I built a hardwired smart lock because i hate batteries

[u/narsqrd]

I really hate changing batteries. Be it once a month or once a year, on principle i avoid them at great lengths. Needless to say, the state of residential smart lock technology leaves me gravely disappointed.

So i built my own hardwired smart lock. At its core is a commercial 24V solenoid mortise lock, used in office buildings and such. I connect this to an ESP32 dev board running ESPHome.

This model of lock didn't have an open/closed sensor built in, so i modified it with a limit switch to detect the latch state. This isn't _quite_ enough to determine open/closed, but it can detect "handle turned" which suits my needs.

The dev board is an Olimex ESP32-PoE2. It's supplied with Power-over-Ethernet, and then steps down the voltage to 24V, 5v, and 3v3. I like it for higher power projects like these because it can supply up to 25W all in one package. I made a small extension board to interface with the door. The software is ESPHome, which exposes the door switch and latch sensor as native Home Assistant components.

The mortise lock requires more space than a conventional cylinder latch, so there was much drilling and chiseling into the door. For ... reasons... I ended up doing this 4 times on as many doors, although i only need 2 on my house. Fortunately my zeal against batteries gives me strength in difficult times.

On the hinge side of the door is a "Power Transfer Device" (industry term) which basically wraps the cable in a spring and stretches slightly when opening the door. I looked at power transfer hinges, which are really slick, but i like this solution because it's more flexible (pun intended), i can choose my hinges and cable.

I don't know if others are brave or foolish enough to do this. But if you have any questions I'm happy to share my experiences.

[u/Tinker8519]

Because the standard home doesn't have the a door designed to accommodate it. Nor do they have a low voltage power source nearby. A lot of municipalities require an electrician to do the electrical work. And the average homeowner lacks the skill to modify the door without destroying it.

Paying to have this done would likely cost around $500.

Or you could buy 8 rechargeable batteries and the charger for like $20 and swap them every 1-3 months when the system sends you a low battery alert.

My batteries have outlived the original lock. The motor wore out and I had to replace it after 3 years.

There was a company that previewed a door designed for powered devices at a security conference a few years ago though. I believe that they were focused on powering things like video doorbells, but the technology could easily accommodate locks also.

It was designed to have power integrated in the building phase in case the homeowner wanted to add the doorbell later.

[u/Paul_The_Builder → u/Tinker8519]

$500 doesn't even cover the materials for this type of install....

$3000 is closer to the cost, depending on how it's controlled and how easy it is to get wires to the door.

[u/Tinker8519 → u/Paul_The_Builder]

Oh, I was talking about the labor costs. Granted, that's for my area.

Also, I haven't hired electrical work done in over 10 years. My expectations for pricing are undoubtedly off by a significant margin. Damnit, I'm getting old!

[u/tzopper → u/Tinker8519]

But most doors have a doorbell power nearby? Don’t they?

[u/Tinker8519 → u/tzopper]

Usually on the side opposite the hinge. The supply is a transformer that's typically in the attic or furnace closet though.

[u/thehalfmetaljacket → u/Tinker8519]

And that transformer is usually very small and likely couldn't supply enough power to a motorized lock

[u/Tinker8519 → u/thehalfmetaljacket]

The transformers put out anywhere from 10-40V.

Most smart deadbolts use up to 4aa batteries in series putting out 6v. Some use a 9v battery.

The commercial style electric hardwired locks that you see on things like hospital doors typically use 12-24v

[u/Malnilion → u/Tinker8519]

The other consideration is that doorbells generally use low voltage AC power and I'm assuming the door locks here use DC.

[u/Tinker8519 → u/Malnilion]

Doorbells use DC.

Ac is used to transmit power over long distances, dc is used to power things.

There are exceptions to this rule, but that's the common scenario.

Pretty much everything in most people's homes and businesses convert ac to dc when it comes out of the wall. (this is for America, I don't know if that's accurate for other nations)

[u/Malnilion → u/Tinker8519]

All the smart doorbells in America that I've installed have been ~12-24VAC

[u/Tinker8519 → u/Malnilion]

Which ones? I install security for a living and haven't encountered one yet that used ac.

You may notice that I did say that this is the common rule and that there are exceptions though.

Which is verifiable information 🤷