fmarzocca
Published © CC BY-NC

UltraV: A Portable UV-Index Meter

A portable small device to verify anywhere the UV index in the sun rays.

BeginnerFull instructions provided13,205
UltraV: A Portable UV-Index Meter

Things used in this project

Hardware components

Arduino Nano R3
Arduino Nano R3
×1
Texas Instruments ML-8511
×1
128x64 OLED display
×1
MT3608 DC-DC stup-up converter
×1
CR2 (3v) battery
×1
CR2 battery holder
×1

Story

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Code

UltraV

C/C++
Code
    /* 
 Fabio Marzocca @ 2018
 Analog to digital conversions rely completely on VCC. We assume
 this is 5V but if the board is powered from USB this may be as high as 5.25V or as low as 4.75V:
 http://en.wikipedia.org/wiki/USB#Power Because of this unknown window it makes the ADC fairly inaccurate
 in most cases. To fix this, we use the very accurate onboard 3.3V reference (accurate within 1%). So by doing an
 ADC on the 3.3V pin (A1) and then comparing this against the reading from the sensor we can extrapolate
 a true-to-life reading no matter what VIN is (as long as it's above 3.4V).

v. 2.0.0 - July 2018
   - moved from 16x2 LCD to OLED
v. 2.0.1 - Sept 2018
   - changed read battery function
*/

#include <Arduino.h>
#include <U8g2lib.h>
#include <Wire.h>

U8G2_SSD1306_128X64_NONAME_F_SW_I2C u8g2(U8G2_R0, /* clock=*/ SCL, /* data=*/ SDA, /* reset=*/ U8X8_PIN_NONE);   // All Boards without Reset of the Display

#define FIRST_ROW_Y 16
#define FIRST_ROW_X 16
#define BOX_H 38

//Hardware pin definitions
const int UVOUT = A0; //Output from the sensor
const int REF_3V3 = A1; //3.3V power on the Arduino board
const int VBATT = A2; //Battery voltage

float maxUV = 0; //Max UV index read


void setup()
{ 
  pinMode(UVOUT, INPUT);
  pinMode(REF_3V3, INPUT);
  pinMode(VBATT, INPUT);
 
  u8g2.begin();

}

void loop()
{
  u8g2.firstPage();
  do {
    int uvLevel = averageAnalogRead(UVOUT);
    int refLevel = averageAnalogRead(REF_3V3);

    //Use the 3.3V power pin as a reference to get a very accurate output value from sensor
    float outputVoltage = 3.3 / refLevel * uvLevel;

    float uvIntensity = mapfloat(outputVoltage, 0.99, 2.6, 0.0, 15.0); //Convert the voltage to a UV intensity level

    readBattery();
    if (maxUV < uvIntensity) {
        maxUV = uvIntensity;
      }
    u8g2.drawFrame(0,FIRST_ROW_Y+1,128,BOX_H);
    u8g2.setFont(u8g2_font_logisoso18_tf);

    //Instant UV
    u8g2.setCursor(10,40);
    u8g2.print(uvIntensity);
    //UV Max
    u8g2.setCursor(70,40);
    u8g2.print(maxUV);

    u8g2.setFont(u8g2_font_u8glib_4_tf);
    u8g2.setCursor(10,52); u8g2.print(F("INSTANT"));
    u8g2.setCursor(75,52); u8g2.print(F("MAXIMUM"));

    showUVCategory();
    u8g2.setCursor(88,64); u8g2.print(F("F.Marzocca"));
    
   } while ( u8g2.nextPage() );
  delay(200);
}

// Reads maxUV and prints the UV category
void showUVCategory() {
  char strCat[12];

  byte categ = (byte)(maxUV+0.5);  //round up
  if ((categ >= 0) && (categ < 3)) {
    strcpy(strCat, "LOW"); 
  } else if ((categ >= 3) && (categ < 6)) {
    strcpy(strCat, "MODERATE");
  } else if ((categ >= 6) && (categ < 8)) {
    strcpy(strCat, "HIGH !");
  } else if ((categ >= 8) && (categ < 10)) {
     strcpy(strCat, "VERY HIGH!");
  } else if (categ >= 11) {
    strcpy(strCat, "EXTREME!");
  }
  
   u8g2.setCursor(0,64);
   u8g2.print(strCat);
  
}

//Takes an average of readings on a given pin
//Returns the average
int averageAnalogRead(int pinToRead)
{
  byte numberOfReadings = 16;
  unsigned int runningValue = 0; 

  for(int x = 0 ; x < numberOfReadings ; x++)
    runningValue += analogRead(pinToRead);
  runningValue /= numberOfReadings;

  return(runningValue);  
}

//The Arduino Map function but for floats
//From: http://forum.arduino.cc/index.php?topic=3922.0
float mapfloat(float x, float in_min, float in_max, float out_min, float out_max)
{
  return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}

void readBattery() {
   long battery = readBattVcc(); 
   long VccMin = 2300; //Battery minimum voltage read on Vcc
   byte batteryBar; //Battery progress bar
   int barStep = 140; //step for battery progress bar (235)

   batteryBar = (battery - VccMin)/barStep;
   
       //battery icon
    u8g2.setFont(u8g2_font_open_iconic_embedded_2x_t);
    u8g2.drawGlyph(1, FIRST_ROW_Y, 73 );
    
    // battery status cursor
    u8g2.setFont(u8g2_font_open_iconic_play_1x_t);
    for (byte i=1; i<=batteryBar; i++) {
       u8g2.drawGlyph( 128-9*i,FIRST_ROW_Y-4,75);
    }
    
    // battery voltage
    u8g2.setFont(u8g2_font_freedoomr10_tu);
    u8g2.setCursor(25, FIRST_ROW_Y);
    u8g2.print(float(battery)/1000, 3);
 
}


long readBattVcc()
{
    int sum=0;
    int sample_count=0;
    long voltage= 0;
    #define NUM_SAMPLES 10
    // take a number of analog samples and add them up
    while (sample_count < NUM_SAMPLES) {
        sum += analogRead(VBATT);
        sample_count++;
        delay(2);
    }
        // calculate the voltage
    // use 5000 for a 5.0V ADC reference voltage
    // 5020V is the calibrated reference voltage (in millivolts) for my project
    voltage = ((long)sum / (long)NUM_SAMPLES * 5020) / 1024.0;
    return voltage; //Vbattery in millivolts
}

Credits

fmarzocca

fmarzocca

3 projects • 13 followers

Comments

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