See the included schematic and PCB layout.

The circuit is intentionally simple, using components I already had on hand. The most critical design requirement was to maintain SELV (Safety Extra-Low Voltage) isolation between the opto-coupler input and the rest of the PCB, as well as the cooktop’s internal electronics.

The PCB was home-etched, which is the fastest and easiest method for a simple board like this. It features a single routed top layer and a solid ground plane on the bottom, which simplifies etching.

To protect against moisture or condensation, the board is finished with a conformal coating.

A 3.5mm jack is used as the input for the external PWM control signal.

For secure installation inside the cooktop, the PCB is mounted using a custom 3D-printed base.