The PZEM-004T is a popular AC energy monitoring module used in IoT, electronics, and smart grid projects. It measures electrical parameters of mains power and sends data to microcontrollers like ESP8266, ESP32, Arduino, and Raspberry Pi through serial communication (TTL / Modbus-RTU depending on version).

Codes
 
#include <PZEM004Tv30.h>
#include <SoftwareSerial.h>
SoftwareSerial pzemSerial(D6, D7);  // RX, TX
PZEM004Tv30 pzem(pzemSerial);
void setup() {
  Serial.begin(115200);
  Serial.println("PZEM004T Test");
}
void loop() {
  float voltage = pzem.voltage();
  float current = pzem.current();
  float power = pzem.power();
  float energy = pzem.energy();
  float freq = pzem.frequency();
  float pf = pzem.pf();
  Serial.print("Voltage: "); Serial.println(voltage);
  Serial.print("Current: "); Serial.println(current);
  Serial.print("Power: "); Serial.println(power);
  Serial.print("Energy: "); Serial.println(energy);
  Serial.print("Frequency: "); Serial.println(freq);
  Serial.print("Power Factor: "); Serial.println(pf);
  Serial.println("--------------------");
  delay(2000);
}