Interactive Matter » Projects

Blinken Buttons for Beginners – a SMT Beginners Kit

Marcus — Sat, 08 May 2010 14:57:25 +0000

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.

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.

SkatePOV

Marcus — Mon, 05 Apr 2010 12:33:02 +0000

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.

µTVBG – World Smallest TV-B-Gone clone

Marcus — Sat, 04 Jul 2009 13:19:50 +0000

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!

Space Invaders Button

Marcus — Mon, 13 Apr 2009 10:33:15 +0000

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: this design is available as Blinken Button in the Interactive Matter Shop!
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:

httpv://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.

Gravitron

Marcus — Tue, 23 Dec 2008 15:54:21 +0000

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:

httpv://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.

How was your day, darling?

Marcus — Wed, 01 Oct 2008 08:24:47 +0000

After some previous testings I did finish the final Version of How was you day, darling? – or shorter “hwydd”:

It is a small object (actually half a ping pong ball), interacting with its owner and environment (and being pretty boring without interaction). The object permanently aggregates light samples (i.e. it measures the every second and stores the average every some seconds). If you take it into your hand it notices the raise in temperature and tells you how it experienced the day (i.e. playing back the light levels of the day in time lapse). It is much more complicated to describe than just to watch the video (after the break).

httpv://www.youtube.com/watch?v=McEpj-86flQ
(Still the old version – youtube is still converting the new video – will get updated as soon as possible.)
How was your day, darling? is an attempt to create an electronic object which completely hides its electronic nature. It acts as part of the environment a user can interact with. The aim was to create a (agreed in a very limited way) emotional relation between the object and the user. Therefore the interaction is done using implicit methods instead of exposed elements like buttons or so).
Basically the micro controller measures the light level 255 times during 14 hours (ends up in about one check every 3 seconds) and stores it in its EEPROM. At the same tame the temperature is checked. If it gets significantly warmer the micro controller assumes that the device is on a hand and plays back the recorded values of the last 14 hours with its white LED in approximately 30 second (The second LED is just there because there was still a pin left and acts as a second method of output – e.g. if a measurement is performed).
Technically the whole project is very simple. It is an attiny micro controller, an light sensor and a white and a colored LEDs. It is completely realized in SMT (because it is cheaper and you get more components per ping pong ball – and I think it looks better):

It is more or less the same as the first prototype, anybody interested in parts or schematics can have a look over there.
It sill got nearly all of the problems as the prototype – but I got bored and want to tinker with something else. Perhaps I will come back later and implement an double voltage high brightness version.

How was your day: The first prototype

Marcus — Mon, 25 Aug 2008 19:00:43 +0000

After the first idea was born a project name and prototype was created:

First prototype of "How was your day darling?"

The project name “How was your day, darling?” or shortly “hwydd” refers to the interaction of the device. After you come home you take it in your hand and the device tells you how its day has been. A neat little reactive device.

As you can see the whole project fits into half a ping-pong ball.

To give you a impression how it works a little video:

httpv://www.youtube.com/watch?v=McEpj-86flQ

If you take the device in your hand the warmth of your body triggers the device. You cannot see it in the video since it is too dark, but the flashing in the beginning signalize that it detected a human interaction (the device is getting warmer over a certain period of time.

In the beginning it is playing back the night (which is obviously quite boring – I will change it later). After the sun goes up and we had a very nice morning – as you can see. The afternoon was quite bad weather – therefore it gets darker – until it gets dark again since night falls

The light is recorded by using a SFH 3310 phototransistor. To react to human interaction a stock thermistor (the small black thingy on the bottom in the first photo). For measuring and storing the results I used an ATTINY45

The schematics is very simple:

Schematics for "How was your day Darling"

The photo transistor and thermistor form voltage dividers and are connected to the analog input of the ATTINY45. The LEDs are simply connected to digital and PWM outputs of the ATTINY. Add a battery and a programming header and you are done.

Translate this into a physical device and you get this (OK, next time I will use a little bit less messy wires):

The internals of the first prototype

As you can see I had to swap the photo diode to a stock one – I simply got the SFH 3310 too late. Next version will have everything.

The bottom line:

The LED is far too dark. 3V ain’t enough for the white LED.
Recording 24 hours is far too much. The twelve hours of night are just boring!
The human warmth detection is OK, but needs some optimizing.
The project was far more complicated than I thought. Especially reducing the power consumption got some serious attention. But in the end it runs for weeks from a single coin cell.

How was your day: The beginning

Marcus — Mon, 11 Aug 2008 19:53:17 +0000

It all started with a simple Pummer:

Some Pummers by m27debord

A Pummer is a BEAM bot, which collects light during the day and transmits it as light pulses in the night. A Pummer is a nice ornament but lacks a bit of intelligence and interactivity.

As you can see in this video (a Pummer by Mark):

httpv://www.youtube.com/watch?v=NjWgBx7wvzM

This Pummer is unusually fast pumming – but you get the idea.

A Pummer consists of a solar cell and a circuit to strobe a LED after dark. Nothing more, nothing less. Due to the solar cell it runs forever and is completely care free.

I really dig the idea of gathering the light of the day and play it by night. But it was somehow quite indirect for my taste. So I came up with the idea of really recording the light and playing it back at night. The first idea was to use an AVR ATTINY micro controller to constantly measure the light and store it in its internal memory.

But playing back the pattern all night was a waste of energy. And when it is night? And is there somebody to watch it? If not it would be a waste of (precious) energy. So I added a temperature sensor to measure the touch of a hand. The light pattern should be played back if somebody takes it in his hand.