[HN Gopher] AppleWatchAmmeter
___________________________________________________________________
AppleWatchAmmeter
Author : rcarmo
Score : 325 points
Date : 2024-09-11 07:01 UTC (1 days ago)
(HTM) web link (github.com)
(TXT) w3m dump (github.com)
| kstrauser wrote:
| That's genius in its simplicity. Wow. Well done!
| 8338550bff96 wrote:
| Simple genius is the only kind I recognize
| bri3d wrote:
| See also:
| https://phyphox.org/wiki/index.php/Smartphones_as_ammeters - I've
| heard of some physics instructors using this in teaching
| settings.
|
| I'm quite surprised that nobody has made an app which can do some
| baseline calibration and produce real-time current measurements
| yet; it would just be a few hundred lines of code at most.
| _Microft wrote:
| Phyphox is amazing: there is a wide variety of different
| experiments available using all sorts of sensors found in
| phones. The iPhone accelerometer seems to saturate at roughly
| 13g, easily achievable by pulling your phone very fast in an
| increasingly narrow arc towards yourself. What were you
| thinking how I found out?
|
| (Fun fact: this is another project that Sebastian Staacks of
| http://there.oughta.be worked(s?) on. You might remember his
| wooden Gameboy shell, the Gameboy interceptor to screenshare
| the Gameboy screen to a PC or his bullettime video booth.)
| londons_explore wrote:
| > iPhone accelerometer seems to saturate at roughly 13g
|
| That surprises me. As soon as a sensor saturates, you can no
| longer use it for dead reckoning (integrating the
| acceleration values to know position).
|
| 13g is way below what you'd expect when tapping the phone
| against a solid object for example - that could easily reach
| 1000g briefly.
|
| I was under the impression that a big part of iphone's
| superior GPS performance was down to the clever use of dead
| reckoning and re-calculating past datapoints in a way android
| manufacturers rarely do.
| foldr wrote:
| Any 1000g acceleration is going to be irrelevant to the
| position of the user of the phone (or they'd be dead!)
| londons_explore wrote:
| Tapping your fingernail on a hard surface, your fingertip
| experiences ~1000g.
|
| Big g-forces are bad if experienced for more than a few
| hundred microseconds. But very briefly, they aren't too
| damaging.
| foldr wrote:
| Sure, but if an entire human person is accelerated at
| 1000g for a period of time that's long enough to lead to
| a significant change in their location...
| avianlyric wrote:
| I don't think the iPhone does naive dead reckoning like
| that, as the sensitivity of the needed inputs is so high
| for it be reasonable in a consumer handheld. The cost of
| components would be way to high, then there's the issues of
| power consumption, because you would need to poll all your
| sensors at a very high rate to get enough accurate data to
| perform naive dead reckoning accurately.
|
| Instead I think the iPhone cheat a bunch, and use a mixture
| of step counting, magneto and gyro inputs to perform dead
| reckoning. The iPhone uses periods when you GPS is in use
| anyway to calibrate your stride length at different speeds,
| which when mixed with magneto data to estimate a course
| direction, would allow an iPhone semi-accurately perform
| dead reckoning, without needing high resolution, wide
| scale, accelerometer input.
|
| In short, the iPhone cheats. It's dead reckoning systems
| take advantage human bio-mechanics to simplify the problem
| of dead reckoning, at the cost of building a dead reckoning
| system that only works effectively in a handheld device
| that semi-permanently lives on your person. A perfectly
| reasonable assumption for a phone, but a terrible solution
| for a more generic dead reckoning system.
| nielsole wrote:
| If my math is right, assuming an iphone deforms linearly on
| impact with 1000g deceleration, it would only give way
| 0,7mm when dropped from 1m height onto concrete. that seems
| too low a deformation? I would expect it to whobble quite a
| bit in slow-mo.
| londons_explore wrote:
| I kinda doubt the glass screen deforms 0.7mm (in the
| plane of the glass - it might bend 0.7 mm out of plane)
| radicality wrote:
| Thanks for that recommendation, really good app. In today's app
| landscape it's almost unbelievable that it's so polished and
| free and without ads / signup links / always-on location
| sharing etc.
|
| It's not even easy to find. Few months ago I wanted a simple
| audio spectrogram app, downloaded some which wanted dubious in-
| app purchases, or had ads. I hadn't come across it earlier, but
| Phyfox does what I wanted better and for free.
| nvalis wrote:
| That's because Phyphox is financially backed by multiple
| public bodys of the German governement, mostly the RWTH
| Aachen and the Federal Ministry of Education and Research as
| pointed out on the landing page [0].
