Product Description

The JARViE RPI PLM HAT is the fourth offering in the the JARViE powerline communications (PLC) evaluation board series. Plug this HAT onto any Raspberry Pi (RPI) with a 40-pin HDR (e.g. Pi 1,3,4 and Zero) and you instantly have a powerful PLC gateway to control your PLC network over the internet. The HAT has an onboard 100-240VAC to +5V AC/DC converter that powers the RPI, as well as, the HAT digital circuitry directly from the powerline. The gateway is a single board computer making it Python developer friendly; PLM communications can be achieved using Python scripting. The gateway can be accessed over the internet via a remote desktop or SSH connection. Like the other JARViE PLM boards, the HAT can bidirectionally communicate with other devices or systems over AC power lines. Applications include lighting control, home appliance control, energy/heating control and up to 3,000 feet data transmission home power networks.

The RPI PLM HAT highlights the NXP TDA5051A home automation modem. The TDA5051A is an amplitude shift key (ASK) power line modem that operates up to 1200 bits per second (bps) from a single +5VDC supply. The receiver portion of the modem employs automatic gain control (AGC) at its input and the transmitter has output power overload protection. An 8-bit A-to-D converter and a narrow digital filter follow the AGC stage in the receiver. The TDA5051A power line modem application solution is compliant with US FCC (Federal Communication Commission), Industry Canada, Japan MPT, and European CENELEC EN50065-1 regulations for signaling in the 125 kHz to 140 kHz and the 95 kHz to 125 kHz frequency bands.

How It Works

The HAT has an NXP TDA5051a powerline modem IC. This modem takes in a digital message from the RPI UART bus and translates this digital message into an equivalent analog message. Additional circuitry on the demo board sends the analog message over the 120/240VAC of your home, if the demo board is connected to a home outlet. Ideally, the analog message will be broadcasted across all the 120/240VAC wires of your home (to all home outlets), so another demo board connected to another home outlet will hear this message. The demo board has special filtering to only receive messages sent by other powerline modem demo boards and reject all other noise or communications between non-demo board devices. Once a demo board receives an analog message sent over the home power lines, it converts it to an equivalent digital message and sends it to an MCU over its UART bus.

Product Features

• Communicates over 100 to 240 VAC power buses at 125kHz (default). Communication frequency can be adjusted from 95 kHz to 148.5 kHz
• Provides +5V @ 2A power to a Raspberry Pi or other microcontroller development board
• Optically coupled zero cross detection for system synchronization and or line frequency measurements
• 32kbit EEPROM for data storage (e.g. unique ID, GPIO configs at RPI boot, etc.)
• Supports modem low-power mode when controlling the modem PD pin
• 1200 bps/baud data rate to modem
• Galvanic power line isolation via high-frequency transformer
• Full digital carrier generation and shaping
• High clock rate of 6-bit D/A (Digital to Analog) converter for rejection of aliasing components
• Fully integrated output power stage with overload protection
• Automatic Gain Control (AGC) at receiver input
• 8-bit A/D (Analog to Digital) converter and narrow digital filtering
• Digital demodulation delivering baseband data

Basic Home Automation Architecture

The JARViE PLM can communicate over power lines from 100 to 240 VAC power lines. The figure below diagrams a home application.

Complete PLM Demo Kit

The complete demo kit provides everything needed to quickly get started with communicating over AC power lines. There's a huge value add that comes with purchasing the kit; all the hardware is proven and software examples are available on GitHub. This gets the developer learning PLM technology on day one and NOT spending days specifying and purchasing hardware and or developing firmware.

Kit contents include,

Getting Started

All info (product documentation, firmware, etc.) for quickly getting started is on the device GitHub page.

Safety Warning

The non-insulated high voltages that are present when operating this product, constitute a risk of electric shock, personal injury, death and/or ignition of fire. This product is intended for evaluation purposes only. It shall be operated in a designated test area by personnel that is qualified according to local requirements and labor laws to work with non-insulated mains voltages and high-voltage circuits. This product shall never be operated unattended.

The board needs to be connected to mains voltage. Touching the reference board during operation must be avoided at all times. An isolated housing is obligatory when used in uncontrolled, non-laboratory environments. This isolation is not according to any regulated norm. Galvanic isolation of the mains phase using a variable transformer is always recommended.

JARViE is NOT liable for any mishaps that occur while using this board. User must consider and take proper safety precautions while working with high-voltages.

Data Transmission

The following image shows the DATA_IN to Tx carrier output delay. The blue trace is a 1 kHz square wave driving the PLM's TDA5051A modem DATA_IN input. The yellow trace is the modulated ASK carrier wave transmitted to all PLMs on the power line network. The capture shows that there is approximately a 170 microsecond delay between setting the DATA_IN input and Tx carrier wave generation.

Data Reception

The following image shows the Rx carrier input to DATA_OUT output delay. The blue trace is the modulated ASK signal received through the AC inputs on the JARViE PLM. The yellow trace is the digital TDA5051A DATA_OUT signal that can be interpreted with an MCU or equivalent UART compliant device. The capture shows that there is approximately a 180 microsecond delay between Rx carrier wave reception and the DATA_OUT output.

AC Zero Cross Detection

The main purpose of the PLM zero cross detection circuitry (ZCD) is to provide a method to synchronize devices to one another. The intent is to not have to share a clock between devices that are meters away. The output of the ZCD goes from 0 to +5V making it compatible with MCUs. By pairing the PLM with an MCU, the ZCD output can be used to trigger event timers, create task schedulers within a PLM network and or send messages when noise on the power line is smallest for best communication results (zero crossing point). The ZCD can also be used to measure the frequency of the AC power line.

• A – 120 VAC zero cross point. Signal begins to rise to maximum amplitude but the PLM H11AA1 bi-directional optocoupler is off so zero cross signal remains HIGH (+5V) due to pull-up resistor.
• B – 120 VAC rises high enough to bias NPN transistor in optocoupler pulling the zero cross detection signal LOW (0V).
• C – 120 VAC zero cross point. Signal begins to fall to minimum amplitude. H11AA1 optocoupler is off so zero cross signal remains HIGH (+5V) due to pull-up resistor.
• D – 120 VAC falls low enough to bias NPN transistor in bi-directional optocoupler pulling the zero cross detection signal LOW (0V).

Why did you make it?

This is the first Raspberry Pi compatible power line communications board on the market! This product was made to provide a reliable and low-cost solution for leaping into Smart Home and Internet of Things (IOT) applications quickly.

What makes it special?

The HAT board + Raspberry Pi enables devices to communicate over meters of 100 to 240 VAC power lines removing the need to have devices closely tethered together with more than two wires. Devices being able to communicate over meters of AC or DC power line enables one to develop a mesh network of two or more distributed devices, each having unique functions. Devices that potentially allow one to close your garage, turn-off a downstairs TV or monitor the power consumption of home appliances while lying in bed is a possibility.