I finished construction of the oven- everything is installed and ALL parts are working (whew...).
The front panel looks kind of crappy, I was messy with epoxy, but the side panel looks great- and it's hinged so I can open easily to reprogram the microcontrollers and when closed will stay shut with help of a simple magnet.
Pictures or demo video will be coming soon
There were several last-minute problems but managed to fix them all:
Problem: One fan could not be switched
Solution: The Drain leg of SOT23 MOSFET was not actually soldered down (looked ok but failed continuity test). Used soldering iron tip and touch of solder to fix.
Problem: Upper heater output LED was dim and only delivered 6mA when on. It should have been bright LED and delivered 20mA to the port.
Solution: SOT23 transistor was damaged. Replaced and it is working.
Problem: TRIAC switchboard did not work to switch 120vac.
Solution: There was a flaw in the design that caused short circuit (on logic side, NOT 120vac side). Controller board had common +5v and switched GND, but switchboard had common GND and assumed +5v to switch it's optocouplers. Had to cut a couple traces and install an extra piece of wire to make common +5v and independent GND.
The last big problem is not so huge, but I have to order some new parts to make the project resiliant. The two TRIACs I ordered are rated at 12.7A, they aren't on a heatsink, and I am switching 10A loads each. They work but if I let them on long enough to get the oven's heating elements red hot, the TRIACs overheat and will not turn off. (Once they cool down again they are fine, which is good for now).
Solution is to order TRIACs rated for 25A and probably use heatsinks. I hate to pay $7 for shipping on $2.50 of parts so I am waiting until I have partslist for another project. I can still get this oven up to proper temperature by pulsing power periodically to give TRIACs time to cool down (last test I did was outside in 50 degree weather.. took about 5 minutes for inside the oven got up to 470 degrees farenheight).
All in all, I'm very happy with how the project has turned out so far, and learned a lot too! All that is left is to fix the overheating TRIACs and write the code for the menus and plotting temperature and etc etc (that is the fun stuff!!)
