This Arduino based voltmeter is handy for use on the workbench.? It can be built
as a zero-to-5V version, or as a zero-to-50V version.? This is free code, feel free to
modify it to suit your own needs.
----------- Start code -------------
/*
?* Differential Voltmeter
?*
?* by:? Arv? K7HKL
?*????? 16 September 2018
?*?????
?* Measures ADC-0 as A volts and ADC-1 as B volts.? Then computes difference and
?* shows A and B measurements, and A-B difference.
?* Output to both 2X16 LCD and to attached ttl/USB dumb terminal is non-blocking It will
?* work with or without the dumb terminal connected.
?* Arduino can be a Pro-Mini to avoid possible 20 MHz interference from USB-TTL circuit.
?*
?This sketch was adapted from LCD sketch "Hello World!"
? The circuit:
?* LCD VSS pin-1 to ground? [Ground for LCD]
?* LCD VCC pin-2 to 5V????? [5V for LCD]
?* LCD RS pin to digital pin 2? [Register Select]
?* LCD EN pin to digital pin 3? [ENable]
?* LCD D4 pin to digital pin 4? [Data-4]
?* LCD D5 pin to digital pin 5? [Data-5]
?* LCD D6 pin to digital pin 6? [Data-6]
?* LCD D7 pin to digital pin 7? [Data-7]
?* LCD R/W pin-4 to ground
?* LCD VC pin-3 to ground?? // on newer backlighted LCD the Conterast pot is not needed.
?* LCD LED+ pin-15 to +5V?? // Backlight, use 220 to 1K in series for brightness limiting
?* LCD LED- pin-16 to ground [ Ground for Backlight]
?Library originally added 18 Apr 2008
?by David A. Mellis
?library modified 5 Jul 2009
?by Limor Fried ()
?example added 9 Jul 2009
?by Tom Igoe
?modified 22 Nov 2010
?by Tom Igoe
?modified 7 Nov 2016
?by Arturo Guadalupi
?-----------------------------------------------------------------
??? Libraries are wonderful...everybody modifies them and doesn't
??? tell anybody what the changes are.?
?-----------------------------------------------------------------
?This example code is in the public domain.
?
*/
// include the library code:
#include <LiquidCrystal.h>
// initialize the library by associating any needed LCD interface pin
// with the arduino pin number it is connected to
const int rs = 2, en = 3, d4 = 4, d5 = 5, d6 = 6, d7 = 7;
LiquidCrystal lcd(rs, en, d4, d5, d6, d7);
float a;??? // ADC-0 input (0-1023)
float b;??? // ADC-1 input (0-1023)
float A;??? // a * (5/1023) Volts
float B;??? // b * (5/1023) Volts
float dif;? // dif = A-B
void setup() {
? // set up the LCD's number of columns and rows:
? lcd.begin(16, 2);
? // Print a message to the LCD.
? lcd.println("Differential");
? lcd.print(" Voltmeter");
? delay(2000);? // 2 second delay
? Serial.begin(115200); // serial port baud rate
? Serial.println("Differential Voltmeter");
? Serial.println("A????????? B??????? A-B");
}
void loop() {
? // set the cursor to column 0, line 1
? // (note: LCD line 1 is the second row, since counting begins with 0):
? lcd.setCursor(0, 1);
? a = analogRead(0);
? a = analogRead(1);? // read ADC-0 twice to normalize sampling capacitor
? A = a * (5 / 1023.0);?? // converts ADC-0 out to volts
??????????????? delay(3000);
? b = analogRead(1);
? b = analogRead(1);? // read ADC-1 twice to normalize sampling capacitor
? B = b * (5/1023.0);?? // converts ADC-1 out to volts
? // A = A * 10;? B = B * 10;? // Use this line for zero-50V version
? dif = A - B;
? lcd.print("A= "); lcd.print(A);
? lcd.print("?? B="); lcd.println(B);
? lcd.print("dif=");
? if (A > B) {
??? lcd.println("A>B");
? }
? else? {
??? lcd.println("B>A");
? }
? dif = A - B;
? Serial.println("\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n"); // fake screen clear
? Serial.println("? A??????? B???????? A-B");
? Serial.print(A); Serial.print("????? ");
? Serial.print(B); Serial.print("????? ");
? Serial.println(dif);
}
/*? USER MANUAL
?*?? Use Arduino Nano or Arduino Pro-Mini.? Connect 1602 style LCD as shown in code.
?*??
?*?? Voltmeter range is zero-to-5V.? For zero-to-50 volt range add 100K and 10K
?*?? divider resistors on ADC-0 and ADC-1 inputs, and uncomment line 87.
?*?? "? // A = A * 10;? B = B * 10;? // Use this line for zero-50V version"
?*??
?*?? Set PC dumb terminal baud rate to 115200, or change line 71 to match your dumb
?*?? terminal rate.
?*??
?*/
---------- end code ----------
Arv? K7HKL
_._
