Studio Contrechoc

design & textile & technology entries

Category Archives: research

CRYSTAL workshop UVA Amsterdam

Crystals are a hype at the moment.

Sugar micro bio fuel cell:



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…



Presentation Version of Victory over the Sun

During the coming e-textile summercamp there will be an exhibition displaying work of all the participants. For the Victory over the Sun project, a game on a wearable between a hand crank and a solar cell this means making a special presentation version, because the exhibition will be displayed in a closed space. No sunlight to play the game.

In fact wearable projects always needs one or several presentation versions.

The two lines of LED’s on the front will be all lit. Normally only two LED’s are indicating the current game situation. From time to time there will be a simulated game between left and right (hand crank and solar cell). That way the silhouet will be “alive” and showing its potential even without players.

vs1   front   vs7    back (if discharging)

The electronics in the perspex casings at the left side will be lit by special bright LED’s, white, inside a kind of small shade. From the top of theperspex the lasercutted text will be nicely visible. The “scary” electronics will be a bit in the dark.

vs2    vs3 right side

In preparation is the next version in this project. Flexible solar cells will be used bent over the shoulders. These cells produce 1.5V each, and the game needs 5V, so another LTC3105 will be inserted. This chip boosts the voltage to 5V and can keep the most efficient load value (MPPT).

The cells of this newest version will be on display too:


The flexible solar cells can be bend to the shape of the shoulders. The LTC chip delivers 5.2V even when the Sun is weak. Compare this to the first version:


The big LED’s are nice but the light is invisible in the Sun. But of course in the latest version the bright LED’s are blinding inside.

Victory over the Sun: Paillard 2015 version

This blog post serves as the documentation for the work on display at Paillard 2015.

vos1 vs1


Energy Harvesting, game


Victory over the Sun is a dress which makes it possible to compare the use of several ways of generating energy. In this version the energy of a solar cell can be compared to the energy generated by rotating a hand crank. The amounts of energy for each source is played out to each other on this wearable. Varying circumstances, inside outside, shade, sun gives different results. Playing this game with this wearable is apropriate because it is easily displaced  in different situations, sun, shadow, twilight etc


By playing the gameit becomes clear that it takes a lot of effort to generate an amount of energy to load the supercap, that the sun generates this energy effortlessly when it shines optimally on the solar cell, but that this solar cell is not always (most of the times not at all) in optimal placement when you run around in this dress.


The material used for this dress is pieces of worn out jeans which are still usable. This recycling of material fits the project concept of harvesting energy, that is using energy which is self generated or “left over”. In theory this using worn out material seems nice, but in practice worn out really means the fabric is weak even if you don’t notice it directly. It can be seen at several places that the fabric is very fragile.


For the course of this energy game two verticals rows of bright LED’s are visible at the front of the dress. These lines of LED’s have a double indication. The main indication will an lit LED at the scale of the energy generated, the higher in the row the more energy, the second is another LED which uses the whole scale to indicate progress.

The second expressive behavior occurs after the game, in the discharging mode. The back light up in red and white and these colors fade gradually depending on the discharging rate.



Left to right: hand crank, supercaps, ATtiny85’s, LTC3105

The energy of the Sun is generated by a solar cell. For the hand crank is used a hacked Ljusa of IKEA. The energy of both sources is stored into two seperated 10F supercaps. Two ATtiny85 monitor the voltage in these supercaps. If the voltage in the supercaps stayes above the 5V a winning indication is flashed over the LED’s.

Then the energy is released. The first idea was using an LTC3105 energy harvesting chip to store the energy back into the lipo, charging the lipo.

The second idea was to use the bright Ljusa LED’s inside the back of the silhouet, so creating “a second” expressive behavior.

vs2   vs3

Presentation mode:

For the Paillard exhibition a special presentation mode is made. The electronics has got its own small shade lamps, and the front LED’s will be lit, simulating a game. After the simulated game the back will be lit as if the supercaps discharge.

Artistic Result:

Victory over the Sun is an artistic research result of a Design & Energy harvesting investigation:

Other presentations:

Victory over the Sun was displayed at the Hochschule für Künste in Bremen in 2015.

Victory over the Sun will also be presented at the Willem de Kooning Academy in Rotterdam in octobre 2015.

Former posts about this project:

First and Second sketch version:

About Interfaces of wearables

Designing a wearable has many aspects. The fabric shape and the functioning are the first concerns. After these parts are solved other things which doesn’t seem important are added.

