Any way to find a lost Kindle inside a house? | Hacker News Reader

Any way to find a lost Kindle inside a house?

ebooks.stackexchange.com

376 pointsmiles115 comments

Wait. So I can put few simple wifi-enabled microcontrollers in corners of my apartment and be able to always check where I tossed my phone just by looking at the tv or computer screen? How's that not a product?

I could even name few usual zones and have the name of the zone that contains the phone displayed on any screen in the house and on smartwatch. Also I could do the same for smartwatch. Can it be done for bluetooth?

Smartwatch <-> Phone finding via bluetooth is builtin mostly.

Because most people aren't interested in buying a bunch of devices to plug in at the edges of their house on the off chance it'll catch a lost charged device reaching out via wireless instead of just cleaning ;).

I don't think this claim is true. And "Most" is not enough. "Nearly all" is required to eliminate a market for alternative.

I guess I'm not most people because I'm definitely doing it.

Most frantinc searches of my phone happen as I'm about to leave the house in hurry. Cleaning is not an option then. I would have to be 'organised' which I absolutely abhore and want to avoid at all cost.

So far my solution was to just have a second phone in a fixed place so I can call my main phone and locate it by sound.

But the wifi triangulation thing sounds like way more fun.

You might benefit from a Tile. Put one on your keys and/or wallet, they locate bidirectionally via sound blasting (e.g. keys > phone, phone > keys). Or maybe Bluetooth beacons would work just as well?

Though if you’re in it for the fun factor then go for the wifi option!

Apple has find my phone. Problem solved

To be fair, Android does as well? Just typing "Android find my phone" into google produces a scary result.

I just ask my Google home to ring my phone

You may call your phone from the landline.

Because I can do that by saying "Hey Google, where's my phone" or logging onto Android Device Manager and asking it to ring my phone.

Likewise for iOS.

Unless you have two factor auth enabled.

For iOS at least you don’t need two factor to access find my phone

I have two-factor auth and I use a U2F key with my phone as backup security key. It still works.

Are you sure? This doesn't match my experience. I've had 2fa enabled on my G account for years, and it still worked.

I have 2fa on my Android and this feature works fine on Google home.

To everyone downvoting: just open an incognito window and try to use Google Find My Phone. You will be asked to grant 2FA through the notification on your phone or Google Authenticator in order to log in.

Also see: https://www.reddit.com/r/Android/comments/63d9ml/google_find...

Just give it a ring!?

Quite easy to locate the device using a Tile or other Bluetooth tracker that lets you ring your device. Or you can command it to ring via your Google account. Personally I've found the most expedient method is to just yell "okay Google!" at the top of my lungs and listen for the acknowledgement beep.

This is technically a product, just not an at home type of product. If you have wireless enabled your phone is whoring you out to anybody trying to listen in, and everyone else's phone. There's a lot of things these sorta devices can pick up on especially if you're genuinely connected to a network such as MAC address.

> To triangulate the signal (for a 2D location), draw a chart with the position of the laptop wifi receivers and for every pair of receivers, draw a line perpendicular to the line going through the points in a point inversely proportional to the square root of the mW power values, as the signal drops of proportionally to the square of the distance (for 3D use at least 4 receivers and a surface between the points).

It's worth noting that this isn't triangulation, it's trilateration. Triangulation involves angles. GPS does not do triangulation, it does trilateration. Similarly, here we are doing trilateration.

Do any of the whole-house Wifi systems have this built in? That would be very cool to have the triangulation be part of the product.

Mesh networking is just starting to get mainstream, so I am sure that this will become a standard feature in a few years.

Maybe, but the point of mesh networks is that each AP only has to see one other AP to work, and a device only has to be in the range of one AP. Because mesh APs generally take efforts to not talk over each other, they usually end up less powerful than other routers, leading to mesh setups like this:

|--a------|

|---------|

|--a------|

|------j--|

|--a---i--|

where a are the mesh APs and i is the item you're trying to find. If i can only be seen by the third/bottom AP, it wouldn't be any more useful than a traditional router (because from the perspective of i, it is a traditional router). Even if it could be seen by two APs (like j, for example), you generally need three sources to accurately trilaterate things so unless you have a minimum of three APs covering every single point of your entire house (which will lead to slightly worse performance and way higher spending, probably around three times the price), this probably won't work very well.

