You may know that the whole spring and summer has been a bit quiet over here at Interactive Matter. And again for a reason. I was asked by a friend to build the electronics for a massive LED installation for the  ‘Hsinchu Biomedical Science Park Exhibition Center’.

The result was very impressive: An 10 meter long installation, consisting of 30 moving triangles with controllable RGB LEDs in them, acting as a moving display.

A XMOS controller driving 60 stepper motors,  with about 100 meters of HL1606 digitally controlled LED strips composing a moving LED matrix of  30×102 pixels. The concept and design was done by Taiwanese partners. Interactive Matter only provided the electronics and programming.

Driving the HL1606 LED strips

As every big project it all started as a very small and manageable looking proof of concept:

The basic idea was simple: The XMOS XC-2 kit has 4 processing cores, three of them having two 12 pin connectors. So each core can support 16 HL1606 LED strips (some control pins and 8 data pins per connector, with two connectors per core). Due to the parallel architecture of the XMOS controllers it was very easy to create some scalable implementation for the HL1606 driver). Implementing the driver was also quite a breeze since adafruit hosts the datasheet there are some good Arduino tutorials for this. The big problem was that the HL1606 only supports 2 grayscale levels, while it was only practical to use just 1 bit control (on or off). So this called for some kind of software controlled PWM. The lenght of the strip and the communication speed controls the update rate of the LED strip. And especially the communication speed varies widely with electric noise, cable length, power supply quality and so on. The solution to this was to implement some pulse density modulation. By this the grey scale modulation the color depth automatically adapts to the image refresh rate on the LEDs. The faster the update of the LED strip in comparison to the update of the RGB data displayed on the LED strip, the higher the perceived color depth. Nice (and necessary).

Driving the stepper motors

For the stepper motors I used the simple pololu A4983 stepper motor driver carrier chained with some Microchip MCP23S08 to adapt the Pololu drivers to SPI. So I could drive up to 32 motors from a single XMOS connector. A simple and effective plan. But at the beginning of the construction phase I completely underestimated how much work it is to solder 60 motor drivers.

But finally it was done, only to learn that there was a mistake in the MCP23S08 footprint. But no design is a good design without fix wires:

The only think keeping me sane during the build period was the fun that Interactive Matter was the workbench for some Taiwanese company.

Assembling everything

Finally the XMOS and the motor drivers were shipped to Taiwan, where the arrived safe and sound. But the result of the unpacking gave the impression of the scale of this project.

And the scale of the project got even more visisble once the stepper motors and drivers where installed onto the base board.

And gosh where we happy when we saw the first light on the installation.

So the next step was to pack everything and reassemble it at the customer site.

And testing it. The first results were at best described as – uhmm – mixed.

Everything that worked nice in the ‘clean room environment’ had a good amount of trouble in the real world. There were a bunch of high voltage or high current cables in the ceiling. Giving the digital communication a hard time. But finally after some debugging and fixing everything was ready for the big show.

The final installation

Even Ma Ying-jeou, the president, attended.

And after some more debugging and fixing we were able to see some very nice results of the installation:

Some final thoughts

There were two facts in this project which really puzzled me. First of all the whole project coordination was done via video conferencing. I was never to Taiwan (yet) and have never seen the final result. It worked very well considering the hassle of communication and time difference. It was great to do a project with the partners from Taiwan. Even though I only did the electronics and programming.

Second the digital communication in the installation could have been better. If you are working with medium distances and/or motors be sure to use some more robust protocol like RS485 or LVDS (more on that topic soon).

I would massively like to thank the people at XMOS and XCore, the XMOS community. This project could have never happened without their help. And it was the first project for me to discover the power of the parallel processors from XMOS. Marvelous stuff. They scale well and are easy to program. One of my new favorite piece of hardware. I would really like to thank XMOS for their open source initiative. It helped this project a lot!

Even though XMOS have a very encouraging open source initiative and even released the base software for this project as open source there is only a HL1606 driver sketch availaible at github. In the mean time Interactive Matter maintains the XMOS Led Tile Appplication, which is the heart of this project. So the HL1606 driver will eventually end up there, so please be patient. The motor driver will never be released as open source. It is just not good enough. But you can expect some activities in that area soon on Interactive Matter.

