# What is this elecrtical device? **URL:** \ **Category:** Factual Questions\ **Created:** [December 11, 2008, 4:23pm UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725 "2008-12-11T16:23:13Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![masterofnone](https://avatars.discourse-cdn.com/v4/letter/m/4bbf92/32.png) [@masterofnone](https://boards.straightdope.com/u/masterofnone)\ **Post date:** [December 11, 2008, 4:23pm UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/1 "2008-12-11T16:23:13Z")
I’m looking for a home version of what we call a power supply at work, but I don’t know what search terms to use. What I want to do is reduce the temperature of a crockpot slightly so that I can use it to make yogurt. The device plugs into 110V, and you plug a 110V appliance into it. It has a dial (variable resistor?) to reduce the current(?) to the appliance. If I search for power supply, I only get computer power supplies. What term should I use? Any other options for doing this? ---
**Author:** ![jayjay](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jayjay/32/6765_2.png) [@jayjay](https://boards.straightdope.com/u/jayjay)\ **Post date:** [December 11, 2008, 4:23pm UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/2 "2008-12-11T16:23:57Z")
A transformer? ---
**Author:** ![engineer\_comp\_geek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/engineer_comp_geek/32/504_2.png) [@engineer\_comp\_geek](https://boards.straightdope.com/u/engineer_comp_geek)\ **Post date:** [December 11, 2008, 4:29pm UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/3 "2008-12-11T16:29:09Z")
Variac or Variable Autotransformer. ---
**Author:** ![Ethilrist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ethilrist/32/4604_2.png) [@Ethilrist](https://boards.straightdope.com/u/Ethilrist)\ **Post date:** [December 11, 2008, 4:30pm UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/4 "2008-12-11T16:30:54Z")
I was going to suggest a Johnson refrigerator thermostat, used in homebrewing to raise the minimum temperature in a refrigerator for the making of lagers, but I see that they have an operating range well below the creation of yoghurt. Perhaps there are other types of thermostat controls available for a higher temperature range? Or, a heavy-duty dimmer switch? ---
**Author:** ![masterofnone](https://avatars.discourse-cdn.com/v4/letter/m/4bbf92/32.png) [@masterofnone](https://boards.straightdope.com/u/masterofnone)\ **Post date:** [December 11, 2008, 4:38pm UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/5 "2008-12-11T16:38:16Z")
> [@engineer\_comp\_geek](#): > > Variac or Variable Autotransformer. Yes - that’s it exactly! Thanks. Unfortunately it appears there is no cheap option for these. > [@Ethilrist](#): > > I was going to suggest a Johnson refrigerator thermostat Thanks! You just answered a question I didn’t know I had - I’ve been trying to figure out how to make an 70 degree incubator for curing pepperoni also. ---
**Author:** ![Small\_Clanger](https://avatars.discourse-cdn.com/v4/letter/s/9fc348/32.png) [@Small\_Clanger](https://boards.straightdope.com/u/Small_Clanger)\ **Post date:** [December 11, 2008, 4:39pm UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/6 "2008-12-11T16:39:33Z")
Beaten to it by Mr **comp\_geek** The device is called a [Variac](http://en.wikipedia.org/wiki/Variac) though I’m dubious about using one to do what you want. ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [December 11, 2008, 5:33pm UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/7 "2008-12-11T17:33:15Z")
> [@masterofnone](#): > > I’m looking for a home version of what we call a power supply at work, but I don’t know what search terms to use. What I want to do is reduce the temperature of a crockpot slightly so that I can use it to make yogurt. > > The device plugs into 110V, and you plug a 110V appliance into it. It has a dial (variable resistor?) to reduce the current(?) to the appliance. > > If I search for power supply, I only get computer power supplies. What term should I use? Any other options for doing this? If all the crockpot has is a heating resistor then a light dimmer will work. If the crockpot has a thermostat which switches the heating element on/off then you would need to re-adjust that thermostat. A power supply is a totally different thing. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [December 11, 2008, 6:18pm UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/8 "2008-12-11T18:18:55Z")
Variacs have always been rather expensive things. Your slow cooker will have some kind of thermostat - otherwise, it would just get hotter and hotter until it burns the food. If the cooker has a mechanical thermostat, it’s still going to heat up to whatever temperature it’s set for. Reducing the voltage with a variac will only make it reach that temperature more slowly. Newer cookers with electronic controls will probably not work at all if you reduce the voltage much below 110 volts - I’d expect it to blank out and refuse to do anything at around 90-100 volts. So, the project is to adjust the thermostat, rather than adjust the electricity. Find what temperature your yogurt needs to incubate at, find a suitable thermostat and fit it to the cooker. ---
**Author:** ![BrandonR](https://avatars.discourse-cdn.com/v4/letter/b/779978/32.png) [@BrandonR](https://boards.straightdope.com/u/BrandonR)\ **Post date:** [December 11, 2008, 6:30pm UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/9 "2008-12-11T18:30:04Z")
For what it’s worth, I know that Alton Brown uses a simple [heating pad](http://www.foodnetwork.com/recipes/good-eats/fresh-yogurt-recipe/index.html) to make his fresh yogurt. Probably a lot cheaper and easier to buy. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [December 11, 2008, 6:47pm UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/10 "2008-12-11T18:47:03Z")
> [@masterofnone](#): > > Yes - that’s it exactly! Thanks. Unfortunately it appears there is no cheap option for these. I scored a big 15 amp variac for $5.00 at a garage sale years ago. It still tickles me pink every time I use it. On the yogurt crockpot: An aquarium immersion heater should regulate the temp in the range you want. I think they’re about $30, but you might score one cheap at a garage sale or thrift store. You could also go with a 40 watt light bulb and the thermostat from an old space heater, but that’d involve a bit more construction on yourpart. ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [December 11, 2008, 6:47pm UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/11 "2008-12-11T18:47:48Z")
> [@BrandonR](#): > > For what it’s worth, I know that Alton Brown uses a simple [heating pad](http://www.foodnetwork.com/recipes/good-eats/fresh-yogurt-recipe/index.html) to make his fresh yogurt. Probably a lot cheaper and easier to buy. Curses! Beaten to it. ---
**Author:** ![Carson\_O\_Genic](https://avatars.discourse-cdn.com/v4/letter/c/cdc98d/32.png) [@Carson\_O\_Genic](https://boards.straightdope.com/u/Carson_O_Genic)\ **Post date:** [December 11, 2008, 8:08pm UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/12 "2008-12-11T20:08:33Z")
Yoghurt needs about 110F. You could trial low wattage incandescent bulbs in your oven’s light socket, continuous run. A 30" oven might need 40w, though it will take a while to attain that temp. ---
**Author:** ![Santo\_Rugger](https://avatars.discourse-cdn.com/v4/letter/s/e95f7d/32.png) [@Santo\_Rugger](https://boards.straightdope.com/u/Santo_Rugger)\ **Post date:** [December 11, 2008, 8:57pm UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/13 "2008-12-11T20:57:59Z")
I thought crock pots used rheostats to control the temperature? ---
**Author:** ![Balthisar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/balthisar/32/2825_2.png) [@Balthisar](https://boards.straightdope.com/u/Balthisar)\ **Post date:** [December 11, 2008, 11:57pm UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/14 "2008-12-11T23:57:20Z")
All of the Indians that I know who make yogurt (okay, one family) do it at room temperature. ---
**Author:** ![SpectBrain](https://avatars.discourse-cdn.com/v4/letter/s/a87d85/32.png) [@SpectBrain](https://boards.straightdope.com/u/SpectBrain)\ **Post date:** [December 12, 2008, 2:47am UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/15 "2008-12-12T02:47:13Z")
> [@Squink](#): > > I scored a big 15 amp variac for $5.00 at a garage sale years ago. It still tickles me pink every time I use it. Sounds like the insulation needs to be checked out. 😃 ---
