• Design hardware part of heating regulator to control three heating elements (2kW ~230V each)
• Design homebrewing control unit which will take care of:
  • Temperature measuring
  • Temperature PID regulation
  • Stirring control
  • Character display GUI controlled by buttons
  • RTC
  • Basic cooking program functionality
• Create own C drivers (display, RTC, …)

Regulator acts as power switch driven by low-frequency PWM signal from MCU. For safety and lucidity purposes, regulator will be placed at separate PCB, its interface to MCU will consist of logic supply pins and single trigger pin for each driven phase.

Power triac was chosen as sufficient switch component in terms of power/price efficiency. Any triac allowing >12A continual working current (incl. 3A margin) would be acceptable (BTA12-600B - TO220 ~0.8$), however these packages do not provide insulation to common terminal (case). This problem would require additional electric insulation between the package and the heatsink, in cost of worsening thermal insulation. In case of common heatsink to all 3 triacs (3 phases), the peak voltage will reach over 500V peak. This lead to use of BTA26B/600V - TOP3 ~3.6$ as one of the cheapest available triacs with insulated package.

Optotriac provides considerable solution for direct drive of power triac, together with ensuring galvanic isolation of power and logic part. MOC3031 is optotriac with builtin logic providing zero-cross switching, which decreases power loss on power triac and significantly reduces EMC.