In the end it was a quite big and fun project. It was great to work with the partners from Taiwan and the people from XMOS. And the result is quite impressive. I hope you will see more of this from Interactive Matter in the near future.

You may know the Blinken Button for Beginners Kit. And you may know that I am quite out of stock at the moment.  But things are changing: The new Blinken Button Kits have arrived!

The best: The now come in red or green (Jimmy liked it – so I added this option) and I got plenty.

This new Blinken Button version sports some enhancements over the old version which came from contribution, wishes and recommendations:

• First of all they now come in red or green – more options for you!
• They include built in self test to give you a better chance to find the nasty solder bridges.
• They now have an optional SPI connector to use them as simple 8×8 displays.
• The PCB is now white (don’t know how this is an advantage – but I like it more so I sell it here as an advantage).

The idea to add an SPI interface cam from Johannes and Gabe. In a unbelievable stunt they hacked the SPI connection in the old version the same night they bought the kit – and added the implementation straight away. So thank them that this it´s now a standard feature. And be sure to check out their spectacular Game Of Life on Blinken Button too!

Please apologize that I did not find enough time to prepare packages – so they will restock in my shop in the next few days. But if you really want one just send me a mail and I will restock on demand (i.e. send you one or some). And if you don’t dare to solder it on your own come to the Chaos Communication Camp near Berlin. I will offer some SMT soldering classes with Blinken Buttons for Beginners there.

Related posts:

• Blinken Button as a SPI Display
• Blinken Buttons for Beginners – a SMT Beginners Kit
• Blinken Button – The LED Matrix Button Kit

It was time again to talk at the Good School ‘Camp Digital’ about the Internet of Things. Instead of choosing a real world example I choose to revive the good old ‘Twitballon‘ and create a new and improved version.

Twitballoon is a simple Arduino installation, which raises a balloon according to the activity of a certain keyword on twitter. The old version was using a hacked servo to move the ballloon but the servo had real problems with temperature stability. Due to the great opportunity to bring the Trinamic stepper driver chips to Arduino the servo was replaced by a stepper motor.

The basic principle of the Arduino sketch is real simple: The Arduino is connected to the internet via the Ethernet Shield and uses the Twitter Streaming API to permanently search for tweets with a certain keyword.  A Tweet raises the level of the balloon for a certain amount and over time the position of the ballloon is lowered again. By this the position of the balloon reflects the activity on Twitter regarding the selected topic.

The stepper motor is driven by an experimental Trinamic breakout board. Interactive Matter provides a first version of the Arduino library for the TMC260/1/2 chip of Trinamic. The Trinamic chip makes driving a stepper motor a breeze. It offers a very detailed configuration, adapting the driver exactly to the given stepper motor, giving a very sielnt and precise control over the stepper. This is a little bit overkill for this project but in the end it made the positioning of the balloon very easy.

The look of Twitballoon 2 is intentionally rough and industrial to give it a technical yet humble appearance. In the end it was a very nice and conversational piece, communicating the playful aspects of tinkering.

Related posts:

• Twitballoon – a Twitter Trend Visualizer

It was a bit quiet in the last months here at Interactive Matter. For a reason!

One happy day in fall 2010 Mitch and Jeff convinced me to prepare some Blinken Buttons for Beginners Kits for a SMT soldering workshops at the 27c3 in Berlin. I was happy that they did! And I suffered massively because they did. Preparing 50 kits, ordering material, reworking How-To’s, packaging packages and packaging my suit case cost me a lot of time (the later was not that complicated). But in the end I was prepared, got everything packed. Unfortunately I completely forgot any marketing material. You know on conferences there are these kind of hosting space called walls where you are supposed to bring up some content on paper, publishing it with stickers. So I had to come up with an impromptu solution. But fortunately with Mitch’s help I could gather all necessary technology and created this wonderful ad shown above.

And best of it all Hackable Devices and Interactive Matter stumbled over each other and made a distribution deal. So as soon as I have restocked again you can get the Blinken Buttons directly from Hackable Devices.

