06 January, 2018

Xiaomi PM2.5 Detector


Remember my air purifier posts?

My search for quantifiable air quality led me to this PM2.5 meter. Random specs:
  • OLED screen (black and white, dot matrix)
  • 2 hour battery life
  • Has wifi, but not very useful
  • Has clock mode
  • There's a tiny fan in the back
Yea... what else do you want to know? This blog probably knows more than me about air purifiers http://www.myhealthbeijing.com/china-public-health/my-quest-for-the-ideal-air-purifier-is-over-xiaomi/
Again, air and water. Everybody needs these. All the time. Yet there is very little, you could say practically none, measurement and control over their purity, done by individuals. People only react to problems when they arise. No prevention and monitoring.
Singaporeans baffled by strong, mystery smell 26 Sep 2017
"A strong odour that smelt like burning chemicals or petrol, along with smoke that stung the eyes, fanned anxiety among many yesterday as it spread from north-eastern parts to the western areas of Singapore."
"The SCDF said at 9.55pm that its monitoring teams have not detected the presence of toxic industrial chemicals in the air.
In an update at 10.34pm, the NEA said it had received feed-back from the public about a gas smell in Sengkang and Punggol around 5pm.
"NEA officers were deployed to those areas immediately to investigate the smell feedback," it said, adding that air quality levels during the period were found to be well within safety limits."
Does anyone see the problem with this? We can only test for specific things, things we expect. Faced with an unknown chemical, we're helpless.

Anyway, sorry, this product won't help with this. It only measures particles. It doesn't detect organic compounds like alcohols. There are some detectors that detect formaldehyde and CO, but, again, these are very specific and won't warn you about other chemicals. Interestingly, the air quality sensors in air purifiers like the Panasonic one I have react to solvents like alcohol, as well as particles. If only there were a way to get a number out of them...

So here are some observations about the Xiaomi one:
  • Has wifi, which doesn't do much. Can connect to the Xiaomi server and let you see remotely, and occasionally log data. You can use it 100% standalone without wifi, then it's a simple display of PM2.5. Wifi can't be turned off though.
  • Seems to be meant for the China market for now. You have to set your locale to China in the Xiaomi app. At least you can switch the language to English.
  • DOES NOT LOG. Not their fault, I don't know why I expected it to. If you're connected to wifi, it seems to save readings every 30 minutes in the server. Doesn't seem to have memory of its own.
  • There's a clock mode, which isn't very useful. Time in 24hr format, date and day in Chinese. Can't be changed. Main problem is it reverts to clock display, which doesn't show PM2.5, you know, its primary purpose. No wait, main problem is IT DOESN'T SEEM TO EVEN MEASURE PM2.5 IN CLOCK MODE. By this I mean when I switch from time display to PM2.5, it acts like it's booting up and you need to wait to get a reading. At least clock mode can be turned off.
  • There's also a night mode, which doesn't do anything that I can see.
  • PM2.5 doesn't seem correlated to visible dust. I mean I still get low PM2.5 readings in dusty environments. I guess dust is bigger.
  • Shuts off in 30 minutes when running on battery.

So far, I think design is good, quality is ok, but it can be so much better with a firmware update. Choose clock faces? Display PM2.5 and time... together? Ok I'm assuming it doesn't even have a few kB of data for logging, which is poor design, but... log directly to the phone? Wifi hosting for portable use?

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