Given the wide range of applications that come under heading “motion control”, there is clearly no single best solution for all problems. Industrial Ethernet offers advanced features that are extremely valuable to designers of large, complex factory systems. However, for smaller, more self-contained applications, simpler technologies such as fieldbus (CANopen, PROFIBUS) or point-to-point wiring (SSI, Bit-Parallel, or even Analog) have a place. POSITAL position and motion sensors, including IXARC rotary encoders, TILTIX inclinometers and LINARIX linear position sensors are available with a full range of communications interfaces.
Incremental Interfaces for Encoders
Incremental encoders generate an output signal each time the shaft rotates a certain amount. The number of signals per turn defines the resolution of the device.
HTL (Push-Pull) and TTL (RS422) are forms of serial connections that are suitable for continuous streams of data, such as would be generated by an incremental encoder (i.e. an encoder that produces a signal each time the shaft rotates through a certain angle.)
Fieldbus Interfaces for Encoders
Fieldbus networks were developed for vehicle, work cell and factory automation systems. Applications range from conveyors and manufacturing facilities to mobile equipment, medical equipment, wind turbines and solar panels. These networks are based on a bus topology, which simplifies wiring for systems with a significant number of devices. They also support powerful diagnostic tools to help with system setup and trouble-shooting.
Profibus is available on many PLCs and one of the most common fieldbus technologies in factory automation and other areas. It is based on RS485.
CANopen is a fieldbus protocol using CAN networks. CANopen is available on many PLCs and widely used in factory automation and mobile machines.
DeviceNet is a fieldbus system based on CAN networks and CIP protocol. DeviceNet is managed by ODVA, widely used in factory automation and available on many PLCs.
The CANopen Safety framework for safety-relevant communication is an add-on to the CANopen application layer and communication profile.
CANopen Lift is a fieldbus protocol for elevator applications. It is similar to CANopen and based using CAN networks.
Interbus is a fieldbus technology developed by Phoenix Contact. Is has been popular in automotive production plants. It can be based on different electrical networks and fiber optics.
SAE J1939 is a Fieldbus standard used for communication by the car and heavy-duty truck industry.
Analog Interfaces for Encoders
Analog interfaces can be cost effective for simple control systems. Using point-to-point wiring, they are easy to implement for small networks (1-5 sensors). Analog installations are common in applications like vehicles, medical equipment and energy management.
A common standard with either a voltage or a current output. Different ranges are available.
Industrial Ethernet Interfaces for Encoders
While it shares core technology with ‘office’ Ethernet, Industrial Ethernet systems incorporate special hardware and software aimed at providing ‘industrial-strength’ ruggedness and performance. Industrial Ethernet supports larger and more complex networks. It also enables seamless connections between the factory network (Industrial Ethernet) and the enterprise network (office Ethernet) which can simplify the integration of production, inventory control and enterprise management systems.
EtherNet/IP is an industrial communication protocol developed by Rockwell Automation and managed by ODVA. It is based on CIP and TCP/IP protocol.
ETHERNET POWERLINK is a real-time communication system based on Ethernet networks and managed by EPSG.
EtherCAT is an open high performance Ethernet-based Fieldbus system. EtherCAT require short data update times with low communication jitter and low hardware costs.
PROFINET is an Industrial Ethernet standard from „PROFIBUS&PROFINET“ International designed for automation.
Modbus is a serial protocol managed by the Modbus Organization.
Serial Interfaces for Encoders
Serial interfaces use point-to-point wiring systems, but with a digital interface that connects directly to digital PLC’s or microcontrollers. They offer good speed, high resolution, flexible cabling and reliable communication over distances up to a few hundred metres.
SSI is a widely used serial interface with point-to-point connection between PLC/Master and encoder. It is based on the RS422 standard.
Parallel Interfaces for Encoders
Parallel interfaces can provide very high-speed communications over short distances but require bulky cables with individual wires for each bit.
All bits of the position output are transferred simultaneously using one line for each bit.