Or you could buy mesh routers that can all be seen from anywhere in your house... which would kill the point of making your network mesh anyway because then you could just use a single AP from that setup to cover your whole house.

They use less powerful TX but it doesn't matter if the location tracking is passive, no?

For triangulation, 2 measurement points are good enough if you only need the 2D location: https://en.wikipedia.org/wiki/True_range_multilateration#Two... - but of course home wifi environment is full of reflections and attenuations caused by the surrounding structures so straight triangulation doesn't work anyway.

As a lower-tech method I would try just setting up a super low TX power/RX gain on a spoofed access point (same SSID, credentials, MAC, etc.) on my ALFA USB adapter and wave it around as an RF scanning device watching for connected clients. Not sure if it would work as I'm not sure I could get it to be sensitive enough, but I bet you could at least get a rough idea of where the device was without too much trouble...

IIRC, Kindles only connect to Wifi intermittently to save battery.

In my experience, a Kindle connected to wifi burns through battery like there's no tomorrow. Like a percentage point every half hour. I absolutely keep it on airplane mode to preserve charge.

> In my experience, a Kindle connected to wifi burns through battery like there's no tomorrow. Like a percentage point every half hour.

It really speaks to the longevity of the Kindle that 50 hours of battery life ("a percentage point per half hour") counts as "[burning] through the battery like there's no tomorrow."

Or maybe it speaks to how little time most devices last, I can't tell.

(To be clear, your expectations are reasonable, as battery is a key selling point of e-ink Kindles.)

It speaks to the other devices.

I remember when I migrated from a flip phone to a smartphone a few years ago. I have been frustrated for as many years. One day I realized I could just buy a charger for every location I might stop for a while. Now I am not frustrated at battery life. I am frustrated with the solution.

It is not unlikely that this will be my next phone: https://www.thelightphone.com/

I love the idea of an e-ink phone.

their faq, under Battery Life, says

> The battery life of the Light Phone II is approximately 1-3 days of 'light' regular usage.

That's roughly equivalent to my iphone. I love the idea of an e-ink display, but it's not clear to me that this saved enough, on its own. Maybe the lack of entertainment/social/goof-off apps will reduce your use so much that you frequently hit maximum theoretical battery life? Is that the justification?

The reviews I've seen mention 3 days as expected battery life. Maybe I shouldn't trust them.

Haven’t had that experience. Just pulled out my Kindle that I haven’t used in a month yesterday and still 90% battery life.

Your Kindle is broken. Mine lasts for months on a charge.

I keep my Kindle on airplane mode all the time so this wouldn't work.

A lot of people do that to make sure it doesn't update itself without a warning and loose their jailbreak

Extending battery life is also a good side (main?) benefit.

This is why I do it.

or wipe your cherished copy of 1984 ;)

Ha! though 'Farenheit 451' would have made for an even more perfectly ironic incident, had Amazon erased it instead (that book was the first thing I thought of when I heard that Amazon was making a reader called Kindle.)

parent may have been referring to actual incident (sorry no citation handy) in the early days of kindle devices, in which 1984 had its contents remotely altered (ie, subtly changed, not deleted). to me that's the most apt conceivable book title to make a pretty chilling point about trustworthy media.

No, it was deleted:

https://www.nytimes.com/2009/07/18/technology/companies/18am...

Whoops! Thanks for the correction! I misremembered.

I have one of the ad supported kindles, which is perpetually in airplane mode to stop the ads.

mine is too, i also just buy the books, strip the drm, and load it up using calibre so i have no need for wifi on my kindle

I'm wondering, why buying a kindle if it's for going to such troubles avoiding using Amazon's services? I though the included store / library was one of the main selling point.

Are kindles that better than standalone competitors?

I went with kindle paperwhite simply because I wasn’t aware of alternatives, at least with electronic ink style display, and I have to assume Amazon is making the nicest e-reader since they have market dominance. Also I was trading a very old kindle keyboard, which took a little bit off the full price of paperwhite.

