shopping list

so here's the list of components we're gonna need, so far. there might be more; if (as expected) i've forgotten something, let me know in the comments and i'll add it to this post via the handy unmistake button.

miniature Philips compass module
MSP microcontroller
transmitter and receiver coils
+ any required control circuitry
rechargeable lith cell
various wires
Sugru, lots
neuroelectrodes, 8 or 16 depending on price
surgical supplies as usual (dressings, suture kit, etc.)
anaesthetic (lidocaine + sterile vials), needles & syringes

once this is complete, i can start deciding what i'm gonna build/test first and we can lay out a prototype diagram. whee.



Max said...

This might actually happen. Whee indeed, my dear friend, whee indeed.

The white crow said...

When faffing about under your skin, you might wanna bring a strong ass array of lights.

Chase said...

Something you may have already seen, but may also be interested in.

Breaching the skin barrier: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2100310/

Oh, and big fan.

Unqualified to speak said...

@Chase: nice find.
Delays have abounded: new job, letting magic smoke out of important components. On the plus side, I can afford whiskey and electronics again. Therefore, update soon. (",)

Ian said...

i'm assuming that you already got the Northpaw kit. if not, you're missing that.

Max said...

you mean Lepht? He's got a northpaw, but the whole point of this project is to build one from scratch. The electronics will have to be smaller than those in the official kit for this to work subdermally. There's gonna be a lot of cables.

Lepht said...

Max - i might be fucked up and busy now, but i promise you all that this will happen. i will realise this if it kills me.

Crow - correct, a torch is always good to search for blood vessels, but it's part of my surgical kit already. thanks for the reminder - i forgot last time, and... well, you saw the blood.

Chase - thankyou. i skimmed it through, and it's quite an interesting development. without anaesthesia, of course, there's not going to be any homebrew bone attachments (i can only withstand so much pain, and that's a fuckton we're talking about there) but it's pretty cool.

Unq - let me know. i'm monitoring this place even if i'm not posting as much. there's no hurry.

Ian - the Northpaw kit isn't a component of the compass. it's an analogue to it, but i had to completely re-implement the idea for subdermal use, as Max explained.


Lepht said...

ps. Chase, there are few people on Earth more alien to the concept of "fans" than i.


Johnny Ennui said...

I have an idea for mounting the induction coil. If you took two to four small rare-earth disc magnets (not the Nd ones you have implanted, just the smaller ones you can get from ThinkGeek or elsewhere) and arranged them evenly around the implant coil, within some Sugru, you could build a corresponding external coil with magnets in the same configuration, mounted in a cloth ankle band. The band would keep the coils in the same general area while the magnets would keep them flush and properly oriented for charging. I know there are some issues with magnet pressure, but as magnetic strength decreases pretty quickly with distance, you could add layers of thin cloth to the coil area until the pull was comfortable (and non-damaging) but still useful.

Unqualified to speak said...

@Johnny: worth looking into. As induction works by magnetic fields, I'm not sure what impact it would have on coil output and efficiency, but it's worth testing, at least.
It would result in Lepht's leg drifting around infringement of Apple's Magsafe patent. Whether that's a a good thing or not depends on your sense of humour, I expect. (",)

Lepht said...

hey, gentlemen, any excuse to fuck up some Apple fanboys is an occasion for me.


Will said...

Just wanting to give some input.

First, I think this is a great idea. However, I see one issue, and that's with the neuro-electrodes. If you just plug them into your nerve, you won't know what kind of stimulus you'll be getting. It could just make your arm twitch cause a pain, or feel like something is touching you. Now having 8 electrodes, that's 8 unpredictable stimuli.

Also, you'll need some way to step the voltage down into the millivolt range.

It's not nearly as cool, but your best bet may just be to have a visual interface of some kid. For instance, you could use LEDs under your skin as an indicator. I don't know how effective those would be at shining through your skin though. You could also use a reed switch in conjunction with a magnet in your opposite hand to turn it on and off, so it doesn't overheat or waste power.

I'm not really an expert, just putting my opinion out there. Good luck, I'd like to see this work out.

Also, sorry for commenting on an old-ish post.

Will said...

Er...I take back what I said about the reed switch. Not a good idea at all, heheh

Lepht said...

Will - you're right about the stepping, i think. i will need a proper electronics guy like Unqualified to take a look at the design a few times.

but you're missing the point: one, i know what electrical nerve stimuli feel like, i've got three installed. two, visual indicators for me are just pointless. i am working with haptic (touch-based or nerve-based) devices, not fancy watches. it's completely failed for me if you have to read it by eye. it's a sense, not a device.

Tiak said...

Hey, so basically just discovered you (via the wired piece, via the Noisebridge cyborg group).

Anyway, as I'm new here, and haven't spent all that much time digging through archives yet, please excuse me if I suggest something that's been brought up and dismissed in this more niche community before, but, what about using microdermals as ports for external chargers and the like? You seem to have sworn off anything transdermal after some failed experiments, but microdermals seem to be a much more reliable platform.

Titanium obviously isn't the most conductive metal, and I don't have a microdermal handy to really test, but my oh-so-very-back-of-the-envelope calculations suggest that you're looking at a few microOhms to get from a wire tied to a growth hole (whatever those are called) to the inside of a riser stem.

It seems like it could possibly even be worth the resistance, and possible heat to switch over to titanium or stainless wiring rather than coatings. It seems like if there is any failure in the coating at any point, you're going to lose the whole wire, and possibly the whole project as a consequence.

I fear my own lack of electrical expertise may be showing, but I've had my own internal dialog on experiments to preform for quite a while now, without ability to conduct them.

Max said...

I second the LED idea. Subdermal LEDs is one of the things I've sworn myself to get myself in some form or another, and combining them with this project seems perfect.

I've got one potential problem for you: What happens when you lie down on your back? The compass module will glitch out, and even if it doesn't, the electrodes surely will, so that your ankle will feel completely weird. You might wanna look into maybe adding a tiny-as-can-get accelerometer (couldn't find much on the topic of chip size, but the chips themselves seem to come in sizes down to 2mm by 2mm by 1.5mm, as seen in the new iPod Nano), to disable the device as soon as your ankle is in 45°+ angle, though that certainly won't make the wiring easier. It'll be hard enough fitting all that stuff into you as it is...

Lepht said...

Tiak - welcome. it's a very niche community, and you're welcome to ask me any questions you want.

my problem with microdermals is twofold: one, the difficulty of attaching anything to them, and two, their very high rejection rate. 50-60% of the cosmetic ones that i have installed have just rejected, spontaneously, after some months. i just don't want to take the risks with transdermal components.

Max, Unq - LED output alone is very bad from my pov, since that makes it another device you have to check. however, additional visual output would be cool.

as for lying down, i'll take Unq's tilt switch for five hundred, Alex.


wireghost said...

Regarding magnets near the coils: this should not be much of an issue if you are going for toothbrush-type induction, since you can use pretty low frequencies (probably 50-60 Hz is common). In fact, they might actually help increase the generated field strength.

However if you are going with resonant charging, you will probably end up with a much higher frequency (10-100 MHz) where losses from magnetic material become much more significant. Also FYI, small coils will have extremely high self-resonant frequencies, so (for the resonant wireless) you will likely need a capacitor across the coil to bring the resonant frequency down to something reasonable.