LamaPLC: Eastron SDM 230 with Modbus Communication

The Eastron SDM230 Modbus MID 1-phase kWh meter is ideal for the precise monitoring of, for example, a solar panel system, a charging station, a heat pump, or another 1-phase group of your choice. On the illuminated LCD screen, you can immediately see how many kWh the respective system consumes or produces, and it is used for official registration and billing of the measurement data. For example, if you want to bill a tenant for the electricity consumption of a specific room.

Key Features

• Measurement: Measures various parameters, including active energy (kWh), reactive energy (kVArh), power (kW, kVAr, kVA), voltage, current, frequency, and power factor.
• Bi-directional Energy: Supports bi-directional energy measurement (import and export), making it suitable for solar PV and battery storage applications.
• Direct Connection: Designed for a maximum 100A direct connection, eliminating the need for external current transformers (CTs).
• Display: Features a blue-backlit LCD screen for easy reading of data.
• Communication: Includes two pulse outputs and a communication port (RS485 Modbus or M-Bus, depending on the model) for remote monitoring and integration with building management systems (BMS) or SCADA systems. Some models also offer Wi-Fi or LoRaWAN communication options.
• Certification: Many variants are MID-certified (Class B EN50470-3), making them suitable for billing applications.
• Design: Compact design (two modules wide, 36mm) for DIN rail mounting.

Technical Specifications

According to Eastron Europe and Camax.co.uk, the general specifications are as follows:

The differences between versions of the Eastron SDM230 primarily involve physical wiring updates, communication defaults, and enhanced firmware features relating to energy measurement.

RS485 communication interface, MODBUS RTU protocol:

• Baudrate: 9600 Baud (default, can be set)
• Parity: Even
• Databits: 8
• Stopbits: 1
• Default slave ID: 45
• Number of Drivers and Receivers: 32 Drivers, 32 Receivers (without repeater)
• Maximum Cable Length: 1200 m
• Maximum Data Rate: 10 Mbaud
• Maximum Common Mode Voltage: 12 V .. –7 V
• Minimum Driver Output Levels (Loaded): +/– 1.5 V
• Minimum Driver Output Levels (Unloaded): +/– 6 V
• Drive Load: Minimum 60 ohms
• Driver Output Short Circuit Current Limit: 150 mA to Gnd, 250 mA to 12 V, 250 mA to -7 V
• Minimum Receiver Input Resistance: 12 kΩ
• Receiver Sensitivity: +/- 200 mV

The registers are read-only.
Float conversion: 32-bit float with big-endian

To use the Eastron SDM230 with an Arduino, you need an RS-485-to-TTL converter module and a library such as the SDM_Energy_Meter library by reaper7, since the meter uses Modbus RTU over RS-485 physical lines.

Required Hardware

• Arduino Board: e.g., Uno, Nano, or ESP32.
• RS485 Converter Module: A module based on the MAX485 or similar chip.
• Eastron SDM230: Ensure its Modbus ID (address) and Baud Rate are noted (defaults are typically Address 1 and 2400 bps or 9600 bps; check your model's manual).

Wiring Schematic (MAX485 module)

Arduino Example Code

This example uses the SDM_Energy_Meter library. First, install the library via the Arduino Library Manager.

#include <SoftwareSerial.h>
#include <SDM.h>
 
// Pins for SoftwareSerial communication (RX, TX)
SoftwareSerial sdmSerial(3, 4); 
 
// Pin used to control the DE/RE pins of the MAX485 converter
#define RS485_EN    2 
 
// Create an SDM object (SoftwareSerial instance, Enable Pin, Slave ID)
// Default address is 1 (0x01)
SDM sdm(&sdmSerial, RS485_EN, 0x01); 
 
void setup() {
  Serial.begin(115200);   // Serial monitor output to PC
  sdmSerial.begin(9600);  // SDM230 default baud rate (Check your meter, may be 2400bps)
 
  Serial.println("\nEastron SDM230 Reader Initialized");
}
 
void loop() {
  // Read Voltage (Register 0x0000)
  float voltage = sdm.readVal(SDM_PHASE_1_VOLTAGE);
  if (!isnan(voltage)) {
    Serial.print("Voltage: ");
    Serial.print(voltage);
    Serial.println(" V");
  } else {
    Serial.println("Failed to read Voltage");
  }
 
  // Read Total Power (Register 0x000C)
  float power = sdm.readVal(SDM_PHASE_1_POWER);
  if (!isnan(power)) {
    Serial.print("Power: ");
    Serial.print(power);
    Serial.println(" W");
  } else {
    Serial.println("Failed to read Power");
  }
 
  // Read Total Active Energy (Register 0x0156 or 0x0048 for Import)
  float energy = sdm.readVal(SDM_TOTAL_ACTIVE_ENERGY);
  if (!isnan(energy)) {
    Serial.print("Total Energy: ");
    Serial.print(energy);
    Serial.println(" kWh");
  } else {
    Serial.println("Failed to read Energy");
  }
 
  delay(3000); // Wait 3 seconds before next read
}

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