1. #include <RunningStats.h>
2.  
3. #include <Filters.h> //Easy library to do the calculations
4. #include <LiquidCrystal_I2C.h>
5. LiquidCrystal_I2C lcd(0x27, 16, 2);
6. float testFrequency = 50;  // test signal frequency (Hz)
7. int Sensor = 0; //Sensor analog input, here it's A0
8. int relay = 9;  //Define output pin for relay
9. float intercept = 0.7; // To be adjusted based on calibration testing
10. float slope = 0.04; // To be adjusted based on calibration testing
11. float current_Volts; // Voltage
12. unsigned long printPeriod = 1000; //Refresh rate
13. unsigned long previousMillis = 0;
14. void setup()
15. {
16.   lcd.init();
17.   lcd.backlight();
18.   pinMode(relay, OUTPUT);
19.   lcd.print("Voltage:");
20.   delay(1000);
21. }
22. void loop()
23. {
24.   RunningStats stats;                // Easy life lines, actual calculation of the RMS requires a load of coding
25.   while ( true )
26.   {
27.     Sensor = analogRead(A0);  // Read the analog in value:
28.    stats.update(Sensor);  // Log to stats function
29.     if ((unsigned long)(millis() - previousMillis) >= printPeriod)
30.     {
31.       previousMillis = millis();   // Update time every second
32.       current_Volts = intercept + slope * stats.std(); // Calibartions for offset and amplitude
33.       current_Volts = current_Volts * (40.3231);             // Further calibrations for the amplitude
34.       lcd.setCursor(9, 0);
35.       lcd.print(current_Volts);
36.      
37.       lcd.print("V");
38.     }
39.     // Case 1 Under Voltage
40.     if ( (current_Volts > 0)  &&  (current_Volts < 150) )
41.   {
42.     lcd.setCursor(0, 1);
43.     lcd.print("Under Voltage");
44.     digitalWrite(relay, LOW);
45.   }
46.   // Case 2 Normal Rated Voltage
47.   if ( (current_Volts >= 150)  &&  (current_Volts <= 260) )
48.   {
49.     lcd.setCursor(0, 1);
50.     lcd.print("Normal Voltage");
51.     digitalWrite(relay, HIGH);
52.   }
53.   // Case 3 Over Voltage
54.   if ( current_Volts > 260 )
55.   {
56.     lcd.setCursor(0, 1);
57.     lcd.print("Over Voltage");
58.     digitalWrite(relay, LOW);
59.   }
60.   }
61. }