Within the interface part a division can be made between the expressive part and the interaction part: the expressivity can be movement (Je Suis, Social Wind), some sort of light information (Solar Rim, Change Partners, Supernova shirt), etc. About this expressivity see this post:

The interaction part is about switching the wearable on and off, charging or changing the batteries.

This last part of the interafce is one of the tricky aspects of every wearable.

Interfaces of the last sort for wearables are tricky because at first it is outside the scope of the design. The on/off switch is added when the project is finished. You have to figure out the most convenient spot on the wearable. It “main switch” also has to be a spot which can be found but also is hidden in the sense that it not obvious. This means you have to solve a paradox.

Then the wearable can have different modes. For instance the normal functioning mode, where a laptop sends data wireless to the wearable for display, and a presentation mode with programmed data without the laptop.

To study possibilities, difficulties etc a list of wearables and interfaces/modes:

Project modes interface
Social Wind, ventilator module normal mode (temperature/humidity sensor), display mode switch, button
Solar Rim dress normal mode, display mode 1: one month of data, display mode 2: block data around the circle of 64 LED’s, display mode 3: epicycle mode. textile switches at sleeves, snap fasteners
Victory over the Sun one normal  game mode switch
Je Suis one normal mode – distance sensor, extra button for activation by hand switch, button
Supernova Shirt and trousers one normal mode switch
Change Partners / Talking Timer one normal mode, interaction soft button switch, conductive patches

Pictures of interfaces:

int2 Victory over the Sun, switch. Hidden

int7  Solar Rim Dress, soft buttons, left mode options, right snap fastener-  switch. Visible

int6Je suis module, back side, switch and button (right top, near motor). Visible

int5 Social Wind, Ventilator Module, switch. Hidden

int4 Social Wind, Led panel module, switch. Hidden

int3 Change Partners, Talking timer, switch.  Hidden

First conclusion:

If the electronics is designed separate from the wearable shape, the switch ends up hidden, on the electronics board. Hidden switches are difficult to find, even for the designer, after a few months.

So, the switch should be part of the wearable design, see the snap fastener design of Solar Rim.


If the switch is part of the fabric design then the electronics gets entangled with the fabric. This has two related disadvantages: testing gets more complicated because you cannot test the electronics without the wearable, and recycling that is separation after use gets more difficult.

The solution could be to add one switch to the electronic design and connect this switch to a second switch in the fabric. After integrating the electronic switch is switched on, and having the material switch in series this last switch will be used after all is assembled.

Victory over the Sun: technical testing

The dress described in former posts was finished finally.

The dress as a result of an artistic research into energy harvesting and design is presenting a game situation. By rotating a dynamo you have to compete with the Sun and a solar panel in generating energy. The game is created in a wearable so that you can change to another location. Playing the game in different locations makes you aware of the power of the Sun’s energy in comparison to your own muscle energy.

The dress is very much a prototype. As can be seen from the electronics a large amount of testing is needed to make some sort of a playable game.

The electronics was fitted inside 4 acrylic casings:


dynamo charger, supercaps/lipo, the brains: 2 ATtiny85’s and bitshifters, and an LTC3105 energy harvesting chip.

then fitted to the side of the dress: (which makes us aware that we should have thought of a better wiring 🙂


Up left: the charging dynamo, up right, the ATtiny85’s, and the bit shifters, down left, the supercaps, and lipo, then bottom right, the LTC3105 for recharging the discharged energy into the lipo.

After fitting the casings will be covered with small pieces of jeans, only the dynamo charger will be visible.


Two out of the three casings covered.

The choice for 2 ATtiny85’s was made from the first version where we had only 4 LED’s for the two sources of energy. But now after making it all we realized that the 2 ATtiny85 with the bit shifters should have been replaced by one ATmega328, with a LED-block script, avoiding the bit shifters. This would have saved one casing. This will be done in the next (third) version of the electronics.


Besides the solar panel a battery pack is installed to make testing in a room without the Sun easier, you can test by switching to battery pack (right side, next to the solar panel). The wiring between all the casings and groups of electronics is done by female – male connectors. This makes testing easier.


The second version of the script discharged the supercaps after winning. Winning is reaching the 5V mark. But what about starting a new game after abandoning a game half way? It was decided to discharge the supercaps at the start, when you switch on. Discharging is not what is seems. Following the voltage of the supercaps to about 0V, you see the voltage rise again without any charging. So discharging is now done in steps, then some delay, then measure the voltage again, if it is above a limit, discharge another round and so on.

