The problem
A sauna out in the weather has to be hot when the guest arrives and safe when nobody is there. That means knowing the temperature at all times, driving the heater from the bookings, and being able to step in from a phone – without driving down to check.
What we built
Vestfjord Sauna runs on HeatBooking, with the physical side of the platform in full use:
- Control on Arduino Opta: firmware written from scratch that holds the temperature steady and reacts to the bookings.
- PT100 sensors read through LKM264 transmitters, for precise measurement where it is actually hot.
- HUUM heaters driven directly over the manufacturer’s API.
- Remote control from a phone: the owner sees temperature and status in real time and can override when needed.
- Booking, payment and access from the platform, so the guest walks straight into a warm sauna.
The stack
The platform is HeatBooking (Next.js and Supabase). The remote-control app is built in React Native and talks to the same backend as booking and admin. The Opta runs its own firmware and reports temperature from the PT100 sensors, while HUUM heaters are controlled over API.
The outcome
Booking, payment, access and heating are one flow, and the temperature is held by a PLC that does not care about the weather. It is software meeting the physical world – exactly the kind of problem we like best.