Newcompact programmable safety controllers offer an alternative to hard-wiredsystems and safety PLCs for systems as small as two to three safety devices. Thenew G9SP controllers from Omron ScientificTechnologies Inc. also provide a software-based solution that can bequickly programmed to satisfy the complex safety control needs of small andmid-sized machines.

"We offer a higher end safety PLC but havenever had a safety controller in this small form factor," says Tony Rigoni, businessdevelopment manager for Omron STI. "Competitive products are basicallyconfigurable relays, and the G9SP is different because of its softwarecapabilities. With a configurable relay, the user can access a block of I/O andconfigure the outputs to create basic logic but there is no programmable logicin the system."

"Software differentiates our systembecause you can use OR logic, NOR logic, counters and timers to provide logicalfunctions found in higher end safety PLCs, but in a smaller size and with lessavailable I/O," Rigoni says.

G9SP programmable safety controllers aretargeting applications in packaging, food and beverage, automotive component,injection molding, and printing where customer-driven machine set-up changesdemand equally flexible safety solutions. The controllers can also seamlesslyconnect to an Omron PLC using the FINS protocol.

The G9SP controllers deliverdiagnostics and monitoring via Ethernet or a serial connection, and supportdirect connection with non-contact switches and safety mats. Three base modelsoffer a range of I/O, and four types of expansion I/O units are available forhard-wired diagnosis or standard signals. List prices start at under $600.

"With the G9SP's programmingsoftware, users can easily design, verify, standardize and reuse safetycontrol," says Rigoni. "And because the G9SP isn't hardwired into the controlsystem, users will benefit from previously unavailable levels of safety systemflexibility by quickly and easily reconfiguring the units when new safetyfeatures are added to their set-up."

In the past, the traditional approach hasbeen to hard-wire safety devices such as light curtains or e-stop switchesdirectly to a safety relay in a one-to-one connection. In many control cabinets, there would be 10 to20 safety relays that normally used a hard-wired type of logic. One relay wouldbe wired to combine an AND signal with another relay, so an e-stop or lightcurtain could shut down the machine.

Rigoni says the systems were troublesome and,if you looked at industry statistics, it cost anywhere from $40 to $60 to wireeach point. On the high end, companies have moved to safety PLCs that generallycost anywhere from $2,000 to 5,000. But to justify the cost of a safety PLC,the system needs to have 20 to30 safety I/O components and systems are normallyinstalled by end users on larger lines in a factory.

"There has been a void in themarketplace for a product that fits the need for a compact programmable safetycontroller," says Rigoni. "The target is systems with at least two to threesafety devices because, if there is only one safety device, it is lessexpensive to run it to a relay."

Using this type of device, all ofthe I/O is basically fixed. The OEM wires a light curtain or e-stop interlocksdirectly into the controller and everything is controlled via software. Using asimple function block diagram, the user can drag and drop a safety mat ande-stop into the diagram to "wire" them together.

The user can add logic to the systemusing constructions such as AND, OR and utilize timers, up and down counters andpulse generators. Users can also implement serial to parallel conversions and abutton or rotary dial to switch programs.

From the standpoint of the machine builder, thesolution provides a high level of flexibility. Many OEMs have core machines withoptions that would require adding a safety relay and re-wiring it into themachine. What the OEM can do now is dedicateI/O for each option, and switch the program to enable that option.

"Most OEMs implement limited safetysolutions primarily as an option, so our business has been focused on end usersand compliance with safety regulations," says Rigoni. "This product provides asolution for OEMs that gives them more responsibility. And with more global standards, OEMs in theU.S. will need to become more safety conscious and add more safety features totheir equipment."