It was big fun! We soldered so may kits (thanks to anyone who bought one). And as always stated by me SMT is easy to solder. After some short introduction and showing some tricks of the trade everybody was able to solder it. We even had some complete soldering beginners who never soldered before, choosing the Blinken Button as first kit! Perhaps more for the look than for the technology. But they did it and they did it well and returned happy with their Blinken Buttons. Some guys even started at the conference to hack the software by adding a SPI interface to it! Cool!

And spending some days with Mitch was a great experience too! Watching him teach and seeing his approach to all this DIY hardware stuff helped me so much. So special thank to Mitch & Jeff again, without your help this great success of Interactive Matter have never been possible!

Related posts:

• Blinken Button for Beginners Version 2
• Blinken Button as a SPI Display
• Blinken Button – The LED Matrix Button Kit

Interactive Matter proudly presents the first joint project with Tinkerlog (the Space Invaders Button does not count, it was me doing a knock-off): The Twitballon.

The nice people of Good School approached us, asking for a simple showcase what tinkering is all about. Nothing less. So Alex of Tinkerlog and Interactive Matter came up with the idea of Twitballoon. Twitballoon is a simple balloon winch. An Arduino controls a small servo lifting or pulling down a balloon according to Twitter activity regarding a predefined topic. To see it in action head up to the video after the click.

Twitballoon is controlled by an Arduino, permanently performing Twitter searches for a predefined keyword. If it finds a tweet the balloon is released a bit and lifts up. Over time it is pulled down again. So the height of the balloon reflects the activity of that keyword on Twitter. It is much easier to understand if you watch the video:

Twitballoon it is a very poetic way to visualize Twitter activity regarding a topic. It is much easier to comprehend then some dry graphs. It was nice to see how the visualization triggered a nice competition for the chosen keywords Kolle and Rebbe.

Since Alex has done all the hardware just check his Twitballoon post for all the nifty hardware details. If you are more interested in the software side of the project read you can find all the implementation details here.

The heart of the project is the Ethernet Shield and its accompanying library. To make the network setup as easy as possible the DHCP and DNS library was used (don’t know why it is not already included in the Ethernet Library). The Arduino acts as a web client, retrieving its IP via DHCP and resolves Twitter via DNS – this setup is much easier than just using predefined IP-Adresses. The HTTP client is used to perform Twitter searches via the Twitter Search API.

The implementation for the balloon behaviour is quite simple. The Arduino maintains a concept of the current level of the balloon. Every time the search keyword is found on twitter a certain amount is added to the height of the balloon. By this the balloon raises. Over time the height is reduced slowly until it hits zero. If you want to check it out yourself just grab the source.

It is a very simple hack. But in the end it was a beautiful trend visualization. Let’s see if there is an improved version soon.

Related posts:

• Twitballoon 2

You all know the Blinken Button Kit (aka Space Invaders Button). One of the biggest flaws of this kit is that it is not really a beginners kit. But with the help of Jeff (really big thanks for that) I was able to convert it to a perfect SMT beginners kit. The design was drastically simplified to make it easy to solder, while maintaining the original functionality.
So head over to the Blinken Button for Beginners in the shop to grab yours, or if you allread got one, check the Blinken Button for Beginners How To to assemble it.
The original Blinken Buton design has undergone some changes to make the desing more SMT beginners-friendly:

• Massively reduced number of components (removing the Arduino comatibility).
• Very clear component marking.
• All resistors and capacitors use a 1206 packaging for ease of assembly.
• Enhanced LED-Matrix footprint for easier testing.

The most important change was to improve the component marking and using hand-solder-friendly 1206 components. It now has a clear marking which component goes where and for the ATMega orientation:

The whole kit can be soldered by SMT novice and is easily testable – so if you was looking for a SMT beginners kit this is the one for you!

The LED matrix footprint has clear markings which pin is an Anode (square pins) or Cathode (round pins) to enhance testability. It is easy to ensure that you have a  working design before you solder the LED matrix to reduce the probabilty of errors.

Related posts:

• Blinken Button – The LED Matrix Button Kit
• Blinken Button for Beginners Version 2
• Blinken Button revisited

SkatePOV brings POV to your skate board. It is a minified version of MiniPOV2 attachable to your skateboard. Draw texts while skating!

