ESP8266 solar powered temperature sensor.
This is the firmware for a ESP8266 based temperature sensor, powered by a small solar panel. It takes a reading from a DHT22 temperature/humidity sensor, and sends the data over TCP to a server (in this case listening on a Raspberry Pi).
This is running on a ES8266-12 module, I tried a few ESP8266 modules and this gave the lowest power consupmtion in deep sleep mode (in the µA range). When the module wakes up it takes a reading, connects to wifi and transmits the data. It then sleeps for approximately 5 minutes (the timer isn't very accurate) before doing the same again. If too many errors occurs it also enters deep sleep mode and retries in 5 minutes.
The power source is three 800mAh AA NiMH batteries, on their own these will give a run time of around one month. A solar panel is connected to the batteries (directly with a Schottkey diode), which even on a not-so-sunny British winter day is enough to keep the batteries topped up. The solar panel is rated at 5.5V and 120mA and cost a few pounds from eBay. The reading also includes the internal voltage of the ESP8266, so the battery level can be monitored. The batteries are connected directly to the ESP8266, even though it is rated at 3.3V it doesn't seem to have any issues running at slightly higher voltages.
The sensor is housed in a plastic food container, with holes pierced in the sides to provide air flow. The sensor has been running for a week now, so the long term longivity is unknown. I will update this as issues occur.
- Setup the ESP8266 toolchain. Docker is the easiest way.
- Copy and edit
user/user_config.h.example. make- Flash it to your device.