Power Line Communications Designs For Automation And Control

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Are you ready for PLC enablement of your home and neighbourhood? It’s now possible to use just the same power cables required to power an electronic device to transfer data or control the device. With a relatively new and exciting area of telecommunication called Power Line Communications (PLC), it becomes easy to connect houses with a high speed network access point without installing new wirings, by sending data, video and voice over existing power cables used for power transmission and distribution. With different PLC techniques, a range of applications can be implemented such as home automation, advanced meter reading (AMR), public street lighting, broadband Internet access, in-vehicle applications, and more.

Like other communication technologies, PLC operates by a sender modulating the data to be sent and adding it to the wiring system, and the receiver de-modulating this data to read it. Some of the modulation schemes used in PLC are Orthogonal Frequency Division Multiplexing (OFDM), Binary Phase Shift Keying (BPSK), Frequency Shift Keying (FSK) and Spread-FSK (S-FSK). Different PLC standards are characterized by different data rates and distance limits. Narrowband PLC uses lower frequencies of 3-500 kHz, lower data rates (up to 100s of kbps), and has longer range of up to several kilometers. Broadband PLC works at higher frequencies up to 250 MHz, high data rates (up to 100s of Mbps) and is used in shorter-range applications. Narrowband PLC has wide applications in smart energy generation by solar micro-inverters. Broadband PLC is helpful in internet access, often called Broadband over Power Line (BPL) and home networking.

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Applications of PLC are not limited as this technology is becoming more familiar. PLC is now seeing wider adoption in applications such as traffic light control, LED dimming, industrial applications such as UPS communicating to a network device and irrigation control, machine-to-machine communications, telemetry, automobiles (e.g. car charging). For home automation, PLC can perform remote control of lighting and appliances. The signals or commands flow over household wiring to the receivers each having a specific address, and then decoded at the receiver. Home devices with Ethernet ports such as home computers and entertainment devices can simply connect using “Ethernet over power” (EOP) or Powerline adapters which plug into power outlets and set up an Ethernet connection using the existing electrical wiring in the home. Automotive PLC techniques allow in-vehicle communication of data, voice, video and music using protocols such as CAN-bus, LIN-bus and DC-bus. In Automatic Meter reading (AMR) system, readings from meters are sent to “master station” which publishes the readings. In two-way AMR, a master broadcasts commands to end devices or meters to obtain readings, or conveying messages, to which the end device responds with a message.

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There are several challenges presented to the designer including high cost of end devices, which should host active controls and communication, and interference with other devices. Thanks to the advanced digital communication techniques that can overcome such situations and enable signal transfer using small-sized silicon chips, which allow lower cost and weight, flexibility and ease of installation. Designers employ robust signaling techniques and hardware to maintain signal integrity over power lines as PL channel is a very harsh and noisy transmission medium. Sometimes, implementing large networks with PLC requires multiple PLC technologies and becomes a complex problem.

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Check out some interesting reference designs to find out little more about Power Line Communications. These designs cover many applications such as industrial control and building automation. Each reference design comes equipped with complete documentation:-

  • PLC for Industrial and Building Automation: Here is a DC (24 V, nominal) Power-Line Communication (PLC) reference design intended for industrial control, lighting, smoke and fire detection and building automation applications. Based on TI’s powerful C2000-microcontroller architecture and the AFE031 (analog-front-end) device, developers can select the correct processing capacity and peripherals to either add power-line communication (PLC) to an existing design or implement a complete application with PLC communications. The MCU runs the PLC-Lite protocol from TI. With an extremely small (approx 1-inch diameter) industrial form factor, the design provides a complete hardware and firmware design of a master (PLC) node, slave (PLC) node with schematics, BOMs, layer plots, Altium files, Gerber Files, a complete software package, and Graphical User Interface (GUI). More on this Reference Design
  • PLC using Power line Networking SoC: This reference design is a smart Power line communication node which is designed to be easily adapted to different frequency bands and applications with slight modifications. The design is built around a ST7580 power line networking system-on-chip (SoC) and an STM32 microcontroller which makes the design flexible and suitable for use as a standalone smart PLC node. The line coupling interface is designed to allow the ST7580 device to transmit and receive on the AC mains line using the band specified for automatic meter reading (AMR). More on this Reference Design
  • PLC for RS-485 Communication: This is a credit-card sized PLC reference design ideally suited for industrial control and automation, process control and PLC. Consuming a little power of 500mW, the design can be used with any application that requires high RS-485 data rates and ESD protection. Important components of the design include two RS-485 transceivers (one full duplex and one half duplex ) from Maxim, 600VRMS data isolation (MAX14850), a STM32F1 microcontroller and a USB-UART bridge. The design comes equipped with device drivers, example C source code, test data, and other required documentation. More on this Reference Design
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