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.
I 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
Interesting 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]
One 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:
The 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?
Bimetallic strips are still used these days, but it is often not the only trigger.
The bimetallic strip is for overcurrent protection over a period of time. For example, if you are running an appliance using a constant 15A on a 10A breaker. The breaker will pop, but not instantly, and I guess you may have to wait a bit for the metal to cool down, though it never happened to me.
But there is also a short-circuit protection, it uses a solenoid to quickly trip the breaker when the current is way over its rating. The fancier types (with GFCI) also pop if the return current is not the same as the input current, this is to prevent electrocution.
Modern 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.
They're still built that way: it has the benefit of properly handling slightly over current for a short period vs massively over-current: the former is permitted and necessary for many loads.
My late model Subaru uses this cheap solution for the protection of the infotainment system. If it trips I need to wait for it to cool down for about an hour.
> 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.)
What’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?
Both. 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.
>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.
From 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.
> 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.
> yogurt requires a constant temperature over a specific length of time.
No it doesn't. I make perfectly good yoghurt in an old glass vacuum flask by heating a litre of milk to 80 C, allowing it to cool to 50 C, adding 60 g of live yoghurt, pouring it into the vacuum flask, putting the lid on and leaving it overnight.
There other inaccuracies. To give just one example:
>One of the key differences between the Japanese and Chinese rice cooker is that the latter has a glass lid, which Chinese cooks demanded so they could see when to add sausage.
The average Chinese rice cooker looks exactly like the Japanese ones. Cookers with glass lids exist but are uncommon in China. In fact if anything, I've most often come across those glass lid ones in the West, not in East Asia. Also the sausage part is so random, lol.
The article is badly researched. A couple of years ago I'd have said I'm shocked a university professor wrote this, but frankly at this point it's to be expected.
right, you don't need a constant temperature to make yogurt.
in india, people don't even measure the temperatures as you mentioned.
we just boil the milk (to sterilize it), let it cool some amount, put in the curd (indian english term for yogurt, dahi in hindi, thayir in tamil) starter (which is just curds from a previous batch), mix, and leave it covered for a while, typically overnight, anywhere in the house, or in a cooler or warmer
part, depending upon your location and ambient temperature. the milk automatically sets, by the action of the bacteria, and becomes curd.
In fermentation the initial heat is usually to harm any microbes other than your preferred ones so the selected microbes have time to make the environment inhospitable to other microbes before they can do the same to the selected microbes.
Vinegar and alcohol in grape juice are two factions fighting for supremacy by trying to poison each other to death.
80c is a convenient temperature for activating naturally occuring enzimes in food for breaking down complex sugars. Similar, but food specific, holding temperatures are used for beer brewing, french fries, and other foods with complex sugars.
Been making yogurt at home for years. I just heat milk to the point when it's just about to boil over. Never measured the actual temperature, but I'm pretty sure it's less than 100C. I just cool it until it's warm to touch (about 40-45C) before adding the culture (a spoonful of last day's yogurt), then leave it overnight in the oven with the pilot light on.
I find that the yogurt is thicker when I initially heat it higher. My understanding is it changes some of the proteins, resulting in a higher curd yield.
It's pasteurisation, your 50C-only yoghurt would potentially not last as long; possibly even succumb to unwanted bacteria before (or the wanted be outcompeted by the unwanted) turning to yoghurt.
I don't measure it to 80C, just heat milk until it breaks then switch off and let it cool. I didn't have a thermometer when I first made it, but now I might measure that it had cooled enough. I wouldn't say it has to be as hot as 50C, you just probably don't want it hotter, so if you're making it without just let it cool to tepid, feeling warm to the touch, then add whatever you're using. Cheese similar, just more specific cultures.
(And I suppose if you really get into it, the specific temps and holding them thing is a lot more true for cheeses - or rather for different types - than it is for yoghurt.)
You should follow the guidance and use a candy thermometer to kill the nasties.
Once you make a few batches, you can usually eyeball it, different milks will act subtly different at temperature. Heating also changes how milk components can consumed by the cultures. I get milk from a farm that doesn’t homogenize it the same way as store stuff - the skin develops on the surface sooner.
Personally, I prefer to use a yogurt maker that keeps it at a consistent temperature. But you can make great yogurt in a variety of lower tech scenarios.
A vacuum flask keeps the temp pretty consistent for a long time though. I doubt anyone thinks it needs to be perfectly consistent, just within the range that the bacteria can survive.
