Received my silk screen and conductive thread today!

I'm going to be working on setting up a circuit using a mosfet driver and looking at j2me stuff for developing a java app for my cellphone. The application I eventually write will be responsible for retreiving data off the net for me, with the help of php.

Talked to Tom and found out how to use a MOSFET driver. I was advised that a MOSFET is the way to go for sending current down threads. I will still be shorting out a battery, but the MOSFET will allow me to control when and which threads get power sent through them via the arduino (or any microcontroller, for that matter). I am going to try to track down a smaller version of the arduino, which is being developed here at itp. It is much more conducive to being sewn into a wearable application than the mini or full-sized arduino, because of its smaller dimensions, including thickness.

Today I'm going to get in touch with a couple people to figure out how to connect to the internet via my cellphone.

current steps outline:
- get cellphone to connect to net and return data to arduino
- build working mosfet circuit with basic on/off code
- try creating a bus.. see how long battery drains when you have multiple threads attached
- see how long battery drains with just one thread attached.
- build circuit with working arduino code, doing data scrape.
- create design for dress
- stitch threads into dress
- screen on design
- stitch in circuitry!
- figure out power source

Much thanks to Marcelo, who has been advising me along the way, particularly with giving me the idea to use MOSFETs in the first place.

Doing more research on ways to heat the thread so as to avoid shorting out batteries. I am looking at peltier junctions, although the problem of power supply suitable for a wearable (and thus, non-tethered) application emerges from going down this road. Peltier junctions consume quite a bit of power. It seems I could power two of them with 5V and 0.7A (as found off this project's page: web.media.mit.edu/~marcelo/pureplay/index.htm).

I am also looking at Joe Paradiso's Parasitic Power Shoes, which harvest excess energy from walking.

Reference: http://www.media.mit.edu/resenv/power.html

I think that's probably going to have to be saved for another project, but wearable technology that is powered from harvesting energy your body creates is a very interesting concept.

I also checked out cute circuit's hug shirt, which transmits a hug over bluetooth to a bluetooth enabled cell phone to another hug shirt.

I can also try using TC4432 MOSFET drivers for sending current down threads, controlled by the arduino. Thermistors can check current temp, to prevent hazardous situations from occurring.

Reference: http://web.media.mit.edu/~marcelo/kukkia_vilkas/berzowska.pdf

Looked at heating elements too: http://www.thermion.com/heaters/

You can custom order heating elements from Thermion, specifying dimensions and input power! That sounds promising.

Today I researched how to connect to the internet via my phone by looking at the (ITP's) mobile ubiquitous computing class' website. I was successful in gettinga text message sent through my phone, to my gmail account, and back to my phone, via php and perl.

I also tested sending current down different conductive threads to affect color change in my thermochromic ink, designed to change color at body temp or above. Threads with higher resistance work best, and I have placed an order for Bekaert VN 14 1/90 thread. It has a resistivity of 70 ohms/meter. Also, the thread is quite thin, almost like regular thread, so I may be able to use a sewing machine (I hope so!)

observe:

before power!


after power!


How to safely power this is still a problem, however. The easiest, yet obviously least desirable way, is to short a battery out while heating the thread. This naturally occurs when you respectively place either ends of the thread you are trying to heat, on the power and negative terminals of a battery; there are no components along the circuit using up all the voltage. It's basically a direct connection from the negative end of the battery terminal to the positive. Sparks fly and smoke wafts... something which is a bit disconcerting.

On getting power to the threads:

So there are two ways of getting heat (created from putting power...) down the threads:

- short-circuiting the battery either end of the threads are attached to
- using peltier junctions or some other heating element

So far, sending current down the wire seems to work well. but there are sparks generated when power is connected! kind of scary..

On thermochromic inks:

There are a few different kinds of thermochromic ink out there. From cti inks, aside from being able to buy different colors, there are also inks designed to respond at different temperatures.

I've found that inks which turn color at body temperature work best when working with conductive threads.

I will try mixing the thermochromic ink with regular speedball screen inks. The idea is to get the thermochromic ink to turn to a different color when they are heated. There are a couple colors available from cti inks, which turn from one color to another, but I didn't like the color combinations they had available. Otherwise, the inks turn from their original color (the cold color), to clear. By mixing in regular screen inks (which will change the thermochromic ink's cold color, so don't forget your color theory), you can create a mixture that goes from one color when cold, to another after heated. When the thermochromic ink turns clear, you will be left with the original regular screen ink color.

I'm going to be using black thermochromic ink, so I won't have to deal with my cold color being changed (since black will mask whatever regular ink i add in). I want to go from black to pink, black to orange, or black to blue. Or maybe all three! We'll see.

I give thanks to Mouna for her advice so far, and have also been digging through Joey Berzowska's pages on working with thermochromic inks.

Project kick-off

This project is going to be a culmination of many interests I've had all year long: thermochromic inks, mobile computing, and bluetooth technology.

Specifically, I am going to design a display system for a dress (which is pre-made, at least for this iteration of the project), whose display is affected by network activity, monitored via a bluetooth connection to my cell phone. The idea is that the cell phone, which maintains constant connection to the net, executes a php script, retreives the data, and then returns it to my garment, which controls the thermochromic display via an arduino.

For those who don't know, thermochromic ink is what Hypercolor was, back in the late 80s (remember those days??). It's ink that changes color with application of heat. Using resistance heating, enough heat is generated from a thread that has current sent down it, to change the color of ink designed to turn at temps above body temperature.

A flow chart, putting those words into a picture, can be seen here.

This is my initial outline for this project:

1. Draw flow diagram, showing how everything is connected

2. Data component
a. figure out how to connect to internet via bluetooth in phone
b. data scrape a site for test data

3. Physical component
a. sew conductive threads into a swatch with ink on it. test different threads for their effectiveness
b. set up circuit that lets me send current down different threads (maybe look at led array that leah buchley made?)

4. Visual component
a. figure out graphic design of print and what I actually want to do with it!
b. silkscreen graphic
c. sew in threads + circuit.