Thanks to the work of github member “Hypfer”, it’s now possible to use the cheap IKEA PM2.5 sensors as a MQTT source. I set it up with my homey as follows:
- Applied the hardware mod with a Wemos D1 Mini
- Put the supplied sketch onto the D1.
- Installed MQTT broker and MQTT client on Homey.
- Set up MQTT on the D1
- Create a virtual device on Homey (type: sensor, air quality) by using the Virtual Devices app
- Add a flow to homey: "
IF
MQTT Client Trigger when a message is received on
“/home/data/pm25/1”
THEN
PM2.5 (virtual sensor) Set the value of a virtual sensor measure_pm25 to “message recived via topic”
It will work like a charm 
And it’s pretty cheap for a smart sensor of this kind.
Find the github repository here:
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Awesome find!
How often does the Vindriktning update PM readings?
A couple of times every minute.
Did you modify the .ino file or did you just uploaded it to the Wemos?
I didn’t modify anything, just uploaded it. Configuration is done through the web portal.
I have done al the steps as mentioned in the first post. Unfortunatly I don’t receive anything from the sensor. In the developer tools I see that it is pushing data to the pm25 sensor. But still nothing is received…
I’m fairly sure your sensor data isn’t being published to /home/data/pm25/1 but to esp8266-vindriktning-particle-sensor/VINDRIKTNING-XXXX/state
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That did the trick (first time MQTT is a little bit a search 
).
Now i’m receiving data: {“pm25”:9,“wifi”:{“ssid”:“ssid_name”,“ip”:“192.168.1.122”,“rssi”:-58}}
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