Published August 30, 2020 © CC BY-NC-SA

MetroWatch - Heat & UVI Edition (inspired by Metro Exidus)

My own version of Metro Watch - which detects heat and UVI but not nuclear radiation.

IntermediateShowcase (no instructions)538

MetroWatch - Heat & UVI Edition (inspired by Metro Exidus)

Things used in this project

Hardware components

Espressif Wemos D1 Mini

ElectroPeak 0.96" OLED 64x128 Display Module

BH1750 Light Intensity Sensor Module

SparkFun Atmospheric Sensor Breakout - BME280

ML8511 UV Detection Module

DS3231 RTC Clock Module

SparkFun Pushbutton switch 12mm

Buzzer, Piezo

WS2812 5050 12 Bits NeoPixel Ring

Breadboard (generic)

Jumper wires (generic)

Story

Note: some libraries seems to interference the WiFi function of the board after update.

While playing Metro Exodus (2019) earlier in the summer, I can't help to notice that the glove (with the Nixie tube watch) Artyom wears has a pretty realistic blue LED on it. It serves as ambient light indicator so that you can sneak past enemies in the "dark".

So the thing is a DIY/Maker product...and that made me want to make one.

The basic model has a watch, a compass and a Geiger counter.

The glove is part of the game GUI.

Of course, there's no nuclear radiation in our real world (unless US and China did declare war to each other in the near future). What the next most dreadful thing? The unbearable heat.

It was so hot in the year 2020 that Arctic ice melt faster then ever, and more people get killed by heat than COVID-19 in Tokyo. When Artyom and friends explore the dried-out desert of Caspian Sea, it's amazing that they can even survive there more than a few days.

Anyway, I decided to change the spec a bit. My version would measure the apparent temperature (the temperature you actually felt) and UVI (Ultraviolet Index). They can be harmful if the levels get too high.

All stuff (including the small power bank) are installed on a cheap sports bracer. I also wore a sports sleeve underneath it.

This is what this glove does:

The TM1637 displays time read from the DS3231 RTC (real time clock) module, just like a real watch.
If you hold the button (it would wait 2 sec on start) when the device "boot up", the ESP8266 would connect to WiFi, query NTP server and update DS3231's internal time. (Then it would disconnect itself.)
The 0.96" SSD1306 OLED displays apparent temperature, which is calculated from temperature, humidity and atmospheric pressure read from BME280. (The formula is listed below.)
The 12-bit NeoPixel ring indicates UVI (2-13) measured from ML8511 with different colors.
When pressing the button, the NeoPixel ring would light up in max brightness level as flashlight.
The Illuminance reading (lux) from BH1750 light sensor would be used to control the blue LED as well as brightness level of TM1637 and NeoPixels. (for the OLED, I simply turn off some of the lines.)
The buzzer beeps three times if the apparent temperature reaches 38*C or UVI reaches 8. This means you'll have to find shade as soon as possible (or try not to stay outside too long).

Power

A power bank (with a single rechargeable 18650 battery inside) provide 5V power to the D1 mini (ESP8266).

The TM1637 and NeoPixels are connected to 5V and the rest are connected to 3.3V.

Calculate apparent temperature

This is from Robert G. Steadman's A universal scale of apparent temperature in 1984:

AT = 1.07T + 0.2e - 0.65V - 2.7

e = (RH / 100) * 6.105 * exp(17.27T / (237.7 + T))

AT is apparent temperature (*C), T is temperature (*C), e is vapor pressure (hPa), V is wind speed (m/sec), RH is relative humidity (%).

Since I cannot measure wind speed, I simply ignore it in the code. Wind can be blocked by buildings anyway.

Calculate UVI from ML8511

The ML8511 datasheet indicates that its analog output between 1V and 3V can be translate to 0-15 mW/cm2:

And according to this:

1 UVI corresponds to an irradiance of 1/40 Watt/m2.

1 mW/cm2 = 10 Watt/m2, so 1 mW/cm2 = 1/4 UVI.

This means you can simply multiply 0-15 mW/cm2 with 4 and get 0-60 UVI. Or you can directly map 1-3V to 0-60 UVI.

Also be noted that the reference voltage is 3.0V (not 3.3V).

One fun fact I also discovered is that phone LED flashlight emit some UV. So you can use it to to quick UV test indoors.

Other issues

It seems that the u8g2 library used by the OLED occasionally cause the board to reset itself. However, since it would not connect WiFi by default, these interruptions are not serious.

