While I ponder and research some on the power supply, I still think I can get some other stuff done. One thing I want to do is create a layout for a PCB that I can use to replace the front panel board and wire into a breadboard for testing. This would be to allow me to interact with the buttons and LCD display that come with the thermostat and I can re-cycle the layout if I create a board with a processor on the back.
Currently I have a 600dpi scan of the face of the board. This required de-soldering the LED used for the LCD backlight and clipping the leads for the thermometer probe and a large capacitor down and then re-flowing them with my iron. Most scanners have a very short focal length, so the board has to lie flat on the glass or else you get blurred images. I added a ruler to the side for scale, but it looks like my scanner does a good job of getting the DPI right.
Once scanned and cropped, I started looking for a way to create a board with contacts in the proper location for the existing items. Mostly this consists of exposed copper traces that use conductive silicon to either register button presses or toggle parts of the display. This has been surprisingly hard to do. All the regular board layout tools have required you to lay out the components first, but I don't have any, just locations for the contacts. So I kept digging. Currently I am using a demo copy of Sprint Layout 6 to test it's features, and I am having some success. Importing a layer that displays the existing board is easy and allows control of the DPI or dimenstions of the file, both sides of the board can be imported independently. I have been able to duplicate the pads and board shape, but I'm still working on the holes for mounting. Unfortunately, saving is not an option in the demo version, but I think I will pay the $50 and get the full copy just for this feature.
Once I have the info I need, I'm going to see if I can pull it into another program and add/edit the board from there, if not, I can still produce the right files to generate a physical board using this tool, so that should be enough for now.