Industrial wireless communications have been used for more than 30 years to provide safe and cost efficient connectivity for industrial automation, motion control, remote monitoring, and other applications. As the diversity and distribution of installations has increased over the years, new wireless technologies have evolved to provide a specialized mix of range, reliability, and power efficiency.
Today, the Internet of Things represents the present culmination of this expansion. Sensors, motion controllers, valves, pumps, Emergency Stop controls, and many other types of devices are used in nearly infinite ways to provide time critical information for installations around the world. To power the industrial side of this Internet of Things (IoT), traditional wired communications and newer wireless technologies such as Bluetooth, ZigBee, Wi-Fi, SigFox, and Cellular WAN each bring a unique solution set to the table. Selecting the ideal solution requires a clear understanding of the strengths and weaknesses of each.
While wired communications are well established as reliable and fast technologies, wireless solutions offer large benefits where movement or deployment efficiency is desired. The first and perhaps most obvious advantage of wireless industrial communications is that they avoid the trouble and costs of installing communications cabling. These costs can become significant in large plants where cable runs could be several hundred meters through harsh environments, or in outdoor installations where it is cost prohibitive to run communications cabling. Maintenance costs are also reduced as technicians do not have to search long cable runs for damage, and can instead concentrate on a limited number of installation points to debug problems. Commissioning time and complexity are reduced as well, particularly in the case of low power battery operated stations and sensors. The combined advantages of wireless solutions make them a very attractive alternative to traditional wired solutions.
Deploying wireless solutions in industrial environments must be carefully planned, however. There are often physical and operational requirements that must be met to ensure reliable and safe operation. Communications devices need to be able to withstand temperature and humidity extremes as well as exposure to water, chemicals, shocks, vibrations, noise, and electromagnetic interference. Devices installed outdoors usually require an IP65 rating, which indicates that the device is completely sealed against water and dust intrusion. Devices that do not meet these strict environmental requirements will often fail in industrial deployments, and this can cause safety concerns as well as the obvious operational problems that result from a failed communication system. Security is one of the other top concerns, as manipulated data could compromise both safety and correct operation. Finally, communications systems also need to meet stringent safety, availability, and response time requirements to ensure that industrial systems continue to operate as intended or shut down during a malfunction. Even temporary transmission or reception failures in isochronous systems can bring an entire manufacturing process to a halt.
Fortunately, there are several different options for wireless industrial control, each having its own unique set of strengths. For localized deployment in and around buildings, 2.4 and 5GHz technologies have become the overwhelmingly dominant solutions, although planning is typically required to ensure proper operation when several devices are operating in the same frequency range. For outdoor installations and widely dispersed devices, some sort of cellular communications are typically used.
Bluetooth operates between 2400-2480 MHz, and is frequently used for industrial serial communications links. Bluetooth Basic Rate (BR) devices can support up to about 780 kbps, while Enhanced Data Rate (EDR) devices have about 2.1 Mbps of throughput. Depending on the class of device used, range in industrial environments can vary from 3 – 100 meters. Adaptive frequency hopping operation on eighty 1 MHz channels results in extremely robust connection for multiple Bluetooth devices, and links are protected by 128-bit encryption. Up to 7 devices can be attached to a single Master device while maintaining full throughput. Bluetooth is also a real-time capable technology, with latency of only 5-10 ms. Certain devices can additionally support links to Bluetooth Low Energy (LE) devices (also known as Bluetooth Smart). TI offers an excellent example of these dual-role capable devices in their CC2564 Bluetooth 4.1 dual-mode Host Controller Interface certified Module. It is suitable for industrial environments, is available with or without an integrated antenna, and simultaneously supports up to seven BR / EDR connections and up to ten active Bluetooth LE connections. Separate buffering ensures that active BR/EDR connections are not impacted when Bluetooth LE connections occur.
관련 상품 참조
Bluetooth Low Energy leverages the robust Bluetooth specification and offers several enhancements specifically targeting energy efficiency and infrequent communications. To save energy, links are not maintained in an active state, but re-stablishing the link takes less than 10 ms. Due to the intermittent nature of the transmissions, higher numbers of active slave devices that can be connected. More devices will result in higher latency in the system, however, so the number of connected devices needs to be balanced to the real-time latency requirements of the system. The tradeoff for the energy savings features is lower throughput, as links are limited to about 270 kbps. Future Bluetooth® Smart 2016 standard enhancements will include Longer Range, Higher Speed and mesh networks. In industrial settings, this makes Bluetooth LE ideal for battery powered sensors, actuators, and other devices that only require short bursts of data on an intermittent basis. TI also has several excellent solutions for Bluetooth LE. The SimpleLinkTMCC2640 device is a Bluetooth LE MCU based around an ARM-Cortex M3, and the CC2540 and 2541 are cost effective System on Chip (SoC) solutions for Master or Slave Bluetooth LE applications built around the industry standard 8051 MCU. All offer a host of I/O connectivity and allow designers to quickly implement designs that meet their unique requirements.
관련 상품 참조
ZigBee is another low power, narrow-band 2.4 GHz wireless mesh technology that is increasingly used for wireless industrial control and monitoring. It is a lower cost solution than a Bluetooth or Wireless LAN systems, but latency is much higher and data rates are limited to 200 kbps (sometimes less, depending on the number of nodes deployed). Due to its wireless mesh topology, ZigBee does have some very unique advantages. Individual links are limited to 30-100 meters line of sight, but in aggregate, very large areas can be connected on a single ZigBee mesh network. Devices can also be configured to add themselves to the network automatically. Traffic control systems, monitoring systems, process data control, and other low data rate applications are prime examples of systems where ZigBee is a preferred choice. Good security is provided, as links are protected by 128 bit encryption. TI has several ZigBee devices that should meet any industrial installation requirements. Their SimpleLink CC2630 is a full-featured wireless ZigBee MCU with an ARM Cortex-M3 CPU and unique I/O capabilities including built-in support for capacitive touch buttons, and the more powerful CC2630 trades some of the unique I/O features for additional flash and SRAM. If an 8051 microcontroller is desired, TI’s CC2530 SoC may be a better fit.
