Compact Programmable Safety

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New compact programmable safety controllers offer an alternative to hard-wired systems and safety PLCs for systems as small as two to three safety devices. The new G9SP controllers from Omron Scientific Technologies Inc. also provide a software-based solution that can be quickly programmed to satisfy the complex safety control needs of small and mid-sized machines.

"We offer a higher end safety PLC but have never had a safety controller in this small form factor," says Tony Rigoni, business development manager for Omron STI. "Competitive products are basically configurable relays, and the G9SP is different because of its software capabilities. With a configurable relay, the user can access a block of I/O and configure the outputs to create basic logic but there is no programmable logic in the system."

"Software differentiates our system because you can use OR logic, NOR logic, counters and timers to provide logical functions found in higher end safety PLCs, but in a smaller size and with less available I/O," Rigoni says.

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

The G9SP controllers deliver diagnostics and monitoring via Ethernet or a serial connection, and support direct connection with non-contact switches and safety mats. Three base models offer a range of I/O, and four types of expansion I/O units are available for hard-wired diagnosis or standard signals. List prices start at under $600.

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

In the past, the traditional approach has been to hard-wire safety devices such as light curtains or e-stop switches directly to a safety relay in a one-to-one connection. In many control cabinets, there would be 10 to 20 safety relays that normally used a hard-wired type of logic. One relay would be wired to combine an AND signal with another relay, so an e-stop or light curtain 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 wire each point. On the high end, companies have moved to safety PLCs that generally cost 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 normally installed by end users on larger lines in a factory.

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

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

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

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

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