I have an iPad but don’t like reading on it (too big and heavy) , and was previously reading on an iPhone XS Max, but even the phone feels heavy to hold while laying down after a while.

> Are kindles that better than standalone competitors?

No, but the nearest competitor, the Kobo Clara HD, is rather recent, is only a tad smaller for the same screen, and also requires a "login" to activate.

However the Kobo takes .epub files without further ado. I think Amazon lost the format war, not that conversion is hard (cf. Calibre-ebook)

There's an additional advantage to the Kobo. The whole operating system is just on an SD card, unencrypted. You can copy it, image it, edit, modify it and so on very, very easily and it's impossible to brick it as long as you made a copy of the SD card.

I recently tried a kobo libra h2o and I had enough minor complaints about the UI that I returned it. I wouldn't say it's bad, just I prefer Kindle in a lot of ways. But if someone never used a Kindle I'd wholeheartedly recommend Kobo

kindle oasis is amazing imho I read a _lot_, and its battery life, form factor, ergonomics, splash-proofness (non-submersible but practically impervious), legibility, speed... ROI in the first few months I owmed it and I've had it for a couple years (and expect to for many more). IOW, they finally got it right.

i got mine as a present. i also sometimes use it with overdrive to take stuff out from the library which is super easy

If you ask Amazon support chat nicely (and persistently) enough, they'll usually disable those for you free of charge.

Interestingly that's the thing I miss most from the Oasis. I wish I could configure it to display a book I'm reading as the cover when it's in standby.

Same, you also get 10x longer battery time in airplane mode!

TL;DR - he found it, by sending a giant PDF thereto and recording network traffic info via 3 computers, extracted the signal strength of the desired device (Kindle), and mapped the convergence of 3 spheres of that signal strength, locating it within a couple feet.

Cleaning/organizing the house would be much simpler and useful I guess...

This you must repeat. Next step is to automate the manual process. Like Tile, but no extra cost and using existing home network infra.

"$Home_Automation_Wake_Up_Command, where did I leave my $device", with $device friendly name associated with hardware address.

RF engineering is just so darn awesome, it can appear to be magic.

The simpler solution is to just remotely set off an alarm. I do this frequently with the "Where is my Android" thing. Internet-enabled devices should include this capability by default, anything more is just over-engineered.

Not supported by all devices. It's unlikely it's easier to get everyone to agree to support this feature than a firmware update to wireless access points (which might even be open source depending on the hardware specd) to support time of flight ranging. If you can ship it, ship it. Don't wait on someone else.

Unless I'm missing something your assuming multiple (3 minimum access points, having worked on a similar project our accuracy required more to make up for inconsistencies and multi-level facilities) at home (where I get away with just a single one) and that they have been calibrated to know where they are in relation to each other.

Yes, I am assuming that is more likely than convincing manufacturers to support alert functionality natively. Considering the rise of wifi repeaters (Google, Eero, Netgear, ec) and other IoT devices, I don't believe my assumption is far fetched. Consumers have smoke detectors, cameras, garage door controllers, and water sprinklers on their wifi now.

You could make a simple 3-part product that does just that. You place them in various parts of your house, they calibrate together (play an inaudible sound and measure delay), and then have them manufacture traffic to your target device to figure out where it is.

I imagine they could be somewhat close together (e.g. same room), which makes setup way easy.

I can't imagine it would be very difficult to make, provided small Wi-Fi capable devices are sufficient, it just needs some work on the details.

As yak shaving goes, I'm not sure how to compare "clever technical hack" vs "clean the house"...

Even easier would be to always return the kindle to a certain spot.

Kids and getting older make this a less bulletproof solution.

Kids can learn not to touch someone else's kindle. And the older I get the more I use habits to help me.

Or, read paper books - won't have a kindle to lose

Nope. Now where did I put that paperback I just had???

My solution would be to hire an estate sale company, who will bring in a team to inventory every item in the house while selling it off to the general public. Give them instructions to sell off everything except Kindle readers. By the end of the week you will have a clean, empty house except for one pile of Kindle readers. Problem solved!

Save yourself some up front money and just Marie Kondo it. If it is not your kindle, it does not bring you joy.

