Background radiation from any radmon.org Geiger counter station in Home Assistant: CPM, µSv/h, an online check and a radiation alert.

Install · Modes · Entities · Dashboard · Automations · Upgrading from 1.x · Docs site

Highlights

☢️ Any station	Follow any of the hundreds of hobbyist Geiger counters on radmon.org, near you or anywhere in the world.
🔑 Owner mode	Running your own counter? Add its data-sending password and Radmon uses radmon.org's official last-reading API, including your station's own µSv/h.
📈 CPM and µSv/h	Counts per minute plus a dose rate, from the station or calculated with a conversion factor you can tune to your tube.
🚨 Radiation alert	A safety binary sensor that turns on above a CPM threshold you choose.
📡 Online check	A connectivity binary sensor that turns off when the station stops reporting.
📍 Location built in	Coordinates, place name and counter model as attributes and on the device.
🛟 Keeps working	A failed poll keeps the last good reading. Diagnostic sensors show poll health and the diagnostics download redacts your password.
🤝 Plays nice	Conservative polling and an identifying User-Agent, so radmon.org stays happy.
🇳🇱 English and Dutch	The UI is translated into both.

Warning

Radmon is not a safety device. Readings come from volunteers' hardware over the internet and can be late, missing or wrong. Never rely on it to protect people. Follow your national authority's advice in an emergency.

Installation

HACS (recommended)

Click the Open in HACS button above, or add the repository yourself:

1. HACS → ⋮ → Custom repositories
2. URL: https://github.com/DonTranQuiL/HA-Radmon, category Integration
3. Download Radmon, then restart Home Assistant

Manual

Copy custom_components/radmon_scrape to /config/custom_components/ and restart Home Assistant.

Configuration

Settings → Devices & services → Add integration → Radmon, or use the Add integration button above.

1. Enter the station name exactly as it appears in the radmon.org station list. It is case-sensitive, for example lImbus.
2. Your own station? Also enter its data-sending password (the one your counter uses to upload). Otherwise leave it empty.

Radmon checks the station (and password) with radmon.org before saving. Add the integration again for each extra station: every station gets its own device.

Owner mode or public mode

	Owner mode	Public mode
For	Your own station	Any station
Needs	Station name + data-sending password	Station name
Source	Official lastreading / lastreadingusv API	Public station page (showuserpage)
Dose rate	Station's own µSv/h (calculated as a fallback)	Calculated from CPM
Default / minimum interval	5 / 1 minutes	30 / 15 minutes

Since May 2026 radmon.org only answers the last-reading API with the station's data-sending password, so that API is for owners. Public mode reads the small public station page instead. radmon.org is a free, volunteer-run community service and has asked people not to hammer station pages, which is why the public interval is 30 minutes by default and can't go below 15.

Switch modes at any time: open the entry → ⋮ → Reconfigure.

Options

Open the entry → Configure:

Option	Default	What it does
Update interval	5 min (owner) / 30 min (public)	How often radmon.org is asked for a new reading.
Conversion factor	0.0057 µSv/h per CPM	Used to calculate the dose rate. 0.0057 suits an SBM-20 tube. Check your tube's datasheet; for example the J305 is often quoted around 0.0081.
Alert threshold	100 CPM	The radiation alert turns on at or above this value. Normal background is roughly 10–50 CPM on an SBM-20.
Offline after	30 min	The online sensor turns off when the latest reading is older than this.

Entities

For a station called lImbus, the device is Radmon lImbus with:

Entity	Example ID	Description
CPM	sensor.radmon_limbus_cpm	Counts per minute. Attributes: station, mode, location, latitude, longitude, device.
Dose rate	sensor.radmon_limbus_dose_rate	µSv/h. Attributes: source (station or derived) and conversion_factor.
Last reading	sensor.radmon_limbus_last_reading	When the station took the reading (timestamp).
Online	binary_sensor.radmon_limbus_online	On while readings are fresh (connectivity). Attributes: reading age and threshold.
Radiation alert	binary_sensor.radmon_limbus_radiation_alert	On at or above the alert threshold (safety).
Consecutive update errors	sensor.radmon_limbus_consecutive_update_errors	Diagnostic, disabled by default.
Last update status	sensor.radmon_limbus_last_update_status	Diagnostic, disabled by default.
Last update time	sensor.radmon_limbus_last_update_time	Diagnostic, disabled by default.

