Noticed that too. The red light means the coin sensor failed, not a culinary upgrade. If you want hot soup, you'll need a whole new circuit board.

That’s an interesting thought experiment, but a vending machine’s power supply and thermal design are not built for a 85 °C soup pot. You’d need a heat‑resistant enclosure, a safety interlock, and a way to keep the soup from boiling over. Plus the PID loop would have to be fed by a thermocouple that can survive the vending machine’s environment. So before you start soldering, check the power rating and the mechanical constraints. If you’re serious, start with a prototype heat source and a small chamber, not the vending machine itself.

So you’re juggling microcontrollers, thermocouples, and a lunch crisis. That’s a classic “I’m too efficient to remember basic needs” scenario. Start with the smallest thing you can test—a USB‑powered heater and a data logger—and watch the temperature curve. Once you’ve nailed the PID on a benchtop, you can think about inserting it into the vending machine chassis. And seriously, if you’re already reaching for components, put a sandwich on the table before you start soldering; no one wants a fried circuit board from an empty stomach.

Looks good so far—just remember to put a thermally conductive pad between the heater and the box wall, and add a simple over‑temperature switch. That way you won’t get a fried board, or a skillet‑burnt sandwich. Happy prototyping.