I've seen an explosion on the market of keyless door locks, keyless dead bolts, and so on. Schlage sells a bunch. From the looks of it, most of them are powered either by a 9V battery or some number of AA batteries. Since there's always an actual key slot, you can rest assured that you can still get in even if the battery dies. But what I'm wondering is if there are any keyless locks that don't require a battery? I'm not sure if such a unit exists in the first place. For something like that to even be possible, you'd likely have to run some power wires through the door frame somehow. I am not sure if that is even possible to do, or if any such unit exists. Are they all battery-powered, or is it possible to have a hardwired keyless lock?
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3Is your goal "no batteries" - in which case the answer of a mechanical keyless lock is a perfect solution? Or is it "electronic lock that doesn't need batteries" in which case "hardwired" is the solution? Keep in mind that (until relatively recently) most electronic locks had to have wires for data to authenticate key cards, etc. so there are lots of different solutions. What is the actual goal?– manassehkatz-Moving 2 CodidactCommented Jun 1, 2020 at 20:08
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1All the ones i've seen are on apartment buildings, offices, etc, which have the access mechanism hard-wired in the frame, not the door. Many consumer smartlocks have hidden battery terminals you can use from the outside if the battery dies, and you can keep an extra battery outside without much risk...– dandavisCommented Jun 1, 2020 at 20:20
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There are several ways to skin this cat in a commercial setting (electromagnetic lockset, electric strike, and so on). Just keep in mind that you must provide for free egress from the inside even if someone has lit the entire access control system ablaze :)– ThreePhaseEelCommented Jun 1, 2020 at 20:38
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You could put the battery in the key...– MastCommented Jun 2, 2020 at 17:23
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1If you're happy with the design and functionality of the Schlage electronic locks, you could always use an off the shelf Schlage, take out the battery pack and replace it with a hardwired power cord (my lock uses 4 AA's, so a 6V DC power supply would do it). Should be much cheaper than any commercial lock option.– JohnnyCommented Jun 3, 2020 at 3:17
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7 Answers
The word you're looking for is "Electric strike".
In this system, the door latch is not powered or operated at all. The door striker plate is. In essence the door frame lets go of the door.
Obviously, since the strike is in the door frame, it's not moving, and running power to it is trivial.
answered Jun 1, 2020 at 23:55
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1Just make sure to specify the correct lockset function so that free egress is permitted Commented Jun 2, 2020 at 2:41
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2@Mazura How is it non trivial? It's just a couple of wires through a fixed door frame. There are plenty of issues that electric strike plates can have (bad alignment, not very crowbar resistant, etc) but how is running the power a problem? Commented Jun 2, 2020 at 8:51
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Some have the actuator in the door leaf rather than the frame (I have these units, I understand they are still the only option which provides multipoint locking, e.g. for uPVC doors, with a single actuator. They were 6 years ago when I installed them). In my case, the unit is externally powered with a continuous 12V supply and a separate unlock signal.– rolingerCommented Jun 2, 2020 at 9:10
There are mechanical combination locks.
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1Further, there are high-quality (rated for use by DoD to secure vaults) combo locks which use the first few spins of the dial to power up the internal electronics, after which one turns the dial until the digitial display shows the desired number. Might be too expensive for the average home Commented Jun 2, 2020 at 19:36
I've seen hinges that carry power in commercial settings. I became aware of one in an office I worked in, when it started having issues and heated up a bit.
A bit of googling and I found that Stanley makes one for about $100
Another option similar to the electric strike is a Maglock or Electromagnetic Lock.
The door needs to be ferrous, so if its not mostly steel then a steel plate needs to be securely fastened to the top corner.
The magnet is mounted under the lintel and wired to a power source. When power is applied, the electromagnet attracts the door with hundreds of kilograms of force, which is more than you can generate by yanking on the handle.
Advantages:
- Doors can all be locked and unlocked by a building control system on a timetable.
- Doors can be briefly unlocked by a swipe card / proximity tag reader and then immediately lock again, to limit tailgaiters.
