HAT Geiger Counter
Product Images
Overview
The HAT Geiger Counter is an outdoor-rated ionizing radiation monitor built on the ESP32-C3. It measures radiation in CPM and µSv/hr using a J321 Geiger tube, integrates natively with Home Assistant via ESPHome, and optionally uploads readings to radmon.org for public radiation monitoring.
The device ships pre-flashed with ESPHome firmware and can be adopted directly from the ESPHome dashboard or provisioned via BLE (ESPHome app) or USB-C (improv_serial).
Features
- Measures ionizing radiation in CPM and µSv/hr using a J321 Geiger tube
- Native Home Assistant integration via ESPHome native API
- Outdoor rated — designed for permanent external installation
- Optional radiation upload to radmon.org every 65 seconds
- Wi-Fi provisioning via BLE (ESPHome app) and USB-C (improv_serial)
- ESPHome dashboard adoption support
- Fallback Wi-Fi hotspot and captive portal
- Safe mode recovery via boot button
- Power via USB-C or 6–36V DC screw terminal
Hardware
| Component | Details |
|---|---|
| MCU | ESP32-C3 (ESP32-C3-WROOM-02U) |
| Geiger tube | J321 |
| Power input | USB-C or 6–36V DC screw terminal |
Getting Started
- Power the device via USB-C or the screw terminal (6–36V DC)
- Provision Wi-Fi using the ESPHome app (BLE) or a USB-C cable (improv_serial)
- Adopt the device in Home Assistant via the ESPHome integration
- Optionally configure your radmon.org username and password from Home Assistant