I recently received some tomato seeds and wanted to get them started ASAP!
The ambient temperature was a little low, and I really didn't want to spend the $30 for a heat mat for seed starting.
So I look around on the 'net, and find a few posts mentioning that Christmas lights can be used.
Enter: Marlin's attempt to start seeds and burn the house down.
Round One, The container sitting on the lights constantly on: The seeds/container was maintaining 100 Degrees F! WAAAAY too hot!
Being the HVAC helper that I am, I cobbled together a quick controls project:
1 - 3D Christmas star
1 - Penn Johnson Controls A419 (which I already had on hand, These things run $60 - $100)
1 - 6 foot Extension cord
Piece of aluminum foil
I cut the extension cord, and hooked it up to the temperature control.
Next, I took the star and wrapped it in aluminum foil. Mainly that was to keep the light contained, so it wouldn't drive me crazy.
Then all I had to do was plug it in and set the temps!
Here it is working maintaining a comfy 77 degrees: