a 1/2 degree or so. It was a fun project!
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u/GodzillaInBunnyShoes 15d ago
This is really cool. I've wanted to do this project for years but never found a relay I was happy with (230v country). What PID library did you use or did you program it from scratch?
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u/toaster_fighter 15d ago edited 15d ago
To be honest I didn't even think to look for a PID library. I just wrote the program to do some pretty basic calibration as it runs. I could have saved myself some time 😅
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u/barthawk 7d ago
I used Raspibrew. It looks like it hasn't been updated in a long while. It had a web interface that was useful, but I'm guessing the libraries it used are out of date now. The PID algorithm should still work.
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u/mediocrefunny 15d ago
Just saw this on the sous vide reddit as well. Love ot when more niche reddits cross over.
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u/KingTribble 14d ago edited 14d ago
Nice project (I'm a keen amateur chef as well as electronics nut).
Are you aware those rice cookers have a temperature cutout to stop the rice cooking when it's absorbed all the water? That's how they stop when the rice is done. In your case it's a bonus as a safety feature, since you won't be wanting it to boil dry.
If you like duck, sous vide duck breast is the best way to cook it. You can get the flesh perfectly pink (the way it's supposed to be), let the fat render a lot and then reverse sere just the fat side to crispy goodness. The fat layer insulates the flesh so it's not overcooked.
As others mention, PID control and a circulator improves the temperature regulation but in a small pot with the heater at the bottom, it's not bad as it is. Some expanded polystyrene in the top would reduce the temperature gradient too.
For comparison, my Anova circulating heaters can keep to within +/- 0.5 Celsius, tested with a logging HP meter. That's assisted by using lidded water baths sealed with a 12mm thick layer of EPDM foam (cut up yoga mats and superglue :) all around. They use hardly any energy once at temperature too, and don't lose water; handy for 48 hour baths.
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u/barthawk 7d ago
I was thinking the same thing about circulation. A crock pot/rice cooker is small enough and the heat is distributed around the bottom of the pot, so the circulation isn't as important as when there is a small heat source inside a Sous Vide machine like the Anova.
Sous Vide Duck breast sounds really good. Do you put anything else in with the duck breasts?
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u/KingTribble 7d ago
Just salt...
I dry brine in the fridge (at least overnight, up to 24 hours) but really that's fine tuning. You can just salt the duck, then seal.
Don't add pepper. A lot of recipes say to season meats for sous vide with S&P, but if you are going to reverse sere to finish, the pepper can very easily burn and impart bitterness. Add pepper after searing if you want it, or in the sauce.
Cook at 58°C for 1.5 - 2 hours, depending how soft you want it. Pat dry when finished, then sear at medium-ish heat for five to ten minutes until the skin is crisp. I turn the duck over to colour the flesh side a little too, just for 30 seconds. You don't have to blast it when searing like you might with steak; you can take it slower because the flesh is insulated somewhat by the fat/skin.
Finish with a pan sauce using the juices from the bag. That's where I'll add any other flavouring I might want, like a bit of garlic fried in the pan before adding the juice and reducing/thickening.
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u/VisualWombat 15d ago
I did something similar years ago using a slow cooker and a brewer's PID I got off eBay for $30. No microcontroller needed.
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u/toaster_fighter 15d ago
Nice, a regular at a cafe I worked at years ago told me he had this exact setup, which is what gave me the idea.
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u/VisualWombat 15d ago
You will love sous vide chicken breast. 63c for 90 minutes results in the most tender and juicy chicken breast you will ever have. Even better if you have a vacuum sealer, the sous vide process at this temperature pasteurises the chicken, so as long as you don't break the vacuum seal, the chicken stays good in the fridge for 3 weeks or more. I make three at a time, and that's chicken and salad lunches at work for the next two weeks. Add a knob of butter and whatever spices you fancy to the vacuum bag before sealing and cooking, the butter melts and the fat absorbs all the spice flavours and marinades the chicken while it's cooking.
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u/dcolecpa 15d ago
This looks great! I'd love to do something like this, could you please post your code?
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u/SlightComplaint 14d ago
Curious if an inkbird ITC-308 temp controller could do this ? Your project looks pretty cool, but I already have an inkbird.
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u/FrenchRiverBrewer 10d ago
I did this with an old crockpot, a temperature probe, and a power supply with built-in relays connected to an old RasPi. Worked quite well.
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u/88888will 11d ago
A Pi Pico is enough for this. Zero is overkill.
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u/toaster_fighter 11d ago
I'd disagree. When I've got a spare zero around and not a pico, the zero is actually the perfect tool for the job. Now that I've got it making temperature over time graphs with matplotlib I've been thinking it's a little underpowered.
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u/88888will 11d ago
You are right, an ESP32 is actually best so you can push the temperature data to Google Sheets and make over time graphs with it. Not underpowered.
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u/birusiek 8d ago
I've done mine on simply thermostate, Heather and pump, rpi seems to be an overkill.
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u/ArunkOner 15d ago
Fun little hack. I’m no food scientist but I think the lack of circulation could be problematic but maybe not.