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Comment by bombcar | Hacker News Reader

All I want for these IoT things is being non-cloud dependent and PoE. I will run a billion wires before dealing with stupid batteries that keep dying, and they’re getting so expensive, too.

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PoE ESP32 for DIY IoT, fyi:

Non-isolated: https://www.olimex.com/Products/IoT/ESP32/ESP32-POE/open-sou...

Isolated: https://www.olimex.com/Products/IoT/ESP32/ESP32-POE-ISO/open...

Awesome, I've been using the wESP (https://wesp32.com/) for most things but I like the size (and price point) of these.

Granted, they fit different use cases as the wESP has more I/O exposed but is quite a bit larger.

These little boards are great - I'd recommend the isolated version for anything that might be referenced back to ground potential.

We have one in an OpenEVSE, it's been ticking along no problems for a couple years now. In that scenario, in theory the PoE allows the ESP32 to detect if the EVSE breaker pops - I've not had that happen, but it seemed like a worthwhile feature to consider ;).

That looks great. The 0-70C operating range is noteworthy if you want to use it for a doorbell, though.

If you're worried about sub-zero temperatures, couldn't you just have it busy-loop or even drive a small heater to generate heat? Just enough to keep the doorbell enclosure warm.

If it's running off PoE it's not like you have to worry about battery budget or efficiency so much.

Not sure if there are insulating materials available that provide good thermal insulation but not acoustic insulation?

Yep. Running the wires once is a big pain but it is linear at worst, more devices requires more wires, maybe even log growth since you can branch at junction boxes that already exist. Changing the batteries once a year is only a little pain, but it adds up fast when you have dozens of them, and it takes place routinely so it no better than linear growth.

The door lock not being able to unlock because the batteries had died trying to keep marginal Wi-Fi operating was the kicker for me. Very annoying.

Home infrastructure for power and data is due for a switch. Copper is expensive, and running 120V at 15A everywhere is really overkill with a 3w led bulb being blindingly bright and needing dc. Electronics largely are all hooked to USB-c chargers at this point. The poe to USB-c splitters are largely 5v at this point, but poe can produce over 70W depending on type, so it doesn't have to stay that way. Ideally, daya could be bridged as well, plug in usb-c start charging and it looks like a network adapter too. The number of things that need more than 70w isn't that high. Kitchen mostly. Bigger TVs. Real beefy laptops or desktop computers. If they made a new POE standard that could support USB PD3.1 you could run anything outside the kitchen other than the a/c. That would probably mean a new cable standard though. Even just as things stand, POE could largely replace electrical wiring outside the kitchen.

It's Big Wallwart, keeping us all down to prop up the transformer industry!

More seriously, would there be any electrical or interference issues with running usb-c power delivery cables everywhere?

The problem with low-voltage is lengths. I don't know how far USB-C as such can reasonably go.

PoE, of course, can go as far as the ethernet (usually) and so any future low-voltage system in homes will probably be based on it (it's already used in some commercial setups).

The other problem is wire size, since the amps go up as volts go down, and the heat generated in the wire is proportional to the amps, not the watts.

So to carry the same power, a lower voltage wire has to be thicker.

Yeah, the advantage is when the power usages is way below normal mains. We already see it (I have lights in my kitchen that have one transformer connected to the mains, and then all the rest of the wiring is low-voltage).

There's a reason why you want higher voltages: to minimize losses in conduits; i.e. you can move more effectively 12W in 120V/0.1A rather than 12V/1A -- the lower current, the lower resistance.

There are no 12V standards for wiring buildings, because effectivity-wise, it make no sense. Even the above-mentioned PoE is 48-56V (56V, so it can be 48V at the other end of up to the 100m long cable). The 5-12-20V USB PD is for relatively short cables, not for something that goes around your house.

Thank you for the informative reply, Lord Patrician!

Is it straightforward to step down the voltage from PoE to something that USB-C can use? My Forest M Mims Electronics book sits unread and dusty in a box somewhere so I'm not really able to interpret the schematics google is showing me :/ (apologies for extra questions)

There are PoE-to-USBC adapters available; random pick on Amazon: https://www.amazon.com/dp/B087F4QCTR (this one is af, 5V/12W and plain USB; no at, no QC or PD. If you need that, you will surely find it).

For DYI, there are dc-to-dc convertors available. Or do you intent to build your own?

It was more for curiosity's sake, but it's really cool that there's already converters. My project is very much in the "hey it would be nice if" stage right now, but I'm on the Python track at Exercism and want some "small" projects lined up once I'm finished there.

The idea is: pull in a quick 3D sketch of a home. Place (USB-C via PoE-power?) ESP32/Pi/Other devices at specific points with very precise measurements between them. Use them to determine the exact position in 3D house-space of Bluetooth low energy beacons. Use that info to help my very ADD wife find the things she loses. (because Tiles often fail)

A lot of the code to calculate position from timings already seems to be out there so I can cargo-cult things over.

In a far-too-roundabout way, that sorta kinda answers your question.

what's the difference in having a 120v->5v wall wart vs 48v->5v one?

Usually it's inside the wall (you can do this with USB outlets, too, which I recommend if you've already got 120v power).

But people who are uncomfortable running mains will often be fine running "low voltage" lines like ethernet.

It's a shame LK-99 didn't pan out. Cheap superconducting wire would have been awesome for this.

> the lower current, the lower resistance

The lower the current, the lower the losses. Resistance doesn't change. I^2*R is what decreases with current.

