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?
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.
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.)
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.
Any 1000g acceleration is going to be irrelevant to the position of the user of the phone (or they’d be dead!)
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.
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...
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.
I kinda doubt the glass screen deforms 0.7mm (in the plane of the glass - it might bend 0.7 mm out of plane)
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.
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.
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].
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)
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.
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.
The pen size of my non-contact voltage detectors make it feel like it couldn't be THAT hard.
As TFA mentions, detecting AC current is rather different from detecting DC current (the article is about the latter).
That’s genius in its simplicity. Wow. Well done!
Simple genius is the only kind I recognize
I wish Nokia was still around, this would be turned into a feature. Think N95 was a smorgasboard of random features.
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
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.
See also ε_0 [0]. 1/sqrt(ε_0*μ_0) = c, the speed of light
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)
Give it a week and these will be for sale on etsy, ali, and amazon.
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?
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
Imagine the joy of getting an MRI and forgetting about that bit of biohacking.
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 ....
What’s it like having magnet in a fingertip?
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.
"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.
Where does the 6 inches come from? Is that the separation between the MRI machine & the patient?
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.
Are you trying to tell me that the anal rail gun story isn’t true? I’m shocked.
Was the MRI needed to hard reset the NFC chips?
Are you real-life Wolverine?
I have an implant and MRIs or Xrays cause zero issues.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4848040/
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.
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.
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.
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
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:
https://dangerousthings.com/product/titan/
The comment that I originally responded to was:
And I was specifically referring to those rare earth magnets.
Your comment then:
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.
I would love to see how TSA reacts to your scans
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.
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)
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.
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.
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.
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).
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 )
This took me longer than it should have. Nicely put.
But wearing a ring, while convenient and safer, is not biO hAcKiNg. It gives no bragging rights.
Neither does MRSA.
Similarly: supposedly superglue a magnet to your fingernail.
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.
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.
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
What am obnoxious mobile site you’ve linked to - unusable because of a persistent floating graphic over the middle of the screen.
Yes, there was but the magnets can break and I believe getting them removed is hard.
Must me useful for emergency proctologists. Neodymium magnets would probably work better for such applications.
http://dangerousthings.com graduated to selling implantable rfid u2f tokens.
https://www.youtube.com/shorts/17l9BucbXec
You can experience the same thing by supergluing a magnet to your pinky.