- The door's state can often be read by the maglock - so if someone has wedged the door open then the current drawn by the energised lock is different, so the building control system can raise a "door not secured, please check" alert.
Some downsides:
- You have to be mindful of tall people though - losing a couple inches out of an average door height puts it into head-banging range for taller people, which is unpleasant.
- The door lock requires power to stay locked - in the event of power failure, the door will fail to an unlocked state. They're normally backed by an alarm battery good for days, but these can be forgotten. The fix is to have a secondary key lock, and after a day of no-power someone has to go in and lock the doors with the key.
- Cost - there's wiring to be done to each door, and a steel plate fastened to the moving part.
- These don't work with sliding doors, but they tend to have motors which can simply be turned off achieving a similar goal.
- One failure case is if the ferrous plate has come off the door then there's no way for the sensor to know the door is insecure. I saw one that had been in this state for possibly years, but noone had tried it when locked.
- Lastly, these are not bank-vault grade locks. Hundreds of kilograms can be generated by a vehicle yanking at the door via a chain. However this will still slow a forced entry giving time for security guards to respond.
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1Note that plenty of cheaper maglocks where I live, can be so bad that you can actually kick the door open despite lock.– GnudiffCommented Jun 2, 2020 at 7:50
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2Are you certain that wouldn't work for a sliding door? I've never seen one in that application, but it does seem to me that it would work to prevent a sliding force as well. Also, unlocking in the case of a power failure is often considered a safety feature - if the power goes out because of a fire, having the doors unlocked allows panicked occupants to safely exit. Of course, if you're not home and someone hits a power pole near your house, then your house is not secured until the utility company gets it fixed, so there's that...– FreeManCommented Jun 2, 2020 at 11:11
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1Maglocks also need extra help to allow free egress while locked... Commented Jun 2, 2020 at 11:42
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1If the ferrous plate has come off the door, then if the lock is "unlocked" won't it fall off completely when the door is opened? (This situation would allow the door to be opened without being "unlocked" though, and the plate would simply stay attached to the magnet) Commented Jun 2, 2020 at 16:40
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1I've been in a hotel that had a magnetic lock. It looks and feels cool, but is a ridiculous waste of power. The coil part of the lock was very warm to the touch and it was running non stop. Commented Jun 2, 2020 at 19:29
There are systems like Opera iControl that allow to have (possibly custom) control unit next to the door frame. This unit is responsible for decision for opening the door and can be mains powered.
The part inside the door itself is battery powered, and activated by the coded infra red signal from the control unit. The IR sender is embedded into the striker and is both powered and activated by the 12 V input that can come from anywhere.
The "in door part" uses very little power to move the tiny control latch somewhere in the lock. The much larger deadbolt is then moved by a human pressing the handle, but for the outer side this can only be done if the control latch permits. The battery finally needs replacement or recharging, but under the normal door usage (few openings a day) it can probably last for many weeks.
These locks can always be opened from inside, with and without batteries, locked or not, by just pressing the handle. From outside, they can be opened with the key if the battery dies.
I have seen many such locks in the hotels of Italy.
While not provided by the manufacturer, it may be possible to design some kind of induction charging for the battery in the lock, with sender and receiver coming into proximity when the door is closed. Both chargers and receivers are available on the market. Depending on where does the door is, a solar battery may also work.
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5The batteries only last for weeks??? Yikes! That sounds like a horrible security nightmare trying to remember to replace batteries on a monthly schedule– FreeManCommented Jun 2, 2020 at 11:13
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@FreeMan I'd guess the batteries are only there as backup, where the main 12V supply drops because of power cut for whatever reason.– CriggieCommented Jun 3, 2020 at 19:48
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1I'm hoping that was a typo, @Criggie, and was supposed to be "years". Though, I suppose "weeks" of functioning (a few minutes here, an hour there) when the main house power is off would be sufficient.– FreeManCommented Jun 4, 2020 at 11:06
There's a European manufacturer called NUKI that makes a hard-wired smart door (https://nuki.io/en/smart-door/) However, it's not available in the US at this time.
There are ways of adding solar panels to the door (assuming it is an outside facing one) so that it recharges the batteries in the lock.
