This part has been a real struggle...

I started with a 1500W resistive cooking plate, but regulating temperature with it was a nightmare due to its inherent delay. I tried everything to optimize the PID control, including lambda tuning, but only very slow regulation produced stable results.

I found two key reasons for this behavior:

• The thermal inertia of the cooking plate causes the temperature to overshoot by more than 5°C after cutting the power.

• During mashing, recovery from an overshoot is very slow, since it only takes a tiny amount of power (about 3% of 1500W) to maintain a steady 55°C.

So I abandoned that approach.

Next, I switched to a cheap 1500W immersion heater—a simple spiral-type element. Temperature regulation was excellent: I could keep the heater at 100% power right up to 1°C below the target without overshooting. But eventually, grain clogged the spiral, which led to burned grain.

After that, I considered using a ceramic cooking plate, assuming it would be more responsive. Unfortunately, I couldn't find an affordable model that met my needs.

Finally, I settled on a 2kW IKEA induction cooker (~40€). I modified it to allow PWM-based power control, and this setup has proven to be both fast and accurate for temperature regulation. For more detail : see https://hackaday.io/project/203350-diy-pwm-controlled-ikea-tillreda-induction-cooktop