Theory & Background

The ATM90E36A performs all 3-phase metering calculations in hardware. Connect 3 CT secondary outputs and 3 VT secondary outputs to designated analog inputs. Configure via SPI registers: set measurement mode (3P4W, 3P3W), calibration constants for CT/VT ratios, phase angle correction for CT accuracy. Read energy registers: APENERGY (accumulated kWh) via SPI every second. Pulse output can drive a standard LED pulse output (1000 imp/kWh typically).

Components & Requirements

10 components required for this project.

#	Component	Purpose	Qty
1	ATM90E36A Metering IC	3-phase energy metering with CT/VT inputs	x1
2	STM32F103 Microcontroller	Meter intelligence and communication	x1
3	SIM800L GSM Module	Remote data transmission and SMS billing	x1
4	Current Transformers (100:5A)	3-phase current measurement	x3
5	Voltage Transformers (230V:5V)	3-phase voltage measurement	x3
6	MFRC522 RFID Reader	Prepaid top-up card reader	x1
7	Optocoupler (PC817)	Input isolation for tamper detection	x6
8	LCD 3.5" TFT Display	Meter display and menu interface	x1
9	Tamper Detection Switches (magnetic)	Detecting cover and terminal tampering	x3
10	Sealed Lead connector + meter housing	Weatherproof IEC-compliant housing	x1

Step-by-Step Implementation

Follow these 3 steps carefully.

1

ATM90E36A Configuration

The ATM90E36A performs all 3-phase metering calculations in hardware. Connect 3 CT secondary outputs and 3 VT secondary outputs to designated analog inputs. Configure via SPI registers: set measurement mode (3P4W, 3P3W), calibration constants for CT/VT ratios, phase angle correction for CT accuracy. Read energy registers: APENERGY (accumulated kWh) via SPI every second. Pulse output can drive a standard LED pulse output (1000 imp/kWh typically).

2

Tamper Detection Implementation

Monitor for common electricity theft attempts: missing neutral (sum of 3-phase currents ≠ 0 by > 5A), terminal cover opening (magnetic switch), meter cover opening (microswitch), reverse current flow (tampered installation), strong magnetic field (meter slowing magnet placed near CT), and bypass detection (current detected in bypass wire via additional CT). Log all tamper events with timestamp and GPS location. Immediately alert utility server via GSM.

3

Prepaid Metering with RFID

Implement a prepaid system: utility loads credit (kWh units) onto RFID cards. Customer taps card on meter's RFID reader. Meter validates card's cryptographic signature, reads kWh credit, adds to balance. As energy is consumed, balance decrements. At 5 kWh remaining: warning beep and SMS alert. At 0 kWh: disconnect load relay and lock until card top-up. This eliminates meter-reading visits and reduces unpaid bill risk for utilities.

Code & Implementation

Core code for smart_meter.cpp:

smart_meter.cpp
  C/C++

// ATM90E36A SPI communication #include <SPI.h> #define ATM_CS 10  uint16_t atm_read(uint16_t reg) {   SPI.beginTransaction(SPISettings(1000000, MSBFIRST, SPI_MODE3));   digitalWrite(ATM_CS, LOW);   SPI.transfer16(reg | 0x8000);    uint16_t val = SPI.transfer16(0);   digitalWrite(ATM_CS, HIGH);   SPI.endTransaction();   return val; }  float getVoltage(int phase) {   uint16_t raw = atm_read(0x00 + phase);    return raw * 0.01;  }  float getCurrent(int phase) {   uint16_t raw = atm_read(0x10 + phase);    return raw * 0.001;  }  float getTotalEnergy() {   uint32_t hi = atm_read(0xA0) << 16 | atm_read(0xA1);    return hi * 0.0001;  }

Testing & Troubleshooting

Test Smart Meter with IoT Integration by verifying each subsystem individually before full integration.

!

Troubleshooting Tips

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

Real-World Applications

*Utility AMI (Advanced Metering Infrastructure) rollout

*Industrial sub-metering for energy auditing

*Campus energy monitoring system

*Prepaid energy metering for commercial tenants

*Net metering for solar prosumers

*Demand response program monitoring

*EV charging station metering

*Building energy management

Extensions & Next Steps

Add time-of-use (ToU) tariff implementation with peak/off-peak rates
Implement power quality monitoring with harmonics analysis
Build a mesh network of meters for neighborhood energy sharing
Add demand forecasting for utility planning support
Integrate with blockchain for peer-to-peer energy trading

Interactive Playground

Coming Soon

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

Frequently Asked Questions

What communication protocols do smart meters use?

Smart meters use multiple protocols depending on the network layer: DLMS/COSEM (Device Language Message Specification / Companion Specification for Energy Metering) for application-layer standardization, ensuring interoperability between meters and head-end systems. Physical/network layers: PLC (Power Line Communication) for wired networks using existing power cables, RF mesh (ZigBee, LoRa) for wireless AMI networks, GPRS/4G for direct cellular connection, and NB-IoT for low-power wide-area applications.

Introduction