Cajoe Geigercounter + Wemos D1 + ESPEasy

While adding additional sensors to my home, I stumbled across a Cajoe radiation sensor on Aliexpress:

It wasn’t too expensive, and the description promised it was easy to connect to an Arduino:

That would mean it wouldn’t be too hard to get data to Homey either!
After doing some research, I came across this topic on the Home Assistant forums:

People mostly use ESPHome there, but I didn’t want to jump through all the HomeAssistant/ESPHome config hoops. After doing some more research, I came across this topic that spoke about using ESPEasy to interface with the sensor:

Setting it all up was fairly easy.
Here are the steps:

  1. Install ESPEasy on your Wemos D1 (or other ESP device)
  2. Configure ESPEasy as follows:

Home Assistant (openHAB) MQTT. Make sure to select this controller on the devices tab as well, otherwise there will not be any sensor data on the mqtt channel.



on System#Boot do
 let,1,0 // total number of cpm's
  let,2,1 // number of measurements

On Geiger#Total do
  TaskValueSet 2,1,[Geiger#Total]*60/%unixtime%

On Geiger#Count do
  TaskValueSet 2,2,[Geiger#Count]*6
  TaskValueSet 2,3,[var#1]/[var#2]
  TaskValueSet 3,1,[Geiger#Count]*6/151 //calculates the Sievert rate for this specific sensor.

These rules make sure the dummy devices get the right values. CPM is the amount of particles captured per minute. The Sievert value is CPM/151 for this specific tube.

  1. Hook up the VIN pin of the sensor to D5, 5V to 5V, GND to GND.

  2. Setup a virtual device in Homey. I added the Geiger counter as a PM2.5 sensor. This is my only gripe with this install, because it doesn’t show the right unit, since Homey doesn’t know any radiation units.

  3. Add a flow to update the virtual device sensor value whenever a message is received on the mqtt topic.

  4. Enjoy knowing whether or not a disaster has happened!

The hardware (don’t mind the piece of insulation tape underneath the ESP. :sweat_smile: )


Great work! Any chance on testing out if it really works? (Without simulating a real nuclear disaster :sweat_smile:) also you got a link to where you ordered from on ali? And are you able to use this data on to setting an alert via homey?

Got it to work, it was a nice project to learn how mqtt works! :slight_smile: