It’s all about finding structure

This is a semi-permanent installation. With that comes certain considerations related to how it withstands the public realm, including but not limited to the work being vandalised, or otherwise used inappropriately.

Since we are dealing with a semi-permanent installation, certain liberties could be taken to speed up the process and reduce the overall cost required to complete this project. This meant that the use of robust components, long-term permanent wiring and a maintenance regime can be set aside without impacting the success of the installation.

Aluminium extrusion profiles, common in the lighting industry, are utilised to help mount the LED strips in a rigid frame. This afforded a clean and relatively easy assembly. A shallow profile was chosen to ensure the beam angle of the 5050 SMD LEDs is not occluded by high sidewalls of the profile. This would have created a less diffuse effect that we were going for.

Cross-section view of aluminium profile sample

Custom spacers that offset the LED strips from the base of the park bench had to be designed. This is to accommodate the various connection wires and power supply going into each row of LED strips, and minimise the tangle of cables dangling from the back of the park bench – something that the city council would definitely not be keen on having. These spacers were 3D printed using the FDM process and uses UV-resistant filament designed for outdoor applications to prevent them from getting brittle too quickly.

Spacers on profile
How the spacers fit into the aluminium profile

The overall rear structure went through a number of major overhauls, for various reasons. The first prototype had LED strips glued onto a sheet of polycarbonate, with cable routes all running through a ‘spine’ in the middle of the park bench. This was sufficient in prototype form as it allowed us to make creative decisions and explorations in lighting, but with the crowded ‘spinal column’ filled with cables, it presented a very messy aesthetic, not to mention the difficulty in troubleshooting the trunk of wires.

The second prototype diverted power lines to the extremities, allowing only data lines up the middle spine. This provided a balanced, leaner layout that works well with the 3D printed spacer modules which would route the 90-degree bends of the cable neatly inside them. The rest of the cabling is housed within split loom conduit to clean up the wiring.

This evolved into the following layout for the LED strip structure:

The intent is to preserve the front-facing appearance of the park bench as much as possible

Sensing lines are a bit trickier – due to the highly sensitive nature of capacitance sensing and tuning required on each electrode, care had to be taken in routing them away from other cables, and from each other. Cable holder arrays were designed to help maintain a consistent layout and distance.

Ease of installation was also an important requirement – neither one of us are stoked about the idea of sitting out in the cold. While some tasks will invariably require extended periods of time aligning and fixing parts, most of the setup will be pre-assembled before site installation.

10 months ago

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