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  • Works with Home Assistant
  • Open source
  • ESPHome

Open hardware for Home Assistant

Plošná ryba makes ready-made sensors for Home Assistant: water tank level, beehive weight, electricity spot price and garden temperature. Everything runs ESPHome, works without a cloud and is open down to the last screw.

See the devices How it works

One board, four heads

PR-CORE

Core board

Jádro (Czech for core) is the ESP32-C6 board that every Plošná ryba device is built on. We also sell it on its own for makers who want to build their

690 Kč Pre-order
PR-HLADINA

Hladina water level

Hladina (Czech for water surface) measures the distance to the water in a tank or well with an ultrasonic sensor and converts it to litres and

1 990 Kč Pre-order
PR-UL

Úl beehive scale

Úl (Czech for beehive) weighs the whole hive on four load cells and measures temperature and humidity inside. It reports over WiFi to Home Assistant,

2 990 Kč Pre-order
PR-SPOT

Spot price light

Spot shows with a coloured LED ring whether electricity is cheap, average or expensive right now. The display shows the current spot price and the

990 Kč Pre-order
PR-SENZOR

Senzor temperature probe

Senzor measures temperature with a stainless DS18B20 probe plus air temperature and humidity with an SHT40. Use it in a compost heap, as a frost alert

1 090 Kč Pre-order

Works with Home Assistant

Once on WiFi, every device shows up in Home Assistant through the ESPHome integration. No coding, no extra app. Entities, graphs and automations live where the rest of your home already is. Not running Home Assistant? Each device has a local web UI and optional MQTT. We have no cloud and no mobile app, and the devices keep working without internet access.

Open hardware

We publish schematics, PCB files, firmware, enclosure models and documentation. Firmware is MIT, hardware CERN-OHL-P-2.0, docs CC BY 4.0. Modify, repair or build your own. When something breaks in a few years, you replace a part, not the whole device.

How it works

Every product is built on one base board we call Jádro (core). It has an ESP32-C6, USB-C or battery power and a connector for a head. The head turns Jádro into a specific device:

  • Hladina measures water in a tank or well with ultrasound.
  • Úl weighs a beehive and measures temperature and humidity inside.
  • Spot shows with colour whether electricity is cheap right now.
  • Senzor watches compost temperature, frost at seedling level and greenhouse climate.

Jádro is also sold on its own for anyone who wants to build their own sensor. We print the enclosures ourselves and UV-print the lids.

Pre-order

The products are not manufactured yet. The shop runs in pre-order mode and we ship once the first batch is produced. We will let you know the date by e-mail. CE testing is planned before regular sales start. All products carry a 24 month warranty, prices are in Czech koruna (CZK) and we ship to Czechia and Slovakia via Packeta, other EU countries on request.

Get one e-mail when batch 0 ships

A single e-mail when production starts. Nothing else, and we delete the address afterwards.