A while back I picked up some old IBM modems that were being retired from the modem pool at work. I was hoping maybe I could convince one to speak Bell 202, but that didn't pan out. Anyway, they have nice boxes and the front panel has a set of buttons and an HD44780 LCD controller, so I held on to it:
The box has a nice power cord and switch built in, so I will be able to just stuff everything inside and put a connector on the back for the heater and temp sensor wires. Then I can use different chambers depending on what size I need. I could also run set it up to run multiple chambers, it only takes a couple more pins to run additional chambers, so I suppose I could set up to run about three. Maybe for version 2.
I wired it up for the LiquidCrystal library, plugged it in and away it went. The controller is only good for 8 characters, so I've got it set up to cycle the display through each setting one at a time. Right now, that's the setpoint temp, the current temp, and the number of seconds left in the ramp.
I also noticed that at some heater PWM frequencies the power supply squeals, so I added start and end cycle beepers. When I switch power supplies I'll probably need to add an actual beeper, but this was kinda fun in the meantime.
I also mounted the heater and temp sensor for real: