The Microelectricitygermkiller site has folders with the schematics
and actual digicam photos of assembling the parts onto a Radio Shack
solderless plug-in board, if anyone does not yet know about it. It's
real easy to do and offers the automatic switching without a relay,
just one LM35 or TL82 or some chip like that. It's a dual something
chip, I dunno, it works.. :)

bob