Built-in project · Arduino Uno R3

PZEM-004T energy monitor on an Arduino Uno

A PZEM-004T v3.0 AC energy meter on Modbus: the Uno prints the voltage, current, power, kWh, frequency and power factor. Drag the mains sliders on the meter. The whole build, an Arduino Uno and 1 more part, runs here in your browser on the firmware below; open it in the editor to change the wiring or the code and run it again.

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The parts retail for about $34. On Mokxi they're free.

PZEM-004T energy monitor · Arduino Uno R3live0.000 s 0.00x

Click to open it in the editor

The circuit itself, running here on the simulator. Press what can be pressed; click anything else to open it in the editor.

The code

The firmware exactly as the editor opens it. Change a line there and press Run: it compiles in the browser.

sketch.ino · Arduino Uno R3

// PZEM-004T energy monitor.
//
// The PZEM-004T v3.0 talks Modbus-RTU at 9600 baud. Its TX goes into pin 2
// and its RX comes from pin 3, through SoftwareSerial, and the PZEM004Tv30
// library does the Modbus: every reading below is one register of the meter.
//
// The meter's mains side is set on the part's sliders here. On the bench it
// is wired to live mains, which can kill: only a qualified person should
// connect one.

#include <PZEM004Tv30.h>
#include <SoftwareSerial.h>

SoftwareSerial pzemSerial(2, 3);  // RX (the meter's TX), TX (the meter's RX)
PZEM004Tv30 pzem(pzemSerial);

void setup() {
  Serial.begin(115200);
  Serial.println("PZEM-004T energy monitor");
  // The library skips any read in the first 200 ms after reset (it returns
  // 0), so give it that long before the first one.
  delay(250);
  Serial.print("Meter address: 0x");
  Serial.println(pzem.readAddress(), HEX);
}

void loop() {
  float voltage = pzem.voltage();
  float current = pzem.current();
  float power = pzem.power();
  float energy = pzem.energy();
  float frequency = pzem.frequency();
  float pf = pzem.pf();

  if (isnan(voltage) || isnan(current) || isnan(power) || isnan(energy) || isnan(frequency) || isnan(pf)) {
    Serial.println("Error reading the meter: is it on the mains?");
  } else {
    Serial.print("Voltage: ");   Serial.print(voltage);      Serial.println(" V");
    Serial.print("Current: ");   Serial.print(current);      Serial.println(" A");
    Serial.print("Power: ");     Serial.print(power);        Serial.println(" W");
    Serial.print("Energy: ");    Serial.print(energy, 3);    Serial.println(" kWh");
    Serial.print("Frequency: "); Serial.print(frequency, 1); Serial.println(" Hz");
    Serial.print("PF: ");        Serial.println(pf);
  }
  Serial.println();
  delay(2000);
}