Sous Vide rocks! Thanks dcarch & FOAS
Many thanks to dcarch and FOAS--I got my sous vide up and running last weekend, and it's great. Everything I cooked in it so far has come out tender and juicy. I'm using dcarch's info and FOAS's advice, and my only contribution is to point out current sources for the parts you need. If you're interested in making one, you can probably cobble together one for under $100 including an Igloo cooler. You may have some of this stuff around the house anyway, so your cost may be even less.
You can buy a ready made sous vide setup for $400-$500, but if you want to make a contraption like this, it's really easy. The heart of the rig is a STC-1000 temperature controller. You can get them online for $15 to $20. For this application it functions basically as an 'open on rise' thermostat: when a temperature is reached, it cuts the power to the heater element. The heat is provided by a 500w aquarium heater element. These are available online for $30-40. (you want the kind without a thermostat; you'll be using the STC-1000 as a thermostat). Another item you might want is a small submersible dc high temp water pump; I got one online for $18. You'll need a cooler, but you probably have one around the house anyway; I got a Igloo Marine 25 qt cooler for about $19 at Walmart. You can get whatever size you think you might want, and the guts of the system are easily moved from one cooler to another if you need a bigger setup.
You'll also need a few inexpensive items to wire it up: an electrical handy box ($2), an electrical outlet ($2), a faceplate, and some sort of enclosure. For a power cord, I used a polarized two-prong extension cord and cut off the socket end; I used a foot of that cord for hookup wire in the box. I also rigged up a little rack made of CPVC pipe to attach the pump. That way I'm not making any attachments to the inside of the cooler.
The STC-1000 is often used by homebrewers to control the temperature of a refrigerator for precise fermentation. It can turn on either a heating element or a cooling element. You can download wiring diagrams for the STC-1000, and if you do just ignore the cooling circuitry--you're only going to be using this to control the heater.
Here are the specific items I obtained:
STC-1000 Available from several places-- you might save a few bucks if you order it on eBay from China:
Aquarium Heater element without thermostat:
(or something similar. A 500w heater brought my water bath from room temp to 131 degrees in a little over an hour, then maintained it +/- 0.5 degrees thereafter) See if the kind you get has little suction cups to mount on the inside of the cooler
Circulation pump--not absolutely necessary, but it'll ensure a stable temp throughout the cooler:
This is one of several small submersible DC pumps available online. Make sure you get one that says 'high temperature--you can't just use an aquarium pump as they aren't made to operate at sous vide temperatures. Google 'submersible DC pump suitable for sous vide' and you'll get lots of hits.
You might need a power supply for your pump. This one works well, and you can select your voltage to match your pump ( although you might have a suitable wall-wart transformer around the house). If you cut into the black cord, you'll find a black and a red wire so it's easy to match the polarity of your pump:
This really is a fun project. If any of you have any questions, let me know. I guarantee if you like rare or medium rare steaks, you'll love how the stuff comes out of this cooker.
Here's the inside of the cooler. The long silver thing at the bottom with the suction cups is the aquarium heater element, the black cylinder at the upper right is the pump, and the cord to the left is the temperature probe that goes back to the STC 1000. The rack is made of CPVC, and the weight of the pump is enough to keep it from floating. But if you make a bigger one, you might need to put sand or gravel in the pipes to keep it from floating. Finally, so that the food pouches don't touch the heater element directly, I bent an aluminum soffit vent (about $2) to shape to make a guard over the element.