At a Distance
Besides decreasing the need for protection by eliminating moving parts, developers also are breaking up traditional IPCs into separate functions. These can be prioritized, allowing some more vulnerable, less easily protected functions to be moved away from hazardous areas, which can greatly reduce costs. This also means that more resources can be devoted to protecting functions that must remain in those areas.
For instance, Wonderware recently introduced its Box PC, which has a processor and hard drive, but no display. It’s designed for machine builders, who want to mount their displays away from their PC units. This allows the PC to be located in a machine panel with PLCs and I/Os, but allows the operator to be situated elsewhere.
Similarly, Ke adds that Wonderware also recently launched its Thin Client computer, which allows users to view and access its InTouch software or Client Server HMI at the terminal/node, while actually working off a server that can be located remotely. “Everything runs on the server, and the thin client just shows up as a session on it,” explains Ke.
Aponte adds that industrial PCs are adversely affected by the greater speed of development in the mainstream PC realm. “The span of motherboards and other PC product lifecycles are very important in how industrial PC are able to develop,” says Aponte. “Typical PC models usually change every three to six months, but industrial and automation application usually demand PLCs with a minimum 10-year lifecycle. The computer industry can’t provide this, so IPCs usually have three to five-year lifecycles.
“For instance, we have automotive production PCs running Microsoft NT, which will soon be unsupported,” says Aponte. “However, the user can’t upgrade to XP, so Siemens took over ownership of this solution, and will provide long-term support of NT on this IPC.”
Aponte adds that he’s seeing IPC technology surfacing in Siemens’ Microbox T embedded XP platform, which creates images of common industrial ports, and runs in a fanless, diskless, DIN rail-mountable in hardware format. Microbox T reportedly provides motion functions that were previously only available in a PLC, while the newly introduced Microbox RTX also offers soft PLC control and visualization.
“Standard IPC and PLC technologies now allow users to buy software from many places, and so we can provide pre-installed, fanless, diskless bundles that eliminate the most failure-prone hard drive and heating problems of traditional IPCs, as well as allowing smaller enclosures” adds Aponte. “We basically put the PC’s functions onto an embedded XP image, which provides electronic write files, and also prevents the addition of unauthorized programs. In fact, even if this software was lost, you could just plug in a new compact Flash card.
While diskless and fanless IPCs now get most of the attention, systems receiving a lot of varied, non-repetitive analog data may still need to use one or more hard drives, according to Derrick Lovado, Kontron’s embedded systems product manager. Besides rugged chassis, some box-type or rackmount IPCs now have hot-swappable fans, redundant power, and multiple hard drives arranged in a redundant, array, inexpensive disk (RAID) system, which is governed by a RAID controller.
“The typical Level 5 RAID system mostly uses three or four disks, and stripes data across all of them,” says Lovado. “This is extremely fast, and gives each drive the data from the other. This means you can recreate any data lost by one drive because the others know what it should posess. These systems are very inexpensive now because the drives cost much less.” He adds that Kontron is releasing in August its new Industrial Silent Server, a rack-mount IPC with an ATX motherboard or passive backplane.
In addition, Stealth Computer Corp. reports that simply implementing the appropriate computer board can deliver essential advantages. For instance, conventional PCs and IPCs locate most of their electronics on one large motherboard or main board, and replacing it requires completely disassembling and removing all cards and cables from the system. Downtimes range from 30 minutes to several hours, and frequent model and device driver changes and scarce replacement parts can increase delays even more. ogy changes literally on a monthly basis, it is sometimes impossible to find an exact replacement. Another concern is the availability of expansion slots because many motherboards don’t have as many ISA/PCI slots as they did in the past.
Stealth adds that single-board computers (SBCs) contain all the functions of conventional motherboards, but are designed as single plug-in caerds, which look similar to a standard ISA/ PCI cards. These SBCs plug directly into the IPCs passive backplane, which simply combines ISA/PCI expansion slots into which the SBC and other cards are inserted. Available backplane configurations typically have two to 20 slots or more.
In addition, Stealth adds SBCs often have built-in watchdog timers that can cause a reset if they determine that the system has either hung up or is no longer executing the correct code sequence of code. In electrically noisy environments, for example, a power glitch may corrupt the program counter, stack pointer, or data in RAM. This means the PC’s software could crash, even if the code is bug free. This is precisely the sort of transient failure that watchdogs will catch.
Environmental Protection Definitions
NEMA and CSA Enclosure Types
In its “Basics of Explosion Protection” whitepaper, R. Stahl covers many of the environmental issues that must be considered by users evaluating protection for workstations, enclosures, and industrial PCs. These types originate from the National Electrical Manufacturers Association (NEMA) and the Canadian Standards Association.