As part of my ongoing air-exchange-based HVAC project, I have an outdoor air quality sensor from Ambient Weather (disclosure: nothing to disclose, no sponsorship, I bought it). It’s battery/solar powered, and that’s fine… except for the part where that doesn’t work here in the winter. We’re too far north and too dark.
But since it plugs in to charge and keeps working when plugged in, winner winner chicken dinner, right?
WRONG! Because first you have to take the bottom off the case, then the charge plug sticks directly out from the bottom facing down, like a goddamn Apple Magic Mouse.
I can’t fix the mouse, but I can fix this, and I have made a printable tray and rack system to let me use it that way. And, of course, I’ve put it up on Thingiverse.
I’m rather pleased with it – I think the design is pretty good – but in all honestly my favourite part is…
you know what they call positive fitment in the machining world? When two things really fit together just right?
This has that. At least with my print settings. It’s just… thonk and then it stays, and it does this with a third object I didn’t even make so had to measure out myself, and that’s just … yeah. Oh yeah. That’s the good stuff.
Ambient Weather unit held over my 3D-printed tray and rack, with the cord going through the tray and rack down to an outlet while plugged into the air sensor. Three of the four mounting rails – the ones that thonk into place – are visible.
Did I already push out another new version of ambient-hvac, this one adding a new seasonal mode for spring/fall? And only a day after pushing out the biggest update since launch?
huge code refactor, it has a config file now, and it has all the added functionality i’ve been talking about for the last few months. it is i will admit still kind of a mess but despite that it still grows ever more l33t. enjoy!
Oh hell yeah the air-exchange vent did the thing! It’s probably not the first time but I did just roll out the code over the weekend and it’s the first time I’ve caught it doing this:
log file output showing ambient_hvac noticing the air outside is better than inside from a 2.5nm ppm standpoint, and opening the air exchange vent to let outside air into the house filtered air circulation loop
What’s happening here is that the system is reporting that indoor air was lower quality than the outdoor air by enough points that even though the temperature directly was wrong, it activated the air-exchange for five minutes anyway to help with air quality. Then it closed it down again.
ambient_hvac at work!
I probably need to fiddle with that buffer number – an indoor of 9ppm is still very good and could even have been a false reading and 4 probably isn’t better enough to care. And I don’t want to be stressing the air-exchanger. But this is all more testing phase so of course it’s going to be a little wibbly at times. I’m fine with that. What matters is: it’s working! 😀
100% live data, folks. Got the new controller hooked up to the actual, real air-exchange system and we’re up and running. 😀
Semi-passive/air-exchange HVAC assistance system running against live data on real hardware. We’re in summer mode and it’s warmer outside than in – building composite temperature 22.0°C, outdoor 22.5°C – so the actual real-life air intake vent for the exchange system is closed, and was closed by the system. Lots of other data shown as well but those are bits that matter. .
So I spun up my air-exchange HVAC system’s test platform in “summer” more with the new air-exchanger controller board set up and programme, and it checked all the temperatures, recognised it was cooler outside than in, overrode the time-of-day basic programme and wirelessly opened the vent to bring in cooler air!
Or turned on the little lamp standing in for the vent, whatever. It’s still proof of functionality! And while it is a test platform – running in parallel to the real one – it’s still working off live data. So it’s literally as real as the production version!
the little white light means it’s working!
Indoor temperature was a warm 21.5°C, so in Summer mode, the system should trigger air exchange and bring in outdoor air to cool the house via the air exchanger. And it did! And then I put it into winter mode and it flipped back to closed, also just as it should.
SMOKE mode closes the vents too – we’ll need that in, well, smoke season.
I set smoke mode manually but again, everything else is live data, including the air exchange status display. It’s querying the board via wireless and getting the correct answer. If you unplug the hardware from power and plug it back in, it’ll see that the board reset itself to all-vents-closed and tell you, before fixing it. 😀
Indoors is 21.5°C and the software and hardware are opening the vent correctly in each mode
I also have a little bit of error handling. Just enough really? But it’s enough in that it tells you it can’t reach the board. After grabbing this capture I changed the code so it’s bold instead of ALL CAPS but it’s the same otherwise. That’s just formatting:
Anyway my plan(?) is to physically hook it up to the actual air exchanger hardware this weekend. Unless I change my mind. It’ll operate in place of a timer that’s down there at the moment, running on a set schedule that I’ve been changing a few times a year. That’s been neither optimal or fun, so having a proper way to do this – a way that actually responds to live data – is going to be pretty great and will hopefully will gain us another few percents of efficiency.
Bonus points: it’ll run off the furnace’s 24V DC system so I won’t even have to get sketchy with running electrical power to the board. All I need is one of my buck converters and it’s ready to wire up.
This is already a good system and it’s going to become a really good system and if I don’t have to flee the country it’s just going to be so nice having it here. Fuck yeah automation. This is gonna be great. 😀
I am finally going to get remote control going on the fresh air intake vent – with expansion for three more. (And I have plans for those relays! Or at least ideas. Ideas. Yes. At least ideas.)
It’s not much to look at right now. I mean, it’s a little block of relays with a wifi transmitter on it. But it’s arduino programmable, which means that once you find all the firmware you need you can use it to turn things on and off using commands over your LAN. If you’ve done more than I have with Arduino, I’m sure it’s really quite straightforward – it’s not conceptually difficult for me, either, it’s just been incredibly fiddly given all the many stupid little things I didn’t already know.
LinkSprite LinkNode R4
The supplied firmware wants to talk to a cloud server in order to use it. Thankfully, Steve in Colorado said fuck that and wrote some replacement code, and it works. And now I’ve learned how to use curl for REST API calls, which I’ve never done before even though it’s like normally the first thing you do instead of the zillionth.
What this is going to let me do is roll actual temperature-driven air-exchange into Summer mode in my passive/air-exchange-driven HVAC assistance system – you know, the one where the core code is on my github. This has been a blocking issue for fucking ages, and I’ve just never had the combination of time and organisation to solve it.
But now it’s fucking solved, mate.
I still have some other things to do. This is a … holy shit I just realised something. I’ve been thinking I’d need to put in a power outlet down by the furnace eventually (which means pulling a permit) just for the stupid little 5v power adaptor, but I don’t, I can draw a little off the 24V DC provision for the current timer-driven system and use a buck converter to get it down to 5V for this thing.
And this after I went to all the trouble of wiring up a mains power 5V adaptor for this thing. Joke’s on me I guess lol – <BelaLugosiVoice>this simplifies everything!</BelaLugosiVoice> xD
Anyway. Once I have software control over the external fresh air intake, I can set it up so smoke mode is always closed, winter mode is… on a schedule I guess, since you always want some fresh air. I’ll have to write something to expose that as an interface clearly. But summer mode can finally be entirely temperature driven (with some kind of minimum exchange time again of course).
Or maybe if I get a CO2 sensor added into the system, I could drive it partly based on that. All year round. Or…
…or if I had an outside air quality sensor too then relative air quality could be a trigger. Whichever is cleaner! And if I can put in more intakes then I could have them on at least three sides of the building without having to open interior walls which means I could pull from the best available source temperature…
…! Lots to think about here. Finally!
Anyway. Um. Right. So I remember:
Turning relays on and off:
curl -X POST http://[boardIP]/api/relay/X/{on|off} where X is between 0 and 3 inclusive.
Turning all relays on and off:
curl -X GET http://[boardIP]/api/relay/all/{on|off}
Status of all relays:
curl -X GET http://[boardIP]/api/relay
This is going to be so fucking cool and I’m going to have it operational before summer. 😀
eta: am I aware of possible covid-19 applications? yes. i am. this is not a medical device. but yeah. i’m aware. 😀
I’ve finally got a github for that air-exchange cooling/heating assistance solution I've built using a combination of ambientweather and arduino leonardo kit. It's very much an alpha - I'm calling it version 0.3 - and more of a "here's some code you can use to build your own thing" than a "here's a software solution ready to install."
Anyway, enjoy ambient-hvac's codebase. There are also some screenshots but they're ones I've posted here before.
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