The estate company will sell my trash for me.

I wonder if RFID would be an effective solution here. They're cheap, small, and don't require batteries, so all you'd need to do is make a device that can generate a powerful, directional signal and you could quickly locate whatever you're looking for. I'm not an expert on RFID, but it should be a workable solution, and would work even if the device is off (e.g. ran out of battery).

Who said the house was not organised/clean? I don't think it's a fair assumption at all. Even ignoring the fact that this wasn't his house (so organising it was probably not an option), he found the kindle in a closet... meaning his mom (or someone else living in the same house) cleaned/organised it and then just forgot about it.

Usually a TLDR of a longer post lets me skip it -- not in this case, I was too intrigued. Kudos to them for pulling that off!

I found the break in a 10m extension cable, by measuring the capacitance at each end and calculating the ratio of the two values. This predicted a break at roughly 1m from one end. Then started probing the cable from 10cm towards the ”short” side, moving towards the long side. Found the break within 15cm, saving roughly 9m of cable.

Now that's pretty sweet!

Unless there was an obvious reason for the break then there could easily be another "nearly broken" fault in the cable e.g. if break was due to stretching.

A partial break has the risk of local overheating.

So perhaps you should biff the cable anyway if it is likely to be unsafe?

This is a good point - the cable is probably 20+ years old and has been used for weed eaters and lawn mowers. It's been regularly uncoiled and re-coiled, not always correctly.

The correct way is using the over-and-under technique: https://www.popularmechanics.com/home/tools/a15873/over-unde...

That's pretty clever. Also if you are interested (not 100% applicable because it's not something most people can do at home) there is a practice for finding breaks/partial breaks in cables using time domain reflectometry (TDM) [0]. You send a pulse in to one end of the cable and measure how long it takes for some reflected energy at the break to return. It's pretty cool stuff and you only need access to one side of a cable. I have used this in my job for finding discontinuities in large RF cables.

If you do have some electrics equipment at home (o-scope, sig-gen) you can make do it yourself [1]

[0] https://en.wikipedia.org/wiki/Time-domain_reflectometer

[1] https://www.allaboutcircuits.com/projects/build-your-own-tim...

We did this in the Navy to check circular wave guides to the ECM antennas in the leading edge of our bombers wings. We had to do this once every 6 months (I think) with a sweep generator to see if the cables needed to be replaced. Also, installing these were a complete PITA! Nothing was a straight run to where it needed to go, so you had to bend them as gently as possible as you fed the new line into the wing. Then you had to test it again.

These were very expensive and I've seen more than a few screwup's while installing them.

A coworker's cat-5 tester also has a TDR function that shows you where an issue is on the line.

I got the capacitance idea from having worked with TDR in the late 80's. As students we used them to tune FM antenna combiners, but I never quite got the hang of it at the time.

Many _many_ years ago we used to have to do that on occasion in our office to find where the break in the coax network was. That brought some amusing memories back for me, thanks :)

Sounds like he would enjoy playing EVE

Did anyone else find this solution to be hilariously technical, whereas a simple cleanup might’ve done the trick? Very cool, but struck me as very funny.

Typical procrastination :) I could totally see myself do the same thing just for the fun of it and to see if it works. Wasting a ton of time when cleaning would be quicker and something that needed to be done regardless.

But on the other hand, one probably wouldn't find the time to try out wifi triangulation if there wasn't some need for it. So that is something!

Yeah, I've thought of very elaborate technical ways to keep track of my keys, phone and wallet.

But the best solution is to have just like 1-3 places in your house you're only allowed to put them. It takes a few weeks to get into the habit, but once you do it's incredibly easy to find them again.

Depending on how big the house is and how much stuff it has (being a parent's house increases the chance that they lived there for long enough to accumulate a lot of stuff), this hilariously technical solution might actually have taken less time than a "simple cleanup". A single cabinet full of stuff can take several hours to properly organize, and a house can have dozens of them.

On the other hand, https://xkcd.com/530/

Why not-solve a riddle when you can solve a riddle?

My parents have more books than a lot of bookstores I've been to. If a Kindle somehow got shelved or put into one of the boxes of books, it could be a lot of cleanup to find it.

