Hello, here is my problem. I have this university project where I am building a measuring tool, but I am facing accuracy issues.
The problem lies in the different results I get from a serial monitor on an Arduino compared to the results displayed on my device.
1.Measuring Resistance.
I have a 1 kΩ resistor, but the measured value on the breadboard device fluctuates between 950-970 Ω. However, when I use another Arduino and check the value on the Serial Monitor, I get a much more accurate reading—between 997-999 Ω or even 1000 Ω. The tutorial I followed is the same code I used as well.
How to Make an Arduino Ohm Meter
- Measuring Capacitance.
Measure Capacitance With Arduino : 6 Steps (with Pictures) - Instructables
This is the tutorial I followed, but I can't say much more because I am encountering the same issue.
If I use another Arduino, the values shown on the Serial Monitor are accurate. For instance, when measuring a 1 µF capacitor, the reading is correct. However, when I measure it on my device, I sometimes get 2 µF, and other times 3 µF or even 6 µF.
I know that all the cable management is bad, i already switched with another ardruino and i get the same value, i just want to know why i get so different values and what i can do, maybe change something in the code, idk.
And when measuring the capacitance the display freeze, the serial monitor is clear too.
I don't expect everything to go right, i know that at least around these values i need to have some accuracy.
// Programming a button to go back from a while menu thing
// https://forum.arduino.cc/t/programming-a-button-to-go-back-from-a-while-menu-thing/1325404
#include <Adafruit_GFX.h>
#include <Adafruit_ST7789.h>
#include <SPI.h>
#include <BH1750.h>
#include <Wire.h>
BH1750 lightMeter;
#define TFT_CS 10 // Chip select (CS)
#define TFT_RST 8 // Reset pin
#define TFT_DC 9 // Data/Command pin
#define PRESSED LOW // Using Pull-up, the button press connects to the GND
#define RELEASED HIGH
int analogPin = 1;
int chargePin = 12;
int dischargePin = 10; //speeds up discharging process, not necessary though
int resistorValue = 10000;
// Initialize Timer
unsigned long startTime;
unsigned long elapsedTime;
// Initialize Capacitance Variables
float microFarads;
float nanoFarads;
int backButtonPin = 5; // Buton Back (BB)
int upButtonPin = 4; // Buton Up (BU)
int downButtonPin = 3; // Buton Down (BD)
int selectButtonPin = 2; // Buton Select (BS)
enum button_t : uint8_t {NONE, UP, DOWN, SELECT, BACK} button;
uint16_t menuLineNumber[] = {0, 30, 80, 130, 180};
// Ohm metru //
const int sensorPin = A0; // Analog input pin that senses Vout
int sensorValue = 0; // sensorPin default value
float Vin = 5.0; // Input voltage
float Vout = 0.0; // Vout default value
float Rref = 999.0; // Reference resistor's value in ohms
float R = 0.0; // Tested resistor's default value
//Ohm metru //
void (*measurePtr)(void) = NULL;
int menuLine = 1; // Meniul curent, începe de la 1
Adafruit_ST7789 tft = Adafruit_ST7789(TFT_CS, TFT_DC, TFT_RST);
void afisaremeniu() {
tft.fillScreen(ST77XX_BLACK);
tft.setCursor(30, 30);
tft.print("Rezistenta");
tft.setCursor(30, 80);
tft.print("Capacitate");
tft.setCursor(30, 130);
tft.print("Intensitatea Luminoasa");
tft.setCursor(30, 180);
tft.print("Informatii");
}
void afisareLine() {
static uint16_t oldMenuLine = 0;
tft.setTextColor(ST77XX_BLACK);
tft.setCursor(10, menuLineNumber[oldMenuLine]);
tft.print('>');
tft.setTextColor(ST77XX_WHITE);
oldMenuLine = menuLine;
tft.setCursor(10, menuLineNumber[menuLine]);
tft.print('>');
}
void setup() {
pinMode(chargePin, OUTPUT);
digitalWrite(chargePin, LOW);
pinMode( upButtonPin, INPUT_PULLUP); // Setare buton Up ca INPUT_PULLUP
pinMode( downButtonPin, INPUT_PULLUP); // Setare buton Down ca INPUT_PULLUP
pinMode(selectButtonPin, INPUT_PULLUP); // Setare buton Select ca INPUT_PULLUP
pinMode( backButtonPin, INPUT_PULLUP);
Wire.begin();
lightMeter.begin();
tft.init(240, 320); // Initializare ecran 240x320 pixeli
tft.setRotation(1); // Rotire ecran
tft.setTextColor(ST77XX_WHITE); // Text alb
tft.setTextSize(2); // Dimensiune text
afisaremeniu(); // Afi?eaza meniul ini?ial
afisareLine();
Serial.begin(9600);
