CWX ESP8266 BME280 Compact Weather Station Board SDK

A local Radio and Electronics Club were looking for a small STEM project which could be used as a platform to encourage electronics and software interests. In addition, for an ATV repeater site, I wanted to put up a weather station. As the site is open to potentially rough elements (being high up!), a standard weather station was not an ideal option, unless a fair amount was spent on a robust commercial route.

Update: 21st November 2022. Due to the huge interest received, an updated version of CWX has been drafted which includes USB D1 compatibility, DC LDO, Deep Sleep link and Battery voltage monitor. The updated board has been ordered and called CWX-2.

Requirements

The main elements we wanted to monitor was temperature, relative humidity, barometric pressure and ambient light. The reason for light was that the site in question is solar powered and monitoring light levels had a purpose in energy management.

Whilst I am not an advocate of creating kits which contain other daughter boards, this weather station proved to be a logical route, purely for cost. The chosen BME280 sensor was in short supply and existing boards were available, although still expensive.

So, armed with the knowledge that I was to use the small BME280 board (not BMP280), it was required to be battery operated, required a light sensor and compact - thus the CWX, Compact Weather Station was created.

Specification

The CWX basic specification was:

• Battery Operated
• ESP8266 ESP12S Based
• BME280 to provide a low power
• Barometric Pressure, 300-1100 hPa
• Temperature, -40 to +85°C
• Humidity, 0-100% Relative (± 3%)
• SFH2440 to provide a high linearity Ambient Light Sensor.
• Spectral range of 400 to 690 nm
• External UART to conserve power (the CH340 was not easy to obtain at the time of design and USB/UART boards were).
• To fit into a standard 85x58x33mm waterproof clear cover plastic enclosure.

Prototyping

Following a couple of iterations of the board, namely to ensure the routing aperture of the board so the BME280 would fit flush and also for the light sensor, in case it was required to be mounted from either side, the CWX SDK was finalised.

Site Testing

Mounting the CWX on the outside of the repeater site, with not easy access in the winter, plus I wanted to develop the code remotely, an extension to the UART was added (as seen in the pic). This CWX then reports outs to to a ThingSpeak channel (although the site power is currently off for maintenance, you can see some history). https://thingspeak.com/channels/1649383

The CWX is also running on my home Domoticz, this and other users reports, are encouraging to see this STEM project evolve.

Progress

The CWX project has proved to be solid and reliable. One can always make improvements but a line in the sand needs to be drawn. That said, now the CH340 is not a current issue and a deep sleep link ideally needs to be added, maybe a small tweak will emerge.....

Supporting STEM

Life is one long exciting learning curve, help others by setting the seed to knowledge.