haptic compass: hardware

i've just recieved a rather large amount of money at an award ceremony, and i know what i'm going to spend it on. food, schmood, because i think i have some better ideas for the control of the haptic compass than using my colleagues' original circuitry, which is rather large.

enter the very tiny MSP430, a little microcontroller i think would do a better job. all i would have to do would be:

- figure out a way to attach the little compass module to the MSP430
- get some fucking neuroelectrodes and attach them to its outputs (jesus christ, but it's hard to get hold of those things)
- bioproof the bundle thereby created (not hard, since all it takes is a hot glue gun)
- stop! scalpel time.

of course, i would also have to program the MSP. i'll need to ask the Noisebridge guys, but i think the logic would go something like this:

while (poweron)
get north direction from compass module;
cast to a degree out of 360;
figure out which electrode's "domain" that number falls into;
activate that electrode;

i'm pretty sure the way to go is to have each electrode responsible for a segment of the compass circle, i.e. 0-45 degrees activates electrode no.1, 45-90 activates no.2, etc. if all went to plan following this design, it'd mean zero transdermal components - the whole thing would be subdermal, which is far easier to keep sterile and far more likely to heal, plus naturally waterproof. it would be a big, big cavity to carve out though; i might need some real anaesthesia.

still, sounds like fun, right guys?



Anonymous said...

so glad you're doing this so I/others don't have to. awesome. good luck.

Lepht said...

hey, thanks. i gotta say though, i didn't aim to do stuff so you wouldn't have to; i'm doing it so you can refine my methods and do it better.


melladh said...

What kind of hot glue do you use? I would imagine most hobby hot glues contain a lot of slow toxins (I apologize for the lack of proper wording here - I haven't studied chemistry, and english is my second language) Depending on what kind of material went into create the hot glue to begin with, it might release all kinds of wonder into your system as it breaks down. What's "safe"?

Antonio Ono said...

This seems like a very elegant design, but if it’s totally subdermal, how is it going to be powered/recharged? Kinetically? Or maybe you could use induction? Either of these ways, it seems like a lot to stuff under your skin.
Keep up the good work.

Divided Mind said...

Care to comment about power and hot glue toxicity issues?

IX said...

I thought about this when I started reading your blog. I was reading about the anklet compass people have worn. My idea was to combine that with your neodymium implants and have an external device oscillate the implants depending on the direction you're facing.

The neodymium implants can offer a wealth of possibilities for modularity... But that does kind of defeat the desire for surgery.

Max said...

There is some room for improvement in the implementation of the microcontroller code.
If you're gonna do such a big implant, you might as well get it to give you a smoother compass.

The way you said would make it snap to a certain electrode, but the whole thing could be a lot better if you could get it to produce a gradient of current between electrodes, so that when north is between two electrodes, you have both firing at half power instead of the signal snapping to one of them.

Also, power and toxicity?
That's gonna be a hell of a lot of wires, m'breda.

Lepht said...

wow, comments a fucking go-go. okay:

melladh - standard hobby-shop type. it claims to be non-toxic, but when i take out the last node from the back of my hand, i'll insert a test blob of the stuff to see what happens. it doesn't actually seem to degrade at all in wet environments, so i'm not particularly worried, and it can come straight back out if anything adverse does occur. dw about your English, by the way; suits me.

Antonio Ono - well, it works on lithiums right now, so i could leave them in there, have them transdermal, or i could get a gyro in there (my Plan A). it's gonna need some working out.

Divided Mind - ibid.

IX - hey, long time no speak. it'd be a fine idea if the nodes were easier to come by; after all, you could probably set them off quite easily just by soldering them to a couple wires. alas, it's getting real fucking hard to find the bastard things; hence the trodes.

there's still a need for surgery, though, in that they work best under the skin; you can't just wear the nodes, or at least not in my experience.

Max - yeah, you're right. some smoother transition would be nice, as well. i think once i have code, i'll put it up here or on stashbox so you guys can chip in, since it's gonna be open source anyway. y'all seem to be pretty savvy.

and yes, yes it is gonna be a lot of wires. that's alright, cause i have a lot of scalpels.

thanks for commenting, y'all. feel free to annoy me via email if i'm not replying quickly enough (seriously); i'm doing finals right now, and i always need more distractions. it's lepht on domain trioptimum dot com.


IX said...

I misspoke when saying it wouldn't need surgery. I was mostly thinking that you'd use it with your current implants in some way and/or add more nodes.

spoon said...

Further to what max was saying:

What we need is a function where we input the angle from north and receive the value of the charge. Here is a simple method:

If there are 2 electrodes close to, but equidistant from North, we want them to have half of max charge, right?

The sort of function we might use may be a quadratic with a parabolic graph.

y = -x^2

Then you would find the angle around your leg which faces north, we'll call it N.

Then you would translate the x-coordinates of the parabola onto N, so that the maximum of the graph is at N.

y = -(x - n)^2

You also want it to be giving you the maximum power at the maximum point so if the max power is P you then have

y = -(x - n)^2 + P


y = P - (x - n)^2

That then might be a suitable function. y is the power of an electrode at the angle x round your leg. Or in (untested) C

/* Return the power of an electrode at the angle round your leg 'theta', given that the direction North is at the angle round your leg 'north', and the max power to be emitted by an electrode is 'power' */

float electrode_power(float theta, float north, float power)
   return power - ((theta - north)^2)

spoon said...

lol semi colon

Ian said...

i was thinking that a good power source, if you are hoping to leave the entire thing subdermal, is an idea created by Jim Mielke, who submitted his idea to Greener Gadgets (http://www.core77.com/competitions/GreenerGadgets/projects/4673). His project is to implant a cell phone-tattoo interface into a person's arm, but the important part is how the battery is charged--a fuel cell connected to your bloodstream converts glucose into electricity. It's not out yet, and it would probably be a bitch to get hold of, but if all else fails, it would probably work.



Lepht said...

Ian - huh. that's pretty cool. i wonder if he has any schematics around or anything... not that i know dick about real electronics, but i can follow instructions like any other monkey. thanks for the pointer.


Michael J Lawrence said...

What award gave you the substantial amount? If they gave you money, why not mention them?

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