LightTrace
Tung D. Ta, Fuminori Okuya, Yoshihiro Kawahara · 2017
The combination of graphic design and printable electronic circuits has brought a large variety of customized elements to create interactive applications. The designers aim to focus on the creative and aesthetic aspects when crafting such applications. However, current technology forces designers to consider the discouraging and complicated electrical behavior of the related circuits. Even a simple application as activating a group of LEDs by means of conductive ink presents specific challenges. For instance, given the relatively high resistance of conductive ink, it is difficult to generate a circuit pattern that evenly lights up the LEDs. Moreover, wiring a large number of LEDs is error-prone and not straightforward. Electronic-circuit designers often use built-in auto-routers from Computer Aided Design tools to route electronic circuit boards. However, these auto-routers usually neglect the resistance of the metallic pattern. This is not applicable in the case of conductive ink where its intrinsic resistance is not negligible. Nonetheless, this characteristic of the conductive ink can be used to eliminate the need for ballast resistors which are used to regulate the current through each LED when they are wired by highly conductive materials (e.g., copper in PCB or highly conductive ink). Our proposal, called LightTrace, is an LED auto-router implemented as an Adobe Illustrator extension. LightTrace computationally designs conductive patterns and adjusts their resistance to connect and evenly light up the LEDs in a single-layer sheet of paper without requiring additional resistors. We use the Traveling Salesman Problem algorithm to achieve the shortest cross-less path through all LEDs, thus reducing the amount of ink consumed.