campy
Measure battery level, temerature, humidity and other things in a caravan
schaltplan.png shows the wiring including a DHT22 temperature sensor, voltage divider to meassure battery voltage (scaled down to max 2.9 V) and a OLED-display to show data when WiFi is turned off. When connected to WiFi AP, the webpage with the battery and environmental data can be accessed at http://192.168.1.1