Technology Connections is generally awesome, but this particular video was even more fascinating than its usual.
Instead of a bimetallic switch like discussed earlier in this same HN thread, there's a lump of metal in contact with the pot, which stops being responsive to a magnet at a certain temperature (past its curie point) and that's what triggers the switch from "cook" to "keep warm" (and yes, of course it all works due to the huge latent heat of water).
So they came up with an alloy whose curie point is just above water's boiling point, and thanks to that, the circuit, nah, the whole thing is comically simple - just a shunt, a spring, a big resistor and the heating element (and ok a led or 2). The weight of the pot is also acting against the spring, ensuring you can't actually select "cook" if the pot isn't there. This is so brilliant.
Came here to point folk to this video. The article seems to gloss over a lot of how modern rice cookers actually work. It involves latent heat of water, magnetism, and the Curie point, as explained in your link.
"It isn't often" doesn't mean "it has never happened".
If anything, only listing 8 only proves their point. To disprove their point you'd need to list hundreds of housewives. Possibly thousands given the number of patents out there.
Entire books have been filled with home remedies, sewing ideas, and cooking methods. You could, perhaps, cite the editors of those books, but the "individual housewives" who contributed them would not have traceable identities.
The ideas and methods were shared among communities, church groups, in schools, and handed down in families. Often by oral tradition and by illiterate people.
In modern times, you could check the archives of Heloise, and magazines such as Good Housekeeping and Sunset. Columnists would usually receive hints and tips from readers, and give credit at that point.
Fumiko Minami(三並風美子)'s knowledge and contribution to the development of the rice cooker is greatly appreciated, but she is rarely mentioned in Japan. I think it deserves more attention.
I loved my automatic rice cooker, but I have given it up for a new love - The Pressure Cooker, in my case from Instant Pot. It does as good or better of a job as my rice cooker, but about 33% faster, and has several other useful functions. It's better at steaming dumplings; With the trivet set they also sell that's perfectly sized I can make a meal's worth of dumplings in twenty minutes with zero effort. The Instant Pot recipe Pulled Pork is almost as good as my local BBQ place, and it cooks in an hour.
On the other hand, one of my friends has a Zojirushi rice cooker, and swears by it. He describes making perfectly fluffy and buttery rice every time.
My parents had a traditional pressure cooker that was both intimidating (they convinced me it could blow up any moment) and useless for recipes when I asked them how to cook things. "Oh, just cook it for two whistles" Two what?
Instant Pot was sooo much easier. Safety interlock, unambiguous timer, much better.
I enjoyed reading the story, AND for most Americans, an electric pressure cooker (e.g. Instant Pot) cooks rice perfectly (12 minutes, 1:1 ratio of rice to water), rendering the rice cooker an unnecessary "single use device."
Bonus: instead of rice, use chicken broth, previously made in the IP, and frozen.
Bonus2: add some coconut milk. freeze the rest of the can in ziploc baggies.
Being a single use device has its benefits. Rice cookers are lighter weight than an instant pot and have a single button, making them extremely easy to operate. I find this is very helpful to me when cooking.
I only press one button ("Pressure") when cooking rice in my Instant Pot.
It remembers the last several settings I've used - one of those is 12:00 for rice.
If you don't have a pressure cooker, that's fine. But for those who DO already own a pressure cooker, I'm not sure how the lighter weight of the rice cooker is relevant. A single-use device takes up more room in the kitchen, and the accumulation of these devices just adds to our environmental disaster.
Our Zojirushi (NP-RC05, it's over 10 years old now) is actually advertised as pressure cooking the rice to make it taste better, so I guess the two devices are merging. And it has 8 buttons (you can select the rice type)
Not if all the liquid is absorbed. I cook rice like this on the stove all the time, and it's really tasty. Works well with various grains, pltho probably pearl barley is a favourite - cooked with good stock, it reminds me of risotto.
I use a pot in a pot for 12 minutes and it's ok. I use those stacking metal pots you can get at an Indian food market. I also have an old rice cooker. The convience of the instant pot is I can set a 30 minute delay to soak the rice. The newer rice cooker my mother in law has in Japan does the delay and has lines on the inside of the non stick pot to measure the water so it makes pretty good rice every time.
What if you're using the instant pot for something else (like beans, or maybe the entire rest of your dish) while you're cooking rice? A rice cooker is the best single use device because 1) you're probably having rice with 25-100% of your meals, and 2) set-it-and-forget-it; you can completely ignore it until you're ready to eat.
You can solve this placing a trivet in the pot with your rice in a bowl on top. I do this when im in a hurry and need to rustle up ruce and lentils on the double. Lentils, stock, trivet, bowl, rice, water, done.
The simple rice cooker can cook rice till all water is absorbed. Can Instant Pot do that? I think the Instant Pot cooks till the timer runs out, not till when the water is all absorbed into the rice.
If you measure the right amount of water (not optional with either solution), 12 minutes should do the trick. And you can just let it sit on the keep warm setting for some time and it will continue to absorb whatever water is left in the pot.
I actually got an instant pot recently but I haven't tried the rice cooking setting yet for the simple reason that I use the instant pot for cooking sauces and other things that would go with the rice. Also cooking rice on the stove isn't actually that hard. I don't see how this saves me time or effort. Just measure out the quantities carefully and you should be fine.
Anyway, I need less carbs in my life; not more. One reason I got the Instant Pot is cooking lentils and beans becomes really easy with it. Also am making lots of tasty meat stews. Works great for that.
Nope, it's a pressure cooker, the cooking vessel is air-tight.
My favourite recipe is to use 1:1 rice to water ratio and the adjust the time depending on the rice. For example, white rice takes 5 minutes, basmati 6, brown 30(!). When it'đ finished, wait at least 10 minutes before opening the lid, let the pressure drop naturally.
A few people mentioning pressure cookers as an alternative. A heavy claypot is the ideal manual alternative for those with a gas stove.
Probably the most popular is “kamadosan”. It makes beautiful rice and you have control over it so eg it is easy to create a crust on the bottom if you like.
Unfortunately I have an induction stove now so a bit hard to use, but I occasionally cook rice on a small charcoal stove when enjoying the slow life.
Readit News
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.
2-ish phase changes when dry ice sublimates, then later for the ice in ice cream
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[0] https://onefromnippon.com/rice-cookers/
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-outsi...
The bimetallic strip is for overcurrent protection over a period of time. For example, if you are running an appliance using a constant 15A on a 10A breaker. The breaker will pop, but not instantly, and I guess you may have to wait a bit for the metal to cool down, though it never happened to me.
But there is also a short-circuit protection, it uses a solenoid to quickly trip the breaker when the current is way over its rating. The fancier types (with GFCI) also pop if the return current is not the same as the input current, this is to prevent electrocution.
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.)
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.
Deleted Comment
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.
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.
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.
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https://users.ece.cmu.edu/~koopman/lectures/ece348/22_contro...
> yogurt requires a constant temperature over a specific length of time.
No it doesn't. I make perfectly good yoghurt in an old glass vacuum flask by heating a litre of milk to 80 C, allowing it to cool to 50 C, adding 60 g of live yoghurt, pouring it into the vacuum flask, putting the lid on and leaving it overnight.
>One of the key differences between the Japanese and Chinese rice cooker is that the latter has a glass lid, which Chinese cooks demanded so they could see when to add sausage.
The average Chinese rice cooker looks exactly like the Japanese ones. Cookers with glass lids exist but are uncommon in China. In fact if anything, I've most often come across those glass lid ones in the West, not in East Asia. Also the sausage part is so random, lol.
The article is badly researched. A couple of years ago I'd have said I'm shocked a university professor wrote this, but frankly at this point it's to be expected.
in india, people don't even measure the temperatures as you mentioned.
we just boil the milk (to sterilize it), let it cool some amount, put in the curd (indian english term for yogurt, dahi in hindi, thayir in tamil) starter (which is just curds from a previous batch), mix, and leave it covered for a while, typically overnight, anywhere in the house, or in a cooler or warmer part, depending upon your location and ambient temperature. the milk automatically sets, by the action of the bacteria, and becomes curd.
nothing to it. even kids can make curd.
Vinegar and alcohol in grape juice are two factions fighting for supremacy by trying to poison each other to death.
I don't measure it to 80C, just heat milk until it breaks then switch off and let it cool. I didn't have a thermometer when I first made it, but now I might measure that it had cooled enough. I wouldn't say it has to be as hot as 50C, you just probably don't want it hotter, so if you're making it without just let it cool to tepid, feeling warm to the touch, then add whatever you're using. Cheese similar, just more specific cultures.
(And I suppose if you really get into it, the specific temps and holding them thing is a lot more true for cheeses - or rather for different types - than it is for yoghurt.)