|
| [0] https://phyphox.org/
| maven29 wrote:
| All you need to do is to start your search on f-droid, the
| app quality is much better (also consider adding the
| IzzyOnDroid repo if you don't care about verified
| reproducible builds)
| _Microft wrote:
| > _A circular coil of wire with N turns and a diameter D will
| generate a magnetic field of B = u0.I /D (u0 is defined to be
| 4.p.10^-7);_
|
| That _u0_ is meant to symbolize _m_0_ (mu zero, with zero being
| subscript) the vacuum magnetic permeability [0], in case you were
| wondering where that magic constant came from.
|
| [0] https://en.wikipedia.org/wiki/Vacuum_permeability
| lapetitejort wrote:
| See also e_0 [0]. 1/sqrt(e_0*m_0) = c, the speed of light
|
| [0]: https://en.wikipedia.org/wiki/Vacuum_permittivity
| cdchn wrote:
| It would be cool to use this as a voltage sensor, to check for
| live circuits, but the downside being you might not want to crane
| your wrist towards said live circuits.
| atoav wrote:
| And: measuring current can be done with any odd hall effect
| sensor, voltage not so much.
|
| I imagine a smart warch with two 4mm banana-jacks isn't going
| to be the next big thing.
| cdchn wrote:
| The pen size of my non-contact voltage detectors make it feel
| like it couldn't be THAT hard.
| ComputerGuru wrote:
| As TFA mentions, detecting AC current is rather different from
| detecting DC current (the article is about the latter).
| boomskats wrote:
| Only somewhat related, but wasn't there a DIY biohacking[0] craze
| a few years ago, with people implanting rare earth magnets into
| the tips of their pinky fingers, waiting for the nerve endings to
| heal around the implant, and then supposedly gaining a 'sixth
| sense' of being able to detect the flow of current via their
| bionic pinky? Is that still a thing?
|
| [0]: https://www.wired.com/story/diy-biohacking/
| Gracana wrote:
| I recall Zoe Quinn wrote about having that done ~10 years ago.
| Article's still up on her site, it's a good read:
| http://www.beesgo.biz/magnet.html
| gxs wrote:
| What am obnoxious mobile site you've linked to - unusable
| because of a persistent floating graphic over the middle of
| the screen.
| zitterbewegung wrote:
| Yes, there was but the magnets can break and I believe getting
| them removed is hard.
| Spivak wrote:
| Given how well-trodden putting hardware in humans is, I'm
| surprised this wouldn't be a <60 minute surgery to affix the
| magnet to your bone. Then it wouldn't look so weird pulling on
| your skin. Then again, the non-invasive version is wearing a
| magnetic ring, $1.34 on Aliexpress.
| ramses0 wrote:
| Similarly: supposedly superglue a magnet to your fingernail.
| carpdiem wrote:
| I tried this once. There was no convincing effect for being
| able to "detect by feel" AC currents, but you could
| definitely notice magnetic materials.
|
| Maybe the most fun, though, was just playing around and
| "picking up" paperclips and tiny screws by flicking my
| finger at them.
| kstrauser wrote:
| Having worked in orthopedics quite a bit, and hanging out
| with my wife who's a foot and ankle surgeon, there aren't
| many ways you could attach something to a bone that wouldn't
| cause problems. Other than the (significantly large, true!)
| hard mineral portion, bones comprise a lot of types of living
| tissue and you don't want to make a hole in them or their
| periosteum wrapper unless you absolutely must. The least bad
| approach might be something like a zip tie that you could
| carefully work around the bone, but even that would have
| ridges to irritate tissues and semi-enclosed spaces for
| bacteria to turn into a strip mall.
|
| I highly recommend just getting that magnetic ring instead.
| fudged71 wrote:
| Based on a quick search, a small gap (less than 500 mm)
| between the implant and bone can actually support
| osseointegration by allowing trabeculae to form. 3D printed
| titanium has been used a lot for osseointegration.
| kstrauser wrote:
| Quite possibly, but 1) you better be A-OK with having
| whatever it is permanently grow into your bone such that
| you'd have to carve it out with chisels or saws, and 2)
| you still need to hold it there long enough for that to
| happen, ideally without whatever mechanism you're using
| for that also being incorporated (like, literally
| incorporated).
| sonofhans wrote:
| > incorporated
|
| This took me longer than it should have. Nicely put.
| yial wrote:
| Titanium encourages / supports due to its structure human
| bones growing into it.
|
| This does not happen as easily or frequently with
| stainless steel.
|
| (There is still a risk of spontaneous rejection however )
| ASalazarMX wrote:
| > I highly recommend just getting that magnetic ring
| instead.
