Ask HN: Any tools to do generic WiFi imaging?
I have an older house (1950s) and I'd really like to see behind my walls without physically excavating so I can try to run some wires without encountering surprise obstructions. There are tools which use WifI to do detect humans[1] (https://www.tomshardware.com/news/wi-fi-routers-used-to-dete...) [2](https://news.ycombinator.com/item?id=40897828) but I'm looking for a way to use Wifi for more general imaging. There's a paper from 2017 ("Holography of WiFi Radiation)[https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.11...] and many other scholarly papers about object detection via WiFi, but I haven't been able to find any off-the-shelf products/projects that would just build a 3D environmental density map without any object detection. The resolution doesn't have to be great - not looking for millimeter scale features e.g. structural weakness. Is there anything out there that comes close? Given recent archaeological uses of drone LIDAR and satellite tomography, I figure the software for interpreting this kind of data should be pretty robust by now, just maybe it hasn't filtered down to the consumer market.
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[ 3.4 ms ] story [ 141 ms ] threadhttps://www.google.com/search?q=endoscope
Good luck.
Drilling gently through wood or gypsum, you will notice immediately that you got through the sheet, before you can even hit a pipe or anything else behind. Then use that hole for the endoscopy to map out the beams and sensitives behind.
Am i being overly paranoid ?
This is a good quality when drilling holes in the walls. Fortunately, technology to the rescue! Plenty of metal/stud/voltage detectors on your favorite hardware or online store.
If you assume that your walls are 12mm gypsum and you stop drilling after 12mm, nothing can happen, start slowly, use the smallest drill, tape your drill as stop reference. If you hit open air you will immediately notice that you’re through. If you don’t hit open air after 12mm, stop, think, reconsider. Maybe you have thicker walls, maybe you hit a beam, etc.
The difference between gypsum, wood and steel is so big you will feel the difference if you go slowly. With gypsum you can almost push a needle through with hand force, from there make the hole bigger. Concrete walls are a totally different story.
Don’t have the intuition for how it feels once you get out on the other end of a plank yet? Dry run using a scrap piece of wood, where you can see the back side. Pin some scrap wire on the back and see what happens when the drill hits a worst case scenario. In a real wall the wire would be assembled before the final panel so there you’d have even more spacing. Logically, the wire will be behind the sheet, not embedded inside it.
Check out the Gosforth Handyman on how to avoid pipes and cables: https://www.youtube.com/watch?v=DeTXAPYzqpY
(Note that the rules he describes on where cables should be are from UK regulations - other jurisdictions will have different rules).
[0] https://en.wikipedia.org/wiki/Borescope
Amazon (in India) turned up nothing when I searched for cool attachments etc.
1) ExpEYES (Experiments for Young Engineers and Scientists) - https://expeyes.in/
2) SEELab 3.0 which is a upgrade of ExpEYES-17 - https://csparkresearch.in/seelab3
I have played with the previous version of ExpEYES (ExpEYES Junior) using the Python software. I also have the Seelab3 but haven't played with it yet. You can buy them directly (don't buy from Amazon due to markup) from any of the dealers listed in https://expeyes.in/hardware.html (i bought my Seelab3 from Novatronics).
There is a Android version of the software for both and so you can use them from your Smartphone/Tablet.
I love that you immediately went to WiFi for this though. Gotta love us tech people over complicating things haha!
Metal detectors work well, but he'd have to go over each wall meticulously. That would probably take quite some time.
That said, if you want the job actually done any time soon, stud finder sounds like a better choice for now.
They're awful and if you don't realize they're awful then you might make regretful decisions based on their slanderous output.
Combine with some knocking to feel/listen for a stud right against the wall vs an erroneously detected pipe 1/4" away.
I'll also use a neodymium magnet in certain situations to look for drywall nails/screws in conjunction with the other methods.
I don't fully trust any of these methods, but together they'll get you as confident as you can be short of having a couple hundred dollar detector or taking the wall apart.
But it was not cheap, cost about $300.
If you just want to just find studs, use magnetic stud finder. Cost about $10. Very easy to use and accurate.
