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Lighting applications for large-size projected capacitive touch panels

Fri, 03/30/2012 - 9:55am
John Blackburn, Senior Electrical Engineer, Ocular LCD
John BlackburnThe demand for projected capacitive (PCAP) touch panels is growing at a rapid rate. The increased durability and enhanced look and feel a PCAP touch panel provides can benefit a wide variety of products. The all glass construction allows for increased optical clarity as well as a clean surface that can withstand dirt, debris and harsh chemicals. Applications that want to eliminate buttons and utilize a PCAP touch panel can increase the lifespan of a product by having a zero-bezel layout that will keep damaging elements and contaminants out of the device.

PCAP touch panels were originally limited in size, but as the technology advances, the size offerings increase. Building larger PCAP touch panels creates challenges, but several leading manufacturers are now able to overcome these challenges and build larger panels in a variety of sizes.

Projected capacitive touch panels have a stack-up that consists of two layers of glass, a bonding adhesive and Indium Tin Oxide (ITO), see Figure 1. The intersection of electrodes creates the touch response. When expanding the size of the touch panel, the amount of nodes needs to increase, otherwise the separation will not deliver the same result. The controller chip scans these electrodes and translates the data into location coordinates as well as interprets pre-programmed gestures. This data is sent to a host processor, typically over I2C in embedded systems, or USB in general purpose computer systems.

Figure 1. PCAP touch panel showing electrode layout

Many applications stayed away from PCAP touch panels due to the size limitations. However, with size options expanding, applications that may not have benefitted from PCAP before can now utilize this rugged touch interface on their devices.

Lighting applications, such as lighting controls for home and office, have been able to use a PCAP touch interface on a smaller scale. Smaller control panels that turn on and off lights as well as open and close shades are becoming extremely common in home and office settings. It is lighting applications at a much larger scale that have been holding off from the use of PCAP due to size limitations.

Currently venues such as theaters, concert halls, clubs and touring systems use either a console or computer based system for lighting controls. The consoles offer the advantage of a more direct manipulation of the lights, or “live” feel, but as system sizes grow, smaller consoles become very cumbersome in accomplishing the task and larger consoles become physically overbearing. Computer based systems allow for more compact control, but a simple point and click style interface is more suited to a pre-programmed approach and does not allow the user to manipulate multiple controls.

A true multi-touch computer based system offers the system designer a unique solution to the modern day lighting system. The current DMX-512 protocol allows for communications to the fixtures, but was originally designed for dimmer based systems. Computer based systems have started to address the issue of adapting automated lighting fixtures into a DMX-512 environment, the addition of touch gives system designers a more efficient way of interfacing with the lights. 3D visualization packages have become a normal part of the better computer based control systems. By adding support for true multi-touch, the software developer can allow direct manipulation of multiple fixtures, add support of pinch/zoom features to control zoom optics, give direct control of rotating gobos using rotate gestures and even create new multi-finger gestures to allow the user shortcuts to required functions quickly and easily. A console view could be created to give access to dimmer based lights and allow the user to manipulate multiple faders at once and touch several “bump” buttons for those that need to directly control the system. A panel designed with chemically strengthened glass would give the user a highly versatile controller in a rugged package that is immune to dust and liquid.

The benefits of projected capacitive touch panels can enhance devices across a wide range of applications. Medical and gaming are two other industries that are rapidly incorporating PCAP in their devices. Durability and enhanced optical clarity upgrades not only the functionality of a device, but also the look and appeal it has to users.
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