Theory & Background

CENELEC regulations (EN 50065) define PLC bands for Europe/India: Band A (3–95kHz) — utility use, Band B (95–125kHz) — consumer in-home, Band C (125–140kHz) — consumer with CSMA protocol, Band D (140–148.5kHz) — consumer use. For smart metering (AMI) applications, use CENELEC Band A (specifically 35–91kHz) with the G3-PLC or PRIME standard.

Components & Requirements

10 components required for this project.

#	Component	Purpose	Qty
1	ST7580 PLC Modem IC	OFDM-based narrowband PLC transceiver	x2
2	PLC Coupling Circuit (transformer + filter)	Coupling PLC signal to power line safely	x2
3	STM32F103 Microcontroller	Protocol stack and data management	x2
4	Band-Pass Filter (5–148kHz CENELEC A-band)	Rejecting mains harmonics from PLC receiver	x2
5	Line Driver Amplifier (NE5532)	Boosting PLC signal for line driving	x2
6	Safety Coupling Capacitors (10nF/630V)	DC blocking for safe coupling to mains	x4
7	Common Mode Choke	Reducing mains noise in PLC receiver	x2
8	LCD Display 16×2	Showing received data at each node	x2
9	Isolation Transformer (signal grade)	Galvanic isolation in coupling circuit	x2
10	Variable Signal Generator	Testing and characterizing the PLC channel	x1

Step-by-Step Implementation

Follow these 3 steps carefully.

1

PLC Frequency Band Selection

CENELEC regulations (EN 50065) define PLC bands for Europe/India: Band A (3–95kHz) — utility use, Band B (95–125kHz) — consumer in-home, Band C (125–140kHz) — consumer with CSMA protocol, Band D (140–148.5kHz) — consumer use. For smart metering (AMI) applications, use CENELEC Band A (specifically 35–91kHz) with the G3-PLC or PRIME standard.

2

Coupling Circuit Design

The coupling circuit connects the PLC modem to the power line while providing: galvanic isolation (safety isolation transformer rated for mains voltage on one side), impedance matching (power line impedance varies 1–100Ω; coupling circuit optimizes signal transfer), DC blocking (coupling capacitors prevent mains 50Hz from damaging PLC electronics), and bandpass filtering (suppresses out-of-band noise). Use a current coupling transformer or capacitive coupling for AC lines.

3

OFDM Modulation Implementation

OFDM (Orthogonal Frequency Division Multiplexing) splits the PLC channel into multiple sub-carriers (tones). G3-PLC uses 36 sub-carriers between 35.9–90.6kHz. Each sub-carrier can be BPSK, QPSK, or 8-PSK modulated based on channel quality. Adaptive modulation: probe channel quality on each sub-carrier (signal-to-noise ratio), use higher order modulation on good sub-carriers, lower order or mute on noisy sub-carriers. This achieves maximum data rate over the noisy, frequency-selective power line channel.

Code & Implementation

Core code for plc_node.cpp:

plc_node.cpp
  C/C++

// ST7580 PLC Modem Communication via UART #include <SoftwareSerial.h> SoftwareSerial plcSerial(10, 11);   struct PLCFrame {   uint8_t  sof;        uint8_t  len;        uint8_t  cmd;        uint8_t  data[64];    uint16_t crc;     };  void sendPLCData(float energy_kwh, uint8_t meter_id) {   PLCFrame frame;   frame.sof = 0x02;   frame.cmd = 0x50;    frame.data[0] = meter_id;      memcpy(&frame.data[1], &energy_kwh, 4);   frame.len = 5;   frame.crc = calculateCRC16(frame.data, frame.len);      plcSerial.write((uint8_t*)&frame, sizeof(frame)); }  void receivePLCData() {   if(plcSerial.available() >= 8) {     PLCFrame frame;     plcSerial.readBytes((char*)&frame, sizeof(frame));     if(frame.sof == 0x02 && verifyCRC(frame)) {       float energy;       memcpy(&energy, &frame.data[1], 4);       Serial.printf("Meter %d: %.3f kWh\\n", frame.data[0], energy);     }   } }

Testing & Troubleshooting

Test Power Line Communication System by verifying each subsystem individually before full integration.

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Troubleshooting Tips

Verify power voltages, check ground connections, use serial monitor for debug.

Real-World Applications

*Smart meter AMI last-mile communication

*Home automation using existing wiring

*Street light remote control via power cables

*Industrial process monitoring over power network

*Building management systems

*EV charging station load management

*Rural electrification AMI deployment

*Substation protection data transmission

Extensions & Next Steps

Implement full G3-PLC stack with 6LoWPAN and IPv6
Add frequency hopping for interference resistance
Build a PLC network analyzer to characterize channel quality
Implement repeater/extender nodes for long network spans
Add mesh routing protocol for multi-hop PLC networks

Interactive Playground

Coming Soon

An interactive simulator will be available here — simulate circuits and run code in-browser without hardware.

Frequently Asked Questions

What data rate can power line communication achieve?

Data rates vary significantly by standard and application: Narrowband PLC (CENELEC bands, used for AMI smart metering): 2.4–500 kbps with G3-PLC and PRIME standards. Broadband PLC (HomePlug AV2): up to 2 Gbps theoretical on indoor wiring for home networking, typically 300–500 Mbps practical. The power line is a harsh channel with high noise, impedance variations, and signal attenuation, so practical rates are much lower than fiber or WiFi but excellent for the AMI use case where data packets are small.

Introduction