I used a free broken 3 cubic foot mini fridge as the incubator. For heating element I used a length of Exo Terra heat cable that was given to me. My total cost was about $160, mostly due to the $120 Helix DBS 1000 thermostat. Instead of the heat cable you can use flexwatt. Additionally a larger CPU fan (120mm), or an additional small one, would probably be beneficial, I'll likely have to install a new fan in the future.
Materials (prices estimation):
screws/nails if building a base for it
wire cutters or pliers
1 front opening 3 sq. ft. mini fridge/freezer (it doesn't have to be functional!)
1 6' (at least) extension cord $5
1 18-24V power adapter/converter $20
1 roll aluminum/metal tape $10
1 80mm computer fan $5
1 Helix DBS 1000 thermostat $120
1 Exo Terra heat 25w cable $30
1 can of Great Stuff $6
1 sheet of egg crate $5
1 Indoor/outdoor digital thermometer $15
1 12"x16" metal baking sheet (measure your fridge to find the right size) $4
plywood or 2x4s to make a base (optional)
4 1" casters $20 (optional)
Total cost about $240 depending on available materials.
Get mini fridge!!
Remove motor, light, freezer compartment and anything else in the back and inside except for the shelves. Clean out the fridge with bleach and let it air out. Cut the bottom section off of the door.
Run the heat tape back and forth across the bottom of the fridge. Secure with aluminum tape.
To wire the CPU fan to be able to plug into an outlet you need to convert the volts of the fan to the volts of an outlet. This is where the 18/24V adapter comes in. On the fan, cut the end that attaches to the computer off. ON the converter/adapter cut the small plug that would attach to whatever device off.
(picture by Damon Salceies Albinochondro.com, since I fail and didn't take a picture of the splice)
Attach the Helix and digital thermometer to the front door of the fridge.
Run the probes from both around the back and through the round hole in the back of the fridge. Lay the heat probe directly on the heat cable. I hung the thermometer probe from the middle shelf.
Run the wires from the heat cable and CPU fan through the hole in the back of the fridge. Seal with Great Stuff. Plug the Helix, CPU fan, and heat cable into the extension cord.
Place the baking sheet on top of the heat cables. I had to use the hacksaw to cut the edges down so it would fit into the fridge. Fill the baking sheet with water or water bottles for heat retention and humidity. Cut the sheet of egg crate to fit inside the fidge and lay on top of the baking sheet. Optionally you can cut small pieces of PVC pipe and apoxy to the egg crate to keep it sturdy.
I used a piece of plywood cut to the size of the fridge then attached a couple 2x4s to one side. Casters were then attached to the ends of the 2x4s. I like the base since now I can wheel it around anywhere I want!
You should be good to go now! Set the Helix to the desired temp and then adjust as necessary using the thermometer to tell you what the inside temp is. I will update with new pics in the future.
If you want something similar without this much work, check out this mini fridge-warmer for $100:
ThinkGeek :: Deluxe Mini Fridge-Warmer w/ Digital Thermostat
Anyone one who wants help feel free to contact me.