|
| But wearing a ring, while convenient and safer, is not biO
| hAcKiNg. It gives no bragging rights.
| kstrauser wrote:
| Neither does MRSA.
| crumpled wrote:
| I think the pulling on the skin part is essential to the
| feeling things part. I don't think people will get any
| sensation if the magnet is held stationary.
|
| I'm only guessing.
| cmsjustin wrote:
| https://www.youtube.com/shorts/17l9BucbXec
| fragmede wrote:
| http://dangerousthings.com graduated to selling implantable
| rfid u2f tokens.
| Onavo wrote:
| You can experience the same thing by supergluing a magnet to
| your pinky.
| surfingdino wrote:
| Must me useful for emergency proctologists. Neodymium magnets
| would probably work better for such applications.
| shagie wrote:
| > ... with people implanting rare earth magnets into the tips
| of their pinky fingers ...
|
| Imagine the joy of getting an MRI and forgetting about that bit
| of biohacking.
| markx2 wrote:
| I had an MRI.
|
| I have tragus piercings where the rings are titanium but the
| balls were steel. It was missed that they were there.
|
| I have surgical steel self-done implants in each hand.
|
| I have a magnet in one of my fingertips
|
| I have NFC chips in both hands.
|
| I did not explode, nothing felt hot, the only sensation was
| my tragus piercings wobbling slightly.
|
| This whole MRI thing ....
| parhamn wrote:
| "Don't take in ferromagnetic metals that would get pulled
| by a 3T magnet with 6 inches of separation" is a bit harder
| to grok for pretty much everyone.
| user_7832 wrote:
| Where does the 6 inches come from? Is that the separation
| between the MRI machine & the patient?
| actionfromafar wrote:
| Are you real-life Wolverine?
| willis936 wrote:
| Magnetic force drops off with the 4th power of distance.
| What is a slight wobble is centimeters away from being a
| bullet. This is pretty easy to experiment with fridge
| magnets to build intuition. I would exercise caution if you
| have embedded magnets though.
| mensetmanusman wrote:
| Was the MRI needed to hard reset the NFC chips?
| taneq wrote:
| Are you trying to tell me that the anal rail gun story
| isn't true? I'm shocked.
| varenc wrote:
| What's it like having magnet in a fingertip?
| markx2 wrote:
| It can lift a paperclip, buckyballs stick to it, and
| moving the fingertip across devices - spinning HD's,
| laptops gives a sensation when the magnetic field
| changes. No real practical use but I knew that.
| edm0nd wrote:
| I have an implant and MRIs or Xrays cause zero issues.
| shagie wrote:
| https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4848040/
|
| > The static magnetic field B_0 of an MRI machine attracts
| ferromagnetic objects and accelerates them toward the
| center of the bore of the MRI scanner. Ferromagnetic
| objects such as coins, hairpins, steel oxygen tanks or
| scissors can be accelerated or torqued by B_0 [4,10] and
| become dangerous projectiles [51]. The MRI safety program
| of the facility needs to warn about the misconception that
| larger objects will resist attraction to the field and need
| to emphasize the relationship between object size, material
| components, and projectile risk. Insufficient MRI safety
| training of ancillary medical personnel has led to fatal
| accidents when medical and other equipment was accelerated
| into the bore of the magnet [50,51].
|
| X-rays would be no problem. Having something that is
| attracted by a magnet (such as another magnet) may cause an
| issue.
|
| https://pubmed.ncbi.nlm.nih.gov/38128958/ has more on the
| "stuff flying into an MRI with concerning force."
|
| Things like a 10p coin imbedding itself 0.5cm into
| ballistic gel. A spoon going in 3.5 cm is a bit more
| concerning.
| edm0nd wrote:
| I don't have the biomagnet implants, I have the NExT RFID
| + NFC chip by DangerousThings in my right hand so its not
| as much of a concern.
|
| Just go read straight from the source instead of linking
| research papers.
|
| It has the warning of:
|
| >MRI COMPATIBILITY WARNING The xG3 and all magnetic
| implant products should be removed before any MRI or
| magnetic imaging procedure. While our x-series
| transponders have tested as compatible with MRI machines
| up to 7T field strength, all magnetic products are
| incompatible with MRI machines and procedures.
|
| https://dangerousthings.com/product/titan/
| shagie wrote:
| The comment that I originally responded to was:
|
| > with people implanting rare earth magnets into the tips
| of their pinky fingers
|
| And I was specifically referring to those rare earth
| magnets.
|
| Your comment then:
|
| > I have an implant and MRIs or Xrays cause zero issues.
