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YEAR OF INVENTION: 2017
CREDITS: Beam
DIMENSIONS: 150 x 110 mm

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DESCRIPTION

With a rectangular piece of carbon non woven, a microcontroller ATtiny85, with two analog inputs and 4 LED’s a device can be made which indicates on which quadrangle of the carbon a droplet of water has been fallen.

Over the rectangular piece of carbon non woven a voltage is applied. In a dry state this will cause a linear fall in voltage. A droplet will disturb this distribution and cause a local more flat and in the surrounding area a more steep voltage difference. By measuring at the middle left and right, and by comparing the change variation of these two analog inputs, the quadrangle where the droplet has fallen can be found. (Variations are: other configurations/shapes of voltage drop or evaporation sensor of carbon non woven.)

This swatch is a micro invention more than design. Following the discussion of last year about production versus personalisation this being an invention doesn’t allow for individuality like my knitted shapes of last year (http://etextile-summercamp.org/swatch-exchange/tiny-knittings/) did. Baudrillard  (Baudrillard, 1968, p 198) has interesting remarks about this: “En effet, au niveau de l’objet industriel et de sa cohérence technologique l’exigence de personnalisation ne peut être satisfaite que dans l’inessentiel.” (Literal translation: Indeed on the level of the industrial object and its technological coherence the demand for personalisation can only be awarded in the inessential.) Refrencing this remark would – indeed – be inessential if it didn’t have it’s consequences. So 25 different words, all from the pages 198 and 199 from this text of Baudrillard are chosen and embroidered on the 25 specimen of the swatches. This makes the specimens unique. The 25 form an essential ensemble. This recursivity and paradoxality is a feature of design which should not be just mindless industrial production.

VIDEO

https://youtu.be/-tWzincoCXo

MATERIALS

main material: carbon non woven, high resistance type eg Eeonyx 50-70k (i still love the summercamp doggy bag of 2013!) and a droplet of water, which can also be a bit of copper sheet, the flat side of a tea spoon.

used other materials: linen, aluminum (cheap from the supermarket), copper sheet on adhesive paper (expensive), Kapton adhesive tape, electric wire etc

for the circuit, 4 smd LED’s, ATtiny85

The smd LED’s farnell.nl: http://nl.farnell.com/osram/lsr976/led-0805-red-50mcd-632nm/dp/1226392. The led orientation – the dot is slightly of center, or the backside has a t shape. When the circuit is oriented like the drawing below, the top of the t should be to the right: -|, which means the dot is too.

the simple text was emboridered using a Janome sewing machine.
the copper was cut using a Silhouette Portrait

copper sheet was bought at conrad.nl: https://www.conrad.nl/nl/conrad-components-cft-50-kopertape-koper-l-x-b-10-m-x-50-mm-acryl-inhoud-1-rollen-542611.html

for step 20 problem solving: Wire Glue, Electric Paint

TECHNIQUES

Theory: Measuring the differential voltage distribution over a carbon non woven, when a droplet of water is dissipated, which flats the resistance locally.

One dimensional (narrow strip of carbon):

Screen Shot 2017-05-24 at 05.47.56

If you measure in the middel of the narrow strip you see that the voltage is lowered at the left and heightened at the right. You can even calculate at what distance from the point of measurement.

Two dimensional: using two points of measurement, you can figure out at which side there is more voltage drop and then perform the one dimensional analysis. This double procedure gives the indication where the droplet has fallen.

ATtiny85 with 4 LED’s and 2 analog inputs PB2 and PB3, using the technique of more LED’s on 1 PIN, in this case 4 LED’s on 3 PIN’s, PB1 and PB4, with PB0 “in the middle”.

SCHEMATIC

circuit

circuit_swatch2017

Pattern to cut with vinylcutter: (can be done on copper strip of width 5 cm on paper).

circ55

traced silhouette file: http://www.contrechoc.com/swatch2017/circ55.studio3

schema of swatch, with carbon, circuit and battery:

swatch_2017_view

CODE

https://github.com/contrechoc/swatch2017

PHOTOS

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Step-by-Step Instructions

  1. cut a fabric of 11 x 15 centimeters
  2. lock the fabric
  3. fold aluminum foil in strips of about 1 centimeter
  4. cut a piece of carbon non woven of 7 x 7 centimeters
  5. fold the aluminum strip around the upper and the lower side of the carbon, stretching over the width of the fabric
  6. sew the aluminum so that the carbon (at the left side of the fabric) is connected well to the aluminum strip
  7. make at the left the aluminum connections to the coin cell battery, upper is 3V lower is GND
  8. cut the coppers sheet using a vinyl cutter in the shape indicated in this post
  9. solder the smd LED’s on this copper shape
  10. program the ATtiny85 with the code on github: https://github.com/contrechoc/swatch2017
  11. program the fuses: avrdude -c USBtiny -P usb  -p t85  -U hfuse:w:0xdf:m -U lfuse:w:0xe2:m
  12. bend the legs of the ATtiny so that it can also be soldered on the copper shape
  13. test the LED’s by connecting a 3V battery: the leds should light up in a Z order
  14. cut the Kapton plastic the size of the copper circuit
  15. put this adhesive Kapton on the fabric
  16. transfer the copper circuit on the Kapton (I used tapes to keep the copper area fixed)
  17. connect the copper strips of the analog inputs to the left and the right middle of the carbon square
  18. connect the 3V and the GND tot the upper and lower aluminum strips
  19. with other pieces of aluminum strip at the right of the fabric: make a connection for the coin cell battery.
  20. Practical problem solving: the transition aluminum foil – carbon can pose a problem. I solved this by putting some conductive paint or glue under the aluminum strip and the carbon. Also the connection of the voltage and gnd wires to the aluminum strip is sometimes not reliable, this was reinforced with copper strip. Probably the whole idea of the aluminum was wrong, it should be done directly with copper sheet.

REFERENCES/LINKS

I looked at the tutorial of Kobakant on cutting a soft circuit but made the circuit with a different strategy – big surfaces, small boundaries.

Mika also worked with the carbon non woven in the swatches of 2016: http://etextile-summercamp.org/swatch-exchange/fish-scale-sensor/.

Marta Kisand, Barbro Scholz, Esther Stühmer presented a water sensor in the swatches 2014:http://etextile-summercamp.org/swatch-exchange/water-connector/

Baudrillard, Jean. (1968). Le système des Objets. Gallimard.


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