AirGradient OSS/OSH Air quality multi-sensor. PMSx003 woos.

• AirGradient OSS/OSH Air quality multi-sensor. PMSx003 woos.
  Posted by paulca on 28 Mar, 2024 17:54
• I bought one of these from the states, in a (shamefully lazy) soldered, partly assembled kit form.
  
  https://www.airgradient.com/indoor/
  
  Out of the box it worked, but pestered for being registered with it's cloud.  I did note that all particulate mater values where 0.
  
  I flashed it with ESPHome based firmware and it works even better now without no cloud... and MQTT data, command and control ala HomeAssistant style API.
  
  Still however there are 0s and "NaN" values for the PM sensor. 
  
  I provoked it by lighting some cardboard on fire, then blowing it out and holding it directly under the sensor.  (CO2 and VoC went nuts)... PM sensor read 0.
  
  What I need to prove next is ... is that sensor duff or the combination of customizations on already 3rd party firmware.
  
  I have two options.
  
  Software:  Add logging debug probes to the various layers ESPHome, PSMx driver, UART LL.  Possibly even to the extent of running it in an Eclipse IDF with a JTag debugger...
  
  Hardware:  Solder 2 probe leads onto the Rx/Tx of the sensor and read it on the scope.
  
  I'm thinking the later is a far better use of my Saturday morning.
  
  Anyone any experiences with these?
• #1 Reply
  Posted by jmw on 28 Mar, 2024 23:20
• I made my own AQ monitor using a sensor that was a rebadge of the Plantower sensor that those devices use. By default they just chatter their readings over the 3.3 V TTL level UART pins. The data format is simple, https://aqicn.org/air/sensor/spec/pms5003-english-v2.3.pdf. If you have USB-UART interface, you can read the raw data frames in a terminal viewer.
  
  They're susceptible to an early death if the fans pull debris into the measuring chamber ... in my case, probably cat hair. They just permanently read the max reading for me. That's probably why the PurpleAir monitors have redundant sensors, mounted with the fans pointing down so things don't settle in.
• #2 Reply
  Posted by airgradient_achim on 29 Mar, 2024 11:46
• Achim, founder of AirGradient here. Thank you for buying our kit and supporting our open source hardware air quality project!
  
  We recently had a few cases where it appears that the PM sensors got damaged during transportation.
  I would like to send you a new one. Could you please send me a message through the support form on our website with a link to this forum so that we can arrange the shipment of the spare part?
  
  Many thanks!
  
  
• #3 Reply
  Posted by airgradient_achim on 29 Mar, 2024 11:49
• We had mostly problems with insects getting into the plantower. What helps for maintenance is to blow compressed air from time to time through the sensor to flush out these kinds of things. We have deployed thousands of these monitors and typically they last quite long.