# How do rice cookers and clothesdryers know when to stop? **URL:** \ **Category:** Factual Questions\ **Created:** [August 24, 2009, 11:17am UTC](https://boards.straightdope.com/t/how-do-rice-cookers-and-clothesdryers-know-when-to-stop/507484 "2009-08-24T11:17:22Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Reply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/reply/32/15952_2.png) [@Reply](https://boards.straightdope.com/u/Reply)\ **Post date:** [August 24, 2009, 11:17am UTC](https://boards.straightdope.com/t/how-do-rice-cookers-and-clothesdryers-know-when-to-stop/507484/1 "2009-08-24T11:17:22Z")
Do they somehow detect moisture levels? Are the two related at all or do they use different types of sensors? ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [August 24, 2009, 11:42am UTC](https://boards.straightdope.com/t/how-do-rice-cookers-and-clothesdryers-know-when-to-stop/507484/2 "2009-08-24T11:42:38Z")
Don’t know much about rice cookers, but clothes dryers sense either humidity or the rise in temperature caused by diminishing moisture. ---
**Author:** ![jjimm](https://avatars.discourse-cdn.com/v4/letter/j/ba8739/32.png) [@jjimm](https://boards.straightdope.com/u/jjimm)\ **Post date:** [August 24, 2009, 11:49am UTC](https://boards.straightdope.com/t/how-do-rice-cookers-and-clothesdryers-know-when-to-stop/507484/3 "2009-08-24T11:49:17Z")
Neither the rice cooker I used to own, or the tumble dryer I currently own, do anything automatically. They used timers. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [August 24, 2009, 12:08pm UTC](https://boards.straightdope.com/t/how-do-rice-cookers-and-clothesdryers-know-when-to-stop/507484/4 "2009-08-24T12:08:33Z")
From [Consumer Reports](http://web.consumerreports.org/dryers/a/Index.html?EXTKEY=SG72A00&CMP=KNC-CROAPPG&HBX_OU=50&HBX_PK=Clothes_Dryer) > [@](#): > > The major differences in clothes dryers are how they heat the air (gas or electricity) and how they’re programmed to shut off once the load is dry (thermostat or moisture sensor). ---
**Author:** ![chrisk](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@chrisk](https://boards.straightdope.com/u/chrisk)\ **Post date:** [August 24, 2009, 12:14pm UTC](https://boards.straightdope.com/t/how-do-rice-cookers-and-clothesdryers-know-when-to-stop/507484/5 "2009-08-24T12:14:57Z")
> [@jjimm](#): > > Neither the rice cooker I used to own, or the tumble dryer I currently own, do anything automatically. They used timers. This is true for the dryers I use, but they’re in a pay laundromat. One quarter gets you five minutes of drying. (Used to be six when I first moved in, darn inflation. 🙂 ) ---
**Author:** ![\_xiao\_wenti](https://avatars.discourse-cdn.com/v4/letter/_/b782af/32.png) [@\_xiao\_wenti](https://boards.straightdope.com/u/_xiao_wenti)\ **Post date:** [August 24, 2009, 12:26pm UTC](https://boards.straightdope.com/t/how-do-rice-cookers-and-clothesdryers-know-when-to-stop/507484/6 "2009-08-24T12:26:42Z")
It’s actually pretty simple with rice cookers. With water present, the temperature is limited to the boiling point of water. Once the water is gone, the temperature can go higher. Put a RTD in there and have it click from cook to warm once it goes above T(boiling). Washing machines (most of them) rely on a timer. Dyson marketed in the UK for a time a washing machine with a moisture sensor (IIRC). ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [August 24, 2009, 12:35pm UTC](https://boards.straightdope.com/t/how-do-rice-cookers-and-clothesdryers-know-when-to-stop/507484/7 "2009-08-24T12:35:51Z")
