Introduction: Monitor - Thinking Skins
This project was part of Multimodal Media Madness 2014, hosted by the chair for Computer Aided Architectural Design (CAAD) and the Media Computing Group of RWTH Aachen University. For more Thinking Skins,
please check this page: http://hci.rwth-aachen.de/m3_ss14
Given were small shared space containers for 6/8 students, built with the WikiHouse technology. A standard facade panel of 562 x 562mm had to be developed, acommodating useful technology that would make the functionality and the “life” in the shared space better. Sensors and micro-controllers had to be used in order to acomplish this assignment. The Idea of our monitoring panel is to give essential information of the inner conditions of the shared space to the outside. Since numerous small containers are to be spread around campus it was important to outline criteria for choosing which one exactly is suitable for every individual. Occupancy, temperature, noise level and air quality are the most important of them and our panel provides real time information for those. Wireless sensors spread around the shared space communicate constantly to an arduino module. The values are being estimated and simplified information is displayed on the front panel that is embeded in the facade itsself.
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Step 1: Things You Will Need
• Arduino Uno (starter kit for the prototype)
• 4 meter LPD8806 Digital RGB LED Weatherproof Strip
• PCB material (double-sided)
• pappel 4mm (Box) and some remains from former jobs
• chopper wire (different colors for less confusion)
• 3 potentiometer (0.2 inch space between pins)
• 4x PSK 254/W3 , 2x /W2, 1x /W4 plug connection
• 20x crimp contact • 1x flip switch (on/off switch)
• 2x powercables (5V, 1.5 to 3 A each)
• 1x power jack RASM 722X
• 4x crimp header 2.54mm
• 1x2, 1x8, 1x6 pin strip
• shrinking hose
• wood glue
• 1x pin wire
• soldering iron
• PCB mill
• crimp tool
• wire stripper
The source code and all important files for the PCB milling machine and the laser cutter are provided
in my github repository. In addition to those files, you have to download the library for the LED strip first. The Adafruit tutorial page provides a nice overview of how the strip works.
Step 2: Design the Panel
The MONITOR is a LED-backlit wooden panel with milled symbols in it. A layer of frosted glass separates the wooden front and the LEDs and diffuses their light. Since you could use the technology to display literary ANY information you first need to design the front panel and the alignment of the shining symbols. Note: Do that AFTER you get your hands on the LED strip since the pieces have certain dimentions that you can not overlap when it comes to positioning. When you know the exact dimentions of the LED pieces you could start positioning the symbols. In our case we used Nemetschek Allplan for the CAD drawings. There are of course free CAD alternatives here. Our panel has 4 info groups describing the conditions in the shared space room - temperature, noise level, occupancy and air quality.
Step 3: Understanding the LEDs
After installing the Arduino IDE and libraries, you can start with connecting the strip to the Arduino Uno as follows. Every 5 meter of the strip comes with a male connector with 4 pins, Ground (GND), 5 Volt input (5V), Data input (DI) and Clock input (CI). Connect 5V and GND to the corresponding pins on your Arduino. For now, connect DI to digital pin 2 and CI to digital pin 3. If you have set up your IDE correctly, you can open an example for the LPD8806 strip with File -> Examples -> LPD8806 -> Strandtest. Compile and upload the program. (Hint: Change the nLEDs variable from 32 to your number of LEDs).
For the layout of the facade you need to separate the strip after every pair of LEDs in order to achieve the necessary distance between the segments for temperature, seats and air. First you have to cut it and then solder it back together with the desired length.I use red for 5V, black for GND, green for DI and yellow for CI. Once you fixed the LEDs on the cardboard and cut out your preferred front-face you are almost done. Make sure to separate the LEDs that belong to the different symbols with cardboard stripes so that a chairs’ LED wont shine through a temperature bar symbol. To achieve a smooth and diffuse illumination you can use cartridge paper.
Step 4: Fake Data
To make sure that your LED design works you could fake some sensor data and let the panel shine. You will need the Arduino starter kit. the LPD8806 and of course the cardboard with the LEDs. To fake the sensor values use three potentiometers for the occupancy, temperature and the air quality. Use random values for the loudness. Connect the potentiometers via a breadboard to the Arduino as shown in the picture. Open the monitor.ino file and load it to the Arduino. You should be able to control the temperature, seats and air values.