관련 상품 참조
Industrial WLAN is a very prevalent 2.4 GHz solution when higher throughput is required, and it offers excellent range, resistance to interference, and very good security. When enhanced by ProfiNET, Profisafe, and other similar technologies, it can be a very effective solution for wireless industrial communications. Versions of this technology have been under steady evolution for over 20 years. Three non-overlapping channels exist in the 2.4 GHz band, and throughput can be up to several hundred Mbps. Bluetooth and ZigBee both contain mechanisms to interact with 2.4 GHz WLAN, and newer versions of the 802.11 standard also add features that help ensure interoperability when the spectrum becomes very crowded. WLAN can also operate on up to 19 non-overlapping channels in the 5 GHz band, each of which completely avoids competing for the same frequencies as Bluetooth, ZigBee, and other 2.4 GHz technologies. Due to the high frequencies used, it is recommended to maintain line-of-sight in 5 GHz applications, but the uncrowded spectrum makes it an attractive choice nonetheless. One of the weaknesses of WLAN is that it can take from 50ms to several seconds to transition between access points. When WLAN links are used to control devices with large ranges of movement, precautions must be made to ensure uninterrupted communications during these transitions. For single access point installations, connecting several widely spaced antennas to a single access point can ensure an uninterrupted link, or the use of so called “leaky” RF cabling can provide the equivalent of a continuous short range antenna along an extended fixed route. For routes with more than one access point, multiple radio implementations are the most reliable. Common scenarios include using one connection for control signaling and another for data, or a staggered system of redundant APs used to allow failover to a second active network when the primary network is transitioning between access points. TI offers several enticing solutions for Industrial WLAN. The SimpleLink CC3200 is a single-IC, ARM Cortex-M4 based 802.11 b/g/n Wi-Fi microcontroller that is well suited for industrial environments. It is capable of running industrial Wi-Fi protocols such as ProfiNET and Profisafe, and offers extensive I/O options. The WL1837 Wi-Fi and Bluetooth/Bluetooth LE radio integrated on one certified module is also available for Linux and Android client device or bridge applications. It combines Bluetooth and 802.11 a/b/g/n RF sections, power amplifiers, clock, RF filters and switches, and power management into a 100 pin MOC package.
For communications over geographically large distances, some sort of wireless WAN technology (WWAN) is typically used. SigFox is an emerging low power WAN network provider that is building out a global, cellular style network for Ultra Narrow Band (UNB) devices. Provisioning is exceedingly low cost, and it is simple to roll out very large deployments without worrying about unique data plans or contracts for each device. Message size is limited to 12 bytes and devices are limited to 140 transmissions per day, but devices can operate for many years on two AA size batteries. Security is somewhat limited due to the message size, but features include anti-replay and message sequencing. SigFox devices are already in wide deployment, and TI offers several two SigFox solutions in the CC112x RF Transceiver and CC1190 RF front end devices. The CC112x is a high performance and ultra-low power single chip transceiver with support for seven ISM/SRD bands between 169-950MHz with data rates up to 200 kbps. It also features enhanced wake-on-radio functionality and packet acknowledgement and retransmission. The CC1190 is a low cost, high performance RF front end that operates between 850-950 MHz and features an integrated low-noise amplifier, power amplifier, RF switches, and RF matching in a compact 4x4mm QFN-16 design.
관련 상품 참조
The LoRa Low Power WAN Alliance offers another solution for geographically dispersed devices. It transmits small amounts of data on an intermittent basis, and battery powered devices can last for years depending on the device class of the remote transceiver. Multiple levels of security are used to ensure data integrity and privacy. It also operates on frequencies that are often a better match for building and obstacle penetration. Like SigFox, deployment costs are very low, but commercial LoRa providers can offer widely varying service levels. For companies looking to deploy a large number of devices in a relatively small area, it is possible to bring up an internally owned and controlled gateway.
Cellular connectivity is a well-established WAN solution and has a global reach. 2G GSM and GPRS links are one of the most common link sources, but many cellular network operators outside of Europe have either already turned off their 2G networks, or have plans to do so before 2020. Where networks will be maintained into the future, 2G GSM remains a good, power efficient method for remote intermittent or low data rate communications. WiMAX has also gained acceptance in markets where it is available, but many networks are transitioning to LTE or have already been turned off. LTE is an exciting area for remote IoT devices, as different end device categories can adapt bandwidth and power needs to the application. Existing Category 3 LTE devices can offer theoretical speeds of up to 150Mbps down / 50 Mbps up, and the newly implemented Category 6 devices can reach 300 Mbps downloads in ideal conditions. On the other end of the spectrum, LTE Category 1 devices and the upcoming LTE Category 0 (or Category-M) release are designed for IoT with a maximum throughput of 1-10 Mbps and much higher power efficiency. Despite the flexibility of these WAN solutions, they are usually have much higher up-front and operational costs, and each device that is placed in the field will require a contract with regional network operators, so deployment does require planning and time.
Whether it’s a short range radio connection or a distributed WAN scenario, TI has made it easy to meet a variety of connectivity needs by providing drop-in devices that speed product development and deliver high value, low cost solutions for wireless industrial communications.
Download the below spreadsheet HERE:
