Does anyone know how self levelling 'laser levels' work?

[e100]

That's the kind you get from a hardware store that projects a horizontal or vertical beam used for aligning things when building rooms in a house etc.

https://youtu.be/xiGTMJGB7vQ?t=7

I watched a bunch of teardown videos but it wasn't entirely obvious if they are purely mechanical pendulums with some kind of damping, or if they are accelerometer based like those fancy gimbal stabilizers used for holding mobile phones as cameras.

They seem quite small for a purely mechanical mechanical system. I kind of imagined something bigger like you would find in a pendulum clock.

[ace1903]

I have two older units, probably something 2000s. One of them is with two separate spirit levels and the other one is with one spirit level with bobble that goes in x-y plane.
On spirit level there is IR sender with two receiver diodes to find it when it is leveled. Maybe newer units have accelerometers but I think that old technology is dirt cheap and intrinsic no drift proved
I also would like to see what is in newer units and in receivers units that make leveling easier.
Attaching pictures of the second unit.

[e100]

Interesting, I did a search for "electronic bubble level" and "LED bubble level" but it didn't turn up any pictures that looked like a combination of old and new technologies.

[RoGeorge]

The ones I know are all based on mechanical pendulums, and from there with all kind of variations.

Some have a rotating laser (or mirror) to "browse" a pointy cylindrical LASER beam, some others have a diffraction grate instead of a rotating spot, which makes a "static" flatten, surface-like, LASER beam.

No matter how they prepare the LASER plane, by rotation or by diffraction, these reference LASER planes are aligned by mechanical pendulums, and inside they have mechanical calibration screws for calibrating the tilt of the laser planes.  They also have some mechanical locking mechanism, to block the pendulum when not in use, so to avoid damage during handling and transportation of the instrument.

[tautech]

The ones I know are all based on mechanical pendulums, and from there with all kind of variations.

Some have a rotating laser (or mirror) to "browse" a pointy cylindrical LASER beam, some others have a diffraction grate instead of a rotating spot, which makes a "static" flatten, surface-like, LASER beam.

No matter how they prepare the LASER plane, by rotation or by diffraction, these reference LASER planes are aligned by mechanical pendulums, and inside they have mechanical calibration screws for calibrating the tilt of the laser planes.  They also have some mechanical locking mechanism, to block the pendulum when not in use, so to avoid damage during handling and transportation of the instrument.

Not so much.
The leveling pendulums have very limited travel and initial leveling adjustments typically with a bullseye bubble place the assembly within a range that the autoleveling pendulums can do their thing. But yes within reason they are a precision mechanism and need be handled with some but not extreme care.
Those I've adjusted just had 2 setscrews at 90^o so to adjust the laser axis to level planes once the auto-leveling had done its thing.

[PlainName]

If they can move they can be rattled until they fall apart, so any reasonable level would have a locking mechanism, even when the unlocked travel is small, for transport (which might be someone's pocket, not necessarily an Amazon tumble drum).

[tautech]

If they can move they can be rattled until they fall apart, so any reasonable level would have a locking mechanism, even when the unlocked travel is small, for transport (which might be someone's pocket, not necessarily an Amazon tumble drum).

When in reality they don't.
Self leveling laser and optical dumpy's have been around for decades and none I've used (several) ever had locks.
Think about, if the level is outside its self leveling capabilities it can self lock the pendulums.

[jpanhalt]

It's not just the travel, but the acceleration.  Imagine a swinging weight on a pendulum.  One could bend the pendulum or upset the bearings.  My Leica Lino L2, which appears to be a mechanical device, has a lock.  My earlier "torpedo" Craftsman level, which was based on this https://datasheet.octopart.com/MXD2020EL-Memsic-datasheet-11764527.pdf Memsic MEMS accelerometer, did not.  Of course, that accelerometer was rated for pretty high g.

[PlainName]

If they can move they can be rattled until they fall apart, so any reasonable level would have a locking mechanism, even when the unlocked travel is small, for transport (which might be someone's pocket, not necessarily an Amazon tumble drum).

When in reality they don't.
Self leveling laser and optical dumpy's have been around for decades and none I've used (several) ever had locks.
Think about, if the level is outside its self leveling capabilities it can self lock the pendulums.

