Low energy temperature and humidity sensor with ESP8266 (Wemos D1 Mini) and Bosch BME 280 publishing to MQTT.
- Wemos D1 Mini
- BME280 on 4 pin board (VCC, GND, SDA, CLK)
- Jumper + short piece of jumper wire
- Battery/batteries with ~3.3V, e.g. 2x AA or 1x CR123A
- Modify defines.h to your needs.
| Parameter | Meaning |
|---|---|
| WIFI_SSID | Your WiFi SSID to connect to. |
| WIFI_PASSWD | Your WiFi password. |
| WIFI_CONNECT_TIMEOUT_SECS | If connection is not possible within WIFI_CONNECT_TIMEOUT_SECS seconds, module goes back to sleep to save power and will try to reconnect in... |
| WIFI_RECONNECT_WAITTIME_SECS | ...WIFI_RECONNECT_WAITTIME_SECS seconds. |
| IP_ADDR | IP address of the module. |
| IP_GATEWAY | Gateway IP address. |
| IP_SUBNET | Subnet mask. |
| MQTT_SERVER | IP address of your MQTT server. In case you want to configure more than that, you have to tweak the code. |
| LOCATION | Used to build the MQTT topic names: home/LOCATION/temperature is temperature in degrees celsius. home/LOCATION/humidity is humidity in percent. home/LOCATION/vcc is voltage measurement between 3V3 and GND to allow to listen to draining batteries. |
| INTERVAL_READ_SENSOR_SECS | Module wakes up every INTERVAL_READ_SENSOR_SECS seconds to read BME280 data. |
| INTERVAL_SEND_DATA_SECS | BME280 data is sent at least every INTERVAL_SEND_DATA_SECS seconds... |
| THRESHOLD_SEND_DATA_TEMPERATURE | ...or at any wakeup if temperature difference (value in 1/10th degrees) is greater than THRESHOLD_SEND_DATA_TEMPERATURE... |
| THRESHOLD_SEND_DATA_HUMIDITY | ...or at any wakeup if humidity difference is greater than THRESHOLD_SEND_DATA_HUMIDITY... |
| ADJUST_TEMPERATURE | Correction value for temperature. |
| ADJUST_HUMIDITY | Correction value for humidity. |
| PIN_BME_* | Pin mapping for BME280 module. |
- Compile code and upload.
- If code is working get rid of unnecessary components on the board. Remove the following parts:
ATTENTION!!! After doing so, you cannot upload code via USB interface. Nevertheless OTA updates (or RX/TX usage) is still possible.
- Solder BME280 module to D1 to D4 (doublecheck pin mapping according to defines.h)
- Solder wire between D0 and RST
- Solder pins for at least 3V3, GND, D6, D7 (see pictures)
- For normal operations put jumper across D6 and D7. For safe mode start (e.g. OTA update) remove jumper.
- Attach power supply (e.g. battery) to 3V3 and GND.
- Enjoy...
- Build a case...