This repeated discharging worked…until the dress was put in the full sun. The solar panel is generating so much energy that the discharging is not fully obtained. The discharging time had to be made bigger.

The installed solar panel is doing 0.1V a second so it will win in 50 seconds if the Sun is not hindered by clouds. At the moment it is practically impossible to win this using this hand crank dynamo hacked from the Ljusa.

Besides that, as could have been expected 🙂 the big LED’s are not visibly on or off in the full Sun. Another interface should be added, or these LED’s like this removed and giving it a try with small superbright LED’s.

A movie of the solar panel racing towards the 5V:

After observing the problem of the LED’s not visibly lit in sunlight, we tested bright LED’s in a simple script at 3V:

So the big 10mm LED’s will be replaced by these 3mm bright LED’s.

Victory over the Sun version 1.0, design and energy considerations

Second version of the Victory over the Sun project.

After the sketch version (see post the recycled jeans dress is totally modified. The front is reordered in horitontal strips, where the big LED’s form two curved lines. These 8 LED’s plus one at the bottom will  report about the game between the solar cell and the dynamo which is operated and powered by your hand and arm.


The back side is decorated with a pattern using the laser cutter.

vic3 backside

The material is recycled jeans. The idea is that there should be a match between the concept of energy generating and the material that is recycled. The jeans were worn for a few years and the worn out parts were removed. From the left over parts, which seemed still ok the dress was assembled. But in handling the fabric it was noted that also the seemingly good parts were deteriorating fast. In total contrast with the energy of course. Energy is energy, even if it is transformed many times. There is no comparison between fabric and energy, although we humans tend to associate green, “nice” energy with green recycling of goods and fabrics. Our tender ideas are not appreciated by reality.

The electronics is improved after the first skethc version. The LED’s are extended to 8. In the dress there are 9 LED’s. The two bottom ones will be used to indicate that a game is going on.


Inside of the dress, connecting the LED’s. The parts of the electronics, LED’s, circuitry, supercaps are all connected using connectors, so that testing is made easier.

In the electronics the supercap of 1.0 for each of the participants was replaced by two supercap’s of 10F at 2.5V in series. Now a player has to work to get to 5V!

One problem remained and remains. After the game a lot of energy is stored in the supercaps of 10F at 5.0V. You can calculate this energy: the formula is Energy of a capacitor = .5*C*V*V.

See for instance:

This means 125 J. In the first version this was only 12.5J because the Cap was 1.0F instead of 10F.

After the game this energy has to be dissipated to start a new game. But this getting rid of the energy costs time. The first try was using a ventilator. Even a cooling ven for a computer running normally at 12V could be used and took minutes to get the voltage of the supercaps down.

vic5 The ven is visible at the left bottom.

The last experiment was to charge the lipo used for the circuitry of the game.

During dissipation the voltage of the supercaps drops from 5.0V to hopefully 0V. The lipo battery is between 4.1V and 3.6V. So to charge the lipo a special LTC chip is needed (LTC3105) , to keep the voltage at 4.2V during charging back the energy of the game into the lipo. This LTC is actually a harvesting chip studied during a research on energy harvesting:

So the supercap should be connected to this chip and the output of the chip fed back into the lipo.


Expected was a fairly normal exponential behavior while discharging. Not quite so!

This is a typical graph of the Voltage over the supercap and the charging current to the lipo:

Screen Shot 2015-04-06 at 19.55.27

The time axis is not linear, noted were values of tens of mA of current and the corresponding remaining Voltage over supercaps. The LTC3588 took care of keeping the charging voltage to the lipo n 4.5V, even till the supercaps were at 1.5V.

There is a spike in the middle of the graph which was reproduced.

The drop-off is not exponential, probably because the charge pump is being cleverly regulated, this LTC 3588 chip is fairly complex.

The discharging is made interesting, but the last problem remains: the charge on the supercaps will not be brought back to 0V, which is the ideal starting point for the game. On the other hand with the 10F caps, the game takes long enough for the human arm to get tired. So maybe we keep this way of discharging.