Just had a quick look at an Amazon search which turned up many different makes and styles: Bosch, Kiprim, KAIWEETS, ANOther, DeWalt, Makita, etc. Range from £26 to £146. All of them had a pendulum lock. Some have it built into the power switch or lens cover so it's not obvious, but it is there. Perhaps you could provide a link to one of the ones you've seen without it?

[tautech]

Leica and Topcon don't but this stuff is in another league to the cheap stuff on the market which is mostly garbage.

[PlainName]

Leica and Topcon don't but this stuff is in another league to the cheap stuff on the market which is mostly garbage.

Easy for you to say, but:

https://www.laser-measure.co.uk/leica-disto/leica-lino-l2-plus.html

[tautech]

Leica and Topcon don't but this stuff is in another league to the cheap stuff on the market which is mostly garbage.

Easy for you to say, but:

https://www.laser-measure.co.uk/leica-disto/leica-lino-l2-plus.html

Yep easy as any construction grade laser I've used didn't have travel locks.
This sort of stuff:
https://www.tradesurvey.co.uk/product-category/levelling-and-line-lasers/rotary-lasers/

[jpanhalt]

Before anyone runs out to buy that Leica, the battery case is crap.  After a short time, the cover broke, can't be repaired, so I hardwired a workaround (rechargeable external batteries).  It doesn't even have rechargeable batteries!

[PlainName]

Leica and Topcon don't but this stuff is in another league to the cheap stuff on the market which is mostly garbage.

Easy for you to say, but:

https://www.laser-measure.co.uk/leica-disto/leica-lino-l2-plus.html

Yep easy as any construction grade laser I've used didn't have travel locks.
This sort of stuff:
https://www.tradesurvey.co.uk/product-category/levelling-and-line-lasers/rotary-lasers/

OK, well you are talking about a different thing there. Recall that I said:

If they can move they can be rattled until they fall apart

The stuff you are talking doesn't have loose stuff to rattle - they are motor-controlled hence not free-floating pendulums amd don't rattle. You can verify that since when the level is manually adjusted it allows you to set it on a slope and then adjust via up and down buttons.

Further, if they did have free-floating pendulums, for the price you would expect the things to automatically lock when you turn off the power. Take one and shake it to see if there is any rattling. I would put money on the answer being 'no'.

[tautech]

The stuff you are talking doesn't have loose stuff to rattle - they are motor-controlled hence not free-floating pendulums amd don't rattle. You can verify that since when the level is manually adjusted it allows you to set it on a slope and then adjust via up and down buttons.

Most rotary lasers have 3 adjustment knobs so to get the laser level enough for autoleveling to work.
Those that have up/down buttons are different beasts, they are gradable lasers and used in commercial pipe laying and sometimes small scale earthworks however GPS systems have become more popular as models can be uploaded into a GPS system to set the limits of an excavation.

[RoGeorge]

The OP was asking about the small ones, for the interior "building rooms in a house".

The big ones for the construction sites, shockproof and good for up to hundreds of meters (but I never had or used any of those), seems to have two internal motors for auto-leveling, so they don't have the usual rattling parts that needs locking.

For the curious, at around minute 6, the inside mechanism can be seen very well.  On a desktop, by pausing the video then pressing the keys "," or "." (same keys with the symbols "<" and ">"), the video can be seen frame by frame:

[MathWizard]

The problem of a self-leveling laser would make for a good design test. Ages ago I tried thinking of how an analog light following robot might work, I never got there yet, but it's fun to think about. I bet I'd get a lot closer now again. I can't wait till my day job slows down again. Then going digital with micro-controllers, that's another route I'd like to try from scratch, that would probably be way easier.

I have a bunch of little sensors like optical position readers and stuff salvaged from printers/etc, but I've never taken the time to do anything with them, even copy and paste. But now as I learn more from EE from books, I can't wait to try to make stuff too. Like remote control curtains's, like Doc Brown might have LOL.

[ConKbot]

The cheap home improvement store ones ones I've seen have just been two line-laser units a in frame suspended from a two-axis pivot. A rare earth magnet on the bottom of the pendulum frame, and copper disc for damping the movement of the magnet.The lasers would blink of the bottom if the pendulum assembly hit a conductive ring around the damping disc so you know it's not level.
The one in the YouTube video in the first post looks like its the same. Between the beam quality looking like a line laser module, and the way the jiggle looks similar to the one I've used, i'd bet its constructed in a similar manner.