MetroWatch

/*
 * MetroWatch (Heat & UVI Edition) on ESP8266 by Alan Wang
 * inspired by the game Metro Exodus
 */

#include <math.h>
#include <Wire.h>
#include <ESP8266WiFi.h>
#include <ESP8266WiFiMulti.h>
#include <WiFiUdp.h>
#include <NTPClient.h>         // https://github.com/arduino-libraries/NTPClient
#include <BH1750.h>            // https://github.com/claws/BH1750
#include <Adafruit_NeoPixel.h> // https://github.com/adafruit/Adafruit_NeoPixel
#include <Adafruit_BME280.h>   // https://github.com/adafruit/Adafruit_BME280_Library
#include <TM1637Display.h>     // https://github.com/avishorp/TM1637
#include <U8g2lib.h>           // https://github.com/olikraus/u8g2
#include "EasyBuzzer.h"        // https://github.com/evert-arias/EasyBuzzer
#include "RTClib.h"            // https://github.com/adafruit/RTClib

// pin mappings
#define UV        A0
#define LED       D0
#define NEOPIXEL  D3
#define LED_BOARD D4
#define TM_CLK    D5
#define TM_DIO    D6
#define BTN       D7
#define BUZZER    D8

// user settings
const char *ssid1 = "";
const char *pw1   = "";
const char *ssid2 = "";
const char *pw2   = "";

ESP8266WiFiMulti WiFiMulti;
WiFiUDP ntpUDP;
NTPClient ntpClient(ntpUDP, "pool.ntp.org");
Adafruit_NeoPixel neopixel(12, NEOPIXEL, NEO_GRB + NEO_KHZ800);
Adafruit_BME280 bme;
BH1750 bh;
RTC_DS3231 rtc;
TM1637Display tm(TM_CLK, TM_DIO);
U8G2_SSD1306_128X64_NONAME_F_HW_I2C u8g2(U8G2_R0, U8X8_PIN_NONE);

const int hour_offset = 8;
const int temp_display_scale[] = {18, 24, 34, 42};
const uint32_t uviColor[] = {
  neopixel.Color(64, 255, 255),
  neopixel.Color(0, 255, 255),
  neopixel.Color(0, 255, 128),
  neopixel.Color(0, 255, 64),
  neopixel.Color(255, 255, 0),
  neopixel.Color(255, 128, 0),
  neopixel.Color(255, 64, 0),
  neopixel.Color(255, 32, 0),
  neopixel.Color(255, 16, 0),
  neopixel.Color(255, 0, 0),
  neopixel.Color(255, 0, 16),
  neopixel.Color(255, 0, 32)
};

int s_prev = 0;
long t;
float lux;
bool colon = true;
bool flashlight = false;
bool uvi_warning = false;
bool tmp_warning = false;

void setup() {

  Wire.begin();
  rtc.begin();

  pinMode(LED, OUTPUT);
  pinMode(LED_BOARD, OUTPUT);
  pinMode(BTN, INPUT_PULLUP);

  digitalWrite(LED_BOARD, LOW);
  delay(2000);

  if (btnPressed()) {

    for (int i = 0; i < 2; i++) {
      digitalWrite(LED_BOARD, HIGH);
      digitalWrite(LED, HIGH);
      delay(50);
      digitalWrite(LED_BOARD, LOW);
      digitalWrite(LED, LOW);
      delay(50);
    }
    
    WiFiMulti.addAP(ssid1, pw1);
    WiFiMulti.addAP(ssid2, pw2);
    while (WiFiMulti.run() != WL_CONNECTED);
    
    ntpClient.begin();
    ntpClient.setTimeOffset(hour_offset * 60 * 60);
    while (!ntpClient.update()) {
      delay(1000);
      
    }

    unsigned long epochTime = ntpClient.getEpochTime();
    struct tm *ptm = gmtime ((time_t *)&epochTime);
    int y = ptm->tm_year + 1900;
    int mo = ptm->tm_mon + 1;
    int d = ptm->tm_mday;
    int h = ntpClient.getHours();
    int mi = ntpClient.getMinutes();
    int s = ntpClient.getSeconds();
    rtc.adjust(DateTime(y, mo, d, h, mi, s));
    
    WiFi.disconnect();

  }

  EasyBuzzer.setPin(BUZZER);
  bme.begin(0x76);
  bh.begin();
  neopixel.begin();
  neopixel.clear();
  tm.clear();
  u8g2.begin();

  digitalWrite(LED_BOARD, HIGH);

}

void loop() {

  if (btnPressed()) {
    flashlight = !flashlight;
    flashToggle();
  }

  setLightlevel();
  displayNeoPixels();
  displayTM();
  displayOLED();
  delay(200);