Here's a little experiment I made with an ESP8266 to passively search for WiFi AP's (not stations, so not helpful here):

https://github.com/tonyb486/ESP8266-WiFiHunter

There's an entire existing engineering field about this: https://en.wikipedia.org/wiki/Wi-Fi_positioning_system

Here's a paper from 2015 that is vocers exploiting the multiple antennas in recent access points, and other techniques: http://conferences.sigcomm.org/sigcomm/2015/pdf/papers/p269....

I can't imagine that this could have "just" worked (simply trilaterating using signal strength). If the laptops & kindle were in outer space, I'd believe it, but wifi signals indoor get attenuated by obstructions, curve around things, and bounce off of things. This is one reason wifi localization uses fingerprinting instead of trilateration.

I'm guessing OP primarily ended up using the signal strength from one of the laptops, and just did a hot/cold chase through the house.

An effective generic strategy to locating missing objects is the Bayesian search theory: https://en.wikipedia.org/wiki/Bayesian_search_theory

It's been used to find several lost ships, planes, and things of that nature. Of course, a casual application of this approach essentially boils down to "look first in the places you think it's most likely to be."

There are so many assumptions baked into a bayesian search inside your own home that it's unlikely to help though. Plus it relies on at least one hypothesis containing the correct search space (i.e the object lies within the search space).

I agree it's probably not very helpful in this case, though there are some general lessons you could take from it that would be helpful. Considering the likelihood that it would have already been found or could never be found if it were in a particular location can help you prune your search.

e.g.

> "It's likely it may have ended up on my kitchen counter, but if that were the case I probably wouldn't think it lost. So I should deprioritize looking on counters."

> "There's a good chance it's in my attic, but my attic is cluttered and I'd probably fail to find it even if I looked there, so I should deprioritize searching the attic until other possibilities have been exhausted."

Wunderfind might help. It just hit the App Store this week, and the Pro version is free for a limited time. (No connection to the developer.)

https://apps.apple.com/us/app/wunderfind-find-lost-device/id...

Discussion at https://reddit.com/r/Wunderfind

Relevant bash

http://bash.org/?5273

Couldn't be have just pinged it instead of waiting for update?

No, because the Kindle only connects to wifi around 6AM in order to download updates, so it wouldn't be available on the network until then.

So set up an `at` job to ping it at 6am? Or just ping it constantly and filter the response.

If it only comes online to do updates then might as well wait for it to update I guess.

There was also a famous Register (and apparently Information Week) article about a lost server at UNC: https://skeptics.stackexchange.com/questions/32502/did-a-com...

> Found the Kindle using the sniffing technique described below.

I read this and, having a puppy at home, I interpreted it as actual sniffing i.e. scent detection (since I've been thinking about training her in that). The only question in my mind was whether he had trained a dog to do it or did it himself Feynman-style.

He should just attach a Tile to it for next time

I don't really understand these things. Wouldn't an RFID sticker work better since it doesn't need a battery? The next step is to make an RFID sensor that can aim a beam so you know precisely where the device is.

Those Tile devices are a little big for my taste and I'd much prefer a sticker I could hide somewhere.

A Tile has a speaker, so once you're in range, you can hear it. An RFID tag on its own just peeps out its own data, but that doesn't help you locate it without additional equipment. You can use a Tile with just your phone.

They do make slightly smaller Tile Stickers, which aren't as loud and don't have replaceable batteries.

Wow, first world problems

I never had trouble finding my phone in my 150 sq ft apartment

TC 65000

RaspPi project, anyone?

Early spring cleaning.

he has to stop lending his mom stuff

They are so cheap, just buy another. ;)

They are as cheap as you are wasteful

The solution presumably requires you to move the receivers around while measuring the signal strength, or am I missing something? Could measuring Round Trip Time for packets be used for easier calculation, or would they be too small to be useful?

Did you the read the whole answer? He used triangulation from non moving receivers.

True, I had originally skimmed the answer; now fully reading it it makes some sense, though I still would have thought that obstructions or reflections would make signal strength quite unreliable for this use case. Maybe he got lucky, maybe I'm not a radio engineer.

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