|
| You gave no indication about what type of implant you
| hand or its manufacturer, and replying to my comment I
| took it in context that it was a rare earth magnet.
|
| Failing any information about the manufacturer, the
| information that I am able to provide to say "this can be
| dangerous" is research papers.
|
| You have further clarified that you only have a RFID and
| NFC chip implanted and not any magnets ... and provided a
| link to another product (rare earth magnet implant) from
| the same manufacturer that indicates that it is indeed
| dangerous when near an MRI machine which agrees with the
| original comment.
| newaccount74 wrote:
| MRIs don't accelerate objects instantaneously. If you
| look at the experimental setup, you'll see that they
| placed objects inside a pipe that allows them to
| accelerate with very low friction.
|
| Implants inside the body cannot accelerate freely. They
| are held in place by the surrounding tissue. A force will
| act on them, and this force can cause complications, but
| implants will not suddenly turn into projectiles.
| leptons wrote:
| Not going to trust "newaccount74" with that info. It
| seems that the experts say that if the metal in the body
| is attached to bone (a screw or a plate), that is okay,
| but not if the metal is not permanently fastened to bone,
| so "surrounding tissue" is not going to stop the metal
| from causing problems.
|
| >MRIs don't accelerate objects instantaneously.
|
| See some of the videos below for evidence to the
| contrary. Large metal objects inside the room can
| definitely accelerate very rapidly and suddenly, and
| unexpectedly and has killed people.
|
| https://www.youtube.com/shorts/2NNJrOsw8vs "Metal objects
| not attached to bone may not be safe"
|
| https://www.youtube.com/watch?v=naAZVCxhEcI
|
| https://www.youtube.com/watch?v=uDfwxoigZZk
|
| https://www.youtube.com/watch?v=5KuzTyn45og
|
| https://www.youtube.com/watch?v=xn6sDYOrOC8
|
| https://www.youtube.com/watch?v=dxcrt1-gmLQ
| dylan604 wrote:
| I would love to see how TSA reacts to your scans
| markx2 wrote:
| They don't see them.
|
| On the two occasions I failed to remove the large
| steel/titanium item in a piercing that set off the
| scatter machine so I was taken to a room and searched.
|
| But the steel in my hands, the LED, chip and magnet in my
| left hand, the Vivokey and chip in my right hand -
| nothing. Even the handheld scanner doesn't pick them up.
|
| One of the NFC chips was useful on my last trip to the
| US. I was constantly pulled over by the TSA and they
| might have wanted to inspect my laptop. So I made a
| backup, saved the minimum I needed, encrypted it on
| another device and uploaded to a domain. Clean installed
| the OS. The NFC chip carried a long string which to me
| gave the directory structure (very nested, no / in the
| string) and the encryption key. It wasn't needed, but it
| was amusing.
| yial wrote:
| I don't have an implant, but I have purchased at times
| copper and metal shirt collar stays.
|
| Once after falling on ice, I had a chest x ray where my
| shirt was unbuttoned but didn't need to be removed.
|
| A very anxious tech came to me a few minutes later asking
| if I had been wounded when I fell, if there was something
| embedded in me, etc.
|
| Very quickly figured it out when shown the images.
|
| Incredibly comical, and obviously not an issue. (Nor
| related to implants)
| brcmthrowaway wrote:
| I wish Nokia was still around, this would be turned into a
| feature. Think N95 was a smorgasboard of random features.
| dcreater wrote:
| N95 is one of the GOAT phones. I hope for a day in the future
| when phones can once again be as diverse and fun
| dang wrote:
| We changed the URL from https://hackaday.com/2024/09/10/the-
| apple-watch-as-an-ammete..., which points to this.
|
| Submitters: " _Please submit the original source. If a post
| reports on something found on another site, submit the latter._ "
| - https://news.ycombinator.com/newsguidelines.html
| deisteve wrote:
| htis is a great hack! I've been looking for a way to measure DC
| currents without breaking the bank. Has anyone tried using a
| similar setup with a Raspberry Pi or an Arduino to create a more
| robust and accurate measurement system?
| C60H92O6 wrote:
| I advise you to add a disclaimer at the bottom that says "this is
| for educational purposes only, try it at your own risk and don't
| rely on it for serious/dangerous measurements". And also change
| the name to "Ammeter for Apple Watch", as some "special" people
| might think that this was made by Apple.
|
| (My learnings from almost getting sued for a simple hobby project
| like this)
| ActionHank wrote:
| Give it a week and these will be for sale on etsy, ali, and
| amazon.
___________________________________________________________________
(page generated 2024-09-12 23:02 UTC)