The question is a difficult one. In which technology should you invest time and money developing your system interfaces? Are industrial panel computers (IPCs) the answer to all your problems, or is investing in IPCs just going to give you more headaches? This article is written to debate the issues and explain some of the realities of IPCs in industry and then, hopefully, you can decide if they are the future of your operator control.
Market information and IPC types
The spread of IPC usage is quite staggering. In the last few years, their availability to industry can be seen from a large variety of manufacturers at every single exhibition in Europe. They are now used in virtually every area of manufacturing and production and come in all shapes and sizes. Estimates put the European marketplace for IPCs at about 600 million Euro per year. The European marketplace, despite recent recessions in other automation equipment, is still growing with an estimated 10% growth rate per annum, but there is still much concern by users about the adoption of this PC-based technology.
IPCs are broken down into three distinct types. Panel-mount, rack-mount (DIN rail mounted inside enclosure) and box type (standalone) versions. Since over 60% of all IPCs sold are panel-mount versions, this is what the article will mainly concentrate on, but most of the information will also apply to box and rack-mount types.
Panel-mount IPCs are broken down into function key versions, touch key versions and touch/function key hybrids. With the cost of touch screens coming down dramatically and durability improving, over 65% of the panel-mounted versions are touch screen types and increasing every year.
Why not personal computers in industry?
Some people may ask: "why not use normal home or office computers instead of IPCs for industrial applications?" The answer is that you can, but before you buy, answer the following questions:
1. Would a PC crash or breakdown give you lost production or cost you money?
2. Is your application in a high electromagnetic noise environment, or do you use large motors?
3. Is there liquid, or dust particles in the surrounding area?
4. Do you want to repair the PC with available spare parts if it fails in two years' time?
5. Do you wish to use the display with the power on without risking electric shock?
6. Is it to be used in environments which need to be frequently cleaned, such as food and pharmaceutical applications?
If the answer is yes to any of these questions, you should consider a panel-mount IPC, rather than an office-based PC. If the answer is no to all of the above questions, then in most applications you can make do with a normal desktop PC.
Passive or active displays?
An important aspect of using IPCs in control applications is their ability to show high resolution graphics. Displays for IPCs are broken down into three distinct types: cathode ray tube (CRT), passive matrix and active matrix LCD types.
CRTs are now an old technology and are not really used on modern automation equipment. Passive displays are mainly SuperTwisted Nematron (STN) types. These displays work by using a cross wire matrix and have an LCD element where each wire intersects. STN displays are very cost-effective to produce, but are not as bright as active matrix and the LCD elements are refreshed at every scan which can give a noticeable update on slow screens.
Active matrix displays use a thin film transistor (TFT) for each pixel. This technology gives a very sharp image and wide viewing angles compared to passive displays, with the pixels only being refreshed if needed, giving extremely fast refresh times. Most IPCs now use TFT displays which have a resolution of 1024 x 768 pixels and have typically 16 million colours, ensuring a crisp, clear image for the user. Below is a list of the most frequently used resolutions with price and performance being high in the decision factor of which to use. The rule of thumb is the higher the resolution, the higher the price. In most applications users should need no more than XGA.
* VGA 640 x 480 pixels.
* SVGA 800 x 600 pixels.
* XGA 1024 x 768 pixels.
* SXGA 1280 x 1024 pixels.
* VXGA 1600 x 1200 pixels.
* QXGA 2048 x 1536 pixels.
Touch screens offer significantly increased functionality
With operators wanting to have increased interaction with machines, it is now becoming very important to display information in a clear format in order to prevent mis-operation. One of the major advantages of using touch key displays over function keys is that it is a very interactive way of communicating operating options. Touch keys can do a different thing dependent on what screen is displayed. This precise method of operation allows a touch screen IPC to have thousands of buttons and switches as opposed to function key types that have a fixed number. Another major advantage of using a touch type terminal is the ability to replace analog instrumentation and control devices with the IPC. Now with modern touch screen IPCs, the touch screen can represent and adjust slider switches, potentiometers, etc, with no limit to the number and they can be displayed alongside all relevant information for that particular part of the process.
Durability is a must for an IPC and they should include a good IP rating. The front rating is what is most important for panel-mount IPCs. When buying an IPC, ensure that it has a rating of at least IP65 which will give it a good watertight seal on the front and is preferably all including the back of a metal construction, aiding greatly in the IPC's strength and noise immunity.
High durability and reliability comes at a premium price. There are one or two manufacturers who produce high mean time between failure (MTBF) IPCs. These products are extremely reliable and incorporate technologies such as silicon disk drives, which can replace the traditional hard disk. Silicon disk drives when combined with a processor and power supply that require no cooling, create a system that has actually no moving parts. A downside of this high reliability approach is that to use a processor that needs no cooling means it is usually of a lower specification than a fan-cooled device (due to the heat generation of high-powered processors), and silicon disk drives are very expensive, compared to traditional hard disk drives.
