When discussing soft circuit components, especially when talking to those unfamiliar with electronics, it's extremely useful to be able to point to a physical device demonstrating how components connect to another and their possible functionality. In that vein, I sewed together all the LilyPad components (with the exception of the XBee) and wrote a small script that ties each sensor to an output device.
When complete, the model demonstrates four functionalities:
1) a light sensor that, when covered, triggers the LilyPad to play a programmed song;
2) an accelerometer that, when shaken, triggers a flashing light;
3) a temperature sensor that, when triggered, vibrates a motor; and
4) a button that, when pushed, triggers a flashing light.
The video below demonstrates all the functionality of all components. The sound board has a low output so turn your speakers up!
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Step 1: Layout of Components
List of Materials:
1 LilyPad Main Board
3 White LEDs
1 Tri-Colored LED
1 LilyPad Power Supply
1 Vibe Board
1 Light Sensor
1 Temp Sensor
1 Button Board
I wanted to expose all the sewing lines, so I thought it best to utilize the circular nature of the LilyPad by spacing the components in a ring around the main board. After placing the components and determining which pins would connect to which components, I sewed everything down, purposefully not sewing the Positive and Minus lines required for power of the main board and all the sensors.
Step 2: Negative Line
To make the sewing easier, I decided to sew two concentric circles of conductive thread to which I could link the components. The inner circle is the Negative and the outer circle is the Positive. Because I am still learning about these materials I wanted to try several kinds of conductive materials as well as sewing techniques. I didn't need the entire loop to be conductive, only areas where sensors were located.
I first cut strips of Garment Shielding which is composed of 70% bamboo fiber and %30 silver. This material is quite similar to cotton fabric which means it frays quite easily. The idea is to lay down strips of fabric and connect the power pins on the sensor components to the strips.
Step 3: Positive Line
When the negative line was complete I began to sew the positive line. This time, however, I wanted to try sewing the conductive thread with a machine. To use a sewing machine, I found that the line with the least resistance was actually just a straight stitch, with the conductive thread being the bobbin thread . Note: if you try to do this, you should play with the tension of the bobbin. Remember, when holding the thread of the bobbin, the tension in the thread should just be enough to keep the bobbin from unraveling due to gravity.
To sew to the positive line I had to make "jumpers." I needed to first stitch a piece of non-conducting fabric over the negative line then sew from the positive end of the component to a piece of conductive fabric on top of the non-conductive fabric.
I also used strips of Copper Taffeta which is very easy to work with (no fraying); however, the taffeta cannot be washed and it will tarnish over time.
Step 4: Finishing Up
I wrote some demonstration code that partially relies on Leah Bucheley's acceleration shirt code. However, this demo setup lets new users play with the software and think about functionality without having to sew all the materials together, thereby gving a better sense of how e-textiles and embedded electronics work.
The code in the zip file connects the accelerometer to the RGB LED, the button board to the three white LEDs, the light sensor to a song by TI (RubberBand Man), and the temperature sensor to the vibration board.
This material is based upon work supported by the National Science Foundation under Grant No. 0855886 to Kylie Peppler. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.