What is it?

This is Bosch's BME280 pressure/humidity/temperature sensor along with Vishay's VEML6040 RGBW ambient light sensor on a small (0.3" x 0.6") add-on board designed to mount directly onto Ladybug, an Arduino-programmable STM32L432 development board. Both sensors require very little power to run and, in combination with the low-power modes of the Ladybug, allow remote, battery-powered environmental sensing in a very small package.

Why did you make it?

I have been interested in remote environmental data logging for a while but the hard part has always been getting the devices to last long enough on a battery to make the effort worthwhile. These two sensors provide a wealth of data about any environment and require very little power to run at a low duty cycle. Similarly, the STM32L4 has several low-power modes that can be used in this application to great effect.

As an example, I ran this add-on mounted on a Ladybug development board powered by a 150 mAH LiPo battery for more than 43 days updating the Sharp memory display at 5 second intervals with pressure, altitude, humidity, temperature, red, green, blue ambient light intensity and time and date. The average power required to do this was <150 uA. The next step is to repeat the experiment using an SPI flash memory add-on board to capture the data for later plotting and analysis. The easy-to-use low power modes of the STM32L4 make such remote environmental data logging practical!

What makes it special?

This is a very small add-on board that still leaves most of the GPIOs of the Ladybug available to the user. It is designed to mount directly on top of the Ladybug to provide a very compact device to keep track of conditions in a greenhouse, garage, basement, refrigerator, etc. Pretty much anywhere you can fit a small LiPo battery you can record the environmental conditions over long periods of time.

Order the pcbs from OSH Park and assemble some for yourself, or buy the fully assembled and tested add-on boards from me and see how easy long-time environmental data logging can be!