Vandal-resistant touch screens
26 May 2009
Capacitive touch screens with multi-colour area-specific backlighting provides protection from vandalism.
Capacitive switching is a well-established technology; the absence of moving parts and the isolation of the operating mechanism from the user provides long life and minimal maintenance. It is particularly beneficial in applications such as public information kiosks, ATM, self-service tills and ticket machines, vending machines and other applications where accidental damage or vandalism are potential hazards. IGT Industries has developed an innovative method of combining the benefits of Capacitive Touch Screens with multi-colour area-specific backlighting. Historically, illuminating capacitive switches has caused problems for designers because the electric field from the light source affects the operation of the capacitive switch. By employing the latest Atmel/Quantum QT chips and thin film light guides with remote LED light sources, IGT has successfully combined the two technologies. The currently achievable screen size is 10.4" with a 6 x 8 touch matrix; larger sizes are available. Units with 7 x 8 matrix are in development and 8 x 8 matrix devices will be available in the future. Depending on requirements of the host system, the MMI / HMI can be supplied with an SPI, UART, RS232, I2C or USB interface.
The backlit capacitive switched touch screen is mounted to the rear of the any transparent non-conductive material, typically either glass or Margard polycarbonate, up to 10 mm thick. The surface does not have to be flat, so the HMI assembly can be embedded into more ergonomic and aesthetically attractive units. Thin film light guides are integrated into the multilayer structure of the touch screen, enabling secret-until-lit areas, colour changes on key operation and colour coded visual directions to be given to the operator.
The MMI/HMI units sealed into ruggedised assemblies, enabling them to be installed in environmentally demanding environments such as onboard ships, in applications subject to shock and vibration such as trains, in manufacturing areas, in public buildings or in the open.
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