> [@\_xiao\_wenti](#): > > It’s actually pretty simple with rice cookers. With water present, the temperature is limited to the boiling point of water. Once the water is gone, the temperature can go higher. Put a RTD in there and have it click from cook to warm once it goes above T(boiling). That’s pretty much how my old el-cheapo rice cooker worked. Put rice+water in a pot, put water in the cooker _under_ the pot. Water under the pot eventually evaporated, allowing the cooker’s temp to increase past the setpoint of a thermal switch, killing power; the rice then coasted to a finish. Newer one just uses a timer. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [August 24, 2009, 12:39pm UTC](https://boards.straightdope.com/t/how-do-rice-cookers-and-clothesdryers-know-when-to-stop/507484/8 "2009-08-24T12:39:24Z")
> [@\_xiao\_wenti](#): > > Washing machines (most of them) rely on a timer. Dyson marketed in the UK for a time a washing machine with a moisture sensor (IIRC). You might be thinking about commercial units. All the home dryers I have had for 30 years in the USA had a moisture or temperature sensor as an “automatic” cycle option, along with timer options, too. Looking at random ads for new home units of several brands, all appear to have that feature (although some specs are a little ambiguous). Since I find that cycle to be the most useful, I can’t imagine having to guess at the time and checking at intervals. Mine just beeps when it thinks the clothes are dry, then continues in a cool-down cycle for a while longer before shutting off. ---
**Author:** ![JKilez](https://avatars.discourse-cdn.com/v4/letter/j/e5b9ba/32.png) [@JKilez](https://boards.straightdope.com/u/JKilez)\ **Post date:** [August 24, 2009, 2:10pm UTC](https://boards.straightdope.com/t/how-do-rice-cookers-and-clothesdryers-know-when-to-stop/507484/9 "2009-08-24T14:10:21Z")
> [@\_xiao\_wenti](#): > > Washing machines (most of them) rely on a timer. Dyson marketed in the UK for a time a washing machine with a moisture sensor (IIRC). Yeah, you lost me there as well. Every modern dryer that I have seen in a house has had both timed and dryness-sensing settings. ---
**Author:** ![Philster](https://avatars.discourse-cdn.com/v4/letter/p/13edae/32.png) [@Philster](https://boards.straightdope.com/u/Philster)\ **Post date:** [August 24, 2009, 2:12pm UTC](https://boards.straightdope.com/t/how-do-rice-cookers-and-clothesdryers-know-when-to-stop/507484/10 "2009-08-24T14:12:35Z")
My rice cooker and clothes dryer either tastes the rice or feels the clothes. She’s the best. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [August 24, 2009, 4:15pm UTC](https://boards.straightdope.com/t/how-do-rice-cookers-and-clothesdryers-know-when-to-stop/507484/11 "2009-08-24T16:15:52Z")
> [@Philster](#): > > My rice cooker and clothes dryer either tastes the rice or feels the clothes. She’s the best. As long as she doesn’t get them mixed up – feels the rice and tastes the clothes. ---
**Author:** ![\_xiao\_wenti](https://avatars.discourse-cdn.com/v4/letter/_/b782af/32.png) [@\_xiao\_wenti](https://boards.straightdope.com/u/_xiao_wenti)\ **Post date:** [August 24, 2009, 9:11pm UTC](https://boards.straightdope.com/t/how-do-rice-cookers-and-clothesdryers-know-when-to-stop/507484/12 "2009-08-24T21:11:27Z")
Sorry – I cook rice (cheap rice maker, again sorry), but I have the same dryer as Philster. ---
**Author:** ![beagledave](https://avatars.discourse-cdn.com/v4/letter/b/6de8d8/32.png) [@beagledave](https://boards.straightdope.com/u/beagledave)\ **Post date:** [August 25, 2009, 7:53pm UTC](https://boards.straightdope.com/t/how-do-rice-cookers-and-clothesdryers-know-when-to-stop/507484/13 "2009-08-25T19:53:41Z")
Fuzzy logic and rice cookers. > **[How Rice Cookers Work](https://home.howstuffworks.com/rice-cooker2.htm)** > > Fuzzy logic rice cookers use computer programming to adjust cooking performance. Learn how fuzzy logic and rice cookers team up in the kitchen.