return to table of content

AppleWatchAmmeter

boomskats
37 replies
1d2h

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/

shagie
18 replies
23h47m

... 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
8 replies
23h5m

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 ....

varenc
1 replies
12h59m

What’s it like having magnet in a fingertip?

markx2
0 replies
10h20m

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.

parhamn
1 replies
22h57m

"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
0 replies
4h30m

Where does the 6 inches come from? Is that the separation between the MRI machine & the patient?

willis936
0 replies
18h45m

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.

taneq
0 replies
15h23m

Are you trying to tell me that the anal rail gun story isn’t true? I’m shocked.

mensetmanusman
0 replies
16h53m

Was the MRI needed to hard reset the NFC chips?

actionfromafar
0 replies
20h50m

Are you real-life Wolverine?

edm0nd
8 replies
22h51m

I have an implant and MRIs or Xrays cause zero issues.

shagie
4 replies
22h25m

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.

newaccount74
1 replies
10h57m

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
0 replies
7h8m

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

edm0nd
1 replies
21h9m

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
0 replies
20h59m

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.

dylan604
1 replies
20h35m

I would love to see how TSA reacts to your scans

markx2
0 replies
10h12m

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
0 replies
19h19m

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)

Spivak
10 replies
1d2h

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.

kstrauser
6 replies
1d

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
3 replies
1d

Based on a quick search, a small gap (less than 500 μm) 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
2 replies
1d

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).

yial
0 replies
19h17m

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 )

sonofhans
0 replies
23h6m

incorporated

This took me longer than it should have. Nicely put.

ASalazarMX
1 replies
22h30m

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
0 replies
21h18m

Neither does MRSA.

ramses0
1 replies
1d1h

Similarly: supposedly superglue a magnet to your fingernail.

carpdiem
0 replies
15h51m

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.

crumpled
0 replies
21h23m

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.

Gracana
1 replies
1d2h

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
0 replies
20h21m

What am obnoxious mobile site you’ve linked to - unusable because of a persistent floating graphic over the middle of the screen.

zitterbewegung
0 replies
1d2h

Yes, there was but the magnets can break and I believe getting them removed is hard.

surfingdino
0 replies
23h51m

Must me useful for emergency proctologists. Neodymium magnets would probably work better for such applications.

Onavo
0 replies
1d

You can experience the same thing by supergluing a magnet to your pinky.

bri3d
11 replies
1d3h

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
7 replies
1d3h

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
6 replies
14h41m

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
2 replies
10h1m

Any 1000g acceleration is going to be irrelevant to the position of the user of the phone (or they’d be dead!)

londons_explore
1 replies
2h57m

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
0 replies
2h28m

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...

nielsole
1 replies
7h33m

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
0 replies
2h33m

I kinda doubt the glass screen deforms 0.7mm (in the plane of the glass - it might bend 0.7 mm out of plane)

avianlyric
0 replies
8h28m

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.

radicality
2 replies
23h24m

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
0 replies
10h32m

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
0 replies
9h28m

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)

cdchn
3 replies
1d2h

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
1 replies
1d2h

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
0 replies
22h7m

The pen size of my non-contact voltage detectors make it feel like it couldn't be THAT hard.

ComputerGuru
0 replies
1d2h

As TFA mentions, detecting AC current is rather different from detecting DC current (the article is about the latter).

kstrauser
1 replies
1d3h

That’s genius in its simplicity. Wow. Well done!

8338550bff96
0 replies
1d2h

Simple genius is the only kind I recognize

brcmthrowaway
1 replies
1d1h

I wish Nokia was still around, this would be turned into a feature. Think N95 was a smorgasboard of random features.

dcreater
0 replies
17h39m

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

_Microft
1 replies
1d3h

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.π.10^-7);

That u0 is meant to symbolize μ_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

C60H92O6
1 replies
5h45m

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
0 replies
3h25m

Give it a week and these will be for sale on etsy, ali, and amazon.

deisteve
0 replies
14h52m

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?