Step 5: The Circuit Boards
To make everything smaller and more compact you could make your own halfshield for the Arduino. For constructing the halfshield as well as the circuit board for the potentiometers and the flip switch you have to install Eagle and open the Halfshield.sch file (or PotiBoard.sch for the potentiometer).
More important is the access to a PCB milling machine. Be sure you use both sided circuit boards for the halfshield. I recommend to start with soldering the vias by using the ends of a normal resistor shown in the pictures. Continue with the pin strips, the power jack and the plug connections. If this is the first time you use a soldering iron, I recommend to watch some tutorials. The board for the potentiometer only needs one side of copper. Solder the 3 potentiometers, the plug connection and the female headers to the board as you can see in the picture.
Step 6: Cables
You could make your own cables in order to avoid cable tangling. Use normal wires with the desired length for each one of them. The cable for the second power supply, which is used exclusively for the “noise level” group of LEDs, consists of 2 cables, the corresponding parts of the plug connections (PSK 254/W2)and shrink hose.
With the crimp tool and 2 crimp headers you can join the cables with a female plug connection. This
has to be plugged to the halfshield. Pull over the shrink tube before starting with the second end. Solder the two cables to the male connector and the female to the 5V and GND input of the first ledsegment which belongs to the sound. Make sure you do not switch the wires within your new cable! The cable for the LED strip uses the PSK with 4 slots. The end that has to be plugged to the arduino is the female one. If the arduino board points to you with the analog pins side you have from left to right - GND, DI, CI, 5V. The other end gets connected to the crimp header.
The last cable has 4 female PSKs with 3 slots glued together by twos on each side. The order of the
wires, with the arduino facing you like above, is GND, 5V, Pin 0, A3, A4, A5. On the board with the potentiometers it is inversely if they point to you. I used two pieces of shrink hose here to cover the wires as good as possible.
Step 7: The Box
The Box, well, is a bit unnecessary for this project because you actually want wireless sensors to feed in the data. But it looks very cool and I wanted to use the laser cutter. The file required for this box is named PotiBox.svg and can be opened with the freeware Inkscape. The Box is generate with Boxmaker (W: 124mm, H: 38mm, D: 42mm, MT: 4mm) . I added the holes for the potentiometers and the flip switch. Furthermore I used a textbox for the font and images for the three symbols. I cut the front face in two jobs. First I cut the black lines with the standard settings for 4mm pappel and engraved the red font with 40 percent intensity. Second I engraved the images with the same intensity. This has to be set up in the program for the laser cutter (Visicut for example). Use normal wood glue and some remains to assemble the box and to fix the board in place. Now you can insert the flip switch. Split the pin wire down the middle and solder one half to the middle pin of the switch and the other one to the pin above. Plug the wire, which is connected to the upper pin to the plug next to the potentiometer and the other one next to it. I glued everything but the top element together therefore I can still remove the cable from the box.
The file for the box with the arduino is ArduinoBox.svg. Again I measured dimensions to cut the holes for the antenna for the optional wireless sensors, the power supply, the USB plug and the cables.
Step 8: Final Assembly
After you have everything blinking in the correct way you could proceed to finalizing the panel by making a proper face for it. Our frame was a 17mm thick Multiplex of 563mm x 562mm. We carved a 7mm x 7mm slot in the frame so that we could slide in the front panel and the panel with the lights. In order to get the light to be diffuse we placed an opal 3mm thick plexiglas. For best results check this.
You first want to glue the LED pairs with hot silicon on the cardboard and then separate the groups with stripes of white glossy cardboard in order for them to shine only through the corresponding symbol.
It is probably a good idea to make prototypes out of gray cardboard and see if the design works for you.
We used a CNC miling machine to cut out our symbols into a multiplex plate with a nice wooden texture. You may basicly use anything from plastic to metal for your front panel. The CAD file is called MONITOR.dwg.
Step 9: Wireless Sensors
Actually this facade element is meant to inform students about the conditions inside the study room. Therefore I recommend to take a look at the project of another group which has developed theses sensors. The code in the repository is ready to handle these data if you have set up everything correctly. Here is the link to their instructions.