PZEM004T LCD I2C 20 x 4

Projects General Guidance
1

Hello all

I made a project with a PZEM 004T sensor and a 20 x 4 I2C LCD. When there is input voltage, the lcd can read voltage, current and frequency well, but when the voltage is removed, the lcd does not display the number 0 perfectly, moreover the frequency, the lcd does not write down number 0, but number 50hz. how to make lcd not display last data before no voltage?

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why does the lcd not display the number 0, while the voltage has been removed?

if you want to display the number 0, then the arduino must be reset

I will upload the program, but sorry if it's messy

#include <PZEM004Tv30.h>
#include <SoftwareSerial.h>
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 20, 4);
float V1;
float C2;
float F3;
unsigned long tm = millis();
unsigned long maxtm = 3000 ;

#if !defined(PZEM_RX_PIN) && !defined(PZEM_TX_PIN) //Arduino
#define PZEM_RX_PIN 2 // Pin 2 Rx Arduino ke Pin Tx Pzem
#define PZEM_TX_PIN 3 // Pin 3 Tx Arduino ke Pin Rx Pzem
#endif
#define RELAY_1 4

SoftwareSerial pzemSWSerial(PZEM_RX_PIN, PZEM_TX_PIN);
PZEM004Tv30 pzem(pzemSWSerial);
void setup() {

    Serial.begin(115200);
    pinMode(RELAY_1, OUTPUT); //Relay
    lcd.init();                      // initialize the lcd
    lcd.backlight();
    lcd.setCursor(0,0);
    lcd.print("anjai mabar"); 
    {
    delay(1000);
    lcd.clear();
    }
}

void loop(){
         
    Serial.print("Custom Address:");
    Serial.println(pzem.readAddress(), HEX);
        
    float voltage = pzem.voltage();
    if (!isnan(voltage)){
      V1 = voltage;
      Serial.print("Tegangan");Serial.print(V1);Serial.println("V");
    }else{
      V1 = 0.0;
      Serial.print("Tegangan");Serial.print(V1);Serial.println("V");
    }

    lcd.setCursor(0,1);lcd.print("Tegangan : ");
    lcd.setCursor(10,1);lcd.print(V1);
    lcd.setCursor(17,1);lcd.print("V");
    
    if(V1 < 220)
    {
    digitalWrite(4, LOW);
    lcd.setCursor(0,1);
    }else if (V1 > 221){
    digitalWrite(4, HIGH);
    }

    float current = pzem.current();
    if (!isnan(current)){
      C2 = current;
      Serial.print("Arus");Serial.print(C2);Serial.println("A");
    }else{
      C2 = 0.0;
      Serial.print("Arus");Serial.print(C2);Serial.println("A");
    }

    lcd.setCursor(0,2);lcd.print("Arus     : ");
    lcd.setCursor(10,2);lcd.print(C2);
    lcd.setCursor(17,2);lcd.print("A");

    float frequency = pzem.frequency();
    if (!isnan(frequency)){
      F3 = frequency;
      Serial.print("Frekuensi");Serial.print(F3);Serial.println("Hz");
    }else{
      F3 = 0.0;
      Serial.print("Frekuensi");Serial.print(F3);Serial.println("Hz");
    }

    lcd.setCursor(0,3);lcd.print("Frekuensi: ");
    lcd.setCursor(10,3);lcd.print(F3);
    lcd.setCursor(17,3); lcd.print("Hz");

    Serial.println();
    delay(2000);
}
2

Apparently, this library returns NaN whenever an update failed.

Instead of assuming the result is 0V, perhaps you can use the previous value instead.

3

@fluks, do not cross-post. Vomit cleaned up.

4

That's what You should expect when nothing is connected. Use a pull down resistor to GND. Else the input acts like an antenna picking up any noice in the air.

5

does the pull down resistor require a push button?

6

No. As a first try, use 10 kOhm. Connect the resistor between the input and GND.

7

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