Owing to the excellent cited characteristics, Zigbee technology has emerged as a preferred technology for short-range communication in wireless industrial automation. Within the industrial environments remote switching, remote monitoring, supervisory or distributed control are the key challenges that require wireless sensor networks for doing all those operations in which cost, distance cover and speed of data transfer are the parameters to be considered. So let us have a look on industrial automation expansion using this Zigbee communication technology.
Introduction to Industrial Automation
Industrial automation is the advancement to the mechanization process wherein an operator is necessary to operate machines based on the load requirements. It is the use of various sensing devices like pressure, level, temperature sensors which are processed by various control strategies like feed forward, feedback and cascade controls implemented in the programmable control devices like PLCs and other PID controllers.
The above figure shows industrial automation structure that consists of different levels, such as sensor and actuator level, field level, control level and HMI or monitoring level. In the sensor level, the process parameters are sensed with the use of different sensors like temperature, flow, level sensors, etc. Furthermore, they consist of final control devices to control the operations such as actuators, valves, servo motors, etc.
In a field level, all these sensors are connected to a communication bus which gathers all the parameter values to a main controller. The communication bus includes profibus, Modbus, etc. In a control level, various advanced controllers like programmable logic controllers (PLC), compact PID controllers, distributed I/O devices, etc., are programmed in such way that they process these parameters and send the command signals to final control devices like actuators, contractors, etc.
In a monitoring or HMI level, overall information is gathered to a central station for implementing supervisory control and data acquisition (SCADA). In this level also the communication link makes the data transfer from a control level to a higher level and vice versa.
By observing the above automation system, communication is the back bone of the industrial controlling and monitoring systems. But, the wired communication systems involve greater complexity of making wiring including all the other configuration processes. This leads to the introduction of a wireless communication technology into this industrial floor as it overcomes the problems that are faced by the wired technology. But all these wireless technologies are very expensive.
Introduction to Zigbee Technology
Zigbee is specially designed for low cost, low data rate and low-power consumption wireless personal area networks (WPANs). Its mesh topology of network makes this network best suited for industrial automation as well for factory floor automation.
This is built on IEEE 802.15.4 standard by Zigbee Alliance as short range communication. This IEEE standard defines physical layer and MAC (Media Access Control) layers, optimized to 250 kbps in 2.4 GHz band. It supports two ways communication between transmitting devices and controllers at 10-100 meters distance.
This ZigBee consists of three types of devices: Zigbee coordinator, routers and end point devices. The Coordinator is the root of the network as it acts as a bridge to other networks. It handles and stores the information for receiving and transmitting operations within the network. Routers pass data to other devices as intermediaries. In order to make longer battery life and less complexity, end point devices are made for limited functionality.
Zigbee operates in two modes: beacon and non-beacon mode. In a non-beacon mode, the receivers of the routers and the coordinators are continuously active, and therefore, in this type of topology, the power supply consumption is more. In a beacon mode, the coordinator periodically awakens and transmits beacons to the routers of that network. These beacons also awaken other nodes of the network for their status of incoming messages. In the absence of any messages, these nodes and coordinators go back to the sleep mode, and thus, the power is conserved in the beacon mode.
Zigbee is quite addressable for several network topologies in an industrial environment, and its star and mesh topologies are best suited for simple as well redundant communication networks. In a star topology, the remote nodes are controlled through a base station where they are connected as a point to a multipoint structure. This is useful in industries where end point nodes are needed to communicate with a single main router, and this is simple and easy to deploy and maintain.
The Mesh topology of ZigBee is low-cost, low-powered structure with a redundancy capability that enables nodes to communicate with the adjacent node. If one node fails, the information passes automatically to the nearby nodes so that the redundancy of data is performed. This type of topology is required in industries where reliability of data transmission is needed. Compared with the other short range wireless communications like Bluetooth and Wi-Fi, ZigBee is cost-effective and low-powered technology as this can be ascertained form the following comparisons.
Application of Short Range Technology to Industrial Automation using Zigbee Technology
Up to now, we have discussed about industrial automation and Zigbee technology. Now, we are going to discuss one application of this technology for industrial monitoring and control process. In the system given below, the industrial process parameters like voltage, current and temperatures are monitored remotely by using Zigbee communication, and thus enable to control various final control devices like relays, motors, etc., with the use of a microcontroller.
In the transmitter section, the Zigbee module is configured in such a way that it receives the data collected from the microcontroller and sends it to the remote receiver. In this system, the microcontroller is programmed to collect the data from an analog to digital converter that continuously monitors temperature, voltage and current parameters.
At the receiver side, the Zigbee module receives all the sent data from a Zigbee transmitter within the range of communication. This data is further transferred to the microcontroller using an embedded circuitry wherein the microcontroller program compares all these data parameters with predefined set limits. If any parameter exceeds its limit, then the microcontroller sends command signals to a relay driver IC, which is responsible to operate different loads such as motors, relays, circuit breakers, etc. All these parameters’ information is also displayed on LCD display as a Human machine interface.
In this way, industrial parameters can be easily monitored and controlled through the short range low cost and low powered Zigbee communication technology. We hope that you might have got satisfied with the explanation and also got an overall idea of this concept. Furthermore, for any queries and doubts on this technology or projects, you can reach us by commenting below.
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