Modern factories rely on computer networks to provide the communications between machine tools, programmable logic controllers (PLCs), robots, and other equipment. Sensors are connected to data-acquisition systems; sensors and actuators connect PLCs and other computers; and all equipment is further networked to larger factory or company computers, usually via Ethernet.
At the sensor and actuator level, fieldbuses provide some of the connections. However, more engineers are turning to another serial interface—IO-Link—for this purpose. This simple serial data standard and protocol is helping improve factory output and efficiency, with new IO-Link ICs delivering the desired operating performance.
Introduction to IO-Link
The next generation of factory manufacturing is referred to as Industry 4.0. Its goal is to create a smart factory that improves efficiency and performance, which largely hinges on communications between the computers, sensors, actuators and other equipment. A mix of networks is usually employed, including 4-to 20-mA current loops, HART, and IO-Link.
IO-Link is gaining popularity because it’s a simple, low-cost serial interface for sensors and actuators, and is backward-compatible with fieldbuses like Profibus, Profinet, and EtherCAT. When building new factories or retrofitting existing facilities, IO-Link becomes an excellent alternative. Here’s a summary of IO-Link facts and features:
- Developed by the IO-Link Consortium.
- Standardized by the International Electrotechnical Commission (IEC) as 61131-9.
- Point-to-point link between a sensor or actuator and a Master controller.
- Uses standard byte transfers that have common UART format with start, stop, and even parity bits.
- Typical data rates are 4.8, 38.4 or 230.4 kb/s.
- A Master controller initiates all access to the sensor or actuator.
- Data is transferred in multiple byte frames called telegrams.
- Common logic levels are binary 0 of 24 V and binary 1 of 0 V; NRZ encoding.
- Cabling is industry-standard 3-wire or 5-wire.
- Connectors are also industry-standard M5, M8, and M12.
- Cabling and connectors are fully compatible with all existing fieldbuses and other interfaces.