I've done a quick first pass on the PCB design for the temperature controller. There are a few things I'd like some feedback on:
1. There are five 0805 discrete components, two 3528 caps and two SOT223 regulators in this layout. The optional thermocouple interface adds one SOIC8 and one 0805 cap. These are all fairly large for surface mount and the board layout is not too cramped so hand soldering should be pretty easy. How do people feel about this level of surface mount? If it seems too hard, I can try to modify the design to use more through hole although the board will get larger (and the thermocouple chip isn't available in through hole anyway). Or else, I'd be happy to help anyone who needs it to get the surface mount soldering done with my hotplate. The bulk of the board is still through hole.
2. All of the inputs and outputs are connected to headers. This seems to be a good compromise since you can either solder in pins to connect plugs to or else you can just solder wires directly to the pads. But if you want something else like screw terminals, I can expand the board to make room. Let me know what kind of connections you would prefer. The inputs are set up for a rotary encoder and a push button. But the encoder inputs are basically just three switches so if you want, you can use those inputs for more switches instead.
3. How about mounting holes? I can make the board a bit bigger to make space for holes at the corners if you want. What size holes, if so?
4. There are both a Dorkboard programming header and a standard AVR 6 pin programming header. Is it worth having both?
There are still labels to add to some of the pins and other cleanups but I'll wait to do that until I get some feedback. And if anyone has any other suggestions for changes, I'd be happy to hear them. Please leave any feedback or suggestions in the comments to this entry. I've attached the Eagle files as well as images of the board layout and schematic.