Human Machine Interface
Increased demand for high- resolution HMIs
By Claus Vogt, head of product management display division, DATA MODUL D
isplay-based HMI (human machine interface) units are now ubiquitous. Modern HMIs are far more than mere providers of information, but
are regarded as indispensable, interactive interfaces in a wide range of applications and industries. Driven by the consumer market, the requirements for industrial use HMI solutions are also changing. In particular, the demand for high- performance displays with high resolution, sharp contrasts and perfect, true-colour reproduction of screen content - even at large diagonals - is increasing. DATA MODUL offers customised display and system solutions which meet these increased demands on the visual performance of an HMI unit and offers additional expansion options which can be adapted according to the customers’ requirements.
The right display technology As the central interface between man and machine, the display of an HMI is very important. Choosing the right display depends on numerous factors and is the cornerstone for efficient and sustainable realisation of modern HMI systems. In addition to customer requirements, the respective area of application in particular determines the parameters for selecting the components. In addition, the demands on performance and design continue to increase. At the same time, the market is full of a wide variety of providers, formats and technologies, which makes researching and selecting suitable components equally difficult. DATA MODUL has a particularly extensive display portfolio from a wide range of manufacturers with diagonals from 0.39” to 110”, as well as a wide range of performance classes and also offers professional advice to select the right solution for customers.
In addition to performance criteria and formats, interfaces also play an important role in HMI systems. They not only determine how a display can generally
44 May 2023
be connected or integrated, but are also largely responsible for performance and efficiency. For standard resolution displays in industrial use, LVDS is still the most common interface. For smaller, high-resolution displays – especially in mobile applications such as smartphones or tablets – the MIPI interface is often used. MIPI interfaces are particularly characterised by low energy consumption combined with greater data throughput. However, the MIPI interface is less suitable for industrial HMIs due to the comparatively short product lifecycle of the displays. For example, an eDP interface as found in notebooks and monitor panels is better suited. Compared to the LVDS interface, eDP has fewer power pairs and thus enables faster data transmission. It is therefore ideal for high-resolution HMIs. For large diagonals, such as in the digital signage sector, the V-by-One interface is best suited, as it allows the transfer of large data volumes with only a few cable pairs.
Components in Electronics
Touch extension for HMI solutions Real added value is offered by HMI solutions that are equipped with additional extensions, such as touch functions. To ensure flawless touch performance at all times, the choice of the right touch sensor is enormously important.
A PCAP touch screen consists of a transparent conductive material (e.g. Indium Tin Oxide, or ITO for short), which is applied to both sides of the carrier material (e.g. glass or PET films). The ITO electrodes are usually diamond-shaped and form a matrix structure. If voltage is then applied, a capacitive field is created between the two electrodes, which changes when a conductive object, such as a finger, enters and triggers the touch event. The touch point or the position of the change in the capacitive field is detected and evaluated by the touch controller used. For large-format HMI units (from 32 inches), DATA MODUL has developed a special USB touch controller board with
the latest chip generation that reliably recognises and evaluates touch inputs, even with large diagonals.
However, when ITO touch sensors are used in high-resolution displays, optical interference such as the so-called Moiré effect may occur due to the overlapping of regular patterns of the conductive paths. The remedy here is PCAP sensors based on metal mesh, which prevent interference due to the irregular arrangement of the conductor paths in a network. In addition, the use of metal mesh-based sensors offers the advantage that the surface resistance is about 25 per cent lower compared to ITO sensors and is thus only about 25 ohms, which leads to improved sensitivity in touch performance, especially with large-format sensors over 30 inches. Thanks to the bendable nature of the metal mesh sensors, special designs, such as curved screens, can also be integrated into a wide variety of HMI solutions.
www.cieonline.co.uk.uk
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