This first picture has been taken at my parents’ home. I used a star filter, which doesn’t really show, except for the reflection in the window. But this filter also gives the entire picture a soft look. Sometimes they have a dog at home, when friends are on vacation. In this picture, Niño can (barely) be seen laying in the shadow. This picture really shows the peaceful atmosphere that’s there.

I like this picture because it shows a typical state of my desk. I’ve used a bit of overexposure, so that the notebook is shown correctly, and everything else is brighter, which looks quite interesting!

This one is the coolest picture I’ve taken so far! Using only a briefcase to support the camera, and an extended shutter button, the timing here is remarkable. A few cars that were very similar approached me, so there is only one very bright line visible. I was also very lucky there was no traffic in the other direction, because now the background is very dark, which is in great contrast with the line. If there was traffic in the other direction, their headlights would’ve enlightened the background. The fact that it rains adds to the atmosphere by having great reflections on the ground.

This is a simple photograph of my friend Hans, but I really liked the colour contrast. He has a nice expression on his face, and the background is just right. Simply a decent picture.

This one has, again, been taken at my parents’ home, and I like the natural chaos that is displayed. A Harry Potter book on the table, some pillows missing or not straightened, the shadows falling in a weird way. It’s just how things are, nothing more, nothing less.

This is an interesting one, because it took a while to get it right. I noticed this bike before my house, and immediately thought about photographing it. The problem is, there are only a few moments each year, in the summer, when the sun is actually in the right position. I had to wait a few weeks, and when the moment was there, I took a few shots. Luckily it was a beautiful day, and the rusted bike with the grass growing through it, in combination with the awesome perspective, makes this one of my favourite pictures so far.

Because of the weird angle my dad’s lower leg is making, I wasn’t quite sure whether to publish this picture. Still, nothing can be totally perfect, and while this is one has great timing, a great expression and good lightning, the imperfections are what make it worthwhile to look at. The ball is mid-air, almost impossible to spot against the white background.

You might see a pattern of organised chaos emerging, and maybe that is the case. But I like this one most because it reminds me of the cool times at SCN. Experimenting with electronics is inherently chaotic.

When I was in Washington, D.C. for a conference, I took many pictures at night while touring the city. Most of them were miserable failures, but this one was unexpectedly great. This is one of the few pictures that looks way better in real life, as it was impossible to scan the moon properly.

A classic airport picture: I couldn’t let the moment pass! The huge amount of air and clouds in this photograph adds to a sense of space, which in this case I’d argue to be a good thing.

Decorating the Christmas tree! This one has been taken with a star filter, and with a shutter time of several seconds.

In 2008 our class graduated, and we decided to hold a hippie festival. Unfortunately, it wasn’t as popular as Woodstock about forty years earlier, but still it was totally awesome! A few weeks ago I found all the video material of that day and decided to make a compilation. The first video is about the morning, giving an impression of the great atmosphere in the school. The second video is the show, which is entirely in Dutch.

You probably know balloon art: done by magicians or clowns, on the street or at children’s parties. Some german guys have taken it to the next level. They thought visualizing the structure of complex molecules would be an excellent job for the famous balloon.

In my final year at high school we made some balloon molecules, and our chemistry teacher absolutely loved it. So here are some hints if you want to do it too:

• Use a balloon-pump! You have to blow up so many balloons, you’ll get completely exhausted when not using a pump.
• Get enough balloons of the same color! Check out the photos, our first model looked more like a rainbow than an actual buckyball.
• Learn the knots and techniques and practice them! We had a lot of balloons popping because we didn’t know how to do balloon art exactly. There are excellent guidelines on how to do the knots and techniques on the site of the professionals.
• Have lots of fun!!

One of the coolest projects I have worked on resulted in the turning of heads when biking through the city, and was also a great challenge as it involves some tricky hardware and software. The result was pretty darn amazing though.

So this was a really cool project that took a lot of my time when I was seventeen years old. Do you know these gadgets that write text in the air? Ever wondered how they work?

It’s pretty simple, actually. There is a row of LED-lights that you swing through the air. Those leds alternate very quickly between on and off, in a very specific pattern. When you move the leds at exactly the right velocity, the pattern will become visible to the human eye, and you can actually read text or see an image.

You are able to see this text because your mind will stitch the images together, like when watching TV. It all happens so fast, that you won’t see the individual frames, but you see the image as a whole. Or in case of the TV, it looks like you’re watching an actual moving scene. This phenomena is called Persistence of Vision (POV), and quite useful when making awesome things. :-)

In theory it’s possible to attach a row of leds to the side your bike, and get the same effect as swinging it through the air. The problem with that is that you have to go fast. Very, very fast. Instead, there is something on the bike that has a much higher velocity than your forward velocity: the angular velocity of the weels.

Depending on the size of the weel and your forward velocity, you’ll get a fair number of rotations per second, enough to make it blurry to the eye. So why not take the row of leds, and put it in the wheel. Sure, you have to do some funky math to get a nice image, but it looks cool, right?!

