You should buy a PurpleAir air quality monitor

Check this out:

Air quality right now in SoCol. One of those is my house.

In July of 2018 I paid $244 to a company called Adrionics for a chunk of PVC stuffed with electronics, the PA-II:

Mine, mounted next to the garage door

It’s a sophisticated, lab-grade piece of hardware – twin laser-based light scattering particulate sensors, and it measures how much junk is in your air. In particular (a pun I am delighted with), the “PM2.5” size range most important to your health and lungs.

It’s rated for indoor or outdoor use. I put mine next to the garage door mainly due to the difficulty of running a power wire outside. Outside is better but you could benefit by having indoor and outdoor if you’re feeling fancy.

You can read about the PMS5003 sensor here, it’s pretty nifty. The PA-II uses twin sensors so you can plot and compare the two readings and thus get better data:

Science! You can connect directly to the sensor (it uses WiFi) and see the full details as well as temp, RH% and breakouts of counts per size range.

Leftover smoke from distant fires, I think.

And even if you don’t own one, head over to and try their map – you can see see local and regional quality at a snap, as with the top image in this post. I can tell, for example, that we’re in fire season as the quality is usually much much better. And if your health is affected (asthma, seasonal allergies or the like) then a sensor makes even more sense. There are other ‘smart home’ air quality monitors with designer enclosures; I don’t recommend them. Do your own research but I found that PurpleAir was a guy who started making these for himself and then for others who asked.

Which, yeah, is a lot like Paul Scurfield in another post in this series. Or Dan Fock.

Each sensor automatically shares its data so you benefit others too – I like that. I’ve done a few experiments with cheap air quality sensors and have come to believe that you can’t get good data without spending a chunk of money, so while this is a non-trivial expense I consider them a good value and recommend buying one.

Or maybe check the map – if someone nearby has one already, then just bookmark the map and benefit from some citizen science.


10gig completed

Two sfp+ transceivers and some reconfigurations layer…

Note the magic “10G” lights!

Full view.

A test via nfs shows 300MB/sec writes and 350 reads. Next I can play with jumbo frames and such. Might put an old SSD in the NAS to see if it’ll speed it up.

But even so it’s super fast.


Sunday prints

Cat and butterfly came out great, the Eiffel not so.

Tomorrow I try a portsfilter stand for a friend.


First 3D print

Much more to do and learn but not bad.


Is it still junk if the boxes are labeled?

How about nice, neat, printed labels? Asking for a friend.



I like having ways to see and measure things. Here is my server build:

Here is a simple AC wattmeter showing its consumption:

And here’s the system in infrared showing hot spots:

Measure and don’t just guess. More on low power Linux to follow;).


Power and energy consumption

I built a system that uses a ‘Raven’ Zigbee USB radio and Raspberry Pi to monitor our SDG&E electric meter, and layered Flask and D3.js on top to display usage.

Sometimes it looks quite cool:

Screenshot 2018-07-18 07.21.01.png

The baseline for the house is 225 to 250W, and the plateaus are the (high efficiency energy star) refrigerator. You can see where I got up, turned on lights and cooked breakfast, too. (Electric range and kettle.)

I’m pretty pleased with our usage and have put quite a bit of effort into reducing our consumption. LED bulbs, of course, but also low power servers and networking (61 watts total!), timer switches on idling electronics and measuring what things use. In-wall insulation is also a huge win year-round.

The code is at this GitHub repo if you want to roll your own.

It’s a weekend or two, but if you’re willing to puzzle it out, the data is nice and it’s purely local – no internet connection needed, no holes in your firewall, no sharing of the data. A few minutes reading should be convincing on why that’s worthwhile.



Sunday mini project

These Baofeng radios are awesomely cheap. All these for price of a Yuasa or Kenwood.