ESP8266, e-Paper display and a DHT 11 sensor make a nice outdoors unit This simple DIY hack uses the following:
- 1 x ESP8266 for the brains (WIFI disabled via deep sleep)
- 1 x DHT11 (blue) for the temperature and humidity measurements
- 1 x 1.54" e-Paper display from Waveshare
- 3 x AA (1.5V) batteries for power-source
To make this work for a long time (expected to last more than 1 yr) the e-Paper display is used only for a few seconds each time. The ESP boots up, starts the DHT library, reads (retry if necessary) the sensor to receive temperature and humidity. Finally, it powers on the e-Paper display and does 1 full write (required) and 1 partial write, drawing two rectangles and the temperature/humidity readings.
It then proceeds to go to deep sleep, making sure the wifi stays off next boot. Hopefully this will make it work.
Use the ESP.getVcc() functionality to read available VCC and signal a low-battery case. Currently, the sensor can be seen operating every 15m by the screen refresh (not very user friendly.)