The LEDs pulse to write the text. By moving the skateboard (aka skating) the blinking is converted into a matrix and the blinking becomes the text. This is the first project in a series to bring more effects to your skate board.

Construction

The schematics is drastically reduced to the original version, the LEDs have been reduced to white 0603 LEDs. and layd out in a very small PCB, small enough to not touch the ground or come anywhere where it is physically endangered (at least on my long-board). And yes, the silkscreen is one of my major fails. I do not know how often I checked the PCB but never spotted the real big mistake – no matter.

On the back there is a small NCP1402 step up converter to power it from two AAA batteries, with some too big capacitors. The ATTiny2313 is used in the very small and convenient MLF Package (a lot of pins on a very small space).

The PCB is mounted vertically on the battery holder. The whole device is attached with Velcro Tape to the skateboard to make it removable (a anti theft prevention?).

The Effect

In the end it gives a very nice (and in this version boring) text while skating around. You cannot see it good enough in the first picture, since it was a bit too dark while I made this photos, here is a better version:

But it was really worth doing it in SMT. What did we learn from this? Doing a daylight POV is much harder than I thought. It works after sunset and of course in the night, but there is much more power needed to be daylight compatible. More powerful LEDs, with a much smaller viewing angle is needed. But it was fun and pimping skateboards with light is a topic too long neglected. I think there is more to come. So stay tuned.

I really like TV-B-Gone by Mitch Altman. The idea to have an universal remote to switch off any TV set is just marvellous! But for some real sneaky operation I wanted a much smaller version which perfectly fits into my pocket. So how about a small experiment how small you can go (and still solder by hand). So here it is: (most probably) the world smallest implementation of TV-B-Gone:

The µTVBG is based on the ATTINY85 implementation by Lady Ada. I just downloaded the schematics and replaced some parts, reduced the number of IR diodes and did a new board layout. Nothing special. Even the firmware works unchanged.The whole board measures a mere 1.4 cm to 2.5 cm – small enough to fit in in every pocket.

All parts are SMT 0603 parts, the transistors are the good old BC850C and as IR diodes I used the Osram SFH 4600 (I think I got quite a soft spot for all those Osram LED stuff, more by accident I use it more or less exclusively – they have great parts, are at least designed by German engineers). The SF 4600 deliver 30 mW of power at 940nm wave length, they look good and can be used flat or as side looker (as I have done here). Currently they are being replaced by the SFH 4641. The switch is a C & K Components KR221G, which is good quality and gives quite an good tactile feeling.

As you can see in the above picture I was able to completely mess up the SFH 4600 footprint – twice as wide as it should be. But with a piece of old wire it was no problem to fix it. You can see, you can even air wire stuff in SMT.

The board is powered by a CR1220 lithium battery, placed on the bottom of the board.

Why an SMT TV-B-Gone clone?

First of all I wanted a real small version – and I achieved that. Second I wanted to test if hand soldering of 0603 is feasible – which it is. 0805 is much easier, but consumes far more board space.

But the main reason is that I want to encourage everybody to try some SMT work. You can do a lot of cool stuff with it, cramp a lot of functionality in a very small board space. And you get real cool components for SMT. Most modern chips are developed as SMT-version only and if you stick to through-the-hole stuff you will never be able to use them (OK, you can get your breakout board at SparkFun). If you managed to do some SMT you are able to pick from thousands of alternatives from major vendors. And the hardest thing about SMT is to get over the fear that it is too small, which it is not – in most cases. So go for it!

The reason I started all this microcontroller stuff was that I wanted to create an animated button displaying space invaders characters. Preferably the same size as an normal button (the ones you put on your jacket, not your panel).
Now here it is:

If you do not see the electronics for this small display read on after the click. And no, I will not stop tinkering.

Update: You can get your own Blinken Button (aka Space Invaders Button).
The whole project was inspired by Alex, especially his LED matrix projector and his tiny 64 pixel project. After some beers with Alex I claimed: “I can do it much smaller in SMT”. Silly me! Not that it was hard enough to build it in SMT, but I also wanted to do it in bi-color (I just got some small bi-color LED matrix laying around, waiting for a project) and I made some real design mistakes (but that is a story for another article). Additionally I wanted an design which still allows me to use the LEDs of the display as light sensor. That was nearly too much – but only nearly!

