The project brief was to design a modular multi-zone lighting control switch to fit a standard single gang slimline electrical wall box (UK). What made this project complicated was the need to be able to adapt the design for various button configurations using modular components. The buttons were back-lit with multi-colour LED's giving a fully configurable switch unit. All this packaged to fit a wall box cavity only 16.5mm deep.
As a premium product, one of the biggest considerations was the feel of the buttons. The design utilised small integrated tactile switches, but on their own, these did not provide enough tactile feedback. So a thin chemically etched stainless steel sheet was incorporated that provided extra resistance adding to the overall tactile feel. The solution was very complicated to engineer as it also needed to allow the buttons to be illuminated straight from the main PCB. Hence, the design of the stainless steel sheet required careful attention.
The design had to cater for multiple button sizes in any configuration, in a single row format or a dual row format and the tolerances involved to achieve this were very high.
One of the biggest hurdles was overcoming lighting bleed around the buttons. Whilst the bleed couldn’t be totally eliminated (given the space available), the use of a black non-reflective sheet in the right places reduced the reflection of light considerably, providing satisfactory results.