7 ms·
This is known as bang-bang control, a very basic form of negative feedback. The key insight, which may not be emphasized enough in the article, is that the ves
by ngneer 2y ago
This is known as bang-bang control, a very basic form of negative feedback.
The key insight, which may not be emphasized enough in the article, is that the vessel can only rise to above 100C once all the water has changed phase (boiled).
I think this is the same principle explaining why beach popsicle vendors can carry many items on a hot summer day without them all melting right away. There is insulation, for sure, but in addition the temperature of what is effectively a large volume ice cube block must rise above 0C before the popsicles can begin to change phase (melt).
In the rice cooker, this property is harnessed while a "bimetallic switch measured the temperature in the external pot". The bimetallic component means that one metal heats and expands faster than the other, eventually breaking the circuit.
If memory serves, this same trick is used in older car model turn signal lights, to produce the periodic on/off switching.
I am not asian but enjoy my rice cooker every day. I love simple robust engineering.
- l33t7332273 2y agoI think the popsicle example may be backwards - they must change phase before they can begin to rise above 0 degrees, and the phase change is a tipping point that takes a ton of energy
- deleted 2y ago[deleted]
- m463 2y agoIf they used dry ice, you would have 3-ish phase changes... 2-ish phase changes when dry ice sublimates, then later for the ice in ice cream
- Etheryte 2y agoThe same bimetallic break was used in old circuit breakers. You would literally have to wait for the metal to cool down before the connection could be restored. Not sure if it's still used or we use something fancier these days?
- delsarto 2y agoMy washing machine door works like that; BigClive has a great teardown which was quite helpful to explain to me why I couldn’t open the door! https://youtu.be/PIm7q_U3UEM?si=K6wUtHJe2Jm8tW6M https://youtu.be/PIm7q_U3UEM?si=K6wUtHJe2Jm8tW6M
- ThePowerOfFuet 2y agoHere's that same YouTube link, but without the tracking parameter linking you to everyone who clicks on it: https://youtu.be/PIm7q_U3UEM https://youtu.be/PIm7q_U3UEM
- praptak 2y agoModern circuit breakers are much fancier. They break not only when the current reaches a threshold but also when the currents passing in both directions (i.e. also back through the ground wire) are unequal. This prevents things like grounding through someone's body.
- deleted 2y ago[deleted]
- schiffern 2y ago> Modern circuit breakers are much fancier. They break... when the currents passing in both directions [is] unequal What you're describing is properly called GFCI[0] — which in some countries is referred to as an RCD[1] — not just a standard circuit breaker. You can get devices which fit into a standard circuit breaker slot which perform both functions. However a conventional circuit breaker (which are still widely available) doesn't do any of that. [0] Ground Fault Circuit Interruptor [1] Residual Current Device
- dzhiurgis 2y agoYep I thought my house has that until I tested cheap LED dome light from Aliexpress. It had an exposed screw and I was bare feet in garage (concrete floor). Lesson learned.
- Buttons840 2y ago> The bimetallic component means that one metal heats and expands faster than the other, eventually breaking the circuit. I thought the circuit that powers the cooking was broken because, when the water has boiled away, heat rises and a magnet holding the circuit closed is weakened by the heat, which allows a spring to pull the magnet away and break the heating circuit. (Magnets are weaker when hot.)
- Buttons840 2y agoI'm getting multiple downvotes here. Am I wrong? What am I missing?
- yreg 2y agoNo idea. You are correct - that's exactly how many rice cookers work. Technology Connections: https://youtu.be/RSTNhvDGbYI https://youtu.be/RSTNhvDGbYI
- gcanyon 2y agoI came to post this video! But I think it's clear that this isn't the design being describe in the original article: that mentions a double-boiler, which is not in evidence here and TC even mentions the double-boiler aspect of earlier designs at around 9:30 in the video. He also says that he was only able to trace the origin of this design back to the '70s. So it's possible that earlier designs didn't use magnetism, and the magnet-based design was a simplification of earlier water-boiling-at-100c-based designs.
- jeffalyanak 2y ago> I'm getting multiple downvotes here. Am I wrong? What am I missing? I wouldn't have downvoted you for it, but it sounds like you missed this from the article: > While the rice cooked in the inset pot, a bimetallic switch measured the temperature in the external pot. While more modern rice cookers may use curie point magnetic switches, that's not what the original rice cooker used.
- dmoy 2y agoThermostats also used to use the bimetal trick
- antegamisou 2y agoThere are also neuro-fuzzy control based devices [Slide #4] https://users.ece.cmu.edu/~koopman/lectures/ece348/22_controls_handouts.pdf https://users.ece.cmu.edu/~koopman/lectures/ece348/22_contro...
