Conductive Glue And Conductive Thread: Make an LED Display and Fabric Circuit That Rolls Up.

Step 7 Conductive Glue and Sew a Picaxe Microcontroller Circuit

I have chosen the 18x Picaxe micro controller for this project because it is inexpensive and perhaps the easiest to wire and program of any micro controller I have seen. The Picaxe micro controllers are also very forgiving. In over twenty projects that I have done, I have often mis wired connections or shorted outputs and have yet to burn one out.

Picaxe chips and programming cables and software are available from: http://www.hvwtech.com/default.asp
Or: http://www.futurlec.com/Components.shtml

A very good manual on programming the Picaxe in Basic is available free from: http://www.rev-ed.co.uk/picaxe/

In this particular project, the 18x Picaxe is programmed to light the 3 by 5 led matrix in a sequence of letters or numbers to spell out messages. By varying the input voltage to an ADC (analog to digital converter) input, the potentiometer (see step 3) made out of flexible conductive fabric, is used to choose different messages. It becomes effectively, a one input multi-switch.

I originally glued in dropping resistors R1-R5 in order to make sure I did not overload the Picaxe outputs. It turned out that the combination of glue joints and conductive thread created enough resistance that the resistors were unnecessary. So, I shorted them out on the back with conductive thread.

The four pin socket was to be for power in and serial programming. It did not work out well as there was not enough room to sew and glue the thread on adequately. The connections eventually came loose with use. In the future, I would solder some short wires on first and splay them out to have more room to glue.

I ran out of time, so I was unable to install a glued battery pack below the Picaxe chip as I had originally planned.

I chose to glue the whole circuit and avoid soldering just to see if I could work out the techniques required. But, it is no doubt faster to solder rather than to glue up the basic connections of a micro controller. A more practical method for future projects would be to solder the Picaxe chip, batteries, plugs, and most of the resistors on a long narrow circuit board. The board would be the width that you want the circuit to fold up at. The thread would then be run to the input switches, potentiometers, or other sensors and the outputs to the LEDs to make the circuit flexible. I have seen several commercial products that roll up done in this way.

If you want to make the circuit more rugged, I would suggest coating all of the IC pins and any other delicate conductive glue joints with clear contact cement so that they are solidly attached to the fabric.

You can download the Basic program code for the Picaxe at: http://www.inklesspress.com/rollupcircuit.txt

For other possible circuits to try that use the Picaxe, you can check out some other projects I have done at: http://www.inklesspress.com/picaxe_projects.htm

The Possibilities of Using Flexible Circuits
I have just begun to explore the possibilities of flexible circuits using conductive materials. You may not want to build a circuit that completely rolls up. But the techniques presented here show how you can make circuits on any flexible material including hats, paper, pants, rubber, T-shirts, gloves, socks, wallets, inflatables, or jackets. You can also make flexible sensors and displays of various kinds. The limit--is your imagination.

Comments

[Richard123]

Ah, Mikey, Mikey--the answer to my online wishes. I replaced two chips in a word processor and the work was successful but I did some damage to a flexible printed circuit. A word processor which works "great" but no space bar action is sub-par I think. A circuitwriter would be $30 and not available at all locally. Besides, the printed circuit includes black resistive lands (for some reason) and so to make a long story short your technology fits the bill. Not only that, but after reading about the liquid tape experiment, I found I could not obtain that locally, but then discovered the later essays. I had graphite and I had the Dap. So I am in business! So far I have been experimenting with acrap print circuit. I found that a looser more flowing mix is not good enough. It must be thicker than what one would desire for ease od application. Unless, the looser batch will improve with age? It is still quite pliable. But the stiffer mix makes a strong enough joint even if it is not smooth. I have not yet attempted a final repair. I will have to approimate the original resistances--even though I don't know why any resistance should be introduced to begin with. But I think I stand a chance. And the investment so far stands at $2.46 for extra graphite just so I have plenty. I cannot praise you ingenuity enough and I think your freedom from inhibiting structures bodes well for your creativity.

[Kasm279]

When you say "word processor" do you mean something like an alphasmart?

[junits15]

he is talking about a very type old computer (I think) a computer made only for word processing. Look up Wang Laboratories, they were based in Massachusetts (My hood!) and their computers could only word process. Their HQ building was in the shape of a W :3

[duckythescientist]

Or keyboard?

[hintss]

or typewriter? or teletype + modem? or replace modem with Altair? also, alphasmarts are awesome. but my netbook is actually the same price as one, and I'm typing this comment on it.

[Kasm279]

$2? :D

[hintss]

$2?!

[Kasm279]

Yup, two AS3K's for 2$ each at a garage sale. Love the things because I can send the stuff i type on there to my Palm m515. Only thing I hate is the keyboard...