Ring mains in UK are 230V and is a more frugal approach to conductor usage, both because of higher voltage and the wiring being a ring.

You tea-lovers can also boil water electrically twice as fast as we can, it's unfair. I've seriously considered adding a UK-style 230v plug to the kitchen so I can use an imported electric kettle.

can you tap into your oven/stove 220v source? unless you're boiling water non-stop while trying to bake the thanksgiving turkey at the same time, there shouldn't be an issue

Most ways of doing that won't be to code. It would be better to add it as a separate circuit.

Code lets you do the weirdest things - you can't tap into the oven circuit with a separate outlet, but you can install a sub panel in place of the oven outlet, then run two lines from the sub panel, one to the oven outlet, and one to the kitchen plug.

All they care about is that you can't run more current down a wire than it's rated for.

My house is over a century old, nothing is to code anyway. I'm wondering if I could get away with a 20A 120v line meant for a microwave, and swap the neutral to the other leg and wire it to a type e connector. Type e is 16a so the current is fine, but the insulation was intended to separate 120 not 240.

The insulation is rated for 600v almost certainly unless you're running the original knob and tube, in which case you have other issues to consider.

Each leg of 240 is only 120, so it'd probably work.

Don't do it! But if you do it make sure it's breakered correctly and use a AFCI/GFCI combo breaker.

I went and asked an electrician. With a 240V 15A breaker it is completely to code as long as there is absolutely nothing else on the circuit. If there are lights or light switches it is a no go, and if there are other outlets, they would have to be either removed or swapped to the type e outlet as well. I find it weird they don't have a neutral ober there.

You can buy UL-certified commercial products that intelligently split a 240V outlet to two different loads.[0] They're popular in the EV community for avoiding the cost of a dedicated circuit for charging.

[0] https://getneocharge.com/products/neocharge-smart-splitter

$300 to not have to unplug your dryer to plugin your EV charger.

Hair straighteners and hairdryers also work better in the UK than they do in the U.S. for the same reason.

We have some IEC 60309 outlets for IT/AV equipment cabinets wired as 2P+E with both phases presented for 240V (no neutral). You can get PDUs which are happy with 200-250V, and the PSUs in a lot of servers and switches are happy with 100-250V 50-60Hz.

Our thermostats are 230V too, so stupid

Ubiquiti are using PoE for almost everything. It’s nice to be able to run a network cable and have it power cameras, wifi access points, switches, etc.

I know they've had their ups/downs in terms of business models and security (and product availabillity!) but I'm moving almost fully to Unifi for that reason. I don't want 120v power cords everywhere, I like the managed aspect of it. Cat6 into either powered PoE switches or PoE to PoE switches that are hard to reach so that multiple nearby devices can be used is so nice.

Leviton already makes the power version of this in my opinion:

https://www.leviton.com/en/products/residential/usb-charger-...

Move the USB-C PD inverters to be integrated into the outlets, instead of plugged in on top. I already did this upgrade for all counter-height outlets in my kitchen, and it's great!

The holy grail, of course, would be ethernet/data as well, but that is far more cost prohibitive

Those are nice for reducing clutter (I have some), but you're still running 120v on 12ga copper into every one of them.

I’m working on building a home and have been investigating this seriously. I want to put multiple POE outlets in every room, and running them to places that are common for automation (eg for cameras, motion sensors, control displays, etc). I wish I could get wired sensors for doors/windows but the pricing is honestly way higher than just Zigbee with a battery once for factor in wires in the walls and a centralized patch panel.

I never thought about converting POE to USBC-PD but that would be a great thing to add to the “office” and locations where someone may very occasionally want power for a laptop (eg near couch, beds)

I’m exclusively using “normal” 120v outlets that also have a 5v usb port on it, and placing extra where I can, which is less crazy but still practical.

If you need to run 15A across the room anyway, might as well use it for everything. 120v can carry more power with less copper.

We have separate lighting circuit that we could switch, but that's about it. And at that point it would be easier just to allow for thimmer 22AWG 120v 0.8A lines or something.

But electric codes assume people might want incandescents, that's not possible with just PoE.

I'd love it if we had wall outlets for USB that look like network adapters to the PC though. Why do we still use RJ45 when consumer stuff doesn't get past 1gbps?

Pretty much all door locks have apps which will tell you weeks in advance to change the batteries. I have a Schlage that has been rocking 4AA batteries for over 2 years.

I find Zigbee a great protocol for that. It runs locally (doesn't even go on wifi), and the sensors last for years on a coin cell.

Yeah, Zigbee works well.

The real killer is when you want to "do something physical" in the real world on batteries, like unlock a door, etc.

That nobody has come up with a powered doorjamb instead of powered deadbolts is annoying; I'll have to build one myself using something like https://www.americanlocksets.com/hes-1006cdb-electric-smart-...

Ah, yeah, mechanical things require a lot of energy, unfortunately.

That said, I'd love an ESP32 for Zigbee. I bought an H2, but the documentation hasn't been good enough that I could make it work.

I want solar powered. The doorbell probably gets pressed what, once in 5 days? Cover the enclosure of that thing in solar panels and have some super-capacitors for overnight power.

Those batteries are really annoying yes. Also these battery devices tend to be unstable. Every week I have to either re-pair something or swap out a battery.

When I get my own place I'll get KNX.

Can't help you with PoE, but Home Assistant is non-cloud by default.

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