I have to use a proof box in the winter but I don't use a dimmer switch, I use a thermostat.  A simple enclosed and vented wooden box that's large enough to contain the proofing dough, a lamp socket and low wattage lamp (far enough away from the proofing dough to prevent hot spots during proofing and far enough away from the wood to prevent a fire) along with a thermostat is all you need.  Your local home improvement store or a well stocked harware store should have everything you need.  The thermostat (at about $50) is the most expensive part.  The type used for furnaces requires some additional transformers and switching circuits that complicate the construction so mine is the type used to control attic fans.  Works great.

I use a light designed for reptile cages that has a dimmer dial on it, sold at most pet supply stores for about $12 without the bulb. They also sell reptile lights that have built-in thermostats in most pet supply stores, but I couldn't find one at the time, so just made due with the dimmer and a separate thermometer to monitor the temp in my proofing box. For the bulb you can use any inexpensive low wattage (under 100 watts) incandescant or halogen flood bulb sold at hardware stores or home centers.

Thanks for the great ideas!

Hello Slimk23,

Here is the one I build.  Very simple.  A light dimmer, 100W bulb, and a long cord.  I use my (turned off) oven as the prrofing box itself.  This has worked very well for me in the past.

Best of luck

Michael

Thank you...pictures are always helpful.  I love this site.  Fabulous ideas!!