}

float mapfloat(float x, float in_min, float in_max, float out_min, float out_max) {
  float value_scale = (x - in_min) / (in_max - in_min);
  return out_min + (value_scale * (out_max - out_min));
}

bool btnPressed() {
  return !digitalRead(BTN);
}

void playTone(int freq, int duration) {
  EasyBuzzer.beep(freq);
  EasyBuzzer.update();
  delay(duration);
  EasyBuzzer.stopBeep();
}

void setLightlevel() {

  lux = bh.readLightLevel();

  if (!flashlight) {
    digitalWrite(LED, lux >= 50);
    tm.setBrightness(map(lux > 600 ? 600 : lux, 1, 600, 0, 7));
    neopixel.setBrightness(map(lux > 1000 ? 1000 : lux, 1, 1000, 1, 128));
  } else {
    digitalWrite(LED, true);
    tm.setBrightness(7);
  }

}

void flashToggle() {

  neopixel.setBrightness(255);

  if (flashlight) {

    neopixel.fill(neopixel.Color(128, 128, int(128 * 0.5)));
    neopixel.show();
    delay(100);
    neopixel.clear();
    neopixel.show();
    delay(200);
    
    for (int i = 0; i < 256; i += 5) {
      neopixel.fill(neopixel.Color(i, i, int(i * 0.5)));
      neopixel.show();
      delay(10);
    }
    neopixel.fill(neopixel.Color(255, 255, int(255 * 0.5)));
    neopixel.show();

  } else {
    neopixel.clear();
    neopixel.show();
    delay(250);
  }

}

void displayNeoPixels() {

  float uv = float(analogRead(UV)) * 3.0 / 1023;
  float uvi = mapfloat(uv, 0.99, 2.99, 0.0, 60.0);

  if (!flashlight) {
    for (int i = 0; i < 12; i++) {
      if (uvi >= (i + 2)) {
        neopixel.setPixelColor(i, uviColor[i]);
      } else {
        neopixel.setPixelColor(i, neopixel.Color(0, 0, 0));
      }
    }
    neopixel.show();
  }

  if (!uvi_warning) {
    if (uvi >= 8) {
      for (int i = 0; i < 3; i++) {
        playTone(294, 50);
        delay(50);
      }
      uvi_warning = true;
    }
  } else {
    if (uvi <= 7) uvi_warning = false;
  }

}

void displayTM() {

  DateTime currentTime = rtc.now();
  int h = currentTime.hour();
  int m = currentTime.minute();
  int s = currentTime.second();

  if (s != s_prev) colon = !colon;
  tm.showNumberDecEx(h * 100 + m, colon ? 0b01000000 : 0b00000000, true);
  s_prev = s;

}

void displayOLED() {

  float t = bme.readTemperature();
  float h = bme.readHumidity();
  float p = bme.readPressure() / 100.0;
  float e = h / 100 * 6.105 * exp((17.27 * t) / (237.7 + t));
  float ap_tmp = 1.07 * t + 0.2 * e - 2.7;

  float ang = mapfloat(ap_tmp, 10, 50, 0, 180);
  String ang_str = String(int(ang));
  int tri_end_x = round(48 * cos(ang * M_PI / 180));
  int tri_end_y = round(48 * sin(ang * M_PI / 180));
  int tri_side_x = round(4 * cos((ang + 90) * M_PI / 180));
  int tri_side_y = round(4 * sin((ang + 90) * M_PI / 180));

  u8g2.clearBuffer();

  if (lux >= 50 || flashlight) {
    u8g2.drawCircle(64, 64, 60);
    u8g2.drawCircle(64, 64, 40);
  }
  u8g2.drawTriangle(64 - tri_end_x,
                    64 - tri_end_y,
                    64 - tri_side_x,
                    64 - tri_side_y,
                    64 + tri_side_x,
                    64 + tri_side_y);

  u8g2.setFont(u8g2_font_tenfatguys_tn);
  for (int i = 0; i < 4; i++) {
    float ang_font = mapfloat(temp_display_scale[i], 10, 50, 0, 180);
    int pos_len = round(mapfloat(ang_font, 0, 180, 68, 48));
    int font_x = round(pos_len * cos(ang_font * M_PI / 180));
    int font_y = round(pos_len * sin(ang_font * M_PI / 180));
    String value_str = String(temp_display_scale[i]);
    u8g2.drawStr(64 - font_x - 2, 64 - font_y + 5,
                 strcpy(new char[value_str.length() + 1], value_str.c_str()));
  }

  u8g2.setFont(u8g2_font_courB08_tn);
  String tmp_str = String(ap_tmp);
  u8g2.drawStr(8, 63, strcpy(new char[tmp_str.length() + 1], tmp_str.c_str()));
  u8g2.sendBuffer();

  if (!tmp_warning) {
    if (ap_tmp >= 38) {
      for (int i = 0; i < 3; i++) {
        playTone(587, 50);
        delay(50);
      }
      tmp_warning = true;
    }
  } else {
    if (ap_tmp <= 36) tmp_warning = false;
  }

}