the recent LTT video where he runs down all the problems with his house feels so vindicating towards my decision to never do smart control of anything in my house.

monitoring on the other hand is pretty neat.

I still want to finish designing my whole-house mains power monitoring system. there are some existing projects that do this but I looked at the schematics and they do a bunch of things wrong, especially around the CT sensing.

@gsuberland The worst bit is waking up boiling hot or freezing cold when some part of the system decides not to work.

@gsuberland to some degree I think that’s a choice people make. It is possible to go fully local only, so many people’s idea of a “smart” home is that the light switch is now buried in three different mobile apps rather than on the wall. That’s not an improvement, and if I were in that situation I’d rip it all out.

@gsuberland my headmate built a "smart home" network with openhab and a bunch of zigbee things (only zigbee) and although it took her a bit to set it all up, it's been working essentially perfectly for 2.5 years with no interruptions outside of brief power outages and no ongoing maintenance that we frankly have no effort to spare for

very happy with how it works

@gsuberland My system has been doing very well but it really hinges on choosing the right parts and the right protocols, a lot of unreliable crap out there

@gsuberland she used lightbulbs that treat a power cut as a command to toggle state so the lightswitches work even if the entire network is down, so everything that's safety-critical like lighting has a local override

@gsuberland in retrospect and from seeing others talk about it, i think her decision to go "zigbee only, no proprietary tech, no 'hubs'" was probably what made all this shit work reliably enough that i forget it's even there

@gsuberland (when reading this, keep in mind that for me "standing up to flick a light-switch" can be a multi-hour process, so a smart home system isn't just a toy but something that i need on an everyday basis, and it has to be reliable too)

@whitequark yeah for accessibility it's a gamechanger for sure, if it works well.

but yeah, getting it to work well is... oof

@gsuberland I use devices from egauges.net which can provide revenue-grade metering, and they are also data loggers with a local API, no cloud service involved. I like the data logging aspect as it means I don't lose any data when the monitoring software crashes or gets upgraded.

@gsuberland I desperately want some kind of fancy (probably TDR) mapper that can tell me where the hell my circuits are. But its probably cheaper to just hire someone to do it.

(My mains panel is 70 years old and kind of terrifying, so that needs … work … first.)

@gsuberland Please do share if you get something nice working. I've got some old SEL gear hooked up, but would like a bit higher bandwidth system to see when fun things happen.

@AMS I do actually have a mostly-completed design but it's from way back, when I wasn't as clued up.

the general topology is one mainboard that's fully low voltage, then pluggable fontend modules for doing the mains measurement.

the modules have a pair of ADuM3473s or similar providing two isolated inputs and six isolated outputs in total, plus isolated bipolar power (with LDOs afterward) referenced to mains neutral. then I use direct resistive division and shunt current measurement.

@AMS the isolated inputs are two clocks used to drive the voltage and current ADCs. the isolated outputs pull the serial data back from the ADCs. so each module can do three power feeds.

the idea behind doing direct in-path resistive shunt measurement is that with CTs you get phase error, which is a bit of a blocker for trying to measure power factor or fast current transients.

and the frontends are modular for easy replacement but also because many ADC ICs go out of prod/stock real quick

@AMS it isn't a cheap design (those isolation ICs are like £10 each) but it's still a lot cheaper than buying a commercial one with half as many features.

@gsuberland My thought was resistive voltage and nice closed loop LEMs (or fluxgate LEMs if I find some cheap) for current.

@AMS yeah that's another way to go with it

thing is, I'm gonna be measuring voltage on each line anyway since I want to be able to see if breakers do anything wonky, for example, so since I already have to have some sort of isolated voltage measurement I might as well do the current measurement while I'm at it

@gsuberland
Isolation amplifiers are good friends.
@AMS

@vxo @AMS they end up being a bit more expensive in total, last I checked. with something like AMC3330 + AMC3302 it's about £10 per voltage + current channel (assuming I use the MCU's ADC to measure the amplified output, and I don't need any more opamps for biasing and such), whereas with the ADuM3473 option I can use commodity ADCs and get three voltage + current channels for about £22.

@gsuberland @vxo Yeah, they're like $4 in ones I guess (I'm used to the 100k+/yr pricing at work). 8mm isolated though and nice >80dB noise floor which makes things nice and easy from an isolation standpoint. Being cheap means I'd probably go non-isolated neutral-referenced power and voltag and isolate the current sense. Wifi makes for cheap and cheerful isolation to get the data out.

@kevin decent but pricey.

the two main reasons I want to implement it myself are that I don't want to pay £800 for it and I also want nerdy features like power factor analysis, THD%, frequency logging, and direct waveform capture during out-of-spec cycles.

one of the things I've been considering is ditching CT entirely and doing in-path resistive current sensing so I can get accurate current phase and even store the current waveform.