The knock test shouldn't be skipped.
https://en.wikipedia.org/wiki/Diffraction-limited_system#Nea...
It has been useful to find pipes and electrical with some confidence, when their location is called for.
Part 1: https://www.youtube.com/watch?v=o6WHhqDHSQ4 Part 2: https://www.youtube.com/watch?v=VABeN4uv03s
It won't show cables, unless they're hot. You can use an AC stud finder for that.
You can flip the photo between the actual and IR image, and it overlays an outline over the image.
I make a video in and out of the house on the hottest and coldest days.
The infriray is the Chinese knockoff brand which is actually better than flir because they don’t have to follow the US weapons law. So with it I get 30(?) fps instead of the ~5 with flir. Resolution is better too. It’s very sensitive and can clearly show a hand print on a surface for a minute or so even if you only touch it for 1/2 a second.
I’ll definitely just get a trigger style one that’s only 3-6ft max next time.
Pixel 4 have SOLI 60Ghz radar chips that allows various object categorization (eventually through walls applications).
Unfortunately the radar API was never released. It's unfortunate because a smartphone already has various sensors that ideally you'd like to use to do some sensor fusion using the camera and accelerometers to determine the position of the sensor and fuse the radar information in the map, like in those 3D photogrammetry room scanning applications.
Various object categorization :
https://www.youtube.com/watch?v=B6sn2vRJXJ4
https://www.theverge.com/2019/1/4/18168083/google-project-so...
Reverse-engineered attempt have been successful (but are locked behind paywalls (since it's a 2021 paper and sci-hub doesn't download recent (>=2021) articles during its trial in india) : "Reverse Engineering the Soli Radar API for Military Applications" : https://ieeexplore.ieee.org/document/9455321/
SOLI chips are based on infineon chips https://www.infineon.com/cms/en/product/promopages/60GHz/
You can find some demo board using the chip :
https://www.digikey.fr/fr/videos/i/infineon-technologies/get...
The walabot referenced in other comments is an example. Based on a different chip from https://vayyar.com/technology/ https://cdn.sparkfun.com/assets/learn_tutorials/7/2/4/walabo...
A drywall cutter is like a cast cutter; it works by vibrating and won't cut through wires, pipes, skin, ect.
If you don't want to use a stud finder, look for electrical boxes and remove the plate. That will tell you where a studs is. The rest of the studs are typically (US) 16" apart, but vary near corners and windows. You can often make an educated guess by knocking on the wall, the sound changes depending on if you knock on the stud.
if they are not in the typical 16" and your not near a corner, try 18" and 24". I'm in a house from an infamous builder in the early days of the cookie cutter developer cutting every possible corner and then finding new ones to cut, they are definitely not on 16". In fact, I doubt there was a tape measure used at any time during the build, and most things just seem to be placed by "that looks about right" measuring system.
Electrical boxes and light switches are the only ones to have faith in. Other types of boxes (like cable or phone) could have been added after the fact and just be attached to the dry wall if there's even a box.
I love my plaster walls but dealing with pipes/electrcial is a huge pain.
I ended up teaching myself to do a passable job with repairing plaster and being content with how it is.
Study the building code to determine with >95% accuracy what is behind the wall based upon surrounding fixtures.
As for following - after the 50's everything was, in theory, built to code with exceptions.
Worse case really is hitting a water pipe.
For your use case, you are primarily concerned with fireblocks. They are unlikely to exist in an older home. They can be detected with a simple stud finder, which range from $30 for the simple (good enough) kind, to $1000 for the radar kind. Simply knocking on the wall is also good for this purpose.
You likely have pretty fixed locations where you want the wires to exit into the room, so you can run a borescope through those places. These are also pretty inexpensive.
An alternative approach would be to use holographic principles, but these require you to measure very accurately the position of your transmitters, whether you use a multiplicity of them placed in different locations or employ Synthetic Aperture Radar methods with a single one (by moving your transmitter).
That is why using 60 Ghz radars (with 4 GHz of bandwidth and Angle of Arrival capabilities) at short ranges would probably be the most promising direction. You can get a dev kit for one of these from Texas Instruments or some other supplier for not too much money.