Flexible Circuitry for Wearable and Physical Computing Prototypes
Zohar Messeca-Fara | Yair Reshef
In this paper we describe a simple DIY design and fabrication methods for creating flexible electronic circuits ,mcu & sensors interfaces, traces and connectors .
Our aim is to bridge the gap between the hardware and the softWARE ,using commonly available tools.
as part of our job running shenkar’s SE prototyping lab we’ve been supporting many wearable and physical computing courses and students projects,
mostly based on arduino platform.
we have noticed our students having hard time with the transition from breadboard development stage to the final physical model or garment.
and we’ve witnessed many (last moment) crash downs, wiring horrors and tragedies.
caused by a lack of skills with wiring ,soldering and/or not enough time spent on the final prototype and embedded circuit design.
- flat and flexible design
- simple connectivity
- versatile interface
- low cost materials (available in local market)
- Easy debugging
The only flex arduino dev board i have seen was an early version of the SEEEDUINO FILM (send some links for more stuff you know).
It seem it was designed mainly for low power wrist applications (smart watch/sensor monitoring).
The circuit is closed you cannot add/remove parts on board you can only cut off parts you dont need,Its also tiny fragile and very delicate .
The pin connections are awful cause you still need to solder headers or wires directly which is total shiiiit.
T-shield can handle high power current/voltage. Circuit design (single layer) is fully customable for your project needs its very easy to add parts like resistors/capacitors/transistors (photo on page 20 original article) Connectivity interface is very simple with snap connectors or soldering directly on coper pads. No headers needed.
- copper tape 60mm
- kapton tape
- cellotape clear
- transfer tape
- A2 pvc transparent sheet 0.2mm
- A4 pvc transparent sheet for laser printer
- R21 instant glue TYPE:MP-2
- wire wrap (3 colors)
- metal snap connectors
- male headers
- 3.7V lipo battery 2000mA
- arduino pro mini 3.3V/5V
- arduino nano
- precision cutting knife
- Long ruler
- Silhouette CAMEO A3 stencil cutter
- A4 laser printer
- soldering station
- silhouette studio
- Arduino IDE
at first we simply cut by hand 3-5mm copper tape traces and taped them on a pvc 0.2mm sheet. I/O of the arduino pro-mini 3.3V MCU we were using in this attempt have been soldered with long headers. the long headers have been bended to fit with the position of the traces we taped before. and soldered directly on the copper trace. adhesive side of copper tape is not conductive!. so we soldered the traces tips at connection points. the male snap connector are soldered directly on a 7x7mm piece of copper tape. for the female snap connector trace we made a 2.5mm hole at the trace tip and solder the connector directly to the trace.
blinking leds clip
Attempt#2 after realising this method actually “works” y.reshef insisted we should make a fine MCU interface design and cut the copper tape precisely with a stencil cutter. so we did . we used Inkscape free open source vector graphics editor that exports to Scalable Vector Graphics (SVG) file which is the format Silhouette studio and Silhouette CAMEO A3 stencil cutter accepts. more info about stencil cutting process here» http://tami.org.il/index.php/Cutting_machine
this stage of research was the moment of birth for T-shield V1.0 . the name came from an old idea making a T-shirt with built-in MCU, shield also came from the popular format of arduino modules and extension boards. the stencil cutting method of the copper tape enabled us to design a much more compact interface for the MCU, we could also make curved traces that we couldn’t cut by hand and finally requires less soldering . at this point we got the idea of making a full wearable development kit for designers. a kit which includes: MCU “brain” interface (arduino promini 3.3V) , 2 and 3 legs sensor/connector interface, traces and extension pads for GND/VCC. full T-shield V1.0 kit (A4 0.2mm pvc sheet)
Sensors & Connectors Interface Proof of concept the project we based our test case on was completed successfully as part of a semestrial collaboration course between shenkar’s software engineering and fashion design departments students. while the outcome was working (yey!) it was a mess of wires and echoed the frustration of meshing softWARE and hardware. Alcoholic Sense Night Outfit created by : alina yanover (Fashion Design) yaron israeli (Software Engineering)
more pics in this gallery https://goo.gl/photos/Jrzg9rmXR93sQ5c3A Test Case
video - https://drive.google.com/file/d/0Bzw39zYn4ZhlWkM0VXVaZ094QWs/view?usp=sharing traces pvc structures for traces and NeoPixels led strips
video - pressing machine tests back side NeoPixel led strips on pvc
front NeoPixel led strips on pvc
video - sewing pvc structure with sewing machine Front
Back side skirt NeoPixels led strips on pvc structure wire wrap wires and led strips connections sealed with kapton tape.
For the connections from skirt to top part we used jst connectors and copper tape pads
Micro Controller Unit Interface (custom design)
Vibration Motors copper tape connection pads on a pvc strip
Power 2x Lipo 3.7V 2000mA voltage step down converter to 4.8V
model: alisa gitnik Future work more tiny MCU’s interface designs wireless & wi-fi communication uCNC > https://www.youtube.com/watch?v=kcXlak7RNV0 Pyralux® flexible circuit materials DIY Flexible Printed Circuits copper coated polyimide fabrication Polyimide is a yellow polymer with a high melting temperature and is sometimes called Kapton. A common type of copper-coated polyimide is DuPont “Pyralux” material. Pyralux sheets come in many different varieties of polyimide thickness, copper thickness and adhesive thickness (the “adhesive” is between the copper and polyimide holding everything together.)