Studio Contrechoc

design & textile & technology entries

Monthly Archives: August 2015

KH-940 and Teensy 3.1

The experience with the knitic board as a shield on an Arduino Due for connecting the machine knitter KH-940 with a laptop was not very positive. The board is very fragile. Connecting and deconnecting making it needing constant repair.

After the e-textile summercamp a week was spent on making a new board, connecting the ULN2803’s and programming the Teensy 3.1.

The Teensy 3.1 microcontroller has enough pin’s, it is small and cheap.

Because the Teensy is running at another speed, 24Mhz, the delay’s between the Serial command sent from the laptop to the Teensy had to be altered.

With the program code of the older board (already reprogrammed to reduce all unneccessary communications) flashed to the Teensy not only whole tours/lines were not read accurately, also single pixels inside a tour:


The mistakes in communication in red, the red borderline below indicates the mistakes in lines.


The mistakes in lines are removed, but inside the line, there are still mistakes in pixels.


Making delays between Serial asking the laptop for data and receiving the data larger, the picture is received without mistakes.

The board connecting the ULN2803’s with the Teensy had to be adapted too, because the Teensy is working at 3.3V while the sensors of the KH-940 require 5V. This 5V is taken from the KH-940. The Teensy runs on the USB. Also the Teensy is not resetting if Processing is started, like it does witht he Arduino. So the initialize function had to be refined.

knit8 ULN 2803

knit7The big connector is printed with a 3D printer

knit5The connector with 10 and 8 pins are made from 2 5 pins connectors

knit6 The board with 2 extra potmeters to make the analog read run at 3.3V.

knit4 The Teensy 3.1

knit2 Testing the knitting from the board

Teensy (arduino script):

Processing sketch:


After the knitting sessions at the e-textile summercamp it became obvious that the next thing to develop was a high-tech machine knitted sock.


This sock is made with a KH-940. This hackable electroknit machine is handled fully manually to produce this sock.

The instructions for making this type of sock can be found at:

The sock consists of acrylic yellow and a middle part of conductive wool.

(Nm10/3 conductive yarn
Company: plug and wear
Characteristics: Nm10/3 conductive yarn, 80% polyester 20% stainless steel, light grey, Surface resistance < 100000ohm)

The connection is reinforced by knitting some tours of silver thread at the ends of this strip.

(High Flex 3981 7X1 Silver 14/000
company: Karl Grimm
Characteristic: Very conductive, Solder-able)

ps4 The two types of conductive yarn.

ps3 The silver thread is visible at the start of the strip. This will distribute the current evenly.

The resistance of this strip between the two strands is around 2K Ohm.

This makes this version not yet fit for becoming a foot warming sock. For real warming up a few Watt at least is needed. P = V * I and V = I * R, so a resistance of 2K at a voltage of 10V results in a current of 5mA. This gives 50 mWatt, not enough for warming up. The resistance has to be reduced to 50 Ohm to be able to produce 500mA needed for (a bit of) warming up.

In the next sock another type of conductive thread will be used for the warming up application. This  higher resistance version can be used for signaling (connecting to another conductive strip) or probing the variable resistance when walking.


2015 e-textile summercamp in pictures

For a week, e-textile designers from all over the world were together in Poncé sur le Loir, in the middle of France as guests of the art center Les Moulins de Paillard.

su3The staggering main workspace

su2filling up totally with projects during the week

Impressive were the projects: tools, education, printing, wifi, mass production amongst others, read more about projects at the summercamp website.

su1the knitting area, we had 4 knitting machines, all “hacked”, that is to say we could transfer images to the knitter using either AYAB, img2track or our own software.

su5 besides the main theater there was a very organized print room, with smart printing experiments

su4 A back stage picture of the exihibition space, also in this bunch of buildings near the Loir river.

A post documenting the Knitting group can be found here: On this site more information can be found, like participants, subject matter, and lot’s of other pictures.

Cuvée 2015: e-textile exhibition 2015 at Les Moulins de Paillard.

At the 2015 e-textile exhibition at Les Moulins de Paillard during the e-textile summercamp 2015 there was a big diversity of exhibited e-textile inventions. Curators of this exhibition were Anja Hertenberger, Irene Posch and Ingo Randolf.

Invitation card:


Some pictures of the exhibition space:


Other participants of the e-textile summercamp at Poncé sur le Loir suddenly called “Victory over the Sun”, differently: “Little sister” – in French “ma soeur” – ……ok … At the vernissage the game between you and the Sun inside this exhibit was explained in both English and French.

The pun of little sister: that generating energy is more easy than getting rid of energy was well understood using the metaphor of ourselves: eating too much is easy, but getting rid of the gained kilo’s is much more difficult!

