This will probably be my last post  for this challenge as I will leave tomorrow morning for a business strip and returning next monday.

hen I experiment, when I test new components and ideas, and also every time I fail, I have fun. So this challenge was really funny to me!

This is my second challenge. The first one (ForgetMeNot) was bit disappointing to me because I have not been able to focus on the challenge requirements. On the contrary in this challenge, in my opinion, I met the requirements and I have been able to work out a working project (obviously with all the limitations due to both limited time frame available and limited personal skills). In more detail

Use of components and services from the sponsors

Texas Instruments

The MSP430FR5969 is the heart of the AirMobile sensor. It's really a good MCU, shipped with good development tools. "Thanks" to delays in the shipping of some components, I had the opportunity to dig into some interesting feature like FRAM retention, in-RAM execution and code protection

Wurth Elektronik

From Wurth, I got the transformer for interfacing the Peltier cell to the step-up converter. Also, they made the AirMobile sensors PCB. In this case, I appreciated the quality of the PCB and the timely delivery

Sierra

All the data is stored to and retrieved from the Sierra AirVantage cloud infrastructure. Even if I initially was a bit perplexed because it was not possible to subscribe to data changes, I then realized the rationale behind that choice. Use of REST API make the AirVantage cloud easily accessible from any platform. Also the use of an XML document to describe data assets makes the tool easy to configure for your own application

Requirements

Low maintenance

The requirements asked for "low maintenance (for example no need for battery)". I tried to push this requirement to the extreme by completing removing batteries and rely only on energy harvesting. Should I go back in time, I will add a backup battery. According to the experience I made, energy harvesting through a Peltier celle is not enough to provide reliable operations in all conditions. Even If I designed the board to use delta-T on Peltier cell's faces as low as 30 degrees, I think it would be very difficult to achieve this in a hot summer day. Also, operations are unreliable when you slow down and there is not enough airflow to cool down the cold face of the cell

Smartphone app

With some minor changes, I adapted an existing application to push data to AirVantage cloud. App lloks good and provides a lot of interesting features

Automation

Thanks to the OpenHAB platform, adding automation based on collected data was not a huge task. I developed two bindings: one to get data from the AirVantage cloud and one to drive a servo control