
Any way to find a lost Kindle inside a house? - miles
https://ebooks.stackexchange.com/questions/7357/any-way-to-find-a-lost-kindle-inside-a-house
======
herpderperator
> 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.

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scotty79
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?

~~~
zamadatix
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 ;).

~~~
scotty79
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.

~~~
pubutil
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!

~~~
fuckyah
Apple has find my phone. Problem solved

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

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VectorLock
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.

~~~
chipperyman573
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.

~~~
fulafel
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...](https://en.wikipedia.org/wiki/True_range_multilateration#Two_Cartesian_dimensions,_two_measured_slant_ranges_\(Trilateration\))
\- but of course home wifi environment is full of reflections and attenuations
caused by the surrounding structures so straight triangulation doesn't work
anyway.

------
folkhack
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...

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

~~~
girzel
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.

~~~
Wowfunhappy
> 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.)

~~~
greggyb
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/](https://www.thelightphone.com/)

I love the idea of an e-ink phone.

~~~
knodi123
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?

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

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

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

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

~~~
flatiron
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

~~~
Eikon
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?

~~~
B1FF_PSUVM
> 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)

~~~
sudosysgen
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.

------
ctdonath
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.

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

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

~~~
everdev
Kids and getting older make this a less bulletproof solution.

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

------
lostgame
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.

~~~
asdfman123
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.

------
bonyt
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](https://github.com/tonyb486/ESP8266-WiFiHunter)

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fulafel
There's an entire existing engineering field about this:
[https://en.wikipedia.org/wiki/Wi-
Fi_positioning_system](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....](http://conferences.sigcomm.org/sigcomm/2015/pdf/papers/p269.pdf)

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rahimiali
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.

------
christefano
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...](https://apps.apple.com/us/app/wunderfind-find-lost-
device/id1458601441)

Discussion at
[https://reddit.com/r/Wunderfind](https://reddit.com/r/Wunderfind)

------
catalogia
An effective generic strategy to locating missing objects is the Bayesian
search theory:
[https://en.wikipedia.org/wiki/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."_

~~~
alfalfasprout
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).

~~~
catalogia
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."_

or

> _" 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."_

------
haecceity
Relevant bash

[http://bash.org/?5273](http://bash.org/?5273)

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

~~~
jagraff
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.

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

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

------
sundarurfriend
> 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.

------
umvi
He should just attach a Tile to it for next time

~~~
beatgammit
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.

~~~
jfengel
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.

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hkai
Wow, first world problems

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

TC 65000

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russfink
RaspPi project, anyone?

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MrFantastic
Early spring cleaning.

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metalliqaz
he has to stop lending his mom stuff

------
dznodes
They are so cheap, just buy another. ;)

~~~
F_r_k
They are as cheap as you are wasteful

------
askvictor
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?

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

~~~
askvictor
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.

