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Seeing such a lightweight, practical, and exquisite little project, I can’t help but share.
This is a weather display device that obtains current and forecast weather data from the OpenWeatherMap API, and provides accurate indoor temperature and humidity through sensors, while also displaying remaining battery and WiFi connection information.
The main components used in the weather display are only two: the ESP32 microcontroller that supports WiFi and a 7.5 inch e-paper (also known as electronic ink screen).
This weather display consumes about 14μA during sleep and is estimated to average about 83mA during wake-up. The interface display can be configured to update at set intervals. When the refresh interval is set to 30 minutes, using a 5000mAh battery, it can run for over 6 months. The device can be powered by connecting to an adapter or computer via USB-C.
From location, time/date format, units, and language to air quality index scale and hourly outlook graph boundaries, all content has configuration options. The hourly weather temperature outlook graph is clearly represented by a line, with shaded bars indicating precipitation probability.
As for the base, a small stand was made from a piece of wood. At the back, a short USB extension cable was used, so when charging the battery, there is no need to remove the components from the stand, which is quite convenient. In addition, a small reset button was connected to manually refresh the display content. Finally, a bottom cover was 3D printed and fixed with magnets. Since the e-paper screen is very thin, a thin acrylic was used to support it.
Let’s talk about the main hardware used in this display:
1) 7.5inch (800×480) E-Ink Display with HAT for Raspberry Pi, SPI interface
The advantage of e-paper is its ultra-low power consumption, but e-paper (or electronic ink) displays are very suitable for low-power applications that do not require frequent display refreshing. E-paper displays only consume power when refreshing the display and do not have a backlight. Even without power, the image will remain on the screen.
The limitation of e-paper is its color—e-paper traditionally is limited to black and white, but in recent years, three-color e-paper screens have started to appear. Additionally, if refreshed too quickly, e-paper displays easily produce ghosting effects. To avoid this, e-paper displays usually need a few seconds to refresh (the unit used in this project is 4 seconds), and will alternate between black and white several times, which can be distracting.
To be honest, the price is not cheap, like this 800×480, 7.5 inch black/white electronic ink screen sells for $57 on the official website. Of course, this project also supports three-color screens.
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Onboard WiFi -
520kB RAM and 4MB FLASH, enough to store a large number of icons and fonts -
Low power consumption -
Small size, offers various small development boards
3) BME280 – Pressure, Temperature and Humidity Sensor
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Provides accurate indoor temperature and humidity. -
Much faster than DHT22, which needs to wait 2 seconds before reading temperature and humidity samples.
4) 3.7V Lithium Polymer Battery with 2-pin JST Connector
Large capacity can be freely determined. Here a 5000mAh battery is used, so the device can run for over 6 months on a single charge. (Maybe longer, time will prove everything). When the battery is inserted into the JST connector of the ESP32, the FireBeetle ESP32 can be plugged into the wall to charge the battery via the USB-C connector.
The wiring is as follows:
Regarding the code, for the latest information and instructions on how to configure, compile, and upload code to the ESP32, you can refer to GitHub:
https://github.com/lmarzen/esp32-weather-epd
OpenWeatherMap API key can be registered for free at the link below:
https://openweathermap.org/api
Original link:
https://www.hackster.io/lmarzen/esp32-e-paper-weather-display-a2f444
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