First_Encounter_ is an Arduino based interactive installation, developed for the course Physical Interaction Design and Realisation at KTH in Stockholm. First_Encounter_ is a hanging art installation consisting of, in our case, 20 triangular modules. Since the code used is modular as well, it is up to you and the calculating capacity of the Arduino to determine how many triangles you want for your version.

Working hard on you next project requires music, this is the First_Encounter_ playlist:

You Ain't Seen Nothing Yet - Bachman-Turner Overdrive
Hot Stuff - Donna Summer
You Oughta Know - Alanis Morissette
Lemon Tree - Fools Garden
Blinded by the Light - Manfred Mann's Earth Band
More Than a Feeling - Boston
Come Together - The Beatles
Pumped Up Kicks - Foster The People
Wire to Wire - Razorlight
Words - Bee Gees
The Final Countdown - Europe

Step 1: Hot Stuff

The supplies you need. The exact amount you need will depend on the number of triangles you want to make:

Wood for laser cutting, 4mm thick
Milky white acrylic for laser cutting (2mm)
Woodglue
Sandpaper
NeoPixels LED-strip, 30 LED's per meter, 6 meter (180 LED's)
Aluminium foil
Electrical wires - ±70 meters various colors
Electrical Tape
Servos - 10x
Screw Terminals - 170 used
Small Screws ±8 mm long - 80 used
Arduino UNO
MPR121 Capsense breakout board - 2x
PCA9685 Servo breakout board
Black Cloth
Hot Glue
5V 12A Powersupply

Step 2: You Oughta Know

The thickness of both the acrylic and the wood as well as the size of the triangle are very important.

Although there are 5mm thick Neopixel LED-strips, we felt that they were not bright enough for the purpose. We used 10mm wide LED-strips and 2mm thick acrylic, adding up to 12mm in total. Therefore the thickness of the wall needs to be 12 mm as well, for the design to work, in our case resulting in 3 layers of 4mm wood.

The size of the triangle is also dependent on the LED-strip you have or the amount you are willing to solder. We wanted 9 LED's per triangle, and went with a Neopixel strip of 30 LED's per meter to accommodate a larger triangle and reducing the amount of soldering. With this set-up 3 LED would precisely fit inside the triangle without the need for extra soldering. With the standard 60 LED's per meter roll, you need to make smaller triangles or use more LED's per side or solder wires in between single LED's.

Step 3: Lemon Tree

The case of First_Encounter_ consists of a total of 5 pieces, which we cut with a laser cutter. The white front plate is one piece of milky white acrylic, the walls of the case is build up from 3 individual triangles and finally there is the wooden backplate. Included with this step there is an Illustrator file that can be used to laser cut the shapes.

For each triangle you want, you need glue the wall triangles together. The biggest triangle goes at the bottom and the smallest on top to form a staircase like shape. Make sure the inside of the wall is as flat as possible otherwise the LED-strip will not fit in properly.

After the glue has dried, sand the outside of the wall and the sides of the backplate backplate at an angle of around 30 degrees. This will allow for the movement we want to have. Try to keep it as symmetrical and similar as possible to ensure proper movement. If You want you can (spray)paint the wood now to get a better finish in the end.

Step 4: Blinded by the Light

Our Neopixels came in a waterproof casing, which needs to be removed in order for the strip to fit in the triangle. Cut the LED-strip in the length you need for your triangles, in our case 9 LED's long. On the input side, as indicated by the arrows, solder wires to all three contact points (black = ground, yellow = data in, red = data out in the picture). On the other side, the output side, solder only a wire to 'data out' contact point (green = data out in the picture). Make sure the wires run along side the LED-strip (see picture), otherwise they are not going to fit! The wires should be about 12cm long.

Isolate the endpoints with electrical tape to prevent short circuits, because they are going to be pressed together.

Finally, after each group of 3 LED's bend the strip at the cut-off points to form a triangle.

Step 5: More Than a Feeling

The way in which First_Encounter senses is through capacitive sensing or capsense. In order for capsense to work as accurately as possible we need a large mass of metal, preferably copper. However coper is rather expensive, we therefore used folded aluminium foil.

The aluminium foil needs to be folded into a triangle, preferably slightly bigger than space inside the wall. We went with 24 layers for our version. The easiest way is to use the waste triangles from the wall, these are exactly the size of the inside of the wall, therefor if you fold it correctly, the triangle will grow slightly.

Lay them down in an S-shape as shown in the picture, this makes it a relatively easy way to fold the triangle.If you need to make many triangles it might be useful to tape them together. At the end of the S-shape you should extent two of the sides of the triangle, this will keep it folded afterwards. Next mark the aluminium foil where you need to cut and then use scissors to actually cut it. This keeps the cuts cleaner then when using a knife.

When you start folding, you can use one of the waste triangle to get the approximate size of the first (few) folds right. When folding, keep the matt side of the foil inside and the reflective side on the outside, the LED-light gets better reflected outwards this way.

Next make a hole (you can use a simple paper hole puncher if necessary) in the folded triangle, roughly at the same place as the hole in the backplate. Fold back two of the layers and attach a wire with a large stripped part. Refold the triangle and make sure the wire comes out of the hole afterwards. The unstripped part of the wire should be about 10cm long. Finally add some (electrical)tape to the edges of the hole, this prevents them from ripping when the wires are pushed through6

Step 6: Come Together

Before continuing it might be useful to test if the LED-strips are soldered correctly.

Easiest way of assembly is to put the sanded wall triangles on the table, with the widest side up. Put the acrylic triangle inside the wall and make sure it goes all the way down to the table. Next put in the LED-strip and glue it all together from the inside with a hot glue gun.

Next, put electrical tape across the edges, to prevent accidental contact between the aluminium and the LED-strip. Pull the wires from the LED-strip through the hole in the aluminium and tape the aluminium to the triangle.

Now take the cloth and layout the shape you want to make with the backplates of the triangles. Leave a tiny bit of space between the triangle to increase movement. Then glue the backplates to the clothe on that location and cut the cloth a little bit at the location of the backplate hole.

Finally pull the wires through and screw the triangles in place.

Step 7: Pumped Up Kicks

Now that everything is assembled, we are going to add movement to the structure. The movement is going to be regulated by a total of 10 servos. We also added screw terminals on the back of each triangle, this way the system can be more or less modular and easy to repair. An important notice here, is to make sure that the wires coming out of the screw terminals are going to the top when hanging, in order to not interfere with the movement.

Due to weight concerns we decided to tape the servos to a small piece of wood and screw that piece onto the triangle. We also put the 5V connections and the ground connections of both the servo and the LED-strip of each triangle in the the same screw terminal, this way only one 5V wire and one ground wire run upwards from each triangle.

Step 8: Wire to Wire

The wiring scheme looks quite complicated, but in fact it is very doable. The power was divided into 5 groups, 1 group for the Arduino and breakout boards and 4 groups for the entire installation. The numbering of the triangles start on the top left triangle, if looked at from the front. This is why the numbering in the scheme seems backwards.

In essence from each panel, 4 wires go up to the top:

2 wires for the power (5V and ground) of both the LED's and the occasional servo.
1 wire for the capsense data output
1 wire for the servo data input

It is very important that the first triangle capsense wire, is connected to the first capsense board and first input point. They have to be in order, otherwise the lighting of the LED's will not work properly. The LED's are connected in series (green wire running across the triangles), therefor the capsense and panel number need to correspond, the same is also true for the servo motors.

We mounted the power supply and multiple screw terminals on a wooden frame, this way the effect of the movement on the connections would be minimised.

When the wiring is done you can put on the servo heads en connect them to the triangles connected.