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FEATURE DISPLAYS & UIS


Functionality in the workplace and the modern era of the industrial interface


Ian Crosby, sales and marketing director at Zytronic explores the latest generation of touch controllers that are transforming the design of the industrial user interface


N


ew developments in touch screen technology are widening their


suitability for industrial control applications. Enhanced sensitivity ensures that screens perform better than ever behind protective cover glass and with gloved hands. New controllers are also less sensitive to electrical noise in the environment, and attractive new features are emerging. The touch controller must distinguish


between genuine and false touches (created by electromagnetic interference, or EMI). A finger pressed firmly onto the screen will give a clear signal – but that signal will be weaker if the user is gloved, touching lightly, or the screen is behind thick cover glass, and/or there’s surface contamination. The key to improving sensitivity is the drive signal applied to the sensors Transmit (Tx) array of electrodes by the touch controller; a low voltage signal can be overwhelmed by EMI from the environment, a high drive voltage can create interference in the sensor itself which can potentially degrade performance. Most p-cap touchscreen manufacturers


are forced to use a Tx signal with a DC current of between 20-30V, due to limitations in available “off-the-shelf” touch control components and ASICs. However, Zytronic’s new ZXY500 range of controllers have been purpose designed to operate at a Tx drive voltage of up to 40V, enabling full multi-touch detection in challenging industrial applications. In addition to directly improving


performance, this new generation of touch controllers combined with Zytronic’s flexible p-cap manufacturing process (Figure 1), provides enhanced opportunities to customise the appearance of the user interface irrespective of quantity. The new controllers allow the border around the perimeter of the touch active areas of the screen to be substantially reduced - i.e. a touch sensor for a 55” display can now be designed with sub 10mm borders, reducing the user interface ‘footprint’. This border reduction is enabled


through new touch detection algorithms in firmware, which allow the transmit and receive electrodes in the sensor borders


8 NOVEMBER 2018 | ELECTRONICS


to be located far closer together without creating interference or “cross-talk”. These controllers also now make it


possible to design “soft” keys around the edge of the dynamic active area of the projected capacitive touchscreen (Figure 2). These fixed touch “buttons” are managed by the same controller and their function can be defined by the system designer. This is useful in applications where sealing and water ingress via mechanical controls could be an issue. The new p-cap controllers support up


to 80 simultaneous touches, enabling true multi-user interactivity and improved “palm” rejection capability. The ASIC used within these controllers also increases the speed of touch detection, updating touch co-ordinates in just 1ms at the controller output. They can also reliably detect touches through more than 8mm of overlaying glass - even with gloved hands, and are


Figure 1:


Zytronic’s flexible p-cap manufacturing process


Figure 2: The new Zytronic ZXY500 controllers also now make it possible to design “soft” keys around the edge of the dynamic active area of the projected capacitive touchscreen


Figure 3:


The smallest p-cap controller has been significantly reduced in size to just 61 x 64mm


unaffected by rain, salt water, oil or ice on the surface of the touch sensor.


PROVIDING TACTILE FEEDBACK These projected capacitive touch controllers use “force” sensing to overcome the issue of touchscreens not providing tactile feedback. Zytronic has developed custom touch detection firmware, which responds to the increased surface area of a fingertip when pressed more firmly onto the screen and differentiates its output accordingly. It is possible to use the graduated


information to activate different functions depending on the applied pressure, such as issuing an audible message when the screen is touched lightly, and then confirming the choice when pressed harder. For example an instrument can say ‘temperature’, ‘pressure’ or ‘time’ as the user’s finger moves across the screen, with a firm press making the selection. A key factor in the success of a user


interface design is how easy it is to integrate the controller into the rest of the system. USB is an extremely popular interface, but there are some applications that require RS232, I2


C or SPI interfaces. Size is also important, and the smallest


p-cap controller in the new range has been significantly reduced in size to just 61 x 64mm to support Zytronic touch sensor sizes up to ~19” (Figure 3). The flexible printed circuits (FPC) connecting the touch sensors to the new controllers have also been reduced to just 120mm in length. Finally, the new controllers have been


designed to be HID (Human Interface Device) compliant and offer ‘plug-and- play’ operation with later Windows operating systems, also supporting Linux and Android builds suitable for multi- touch input. Using these latest pcap touch controllers brings huge potential. High levels of EMI and exposure to contaminants are no longer issues with a rugged, responsive user interface ideal for outdoor and unattended applications.


Zytronic


www.zytronic.co.uk T: 0191 414 5511


/ ELECTRONICS


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