One might get anxious about the lipo. If the lipo is charged to quick, things may get nasty. But the voltage of the lipo changed during charging only 1mV, from 3.81 to 3.82. The energy density of the lipo is far more bigger than the supercaps:

Lipo battery of 1400mAh * 3.8V = 3600 * 1.4 * 3.8 =~ 19000 J. So the 120 of the supercap does not really impress the lipo.

Adding an oscilloscope picture:


Yellow line: voltage over the supercap,

Blue line: inverted voltage over a shunt of .5 Ohm. For a square this means 10 mA. Maximum current 24mA. The current is different from the former graph because of the shunt

Start: first 4.9V being above the voltage fed to the lipo 4.2V (so the chip DC-DC downwards), then you see the crossing of this set voltage, the chip has to DC-DC upwards to 4.2V, there is a discontinuity, the current delivered is bigger -more efficent? After that the exponential. The last part is still interesting, the chip really keeps the voltage up to 4.2V while the supercaps ar at 1.5V.

2015 NASA App Challenge

Two years ago we participated with friends in the 2013 NASA App Challenge with a wearable. Last year we did a game for the 2014 App Challenge. Now we do another wearable challenge in the 2015 NASA App Challenge:

This is the first time we really try to make “intelligent” garments. We will integrate a neural network in the wearable. This network will “learn” by trying to recognize patterns. This learning will be made visible by changing the shape of the wearable, or even morphing.

The neural network will be small, and the learning capacities will be very limited, but this is a start at “really (somehow) smart” fashion.

Details about this project can be found in this hackpad:

images will follow next week when we try to finish two wearables in one weekend, where normally it takes about a month for a wearable…

But now we come with a group of expert programmers, designers and e-textilers, together with a car full of equipment…

(Making tags for this post … nearly all tags created for this blog are indicated, which means that something will be happening!)

Project page:

Victory over the Sun – (sketch version)

(see for a more advanced version)

This wearable is part of a research into energy harvesting, which can be found here: (Slow Raspberry pi server!)
The purpose of this wearable is to compare two sources of energy, not just showing a charging wearable.

The title of this project has changed a few times:

  • 1. Not another solar dress
  • 2. Energy battle dress
  • 3. Victory over the Sun

The first title is indicating that this project is not another mobile phone charging wearable. There is a solar panel, but also a hand crank device in the dress. But it is not about charging anything, because charging from a wearable is anyhow not very efficient.

The second title is indicating that the purpose of this wearable is comparing two sources of energy together in a game. The two source compete against each other. Which one will win? The solar energy or the muscular energy?

The third title is a reference to the oper of the Russian avant garde in the Bauhaus time:
Malevich and El Lissitzky made this oper famous, contributing to the stage design and the graphical displays.

There is some sarcasm in this third title, because it is rather impossible to win from the Sun in this game, only at night you have a chance, the solar panel is even charging slowly in normal daylight without direct sunlight.

Appropriately for the material old discarded jeans are chosen. Thus the material is recycled. The wearable is a simple dress with possibilities to add panels and the hacked Ljusa hand crank.

From the parts of jeans which were not totally worn out pieces were cut and these pieces were sewn together. An interesting folding problem popped up which will be described in another post.

Picture of the wearable in progress: (The hacked Ljusa, with the white card board and the red crank will be redesigned and more properly inserted into the wearable of course)

2015-03-12 07.51.57#1

Wearable made of recycled jeans material.

For the hand crank I have chosen the Ljusa of IKEA, which is a toy generating some power. It stores the power too in a 1.5F supercap. The second source of energy is a solar panel. Added to this is also a 1.5F supercap. With a ATtiny85 and 8 big LED’s – 4 LED’s for each energy source – the winning source can be made visible.

The electronics idea was to show the current Voltage for the two sources in two rows of 4 LED’s. The microcontroller which can just be used is a ATtiny85. Two analog PIN’s and two PIN’s for a multiplexer chip. One PIN is left for one other purpose.

Although the sources are generating energy, there has to be another energy source for the microcontroller at the moment. It would be an nice idea to have the sources (solar and muscle) first generate enough energy for the game to start, but this has to be figured out yet.

The third energy source is a rechargeable lipo battery.
Then there has to be a discharge for the game to restart. This is done using a FRT5 DC5 relay.

The number of difficulties in the electronics were plenty: besides the usual stupid mistakes like connected the LED’s the wrong way there were a few real “Zen master” problems (which means you have to learn something besides correcting stupid mistakes).