}
void loop() {
static button_t oldButton = NONE;
Serial.print("UP: ");
Serial.println(digitalRead(upButtonPin));
Serial.print(" | DOWN: ");
Serial.println(digitalRead(downButtonPin));
Serial.print(" | SELECT: ");
Serial.println(digitalRead(selectButtonPin));
Serial.print(" | BACK: ");
Serial.println(digitalRead(backButtonPin));
delay(100);
if (digitalRead( upButtonPin) == RELEASED) { button = UP;}
else if(digitalRead( downButtonPin) == RELEASED) { button = DOWN;}
else if(digitalRead(selectButtonPin) == RELEASED) { button = SELECT;}
else if(digitalRead( backButtonPin) == RELEASED) { button = BACK;}
else { button = NONE;}
if (oldButton != button) {
oldButton = button;
switch (button) {
case UP: // Navigare în meniu folosind butonul Up (BU)
if (menuLine == 1) {
menuLine = 4; // Revin la ultimul meniu daca scade sub 1
}
else {
menuLine--; // Mergem la meniul anterior
}
afisareLine(); // Actualizeaza meniul pe ecran
break;
case DOWN: // Navigare în meniu folosind butonul Down (BD)
if (menuLine == 4) {
menuLine = 1; // Revin la primul meniu daca depa?e?te 3
}
else {
menuLine++; // Trecem la urmatorul meniu
}
afisareLine(); // Actualizeaza meniul pe ecran
break;
case SELECT: // Executa ac?iunea selectata cu butonul Select (BS)
actiune(); // Executa ac?iunea pentru meniul curent
// bs_apasat = true;
break;
case BACK: // Back
measurePtr = NULL;
afisaremeniu();
afisareLine(); // Actualizeaza meniul pe ecran
break;
}
}
if (measurePtr) (*measurePtr)();
delay(100);
}
void actiune() {
switch (menuLine) {
case 1:
tft.fillScreen(ST77XX_BLACK);
tft.setCursor(10, 10);
tft.print("Masurare rezistenta:");
measurePtr = masurareRezistenta;
break;
case 2:
tft.fillScreen(ST77XX_BLACK);
tft.setCursor(10, 30);
tft.print("Masurare Capacitate:");
measurePtr = masurareCapacitate;
break;
case 3:
tft.fillScreen(ST77XX_BLACK);
tft.setCursor(10, 30);
tft.print("Masurare Iluminarii");
measurePtr = masurareLumina;
break;
case 4:
tft.fillScreen(ST77XX_BLACK);
tft.setCursor(10, 30);
tft.print("Testate Meniu 4!");
break;
}
}
void masurareRezistenta() {
Serial.print('.');
// Cite?te valoarea senzorului
sensorValue = analogRead(sensorPin); // Cite?te Vout pe pinul analogic A0
Vout = (Vin * sensorValue) / 1023.0; // Conversie la vol?i
R = Rref * (1 / ((Vin / Vout) - 1));
tft.fillRect(10, 50, 220, 30, ST77XX_BLACK); // Cura?a zona de afi?are
tft.setCursor(10, 50);
if (R > 500000.0) { // Rezisten?a infinita sau foarte mare
tft.print("R: Inf");
}
else if (R > 999.0) { // Conversie la kOhm
tft.print("R: ");
tft.print(R / 1000.0, 2); // 2 zecimale pentru precizie
// tft.print(" kΩ");
tft.print(" kOhm");
}
else { // Rezisten?a în Ohmi
tft.print("R: ");
tft.print(R, 2); // 2 zecimale pentru precizie
// tft.print(" Ω");
tft.print(" Ohm");
}
}
void masurareCapacitate() {
delay(300);
digitalWrite(chargePin, HIGH); // Begins charging the capacitor
startTime = millis(); // Begins the timer
while(analogRead(analogPin) < 648)
{
// Does nothing until capacitor reaches 63.2% of total voltage
}
tft.fillRect(10, 50, 220, 30, ST77XX_BLACK); // Cura?a zona de afi?are
tft.setCursor(10, 50);
elapsedTime= millis() - startTime; // Determines how much time it took to charge capacitor
microFarads = ((float)elapsedTime / resistorValue) * 1000;
Serial.print(elapsedTime);
Serial.print(" mS ");
if (microFarads > 1) // Determines if units should be micro or nano and prints accordingly
{
tft.print((long)microFarads);
tft.print(" microFarads");
Serial.print((long)microFarads);
Serial.println(" microFarads");
}
else
{
nanoFarads = microFarads * 1000.0;
tft.print((long)nanoFarads);
tft.print(" nanoFarads");
Serial.println(" nanoFarads");
delay(500);
}
digitalWrite(chargePin, LOW); // Stops charging capacitor
pinMode(dischargePin, OUTPUT);
digitalWrite(dischargePin, LOW); // Allows capacitor to discharge
while(analogRead(analogPin) > 0)
{
// Do nothing until capacitor is discharged
}
pinMode(dischargePin, INPUT); // Prevents capacitor from discharging
}
void masurareLumina() {
float lux = lightMeter.readLightLevel();
tft.fillRect(10, 50, 220, 30, ST77XX_BLACK); // Cura?a zona de afi?are
tft.setCursor(10, 50);
tft.print(lux);
tft.print(" lx");
delay(1000);
}
