Wireless Energy Meter Reading System using LoRa for Apartment Complexes

This Wireless Energy Meter Reading System using LoRa for Apartment Complexes replaces door-to-door manual meter reading with a radio link: a meter node fitted at each flat measures that flat's electricity use and sends the reading over LoRa to a gateway, which shows every flat's consumption in one place. Each node uses a PZEM-004T module clamped onto the flat's live wire — the module measures 80–260 V AC and 0–100 A with ±0.5% accuracy — and an ESP32 reads those values over Modbus-RTU and hands them to an SX1278 LoRa radio at 433 MHz. LoRa works here because it spreads each bit across a rising-frequency chirp, letting the receiver decode signals buried below the noise floor, so the link keeps working through concrete floor slabs that stop Wi-Fi. The gateway, an ESP32 with an SX1278 radio, listens for packets tagged with each flat's ID and shows the latest reading per flat on a 16x2 LCD.

The complete path runs from the flat's live wire to the gateway display in six stages: the PZEM-004T measures the flat's electrical quantities, the ESP32 reads them over Modbus-RTU, the node packs them with its flat ID, the SX1278 radio sends the packet over LoRa, the gateway radio receives it, and the gateway ESP32 updates the display and the serial log. Each node works on its own schedule, so the gateway simply listens and updates whichever flat's packet arrives next, and a node that misses one transmission window sends a fresh reading at the next interval. Because the packets are tiny — a few dozen bytes carrying six measured values and an ID — the link stays reliable even at the slow spreading factors that push the signal through concrete floors.

1. The split-core CT clamp is fitted around the flat's live wire only, and the PZEM-004T measures voltage, current, active power, energy, frequency and power factor for that flat.
2. The node ESP32 reads the six values from the PZEM-004T over UART using Modbus-RTU at 9600 baud, polling the module at the configured reading interval.
3. The ESP32 packs the values into a short LoRa packet together with the node's flat ID, so the gateway can attribute every reading to the correct flat.
4. The SX1278 LoRa radio transmits the packet at 433 MHz using chirp spread spectrum, which carries the signal through concrete floors to the gateway in the meter room.
5. The gateway ESP32 receives the packet on its own SX1278 radio, checks the flat ID, and stores the values as that flat's latest reading.
6. The gateway updates its 16x2 LCD to show the flat's voltage, current, power and accumulated energy, and prints the same reading over serial for logging.
7. The cycle repeats at the configured interval, so the gateway display always reflects the most recent reading from each flat in the complex.

Tech stack:

• ESP32 (node and gateway controllers)
• PZEM-004T energy meter module with CT clamp
• Ra-02 LoRa module · Semtech SX1278
• Arduino IDE (ESP32 firmware)
• Modbus-RTU over UART (9600 baud)
• 16x2 LCD display (gateway readout)
• arduino-LoRa library (SX1278 driver)
• 5 V DC power supply (USB adapter per unit)

The three capabilities that define this build are the per-flat measurement, the multi-node LoRa link and the single-point collection. The PZEM-004T at each flat measures voltage, current, active power, energy in kWh, frequency and power factor, so the gateway receives a complete electrical picture rather than a single pulse count. The LoRa link carries those readings from every flat to one gateway without Wi-Fi, broadband or a SIM card, and each packet is tagged with its flat's ID so readings never get mixed up between neighbours. The gateway shows the latest reading for each flat on its LCD and also prints the same data over serial, so the reading can be logged on a laptop during a demonstration or a reading round. A builder note from the demo build: the gateway antenna was moved out of the steel meter cabinet onto the cabinet door, because inside the cabinet packets were lost.

• [Per-flat energy measurement] Each meter node uses a PZEM-004T module with a split-core CT clamp to measure voltage, current, active power, accumulated energy, frequency and power factor for one flat, with ±0.5% accuracy (datasheet value).
• [Multi-node LoRa link] Every node carries an SX1278 LoRa radio at 433 MHz and transmits its reading in a short packet tagged with a unique flat ID, so one gateway can tell Flat 301 apart from Flat 302.
• [Single gateway collection] The gateway unit receives packets from all nodes, keeps the latest reading per flat, and shows flat-wise voltage, current, power and energy on its 16x2 LCD without any visit to the flats.
• [No internet or Wi-Fi needed] The meter-to-gateway link is a direct LoRa radio link, so readings keep flowing in basements and stairwells where Wi-Fi does not reach and no broadband connection is required.
• [Non-invasive CT installation] The split-core CT clamp fits around the flat's live wire without cutting it, so a node can be fitted at an existing meter point without breaking the circuit.
• [Configurable reading interval] The time between transmissions is set in firmware (default 60 seconds) and can be shortened for a fast demonstration or lengthened to reduce radio traffic.
• [Per-flat energy totals] Each node tracks accumulated energy in kWh, so the gateway shows both the current load and the running total that a monthly bill is based on.
• [Serial reading log] The gateway prints every received reading over its serial port, so readings can be captured on a laptop and saved as a record of a reading round.

• Working meter node hardware (per quoted flat count) with PZEM-004T, ESP32 and Ra-02 LoRa module
• Working gateway unit with ESP32, Ra-02 LoRa module and 16x2 LCD display
• Complete firmware source code for node and gateway
• Circuit and wiring documentation, including CT fitting and LoRa antenna placement notes
• Project report PDF (background, methodology, architecture, results, limitations)
• Project abstract PDF
• PPT presentation for final review
• Viva Q&A preparation document (PZEM-004T, Modbus-RTU, LoRa chirp spread spectrum, multi-node addressing)