**Author:** ![masterofnone](https://avatars.discourse-cdn.com/v4/letter/m/4bbf92/32.png) [@masterofnone](https://boards.straightdope.com/u/masterofnone)\ **Post date:** [December 12, 2008, 2:49am UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/16 "2008-12-12T02:49:37Z")
Thanks everyone! Seems I was way off base comtemplating using a variac to do this - I thought they were most likely variable resistors, but since they’re variable transformers, it’s not going to work. Obviously, I don’t know what the hell I’m doing, but I never let that stop me before. I’ve determined that I can just raise the porcelain part of the crockpot with mason jar bands to get the right temp. I’m still interested in other methods, and I will definitely dig out the heating pad we’ve got around here somewhere, and the aquarium heater I’ve got at work, and try different wattage bulbs in the oven. Balthisar - Thanks, but I’m just going by the recipe I’ve found. Most of which say 110F, some of which say 116F. I’ll experiment once I repeat the original recipe. Squink - But how would I use the thermostat? I’m most likely wrong, but I presume they are temperature specific, and most often not at the temperature at which I want them. If the thermostat is not calibrated to 110 - 116F, isn’t it worthless to do what I want, or do I just not know what I’m doing? ---
**Author:** ![Santo\_Rugger](https://avatars.discourse-cdn.com/v4/letter/s/e95f7d/32.png) [@Santo\_Rugger](https://boards.straightdope.com/u/Santo_Rugger)\ **Post date:** [December 12, 2008, 3:00am UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/17 "2008-12-12T03:00:22Z")
> [@masterofnone](#): > > Squink - But how would I use the thermostat? I’m most likely wrong, but I presume they are temperature specific, and most often not at the temperature at which I want them. If the thermostat is not calibrated to 110 - 116F, isn’t it worthless to do what I want, or do I just not know what I’m doing? I’m not sure what kind of thermostat it is, but we had a coil type thermostat at a house I lived in in college. My “frugal” roommate insisted the heat not be turned up past 65, which would have been fine, except the furnace and thermostat were _both_ in his room, not to mention he lived on the south side of the house. My other roommate and I got tired of always being cold in the morning, so one time when he wasn’t home we sneaked into his room and bent the coil. Walaa! The thermostat read 65, but was set at 70. Good times! ETA: My point is, it may be possible to adjust the thermostat with a little bit of intrusive maintenance. ---
**Author:** ![mangeorge](https://avatars.discourse-cdn.com/v4/letter/m/d78d45/32.png) [@mangeorge](https://boards.straightdope.com/u/mangeorge)\ **Post date:** [December 12, 2008, 3:21am UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/18 "2008-12-12T03:21:39Z")
> [@SpectBrain](#): > > Sounds like the insulation needs to be checked out. 😃 😃 ---
**Author:** ![mangeorge](https://avatars.discourse-cdn.com/v4/letter/m/d78d45/32.png) [@mangeorge](https://boards.straightdope.com/u/mangeorge)\ **Post date:** [December 12, 2008, 3:26am UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/19 "2008-12-12T03:26:34Z")
You can buy yogurt makers all over the place, including [amazon.com](http://amazon.com), for under $50. Way under, actually. ---
**Author:** ![Rhubarb](https://avatars.discourse-cdn.com/v4/letter/r/59ef9b/32.png) [@Rhubarb](https://boards.straightdope.com/u/Rhubarb)\ **Post date:** [December 12, 2008, 3:42am UTC](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725/20 "2008-12-12T03:42:22Z")
> [@mangeorge](#): > > You can buy yogurt makers all over the place, including [amazon.com](http://amazon.com), for under $50. Way under, actually. Someone upthread mentioned a Johnson thermostat, but it didn’t have the right range. Well, Johnson Controls makes LOTS of thermostats at different ranges and 110 °F to 116 °F is not an unusual range. However, given **mangeorge** ’s quote above, getting a thermostat to control your crockpot is the more expensive route. [Next page](https://boards.straightdope.com/t/what-is-this-elecrtical-device/476725.md?page=2)