- tdeck 2y agoOne thing this article completely glossed over is that most rice cookers you find these days don't have an outer water reservoir that boils away like the one described in the article (until reading this I thought of those as "Taiwanese style rice cookers" because the only ones I had seen like this were from Taiwan). There is a difference between waiting for one cup in the outer reservoir to boil completely away for 20 minutes, and waiting for the rice+water mixture to come to a certain temperature. Edit: I ended up down a rabbit hole about why Taiwanese rice cookers more commonly use indirect heat and found this great article: https://www.taiwangazette.org/news/2021/10/23/thinking-outside-the-pot-the-bond-between-the-steam-rice-cooker-and-taiwan https://www.taiwangazette.org/news/2021/10/23/thinking-outsi...
- CarVac 2y agoInteresting, so in Taiwan at 110V a Tatung won't have the lid rattle around like mine does at 115-120V in the US?
- rendaw 2y agoTatung even makes rice cookers with stainless steel bowls!
- CarVac 2y agoThat's what I use.
- atombender 2y agoFor those in the U.S., Aroma and Elite also make stainless steel inner pots.
- bmikkelsen 2y agoInteresting tidbit: It was Sony who actually tried to build the first rice cooker, but they failed so badly that they gave up and pivoted to radios [0] [0] https://onefromnippon.com/rice-cookers/ https://onefromnippon.com/rice-cookers/
- blackeyeblitzar 2y agoWhat’s with so many Asian rice cookers advertising “fuzzy logic” and now “neuro fuzzy logic”? Is that just a meaningless buzzword? Or is it something actually useful?
- eurleif 2y agoSee: https://en.wikipedia.org/wiki/Fuzzy_control_system https://en.wikipedia.org/wiki/Fuzzy_control_system
- blackeyeblitzar 2y agoI guess to me that feels basic? Is it really something worth advertising?
- bobmcnamara 2y agoIt's typical for 50+ year old technology to be considered basic. Especially by those who may not remember the before times.
- silisili 2y agoBoth. Almost everything today uses some form of it. I think the term stuck with rice cookers because they were advertised that way as an advancement from the binary type cooker described in the article. In that sense, it's a buzzword of sorts. There's a lot of examples of that, like it still being called Unleaded Gas despite it having been so by default for how many decades? Is it useful? Hard for me to answer - I don't like rice, but most of my family does. They all swear by their Zojirushis and Tigers, so I have to imagine it provides a better cook than the old style.
- seanmcdirmid 2y agoZojirushi offers a wide range of rice cookers. We just have the basic one and it works well, but they have higher end ones that cost 4x the price that we bought ours, I’m not sure if the rice is actually better in the higher ends Zojirushis. They even have cheaper ones that use fuzzy logic, it looks more like an economy thing over the traditional non stick pressure based rice cookers.
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- bobmcnamara 2y agoThis same mechanism is how a dryer knows when the clothes are dry.
- Suppafly 2y ago>This same mechanism is how a dryer knows when the clothes are dry. I've never had a dryer where that feature actually worked. My newer samsung claims to have that, but the drying time still seems to just use the timer (even when using the sensor setting) and they clothes are almost never 100% dry when the timer runs out. I suspect maybe it'd work if the clothes got dry before the timer ran out, but the timer settings always seem to be just short of how long it'd take to dry a load.
- dzhiurgis 2y agoHeat pump driers are known not dry clothes 100% too.
- bobmcnamara 2y agoUsually for me it struggles if I'm mixing types of cloth. If there's one pair of denim jeans it'll stop when everything else is dry, but the denim isn't.
- Scoundreller 2y ago> There is insulation, for sure, but in addition the temperature of what is effectively a large volume ice cube block must rise above 0C before the popsicles can begin to change phase (melt). hopefully the "large volume ice cube" is something like a saturated salt or sugar solution so that the ambient temperature it tries to hold is colder than the melting point of the popsicles.
- billfruit 2y agoDo the InstantPot has this basic control circuit which even the cheapest rice cooker has. I ambnot finding clear information on this online.
- luckystarr 2y agoFrom my experience operating it I reckon it does the following: after you fill it and start, it starts heating and measures the time it takes to reach 100°C. This allows it (in the rice program) to figure out the amount of mass present and adjust the simmering time under pressure accordingly. Using the same trick (in alll programs) it figures out overfilling and aborts for safety reasons. Edit: I think the only sensor needed is a temperature sensor.
- billfruit 2y agoIf it had a temperature sensor it could just figure out when the temperature starts rising above the boiling point of water.
- killingtime74 2y agoNo it doesn't. Still prefer my instant pot though because it is so much faster and can make much larger volumes of rice
- dzhiurgis 2y agoCan one make towel rack/drier using same way?