Epaper Weather Station Receiver

1. Introduction

The project is a part of bigger IOT system. Weather Station receiver measures basic parameters, such as temperature, pressure, humidity, but also CO2, TVOC level. Other parameters, like outside temperature, weather forecast can be received by MQTT and displayed on 4.2" Epaper display.

2. Features

• 4.2" E-paper display with additional NeoPixel backlight
• Backlight colour depends on CO₂ in room
• Li-Ion battery as backup PS
• Additional fan for better air flow
• Temperature, humidity, pressure measurements
• CO₂, TVOC level measurements
• PIR sensor
• Time, date, sunrise/sunset time display
• Current weather forecast with description
• Weather forecast for next 5 days
• Outside temperature, felt temperature display
• All displayed parameters/icons can be easily changed
• All not measured parameters are send to/from weather station by MQTT

3. Bill of Materials

Main components:

Device	Description	Price
ESP32 DEVKIT V1	Main IC	$3.50
BME280	Temperature, humidity, pressure sensor	$2.10
MCP9808	High accuracy temperature sensor	$0.75
CCS811	CO2, TVOC sensor	$5.89
HC-SR505	PIR sensor (AM312)	$1.15
J5019	Battery charger with DC-DC converter	$0.69
4.2" Epaper	Waveshare E-paper Display Module	$28.47
25mm fan	5V fan (25x25x7mm)	$1.22
SK6812	RGBW NeoPixel LED	$0.25
1000mAh Li-Ion	Battery	$2.50
PCB	Custom PCB
Housing	Custom housing (3D printed)

4. Libraries

• GxEPD
• Adafruit GFX
• PubSubClient
• ArduinoJson
• Adafruit MCP9808
• Adafruit BME280
• Adafruit Sensor
• Adafruit CCS811
• Adafruit NeoPixel

5. Getting Started

To run Weather Station, user should change some settings in data.h file:

Basic WiFi settings

// WiFi Settings
const char* ssid = "YOUR_SSID";
const char* password = "YOUR_PASSWORD";

Choose, how many NeoPixel LEDs you want to use. You can solder up to 10 LEDs. If you use less than 10, you should make shorts everywhere, where you do not use LEDs (Designators R2 to R7)

// NeoPixel settings
 ...
#define LED_COUNT   6       // No of LEDs

Uncomment, if you use MQTT user and password

// MQTT Settings
const char* mqtt_server = "MQTT_SERVER_IP";
//const char* mqtt_user = "MQTT_USER";
//const char* mqtt_password = "MQTT_PASSWORD";

You can adjust, how often display will be refreshed, and how often presence will be checked using PIR sensor (it also defines minimum backlight time)

// Refresh time in seconds
#define REFRESH_TIME	30
#define PRESENCE_TIME   5

Define altitude of your home (for pressure measurements)

// Sensors config data
#define ALTITUDE        515.0 //define altitude of location

Define MQTT Publish and Subscribe topics compatible with your server

// MQTT Input topics
#define TEMPOUT_TOPIC       "home/weatherstation/tempout"
#define TIME_TOPIC          "basic/time/time"
#define DATE_TOPIC          "basic/time/date"
#define SUNRISE_TOPIC       "conditions/weather/sunrise"
#define SUNSET_TOPIC        "conditions/weather/sunset"
#define DESCRIPTION_TOPIC   "conditions/weather/description"
#define WEEKDAY_TOPIC       "basic/time/day"
#define WEATHER_ICON_TOPIC  "conditions/weather/icon"
#define FELT_TEMP_TOPIC     "conditions/weather/tempfeel"
#define FORECAST1_TOPIC     "forecast1"
#define FORECAST2_TOPIC     "forecast2"
#define FORECAST3_TOPIC     "forecast3"
#define FORECAST4_TOPIC     "forecast4"
#define FORECAST5_TOPIC     "forecast5"

// MQTT Output topics
#define PUBLISH_TOPIC       "home/station"

6. Description

The main functionality of Weather Station is to measure inside conditions and display parameters on Epaper display.

Measurements

• Temperature: measured by MCP9808 to ensure high accuracy (0,25ºC)
• Humidity, Pressure: measured by BME280
• CO₂, TVOC: measured by CCS811
• Presence: measured by HC-SR505 PIR sensor, used to detect presence and to switch ON backlight
• Other: battery voltage can be measured using analog input

Display

Not all measured parameters are displayed on Epaper. I use only few most important indicators.

A Temperature inside (measured)
B Temperature outside (MQTT)
C Felt temperature (MQTT)
D Pressure inside (measured)
E Humidity inside (measured)
F Empty space, to be used
G Actual weather icon (MQTT)
H Time (MQTT)
I Date (MQTT)
J Weather description (MQTT)
K Sunrise time (MQTT)
L Day of week (MQTT)
M Sunset (MQTT)
N Forecast date (MQTT)
O Forecast icon (MQTT)
P Forecast temperature (MQTT)

Input parameters

All MQTT subscribed topics should provide data in format:

Topic	Type	Example	Note
TEMPOUT_TOPIC	String	30.75
TIME_TOPIC	String	10:02
DATE_TOPIC	String	12-08-2020
SUNRISE_TOPIC	String	04:29
SUNSET_TOPIC	String	19:06
DESCRIPTION_TOPIC	String	Sunny
WEEKDAY_TOPIC	String	Monday
WEATHER_ICON_TOPIC	String	1	See picture below
FELT_TEMP_TOPIC	String	31.56
FORECASTx_TOPIC	JSON	See example below
SERVICE_TOPIC	String	See service

Weather Icons codes

Forecast JSON example

{
"time1":"12-08",
"icon1":"1",
"temp1":22.23
}

Output parameters

Parameters send by device in PUBLISH_TOPIC are in JSON format:

{
"tempIn":24.7,
"humIn":44.9248,
"pressIn":1022.372,
"co2":1065,
"tvoc":101,
"bat":4.174172
}

Service commands

Some simple service commands can be send to Station using SERVICE_TOPIC:

RESTART - force ESP restart
SENSORS - send sensors statuses, 1 if sensor was correctly initialized
STATUS - send online time

Feedback will be send in DEBUG_TOPIC

7. Changelog

2021-01-10 V1.0 Stable version - little bit optimized, added STL files
2020-08-25 V0.1.5 Stable beta - not optimized, without STL files (Public)
2020-08-11 V0.1 First Beta Release - not optimized, without firmware code (private)

8. Task list

• Software:
• Firmware code optimization
• Service commands (sensors statuses, online time)
• Battery voltage measurements

9. Pictures