But of course, it already exists: SpokePOV by the artist/engineer Ladyada (who, by the way, makes very cool things!). Lucky for me, those kits only come in one color. What could be cooler than making a full-color SpokePOV?

After carefully selecting parts – RGB-leds are expensive! – the drawing began. For this I usually use KiCAD, an awesome open-source electronics CAD program.

Designing the circuit board was a devilish job. The routing of all the lines to the leds took a lot of time to perfect, not to mention fitting it on a board that is as small as possible. A cool thing about Kicad is that you have an awesome 3d viewer. But a 3d model with missing components kinda sucks, so I drew a few models myself in 3ds Max.

All that done, the schematics were sent to Niels at MakePCB, who also supplied most of the components. And how awesome, a few weeks later an envelope with the circuit boards arrived. A few hours of soldering later, and the hardware was finished.

But the hardest part was yet to come: the software. Luckily Microchip supplied an excellent USB bootloader, which I tweaked a bit to use the leds as status indicators. The embedded software is all about performance: it has to be able to keep up with the speed of the weel. Therefore it was necessary to supply the program with an image in a format that is easy to decode, and small at the same time.

First, a computer program in Java converted a normal image to a rotational image using some simple trigonometry. Normally, when composing images, pixel data consists of 3 bytes per pixel: one for each color. Uncompressed, this took way too much space for a small PIC microcontroller. JPEG or PNG compression was not an option: way to complex to decode. So the color data was reduced to 1 byte per pixel: 3 bits for red, 3 bits for green and 2 bits for blue. Why the reduced count for blue? Well, there are 8 bits to the byte, so some color has to go down, and blue is the best choice as the eye is the least sensitive to that primary color.

To display the colors some standard techniques are used such as pulse-width modulation (PWM) and LED-multiplexing, which I won’t cover in detail. However, the decoding of the pixel data to 3 bytes is kinda interesting. The C implementation was too slow, so it had to be done by hand, in assembly. Using assembly for this critical piece of code (which is only a few lines long) improved the speed of the whole program by a factor 6.

TBLRDPOSTINC
MOVF TABLAT, 0, ACCESS			// Read TABLAT to WREG; WREG = RRRGGGBB
MOVWF CurrentPixel, BANKED		// Put WREG in CP (CurrentPixel)
RLNCF CurrentPixel, 1, BANKED		// Shift CP to left;    WREG = RRGGGBBR
MOVF CurrentPixel, 0, BANKED 		// Put CP in WREG
ANDLW 0x06				// AND WREG with 0x06;  WREG = 00000BB0
MOVWF PWM2_0, BANKED			// Put WREG in blue channel

RLNCF CurrentPixel, 1, BANKED		// Shift CP to left;    CP   = RGGGBBRR
RLNCF CurrentPixel, 1, BANKED		// Shift CP to left;    CP   = GGGBBRRR
MOVF CurrentPixel, 0, BANKED 		// Put CP in WREG
ANDLW 0x07				// AND WREG with 0x07;  WREG = 00000RRR
MOVWF PWM0_0, BANKED			// Put WREG in red channel

RLNCF CurrentPixel, 1, BANKED		// Shift CP to left;    CP   = GGBBRRRG
RLNCF CurrentPixel, 1, BANKED		// Shift CP to left;    CP   = GBBRRRGG
RLNCF CurrentPixel, 1, BANKED		// Shift CP to left;    CP   = BBRRRGGG
MOVF CurrentPixel, 0, BANKED 		// Put CP in WREG
ANDLW 0x07				// AND WREG with 0x07;  WREG = 00000GGG
MOVWF PWM1_0, BANKED			// Put WREG in green channel

The algorithm of the program is pretty simple: take the time of one complete cycle (360 degrees). This time is measured by using a magnetic switch, with a magnet on the frame on the bike. The time is divided by 256, and a timer is set to fire a function. This function will take the next pixels, decode the colors for all the leds (on the front and on the back of the device), and feed this color to the leds using PWM and multiplexing. Result: people watching you as you go down the street at night. Mission accomplished.

As you can see on the photos, I ended up mounting two boards on the wheel. Otherwise you had to drive quite fast.. The synchronization of the two boards happens automatically, because they will both align to the magnet. Except when accelerating or slowing down, both boards remain in sync quite well.

I managed to get this project approved as an assignment for school (‘profielwerkstuk’), so the documentation is quite extensive. It can provide an interesting read if you like to know more about the used components, programs and techniques. You’ll also read about some major design decisions. It’s only available in Dutch though.. Download.

There are still a few un-soldered boards laying around here, as well as all the hardware designs and software code. However, I won’t post it here as many things are unfinished and not at all ready for production. Also, the parts are pretty expensive, especially when taking into consideration you need at least two boards per wheel. If you’re interested though to take this to the next level though, feel free to contact me and we can talk about it. But be warned: a lot of work needs to be done to have it work really well.

Update: it seems that around the time I built this, some other guys also got the idea and commercialized it. Their simple version does not support images or synchronization of the units, but looks awesome nevertheless. Their pro version is very cool and even supports animations and on-the-fly wireless programming but is priced at thousands of dollars. It seems though, they have done a great job! :-)