Thursday, 17 July 2008
Kiln controller almost works....
So very close. I have the kiln controller reading ambient temp, reading the type-s thermocouple, and sending UDP packets with its updates. I need to get it receiving
packets, to control its duty cycle. The solid state relay already can be switched.
Once this is done, I can then have most of the controll logic in a simple .NET app.
Lessons learned (and applied) in this build:
Voltage reference is on board.
Hooked up all pins properly, for example, RB2 for the interrupt.
Properly managed the 5V and 3.3V portions of the board with no ground loops.
Checked all pins before plugging in expensive part.
I screwed up the TC amp again, but I use SPICE to design a new Layout, which is now on a tiny dauther board, preventing another pcb.
I bought at least two of each required part. this came in handy.
I had stocked up on basic opmps and a wide variety of resistors/caps/etc Prior to the build, this too came in handy.
I discovered that opamps have an input offset voltage. The TLC272 ended up having about 1.1mV. Which ends up being quite a few degrees C if I didn't compensate for this in the software. Ill have to watch out for this in the future.
Grounding as much of the copper as I can seems to help tremendously. This board has yet to crash or reboot. (cross fingers)