To give you an imagination how it will look like lets take a look at a video:

http://www.youtube.com/watch?v=KlpE1WtwF9Q

At the end I attached a fixing pin at the battery holder, to wear it as a ‘real’ button:

My girlfriend loves it! Of course she got some special animations and texts.

Schematics

After some research I choose the ATmega164P as platform. It had enough input pins to drive all the 24 pins of the matrix and still some spare for programmer. The current is supplied to the rows by a transistor (a conveniently prebiased one: DDTC123TUA, it comes with an built in base resistor), the ATmega controls the column diodes by sinking its current. In the I came up with an very simple schematics:

The port usage and layout of the connection was optimized for easy PCB layout. I decided to do all the mapping in software.

PCB

If you layout on an PCB, you end up with some real trouble, but it ends up in something like this:

It dimension are a bit smaller than the matrix. It features a nice little SMT switch (C&K Components AYZ0102AGRLC ) on the edge of the board. As you can see the SOT323 format is perfectly small. The current limiting resistors are 4*0402 arrays. The decoupling capacitors are 0402 SMT capacitors. And the PCB is still dirty from flux and solder spots.

This is the whole unit in comparison to an one Euro coin:

Code

The implementation is basing heavily on the code of Alex’ 64 pixel project. But instead of rendering a bit buffer I used an buffer which contained all pin settings (so 4 bytes for PORTA to PORTD).During load time of an sprite its bits are converted into the various port configurations. This allows me to use an really fast update routine of about 800 Hz.This reduces massively any flicker (which is critical if you want to go dancing with the button on).

Beside from that, and some real mistakes it is nothing special. Therefore no code posting here. You can find it on Alex’ site.

Learnings

Avoid 0402 capacitors whenever you can. They are just too small. And if you use them never place vias in the pads. Since the vias suck up the solder and the capacitor stands up, literally. I ended up with more than one capacitor going 90°.

The 4*0402 resistor arrays are great. You need an hot air rework station to solder them, but they are easy to solder and in an very convenient package. I just stock up on them – they are really nice!

The SOT323 transistor package is perfect for small signal transistors. It is considerably smaller than SOT23 or TO92 and still quite easy to solder. This will be my preferred transistor packaging!

The pre-biased transistors are neither very handy nor very practical. But they are expensive, you have to choose the biasing resistor wisely and always order the wrong parts. There would have been some space for some resistors left – so no real reason to use the pre-biased stuff. I will never use them again.

Related posts:

• Blinken Button – The LED Matrix Button Kit
• Blinken Buttons for Beginners – a SMT Beginners Kit
• Blinken Button as a SPI Display

Playing around with gravity:

A basic piece exploring interaction with gravity. It is (again) half a ping pong ball. On the rim there is a red dot, which always stays up. You can turn it as you want – the red dot will go up again. Video after the click.

It is much easier to see it in real:

http://www.youtube.com/watch?v=m31_mkeNV3g

Basically it is a very small “physics engine” which tries to hold the dot up. Which side is up is determined by an accelerometer. The measured gravity creates a force which drags on the dot and by that it is always dragged upwards. By applying the right force you can even try to toss the dot in circles.‚ The whole project does nothing real useful – but using accelerometers is a nice way to interact with electronics objects

The internal construction consists of 12 Micro SideLeds (simliar to but completely independent of the Led Lighthouse), arranged in a circular shape, connected to an ATmega168 controller. There was nothing fancy used like charlieplexing the LEDs. The ATmega168AU has enough pins and a extremely small form factor. An ADXL322 is used as accelerometer:

The whole project was done again using only SMT parts. Mostly due to availability (e.g ADXL322), size (e.g. getting a whole ATmega168 in an ping pong ball) or aesthetics:

The source code can be found in the Gravitron source archive. Perhaps it can help you with anything – perhaps not. Hopefully it does not hurt anybody or destroy anything. If it does – I am not responsible.