The last Volt of the supercaps is like the last kilo. Even a plain short circuit will take a long time to dissipate this energy. After opening the circuit again, the voltage simply restores itself…this is apparently an sensitive area where theory (short circuit means 0V) and practice (used materials and chemistry) don’t converge.

At the exhibition solar cells and hand crank devices were added at a table near the silhouet.


For the exhibition, lasting a week, a special presentation mode was developed. The room was rather dark, which was good for showing the discharging LED’s at the back. But the Sun could never participate. And also, the current hand crank dynamo is too fragile for a big audience.

In presentation mode the dress was charging itself using a TIP122. Aha! – As you already remarked … this was not the right transistor, being NPN. Because for charging the supercaps, being connected to the GND of the microcontroller side, the same GND is connected to both the Collector and the Emittor…

This glitch occured because the presentation mode was added at hoc and of course at the last moment. In this case of charging the supercaps, the transistor should have been PNP, not NPN. Somehow, by using two different adaptors, the common GND could be fooled and the presentation mode worked also with the TIP122. But this TIP122 (NPN) will be soon replaced by the right kind TIP125 (PNP).




Solar cells versus hand crank dynamo’s

Solar cells

In Paillard in France (where the Sun should be present) during the e-textile Summercamp 2015 the week started with a lot of sunshine, making it fun to play around with a few solar cells and a water pump.

sc2 sc1

It was easy to generate the necessary energy for the water pump and generate a nice splashy water sound. But you had to replace the bench quite often, because the Sun is moving in the sky faster then you happen to be aware off.

Then clouds and rain – even in France -, days without sunshine for the solar cells. The nice installation was getting dusty and was removed.

After a week the Sun came back, it was hot and you look for shady places. I charged small lipo’s using the LTC3105 (for setting a 4.2V even when using solar cells of only 0.5V):


(Using these 0.5V flexible solar cells.)

But then also: situated under a tree, the spot where the sun shines moves rather quickly.

Then warm wheather, but a slightly clouded sky, considerable less energy generated. I tried charging an Ipad with the small bunch of solar cells, but the energy generated with the small solar cells is insufficient, the Ipad tells you that the source is not adequate.

Concluding about the smaller solar cells: During these last years of experimenting using these small solar cells in the Netherlands and France, but this means Northern Europe, even during the summer it is practically not possible to generate the energy needed for charging cell phones and lipo’s. Using the solar cells in a coat is only adding problems: you don’t wear a coat when it is warm – you go in the shade when it is warm – if you like to sunbade, you wear the less textile possible …

If the sun really shines, and you have a window, a spot which is really good, then indeed you can get plenty “free” solar energy, but even then it takes many hours before an average lipo or comparable is charged, just like with a normal charger using an adaptor.

It doesn’t mean that the cells don’t generate energy, it is just the level which our devices are used to is still big, requiring much time, mostly more than a day of “real” sunlight.

Hand crank devices:

The smaller cheap ones (1-5 euro’s) can be really crappy:

Chinese light torch (ACTION) : pinching action, throws away half of the energy (using the LED’s as diode for the alternating current), fun for exploring, but bad for energy generating…mind the RSI in your hand after some pinching!

Screen Shot 2015-08-12 at 10.37.43

The emergency hand crank dynamo’s, bought at cannot store energy, gears made of plastic wear out fast.


Still in the range is the IKEA Ljusa, which has a 1F supercap. About 90 seconds of light, dimming quickly:


Better are the small hand crank light torches bought at ACTION: charging a coin cell battery. This light stays on really longer


The bigger more expensive ( 10-20 euro’s) ones are really good for using as a torch at night, storing energy for 30 minutes easily. Some have multiple ways of generating energy, like the Conrad (nr 5755) version, which has a pulling cord, but also a solar cell. The VARTA 71680 has a bigger crank.


All together for the sizes:


The energy these hand crank devices deliver is mostly used for LED’s. Really charging cell phone devices will require long cranking or bigger dynamo’s. You must think of the bicycle shaped installations you can find in airports or IKEA – even then it costs a considerable amount of time  to really charge your cell phone.


Concluding about hand crank: this works always (not depending on the Sun, but rather your energy). But is shows that we as humans – at this moment – consume far more energy,  – and finding this normal – then we could ever generate by muscle power.

Concluding about small solar cells and hand crank devices: We like to think we can go “green” with either a bit of muscle power or a bit of sunlight and technology – and making this work, the sun or the muscles, is possible. But we underestimate the required energy and we quickly get frustrated by the time it takes to charge our cell phone either by sunlight or by hand cranking…