Published October 2, 2021 © GPL3+

DIY Zambretti Weather Forecaster on VFD Display

Weather forecaster, which displays the weather forecast on the screen in the form of descriptive text.

BeginnerFull instructions provided2,248

DIY Zambretti Weather Forecaster on VFD Display

Things used in this project

Hardware components

Arduino Nano R3

VFD Display with 20x2 characters

MyOctopus i2c Barometric Air Pressure Sensor BMP280

Maxim Integrated DS3231M - ±5ppm, I2C Real-Time Clock

Software apps and online services

Arduino IDE

Hand tools and fabrication machines

Soldering iron (generic)

Solder Wire, Lead Free

Story

In one of my previous videos, I described how to make a cheap Advanced Barometer, used by sailors, yachtsmen, etc. It is a great weather forecasting device but still requires some knowledge in the field of meteorology.

This time I will show you how to make a Zambreti weather forecaster, which displays the weather forecast on the screen in the form of descriptive text. It contains a total of 26 reports that describe in detail the weather forecast.

The original Zambretti Forecaster was developed in 1915 by precision instrument makers Negretti and Zambra. It was a hand-held disc calculator, that provided on-demand short-term forecasts of up to 12 hours. It consists of 3 plastic discs of descending radius, arranged concentrically and secured together by means of a rivet. The large outside disc A has a short scale calibrated in wind direction, the middle disc B, has an index to be aligned appropriately with the wind direction scale on A, and itself carries a scale calibrated in units of barometric pressure (inches of mercury or millibars). The inner disc C has an index settable to the atmospheric pressure on B and three windows which allow the selection of a reading based upon of the rising or falling of the barometer in Winter or Summer. Through the appropriate window, an alphabetic letter is visible ( printed on disc A) and this letter is the key to the forecast which can be read off on the obverse side of the instrument. It is reported that the forecasts are most accurate when generated at 9.00 am local time. The calculator uses the mean sea level pressure (MSLP) and pressure trend (steady, rising or falling) as the primary input. The season (Summer or Winter) and the wind play a minor role in determining the forecast.

This device was an electronic version of this calculator that automatically generates reports on the display. It is very simple to make and consists of several components:

- Arduino Nano microcontroller

- 20x2 VFD display from old POS Terminal

- DS3231 Real time clock module

- and BME or BMP280 sensor board

Also in one of my previous videos I showed you how to control an unknown VFD display via a tx-rx connection with Arduino (https://www.youtube.com/watch?v=FZi8vyAs57w&t=83s).

DS3231 Realtime clock module serves only to determine the season (winter or summer). Of course with very small changes in the code this device can be made with a 16x2 LCD display which is much easier to control. As a basis, I used Fandonov's code for an e-paper weather station (https://github.com/fandonov/weatherstation/)

Immediately after switching on, a short time report and the current value of the Relative Atmospheric Pressure appear on the screen. This weather report is based on momentary pressure and is not realistic. The first realistic weather report appears after one hundred minutes and is updated every 10 minutes. The current Relative Atmospheric Pressure is displayed in the lower right corner and is updated every minute. There are a total of 26 weather forecasts that describe in detail what the weather will be like in the next 12 hours:

1. Settled Fine

2. Fine Weather

3. Becoming Fine

4. Fine Becoming Less Settled

5. Fine, Possibly showers

6. Fairly Fine, Improving

7. Fairly Fine, Possibly showers, early

8. Fairly Fine Showery Later

9. Showery Early, Improving

10. Changeable Mending

11. Fairly Fine, Showers likely

12. Rather Unsettled Clearing Later

13. Unsettled, Probably Improving

14. Showery Bright Intervals

15. Showery Becoming more unsettled

16. Changeable some rain

17. Unsettled, short fine Intervals

18. Unsettled, Rain later

19. Unsettled, rain at times

20. Very Unsettled, Finer at times

21. Rain at times, worse later.

22. Rain at times, becoming very unsettled

23. Rain at Frequent Intervals

24. Very Unsettled, Rain

25. Stormy, possibly improving

26. Stormy, much rain

I should also mention that the code should include the altitude of the place where the device is located, in the row:

int altitude = 723; // Here you should put the REAL altitude

Also in the upper left corner, there is a sign that shows us the trend of atmospheric pressure (raising, steady, or falling).

Finally, the device is built into a suitable box made of PVC board coated with self-adhesive colored wallpaper.

Code

Arduino Code

#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BMP280.h>

#include "RTClib.h"

#define SEALEVELPRESSURE_HPA (1013.25)

RTC_DS3231 rtc;   // initialise the RTC DS3231
Adafruit_BMP280 BMP;  // initialise the BMP280 sensor

unsigned long delayTime;  // refresh rate for the readings
int t_hour = 0;
int t_minute = 0;
//int t_second =0;

int pressureArray[10] = {0};  // here we store the pressure readings 
byte counter = 0;
byte delta_time = 0;
int Z = 0;

char tStr[21];
char pStr[22];
char hStr[20];
char pseaStr[26];
char timeStr[6];
char dateStr[12];
char zambretti[10] = "N/A";
char pressureHistory[57];
char pressureHistory2[57];

int temperature;
int humidity;
int pressure;
int altitude = 724;   // Here you should put the REAL altitude of the iGnome


void setup() {
  bool status;
  Serial.begin(4800);   // default settings
  
  Serial.print(" Zambretti Weather      forecaster      ");
  delay(5000);
  if (! rtc.begin()) {
    Serial.write("Couldn't find RTC");
    while (1);
  }

  if (rtc.lostPower()) {
    Serial.write("RTC lost power, lets set the time!");
    // following line sets the RTC to the date & time this sketch was compiled
    rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));

  }
  status = BMP.begin(0x76);
  if (!status) {
    while (1);
  }
  delayTime = 20000;

}


void loop() {

  temperature = (int)BMP.readTemperature();
 // humidity = (int)BMP.readHumidity();
  pressure = (int)(BMP.readPressure() / 100.0F);

  // Let's see the reading that will determine the forecast

 // Serial.print("Measured altitude ");
 // Serial.write((int)BMP.readAltitude(SEALEVELPRESSURE_HPA));

  int seapressure = station2sealevel(pressure, altitude, temperature);

 
 
  DateTime now = rtc.now();
  int t_hour2 = now.hour();
  int t_minute2 = now.minute();
 // int t_second2 = now.second();

  if (t_hour2 != t_hour or t_minute2 != t_minute) {
    delta_time++;
    if (delta_time > 10) {    // every minute we increment delta_time, then every 10 minutes
      delta_time = 0;         // we store the value in the array 

      if (counter == 10)  // if we read 10 values and filled up the array, we shift the array content
      {
        for (int i = 0; i < 9; i++) {   // we shift the array one position to the left
          pressureArray[i] = pressureArray[i + 1];
        }
        pressureArray[counter - 1] = seapressure;
      }
      else {        // this code fills up the pressure array value by value until is filled up
        pressureArray[counter] = seapressure;
        counter++;
      }
    }

    Z = calc_zambretti((pressureArray[9] + pressureArray[8] + pressureArray[7]) / 3, (pressureArray[0] + pressureArray[1] + pressureArray[2]) / 3, now.month());

// From here is just for debug purposes on the serial monitor
/*
    sprintf(zambretti, "Z=%d", Z);
    sprintf(tStr, "%d C", temperature);
    sprintf(hStr, "%d %%", humidity);
    sprintf(pStr, "%d hPa", pressure);
    sprintf(pseaStr, "%d hPa", seapressure);
    sprintf(dateStr, "%02d.%02d.%d", now.day(), now.month(), now.year());
    sprintf(timeStr, "%02d:%02d", now.hour(), now.minute());
    sprintf(pressureHistory, "%d,%d,%d,%d,%d,%d,%d,%d,%d,%d,", pressureArray[0], pressureArray[1], pressureArray[2],
            pressureArray[3], pressureArray[4], pressureArray[5], pressureArray[6], pressureArray[7], pressureArray[8], pressureArray[9]);

    Serial.write(zambretti);
    Serial.write(tStr);
    Serial.write(hStr);
    Serial.write(pStr);
    Serial.write(pseaStr);
    Serial.write(dateStr);
    Serial.write(timeStr);
    Serial.write(pressureHistory);
    Serial.write(pressureHistory2);
*/
// END of testing purposes

    if (pressureArray[9] > 0 and pressureArray[0] > 0) {
      if (pressureArray[9] + pressureArray[8] + pressureArray[7] - pressureArray[0] - pressureArray[1] - pressureArray[2] >= 3) {
        //RAISING
        Serial.print("[>] ");
     if (Z<2){
          Serial.write("Settled Fine                    ");
        }
        else if (Z>1 and Z<=2){
          Serial.write("Fine Weather                    ");
           }
        else if (Z>2 and Z<=3){
          Serial.write("Becoming Fine                   ");
        }
        else if (Z>3 and Z<=4){
          Serial.write("Fine Becoming   Less Settled    ");
          }
        else if (Z>4 and Z<=5){
          Serial.write("Fine  Possibly   Showers        ");
           }
        else if (Z>5 and Z<=6){
          Serial.write("Fairly Fine     Improving       ");
            }
        else if (Z>6 and Z<=7){
          Serial.write("Fairly Fine Pos.Showers, early  ");
           }
        else if (Z>7 and Z<=8){
          Serial.write("Fairly Fine     Showery Later   ");
           }
        else if (Z>8 and Z<=9){
          Serial.write("Showery Early   Improving       ");
           }
        else if (Z>9 and Z<=10){
          Serial.write("Changeable      Mending         ");
            }
        else if (Z>10 and Z<=11){
          Serial.write("Fairly Fine     Showers likely  ");
          }
        else if (Z>11 and Z<=12){
          Serial.write("Rather UnsettledClearing Later  ");
          }
        else if (Z>12 and Z<=13){
          Serial.write("Unsettled Prob. Improving       ");
          }
        else if (Z>13 and Z<=14){
          Serial.write("Showery Bright  Intervals       ");
          }
        else if (Z>14 and Z<=15){
          Serial.write("Showery BecomingMore Unsettled  ");
           }
        else if (Z>15 and Z<=16){
          Serial.write("Changeable      Some Rain       ");
          }
        else if (Z>16 and Z<=17){
          Serial.write("Unsettled Short Fine Intervals  ");
        }
        else if (Z>17 and Z<=18){
          Serial.write("Unsettled       Rain later      ");
          }
        else if (Z>18 and Z<=19){
          Serial.write("Unsettled       Rain at time    ");
          }
        else if (Z>19 and Z<=20){
          Serial.write("Very Unsettled  Finer at time   ");
          }
        else if (Z>20 and Z<=21){
          Serial.write("Rain at times   Worse later     ");
          }
        else if (Z>21 and Z<=22){
          Serial.write("Rain at times   Bec. Very Uns.  ");
          }
        else if (Z>22 and Z<=23){
          Serial.write("Rain at Frequent Intervals      ");
          }
        else if (Z>23 and Z<=24){
          Serial.write("Very Unsettled  Rain            ");
          }
        else if (Z>24 and Z<=25){
          Serial.write("Stormy possibly Improving       ");
          }
        else if (Z>25 and Z<=26){
          Serial.write("Stormy     Much Rain            ");
         
          }
      }

        else if (pressureArray[0]+pressureArray[1]+pressureArray[2]-pressureArray[9]-pressureArray[8]-pressureArray[7]>=3){
      //FALLING
        Serial.print("[<] ");
     if (Z<2){
          Serial.write("Settled Fine                    ");
        }
        else if (Z>1 and Z<=2){
          Serial.write("Fine Weather                    ");
           }
        else if (Z>2 and Z<=3){
          Serial.write("Becoming Fine                   ");
        }
        else if (Z>3 and Z<=4){
          Serial.write("Fine Becoming   Less Settled    ");
          }
        else if (Z>4 and Z<=5){
          Serial.write("Fine  Possibly   Showers        ");
           }
        else if (Z>5 and Z<=6){
          Serial.write("Fairly Fine     Improving       ");
            }
        else if (Z>6 and Z<=7){
          Serial.write("Fairly Fine Pos.Showers, early  ");
           }
        else if (Z>7 and Z<=8){
          Serial.write("Fairly Fine     Showery Later   ");
           }
        else if (Z>8 and Z<=9){
          Serial.write("Showery Early   Improving       ");
           }
        else if (Z>9 and Z<=10){
          Serial.write("Changeable      Mending         ");
            }
        else if (Z>10 and Z<=11){
          Serial.write("Fairly Fine     Showers likely  ");
          }
        else if (Z>11 and Z<=12){
          Serial.write("Rather UnsettledClearing Later  ");
          }
        else if (Z>12 and Z<=13){
          Serial.write("Unsettled Prob. Improving       ");
          }
        else if (Z>13 and Z<=14){
          Serial.write("Showery Bright  Intervals       ");
          }
        else if (Z>14 and Z<=15){
          Serial.write("Showery BecomingMore Unsettled  ");
           }
        else if (Z>15 and Z<=16){
          Serial.write("Changeable      Some Rain       ");
          }
        else if (Z>16 and Z<=17){
          Serial.write("Unsettled Short Fine Intervals  ");
        }
        else if (Z>17 and Z<=18){
          Serial.write("Unsettled       Rain later      ");
          }
        else if (Z>18 and Z<=19){
          Serial.write("Unsettled       Rain at time    ");
          }
        else if (Z>19 and Z<=20){
          Serial.write("Very Unsettled  Finer at time   ");
          }
        else if (Z>20 and Z<=21){
          Serial.write("Rain at times   Worse later     ");
          }
        else if (Z>21 and Z<=22){
          Serial.write("Rain at times   Bec. Very Uns.  ");
          }
        else if (Z>22 and Z<=23){
          Serial.write("Rain at Frequent Intervals      ");
          }
        else if (Z>23 and Z<=24){
          Serial.write("Very Unsettled  Rain            ");
          }
        else if (Z>24 and Z<=25){
          Serial.write("Stormy possibly Improving       ");
          }
        else if (Z>25 and Z<=26){
          Serial.write("Stormy     Much Rain            ");
        }
      }
      else{
       //STEADY
          Serial.print("[=] ");
   
     if (Z<2){
          Serial.write("Settled Fine                    ");
        }
        else if (Z>1 and Z<=2){
          Serial.write("Fine Weather                    ");
           }
        else if (Z>2 and Z<=3){
          Serial.write("Becoming Fine                   ");
        }
        else if (Z>3 and Z<=4){
          Serial.write("Fine Becoming   Less Settled    ");
          }
        else if (Z>4 and Z<=5){
          Serial.write("Fine  Possibly   Showers        ");
           }
        else if (Z>5 and Z<=6){
          Serial.write("Fairly Fine     Improving       ");
            }
        else if (Z>6 and Z<=7){
          Serial.write("Fairly Fine Pos.Showers, early  ");
           }
        else if (Z>7 and Z<=8){
          Serial.write("Fairly Fine     Showery Later   ");
           }
        else if (Z>8 and Z<=9){
          Serial.write("Showery Early   Improving       ");
           }
        else if (Z>9 and Z<=10){
          Serial.write("Changeable      Mending         ");
            }
        else if (Z>10 and Z<=11){
          Serial.write("Fairly Fine     Showers likely  ");
          }
        else if (Z>11 and Z<=12){
          Serial.write("Rather UnsettledClearing Later  ");
          }
        else if (Z>12 and Z<=13){
          Serial.write("Unsettled Prob. Improving       ");
          }
        else if (Z>13 and Z<=14){
          Serial.write("Showery Bright  Intervals       ");
          }
        else if (Z>14 and Z<=15){
          Serial.write("Showery BecomingMore Unsettled  ");
           }
        else if (Z>15 and Z<=16){
          Serial.write("Changeable      Some Rain       ");
          }
        else if (Z>16 and Z<=17){
          Serial.write("Unsettled Short Fine Intervals  ");
        }
        else if (Z>17 and Z<=18){
          Serial.write("Unsettled       Rain later      ");
          }
        else if (Z>18 and Z<=19){
          Serial.write("Unsettled       Rain at time    ");
          }
        else if (Z>19 and Z<=20){
          Serial.write("Very Unsettled  Finer at time   ");
          }
        else if (Z>20 and Z<=21){
          Serial.write("Rain at times   Worse later     ");
          }
        else if (Z>21 and Z<=22){
          Serial.write("Rain at times   Bec. Very Uns.  ");
          }
        else if (Z>22 and Z<=23){
          Serial.write("Rain at Frequent Intervals      ");
          }
        else if (Z>23 and Z<=24){
          Serial.write("Very Unsettled  Rain            ");
          }
        else if (Z>24 and Z<=25){
          Serial.write("Stormy possibly Improving       ");
          }
        else if (Z>25 and Z<=26){
          Serial.write("Stormy     Much Rain            ");
        }
      }
    }
    else {
      if (seapressure < 1005) {
        Serial.write("    Rainy                           ");
       
      }
      else if (seapressure >= 1005 and seapressure <= 1015) {
        Serial.write("    Cloudy                          ");
       
      }
      else if (seapressure > 1015 and seapressure < 1025) {
        //Serial.write("[=] ");
        Serial.write("    Sunny Cloudy                    ");
       
      }
      else {
        Serial.write("    Sunny                           ");
      
      }
     
    }

if (seapressure <=999)
{
  Serial.print("*");
  Serial.print(seapressure);
  delay(2000);
}
    else {
      Serial.print(seapressure);
      delay(2000);
    }

    t_hour = t_hour2;
    t_minute = t_minute2;
   // t_second = t_second2;
 