Cheapest is not necessarily best
On the other extreme, there are manufacturers who basically search the world for the cheapest possible domestic PC component parts, put them together in an industrial looking IPC box and sell them off at a low cost. They work, of course, but they are not really reliable enough to be used in some manufacturing areas where noise, vibration or extreme environments are encountered. Also, with this low cost approach as per the low-end domestic PC market, there is usually no consistency of spare parts if any parts are actually serviceable.
There is a mean path which is a good compromise solution. In this area, the key components are both designed and made to be used in an industrial environment, or domestic boards are used and industrialised to be more resistant to working pressures (Beijer Electronics believes that its new model IPC-15 is a good example of a competitive price performance IPC, being of a reasonable cost, having a fast processor, is fully industrialised, with a good TFT display).
Always compare apples with apples
Remember when comparing IPCs not to look at just the price. Always try to compare apples with apples and check the five fundamentals closely:
1. Processor used: the faster the processor, the later the technology, the more it will cost. Also check the make of processor. Some processors have a premium price for good reasons.
2. Memory: do not just compare hard disk memory, check user RAM and video memory. With most applications you will need at least 256 MB of user RAM.
3. Devices that are intrinsic: compare if the IPC comes with a CD-ROM drive, floppy disk drive or communications options, such as integral USB and Ethernet.
4. Ability to be expanded and connect to other devices and upgradeability.
5. Operating systems: remember some companies offer IPCs without an operating system installed. This, of course, makes an IPC cheaper than one that comes with everything installed, but does give you additional work and licence costs. Some operating systems are more expensive than others. Also compare if the IPC comes with a recovery CD, as without it you could have extended downtime if the operating system crashes or is altered.
From Beijer Electronics' experiences using IPCs in industry applications, the company always recommends a system that is more than the minimum specification required for the proposed task (usually dictated by the operating system and the application software to run on the IPC). This is for good reason, as there have been times where an end customer has bought an IPC that just meets the minimum requirement, and then gets disappointed with using IPCs due to slow update speeds, refresh times and communications.
IPC compatibility problems
One of the major problems facing IPC users is the compatibility problems that are encountered when buying software from one manufacturer and trying to find appropriate hardware for it. How many times have you bought software for your home computer and then found out that you do not have enough RAM or that the processor is too slow, or even that it is for the wrong operation system? These things drive people crazy in their personal life, but when it happens in the business environment it costs money, and can cost valuable downtime.
A solution to compatibility problems is to purchase from a manufacturer who offers both the hardware platform and the software to run on it. If the units are bought from one manufacturer they are obliged to ensure compatibility and ensure satisfaction. If you want also to ensure continuity to dedicated HMI products then also look for manufacturers who make their own HMIs, IPCs and PC-based HMI software.
Beijer Electronics, from its early experiences of selling PC-based HMI products, soon realised that to provide the HMI software alone was not enough to ensure customer satisfaction. The company discovered that when it sold a PC-based HMI software that its technical staff were encountering technical problems not associated with the HMI software but with supporting the IPC which it ran on, and the operating systems resident on the IPC. The solution to this was to create an IPC family to run Beijer Electronics' PC-based software on. The company now offers a solution that ensures that the customer is satisfied and has to do as little to the IPC as is absolutely necessary, ensuring fast project development. What Beijer Electronics has achieved is an IPC which is preinstalled with the actual software components needed to run its, and many other, software applications, ensuring that all appropriate communications drivers, screens drivers and components, such as Active X are all already resident on the IPC.
Operating systems and associated problems
With regard to the operating system, how many times have you had to re-install the operating system on your PC at home? We have heard of PC-users that have had to do it three times in a year. Do you think this acceptable to do this on a working production line? When an IPC supplier sells the IPC with an installed operating system and supplies the application software to run on it, they are constantly able to develop the hardware and software products to overcome any operating system problems, and certainly their knowledge base of remedying these problems will be much greater than a supplier who sells only one component part.
When choosing an IPC, Beijer says to remember that Microsoft is not supporting any more developments in Windows NT. So to ensure a current operating system, then one should install Windows 2000 or Windows XP, or a non-Microsoft operating system, such as Linux.
Future of IPCs and embedded HMIs
Where is the dividing line drawn between HMIs and IPCs? Good question. Beijer believes it is now in the areas of screen technology, stability, data usage and new technology adoption. One major advantage that IPCs have over smaller embedded HMI solutions, is in the usage of large screens. The processing power required to drive a full 12-inch plus TFT display is immense, and if this was to be controlled even by a cut-down embedded version of, say, Microsoft Windows in an HMI, then it would greatly affect its performance of processing and refreshing screen data.
With the increasing number of embedded type HMIs (running operating systems, such as Windows CE), coming onto the marketplace, this will reduce the need for small IPCs, but they will no doubt want stability first and PC functionality second. Even though embedded HMIs are little IPCs, they will be more stable, but will lack the flexibility, data processing/storage and connectivity of IPCs.
A major plus factor in the IPC camp is the technology drive of the home and office computer marketplace. As Moore's law states that the number of transistors per square inch has doubled every year, so will following technologies including PCs. IPCs have the advantage of being able to use the same components as their domestic cousins, whereas embedded HMI solutions will develop slower, due to there not being so many technology developments in the embedded area due to lower competitiveness.
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