Sleek and elegant: New touchscreens for embedded control

15 April 2009

With the decentralisation of automation tasks, traditional control cabinets are becoming increasingly smaller—and may disappear entirely. If there is little or no cabinet, where will you put the Human Machine Interface (HMI) device?

The preferred position is directly at the machine site, so various support arm and pedestal systems lend themselves to the installation. But most HMIs are too big and heavy for this type of fitting.

Up to now, the ‘front end’ of many such solutions has been—for lack of alternatives—a large and shapely protective housing surrounding a conventional operator device, designed for the installation into control cabinet doors. These housings are much too heavy for suspended installations from ceilings.

Add to this the aesthetic limitations, especially at smaller, compact machines. Who wants to see a big bulky operator box right next to a well-designed, compact, clever machine?

Indeed, the outward appearance is more often among the purchase-deciding factors. It is certainly not the last reason why ergonomic HMI devices with good design are becoming increasingly popular. In the process, the screen diagonals are becoming larger, to display more functions simultaneously and to offer better readability from a greater distance.


With these corner points in the requirement specifications, the product designers of Siemens went to work on developing a new generation of machine-oriented, freely positionable operator devices. The first practical results are three especially lightweight SIMATIC HMI devices which enable different uses, ranging in use from separated operator control and monitoring up to an integrated soft PLC.

At the top of the list of requirements for on-site operator devices is maximum industrial strength. It not only has to be resistant to vibration and shock, but also be dust-proof and jet-water-proof. The latter especially applies to the use in the food and beverage as well pharmaceutical and chemical industries, where machines often are subject to high water pressure or treated with aggressive cleaning agents.

In the previous approach to operator device construction, manufacturers used a protected faceplate, installed in a corresponding protective housing. Now the devices are made in IP65 protection rating, all-around.

Separate extension units on the side allow for extra safety pushbuttons
Separate extension units on the side allow for extra safety pushbuttons

The new SIMATIC PRO devices (PRO stands for ‘protected’) have a mechanically stable, one-piece rear panel cover. It can be easily removed, even from mounted devices, so that all interfaces as well as memory card slots are quickly and easily accessible for service work. There is no fan.

To safely dissipate the heat developing inside to the surroundings, the developers decided on a chassis made of aluminum. Particularly heat-intensive components – the average total power dissipation is between 20 and 60 W – are contacted by special “domes”, which safely dissipate the heat to the large-surface exterior of the aluminum enclosure. As a result, a safe heat removal is assured even at inclination angles of up to ±45° in overhead or console installations, and that exclusively through convection. That is, there is no fan, which could fail or require maintenance. As upper limit for the continuous operation, +45 °C is specified. Machine constructors can thus be certain that the ready-to-install units operate lastingly also in warmer and more humid regions, and do not have to prove this first in lengthy tests, which is often the case with built-in HMI devices in housings. This can considerably reduce the time-to-market at the customer.


There are three device classes, all with resistive 15 inch touchscreen displays that can be operated with gloves:

1. The SIMATIC Thin Client PRO is designed for the use as a cost-optimised second, separated operator terminal at larger machines—in client-server architectures for distributed plants or as Web client. It requires neither an installation, nor licenses, nor additional software.

2. The SIMATIC Flat Panel Monitor PRO is the standard HMI. As a stand-alone device it can be installed up to 30m away from the computing unit. It withstands vibrations up to 1 g and shock loads up to 5 g, which permits highly flexible uses in decentralised automation structures.

3. The SIMATIC Multi Panel MP 377 PRO provides the user with the versatility and performance of a multifunctional platform. With additional Windows CE applications—such as Media Player, Internet Explorer, or viewers for displaying Word, Excel, and PDF files—completely new possibilities arise for the operator guidance or during service calls. Furthermore, the device is optimised for the use of the soft PLC SIMATIC WinAC MP. It can be an economical and robust solution for machine-oriented visualisation and control tasks, to which also a Thin Client PRO can connected.

The HMIs can be mounted with popular mounting systems by leading vendors
The HMIs can be mounted with popular mounting systems by leading vendors

Because the stocking of spare parts always creates expenses, the three ‘PRO’ devices are designed so that they can be mounted without modification to a support arm (from the top or bottom) as well as to a pedestal.

With a weight of only 6.5 to 7.5 kg, the 15-inchers are noticeably lighter than the standard built-in models in an extra protective housing, and thus particularly suitable for mounting on a support arm. The lower weight allows the use of smaller supporting structures, which normally are priced lower.

Moreover, the lighter weight enables the mounting to ceilings—and with that an even more flexible arrangement as well as changeover of the thus separately positioned operator device and machine. A single person can usually handle the installation.

In the near future, the product range is to be supplemented by so-called Extension Units for additional, permanently wired control elements such as emergency stop switches and user-assignable pushbuttons/illuminated pushbuttons. The units are matched in design and size to the panel enclosure, and dock to the side of the panel.

The fully enclosed, IP65-rated 15 inch and 19 inch operator devices open up numerous innovative concepts to manufacturers in the machine and plant construction—to differentiate themselves and stand out from the competition. The units have proven HMI functionality, and upon request can also have control functionality, in a compact, attractively designed enclosure. With adequate quantities ordered, the device front is of course also available in custom designs.

Especially with smaller and more complex machines, the outward appearance is more and more often among the purchase-deciding factors. This is certainly not the last reason why ergonomic HMI devices with good design are becoming increasingly popular. In the process, the screen diagonals are becoming larger, be it to display more functions simultaneously or to offer better readability from a greater distance. Siemens is aiming exactly in this direction with the current further developments of the PRO device family. For instance, the expansion of the concept is planned to include the spectrum of the ready-to-run SIMATIC Embedded Automation systems.

—Dipl.-Ing Alexander W. Fiedel and Dipl.-Ing. (FH) Sandra Schrickel, Siemens AG Industry Automation, Industrial Automation Systems, Nürnberg, Germany

Read Control Engineering Europe's article, "Embedded control: Automation's fastest growing segment" by CLICKING HERE

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