The ATtiny85 uses USI instead of SPI, code for this was found at:

Then the implementation of the use of the analog PIN’s proved time consuming. In the end the soution was found in connecting the PIN’s to the GND using a 1M Ohm resistor.

Then the coding of the LED’s, in two groups of 4 inside the bigger group of 8 was proving not straightforward. Apparently the number read using the ADC code is not a “normal” INT number and you cannot use all math available, like subtracting 512 from the value read between 0 and 1024.

The final code can be found here:

Testing pictures of the electronics:
Testing is better down as much as possible outside the wearable. In the end the electronics is on the board and the ATtiny85 had to be removed and placed in the programmer breadboard way too often again, I could have better soldered programming the wires to the board right away…

  • testing first the ATtiny85 and multiplexer on a breadboard
  • testing the LED’s on a piece of jeans
  • the PCB with the supercap, multiplexer, relais and ATtiny85

2015-03-16 08.09.00 2015-03-16 11.18.50

2015-03-17 10.38.49

Remarks about the PCB:

  • One relais too much, two components right upper side FRT5!
  • At the left side the two energy sources can be connected.
  • The green component is the 1.0F 5.5V supercap
  • The Ljusa has it’s own supercap (storing energy), the solar panel uses the supercap (green thing) on the board.
  • Middle under, ATtiny85, left under hd74ls164p shift register
  • The PCB can be redesigned more efficiently!

Preparing Knitting Images

Documentation for a workshop “Machine Knitting” at In this workshop we will explore possibilities of tuck, skip, lace, Jackard, and other knitting techniques. In former blog posts is documented how an image is uploaded using my own software together with the board made at a session of in Bruxelles.

With an accessoire it is possible to knit with different colors using the double bed.

2015-03-01 15.25.36 A so called color changer.

The way to knit an image in a double layer, avoiding the loose thread of Nordic Knitting can be seen in this video of the Japanese knitlabo: (Double bed jacquard knitting)

Using the Due to transfer the images and not the img2track (see below) the procedure of sending the right image had to be found.

2015-03-01 15.25.44

After the normal setup of the double bed the settings are:

Main bed slider: both PART buttons,KC(II)

Double bed slider: left PR slider, circular knobs press and turn, bottom lever: center.

2015-03-01 18.53.17

But just sending the image as done in other posts, like the single bed TUCK, slip, lace and Jackard is not possible.

Exploring the patterns stored inside the KH-940 it could be seen that knitting from right to left prepared the pattern at the top side of the needle board (first bed), while going from left to right stayed on this line. The second color did the reverse in color: the “black” in the pattern was at the bottom side of the needle board, and maintained while knitting to the left.

So this meant that the “pixels” of the image should be twice as long (two tours of knittings), but also that the tours (of left and right) had to be alternating in base-color.

The prepareation process can be shown in these images:

Screen Shot 2015-03-01 at 14.06.54

Normal image, the pixels are two high, which still gives half height as shown below. So multiply again by 2 (Using the setting “Nearest neighbor – preserve hard edges” stting in the scaling menu of Photoshop.)

Screen Shot 2015-03-01 at 14.07.06

Making the image 4 times the height, 2 x 2 pixels in height.

The next step is making the lines alternating in base color. I used for this a second layer with black lines of 2 pixels high. These pixels were selected and with the selection the alternating horizontal lines of 2 pixels were inverted:

This resulted in a real “encoding”, the text cannot be read anymore:

Screen Shot 2015-03-01 at 14.07.53

Using this in the Processingg sketch and sending it to the KH-940: (horizontal direction inversed)

Screen Shot 2015-03-01 at 14.11.15

This result was knitted: (the knitting is one layer thick, front side has the image, back side the stripes.

2015-03-01 15.26.02

The reason to mutliply by 4 and not 2 is because the setting is the PART mode, with one tour knitting, you knit only half. If you multiply just by 2, you get a diminished height:

2015-03-01 15.26.08

As can be seen, the bind off isn’t really perfect. The trick for binding of is to switch to another color, knit this color further in round knitting, getting the knitting of the machine and crochet the stitches together of the last row of the knitting. Then get rid of the last color. In the references is the video.


one bit images

around the Jacquard:

double jacquard:

Software: i use my own program (Procesing sketch and Arduino Due code), and having this fun of discovering the image encoding, but you could also use img2track, like in the video, this uses the adafruit hack to transfer images, free for max 100 needles.

Binding off: