In contrast, Opto 22 controllers are logic-driven devices. An Opto 22 groov EPIC® (edge programmable industrial controller), a SNAP PAC (programmable automation controller), or even a legacy mistic controller (dating from the early 1990s) does not have to look at I/O or variables until the logic in the controller requires it. When logic requires I/O or variable values, an Opto 22 controller immediately gets only the values needed. The values are fresh, and the controller doesn’t have to waste processing power continually scanning I/O.
An Opto 22 control system also works differently from a PLC system because it utilizes a distributed architecture. The controller runs the control program, but an intelligent I/O processor in each I/O rack handles many functions independently. These functions include counting, latching, pulsing, frequency and period measurement, watchdogs, totalizing, minimum and maximum values, scaling, clamping, ramping, and more. An I/O unit can also run multiple PID (proportional integral derivative) control loops independently. All of this distributed intelligence reduces the load on the controller.
Most PLCs are part of proprietary systems built by one manufacturer and designed to be used with their own products. Opto 22 systems, however, are built on open standards—not only automation standards such as OPC UA and Modbus, but also internet and IT (information technology) standards such as Ethernet, HTTPS, and MQTT.
Comparing PLCs and Opto 22 Control Systems
The combination of logic-driven control, a distributed architecture, and open standards gives Opto 22 control systems some distinct advantages, including efficiency, scalability, and the computing capacity for abilities far beyond control.