  }

}


int calc_zambretti(int curr_pressure, int prev_pressure, int mon) {
  if (curr_pressure < prev_pressure) {
    //FALLING
    if (mon >= 4 and mon <= 9)
      //summer
    {
      if (curr_pressure >= 1030)
        return 2;
      else if (curr_pressure >= 1020 and curr_pressure < 1030)
        return 8;
      else if (curr_pressure >= 1010 and curr_pressure < 1020)
        return 18;
      else if (curr_pressure >= 1000 and curr_pressure < 1010)
        return 21;
      else if (curr_pressure >= 990 and curr_pressure < 1000)
        return 24;
      else if (curr_pressure >= 980 and curr_pressure < 990)
        return 24;
      else if (curr_pressure >= 970 and curr_pressure < 980)
        return 26;
      else if (curr_pressure < 970)
        return 26;
    }
    else {
      //winter
      if (curr_pressure >= 1030)
        return 2;
      else if (curr_pressure >= 1020 and curr_pressure < 1030)
        return 8;
      else if (curr_pressure >= 1010 and curr_pressure < 1020)
        return 15;
      else if (curr_pressure >= 1000 and curr_pressure < 1010)
        return 21;
      else if (curr_pressure >= 990 and curr_pressure < 1000)
        return 22;
      else if (curr_pressure >= 980 and curr_pressure < 990)
        return 24;
      else if (curr_pressure >= 970 and curr_pressure < 980)
        return 26;
      else if (curr_pressure < 970)
        return 26;
    }
  }
  else if (curr_pressure > prev_pressure) {
    //RAISING
    if (mon >= 4 and mon <= 9) {
      //summer
      if (curr_pressure >= 1030)
        return 1;
      else if (curr_pressure >= 1020 and curr_pressure < 1030)
        return 2;
      else if (curr_pressure >= 1010 and curr_pressure < 1020)
        return 3;
      else if (curr_pressure >= 1000 and curr_pressure < 1010)
        return 7;
      else if (curr_pressure >= 990 and curr_pressure < 1000)
        return 9;
      else if (curr_pressure >= 980 and curr_pressure < 990)
        return 12;
      else if (curr_pressure >= 970 and curr_pressure < 980)
        return 17;
      else if (curr_pressure < 970)
        return 17;
    }
    else
      //winter
    {
      if (curr_pressure >= 1030)
        return 1;
      else if (curr_pressure >= 1020 and curr_pressure < 1030)
        return 2;
      else if (curr_pressure >= 1010 and curr_pressure < 1020)
        return 6;
      else if (curr_pressure >= 1000 and curr_pressure < 1010)
        return 7;
      else if (curr_pressure >= 990 and curr_pressure < 1000)
        return 10;
      else if (curr_pressure >= 980 and curr_pressure < 990)
        return 13;
      else if (curr_pressure >= 970 and curr_pressure < 980)
        return 17;
      else if (curr_pressure < 970)
        return 17;
    }
  }
  else {
    if (curr_pressure >= 1030)
      return 1;
    else if (curr_pressure >= 1020 and curr_pressure < 1030)
      return 2;
    else if (curr_pressure >= 1010 and curr_pressure < 1020)
      return 11;
    else if (curr_pressure >= 1000 and curr_pressure < 1010)
      return 14;
    else if (curr_pressure >= 990 and curr_pressure < 1000)
      return 19;
    else if (curr_pressure >= 980 and curr_pressure < 990)
      return 23;
    else if (curr_pressure >= 970 and curr_pressure < 980)
      return 24;
    else if (curr_pressure < 970)
      return 26;

  }
}

int station2sealevel(int p, int height, int t) {  // from pressure at our height to sea level
  return (double) p * pow(1 - 0.0065 * (double)height / (t + 0.0065 * (double)height + 273.15), -5.275);
  }

Credits

Mirko Pavleski

116 projects • 1164 followers

DIY Zambretti Weather Forecaster on VFD Display

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Schematics

Schematic diagram

Code

Arduino Code

Credits

Mirko Pavleski

Comments

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DIY Zambretti Weather Forecaster on VFD Display

DIY Zambretti Weather Forecaster on VFD Display

Things used in this project

Hardware components

Software apps and online services

Hand tools and fabrication machines

Story

Schematics

Schematic diagram

Code

Arduino Code

Credits

Mirko Pavleski

Comments

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