CPM and dose rate have a measurement state class, so you get long-term statistics and history graphs for free.

Dashboard example

type: vertical-stack
cards:
  - type: entities
    title: Radiation
    entities:
      - entity: sensor.radmon_limbus_cpm
      - entity: sensor.radmon_limbus_dose_rate
      - entity: sensor.radmon_limbus_last_reading
        format: relative
      - entity: binary_sensor.radmon_limbus_online
      - entity: binary_sensor.radmon_limbus_radiation_alert
  - type: gauge
    entity: sensor.radmon_limbus_dose_rate
    name: Dose rate
    min: 0
    max: 1
    severity:
      green: 0
      yellow: 0.3
      red: 0.6
  - type: statistics-graph
    title: CPM, last 7 days
    entities:
      - sensor.radmon_limbus_cpm
    days_to_show: 7
    stat_types: [mean, max]

Automation examples

Notify when the alert turns on:

automation:
  - alias: Radmon radiation alert
    triggers:
      - trigger: state
        entity_id: binary_sensor.radmon_limbus_radiation_alert
        to: "on"
    actions:
      - action: notify.mobile_app_your_phone
        data:
          title: "☢️ Radiation alert"
          message: >
            {{ states('sensor.radmon_limbus_cpm') }} CPM
            ({{ states('sensor.radmon_limbus_dose_rate') }} µSv/h) at station lImbus.
            Check radmon.org and official sources before acting.

Tell me when my own counter stops uploading:

automation:
  - alias: Radmon station offline
    triggers:
      - trigger: state
        entity_id: binary_sensor.radmon_limbus_online
        to: "off"
        for: "00:30:00"
    actions:
      - action: notify.mobile_app_your_phone
        data:
          message: "My Geiger counter hasn't reported to radmon.org for an hour."

Upgrading from 1.x

Version 2.0 is a full rewrite, and existing setups upgrade in place:

• The domain stays radmon_scrape, so your entry is migrated automatically to public mode with a 30-minute interval.
• Unique IDs are unchanged, so the CPM and dose rate entities keep their IDs, history and dashboard cards.
• Delete the old custom_components/ha-radmon folder after updating. The new code lives in custom_components/radmon_scrape, and if both folders exist Home Assistant may load the old one.
• The device is now named Radmon <station>.
• Want owner mode? Entry → ⋮ → Reconfigure → enter the data-sending password.

See the changelog for everything that changed.

How it works

Mode	Request	Example answer
Owner	radmon.php?function=lastreading&user=…&password=…	18 CPM on 2022-12-03 17:49:31UTC at Blackpool, …
Owner	radmon.php?function=lastreadingusv&user=…&password=…	0.225 uSv/hr on …
Public	radmon.php?function=showuserpage&user=…	Small HTML page with the latest CPM, time, coordinates and counter model

Owner mode also loads the station page once a day for location metadata. Radmon never downloads the full station list or graphs, which radmon.org restricts.

A daily API watcher checks that these endpoints still answer as documented and opens an issue if they change.

Troubleshooting

Problem	Fix
Station not found	Names are case-sensitive. Copy the name from the station list.
Invalid password	Use the data-sending password your counter uploads with, not your forum login.
Asked to re-authenticate	radmon.org rejected the password, for example because you changed it. Enter the new one.
Online is off	The station hasn't reported within the Offline after window. Check its page on radmon.org.
Dose rate looks off	In public mode it's calculated. Set the conversion factor for the station's tube.
Sensors not updating	Enable the diagnostic sensors and check the last update status, then download diagnostics from the entry.

For debug logs, add this to configuration.yaml:

logger:
  logs:
    custom_components.radmon_scrape: debug

Credits

• Data from radmon.org, run by volunteers (thanks to Simomax and mw0uzo for the service and its API) and fed by its community of station owners
• Original 1.x integration by TranQuiL (@Malosaaa)
• Built and maintained by DonTranQuiL

radmon.org is free and costs its volunteers money to run. If you use it a lot, consider supporting it.

Disclaimer

Unofficial. Not affiliated with radmon.org. Radmon is not a safety device and its readings must not be used to protect health or life.

Support

• Docs: dontranquil.github.io/HA-Radmon
• Issues: GitHub Issues
• Community: Discord
• Tip jar: Ko-fi · Liberapay

License

MIT, see LICENSE.