Once you make a few batches, you can usually eyeball it, different milks will act subtly different at temperature. Heating also changes how milk components can consumed by the cultures. I get milk from a farm that doesn’t homogenize it the same way as store stuff - the skin develops on the surface sooner.
Personally, I prefer to use a yogurt maker that keeps it at a consistent temperature. But you can make great yogurt in a variety of lower tech scenarios.
Instead of a bimetallic switch like discussed earlier in this same HN thread, there's a lump of metal in contact with the pot, which stops being responsive to a magnet at a certain temperature (past its curie point) and that's what triggers the switch from "cook" to "keep warm" (and yes, of course it all works due to the huge latent heat of water).
So they came up with an alloy whose curie point is just above water's boiling point, and thanks to that, the circuit, nah, the whole thing is comically simple - just a shunt, a spring, a big resistor and the heating element (and ok a led or 2). The weight of the pot is also acting against the spring, ensuring you can't actually select "cook" if the pot isn't there. This is so brilliant.
* https://www.fastcompany.com/3047428/how-two-bored-1970s-hous...
* https://en.wikipedia.org/wiki/Margaret_Rudkin
* https://en.wikipedia.org/wiki/Harriet_Tubman
* https://en.wikipedia.org/wiki/Roberta_Williams
* https://en.wikipedia.org/wiki/Susan_B._Anthony
* https://en.wikipedia.org/wiki/Anna_Sutherland_Bissell
* https://en.wikipedia.org/wiki/Elizabeth_Blackwell
* https://en.wikipedia.org/wiki/Mercury_13 - Not housewives, but absolutely worthy of more praise and attention, especially Jerrie Cobb.
And many more
"It isn't often" doesn't mean "it has never happened".
If anything, only listing 8 only proves their point. To disprove their point you'd need to list hundreds of housewives. Possibly thousands given the number of patents out there.
The ideas and methods were shared among communities, church groups, in schools, and handed down in families. Often by oral tradition and by illiterate people.
In modern times, you could check the archives of Heloise, and magazines such as Good Housekeeping and Sunset. Columnists would usually receive hints and tips from readers, and give credit at that point.
This feels like an argument only for the sake of hearing one's self out loud, a poor man's denying the antecedent fallacy.
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On the other hand, one of my friends has a Zojirushi rice cooker, and swears by it. He describes making perfectly fluffy and buttery rice every time.
If your rice is buttery I think they're doing something wrong.
Instant Pot was sooo much easier. Safety interlock, unambiguous timer, much better.
https://www.amazon.co.jp/s?k=%E5%9C%A7%E5%8A%9B%E7%82%8A%E9%...
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Deleted Comment
Bonus: instead of rice, use chicken broth, previously made in the IP, and frozen.
Bonus2: add some coconut milk. freeze the rest of the can in ziploc baggies.
It remembers the last several settings I've used - one of those is 12:00 for rice.
If you don't have a pressure cooker, that's fine. But for those who DO already own a pressure cooker, I'm not sure how the lighter weight of the rice cooker is relevant. A single-use device takes up more room in the kitchen, and the accumulation of these devices just adds to our environmental disaster.
(Rice Cooker calrose recipe: Weigh the rice. 1.1 times the mass of the rice is the amount of water you need.)
It's funny how upset some people get by that method.
Now soups, veggies, artichokes, enchiladas, ... For those things, the instant pot is awesome. =)
I actually got an instant pot recently but I haven't tried the rice cooking setting yet for the simple reason that I use the instant pot for cooking sauces and other things that would go with the rice. Also cooking rice on the stove isn't actually that hard. I don't see how this saves me time or effort. Just measure out the quantities carefully and you should be fine.
Anyway, I need less carbs in my life; not more. One reason I got the Instant Pot is cooking lentils and beans becomes really easy with it. Also am making lots of tasty meat stews. Works great for that.
My favourite recipe is to use 1:1 rice to water ratio and the adjust the time depending on the rice. For example, white rice takes 5 minutes, basmati 6, brown 30(!). When it'đ finished, wait at least 10 minutes before opening the lid, let the pressure drop naturally.
Probably the most popular is “kamadosan”. It makes beautiful rice and you have control over it so eg it is easy to create a crust on the bottom if you like.
Unfortunately I have an induction stove now so a bit hard to use, but I occasionally cook rice on a small charcoal stove when enjoying the slow life.
Review: https://thejapanesefoodlab.com/kamado-san/ Recipes: https://toirokitchen.com/blogs/recipes