Research feasibility of solar power

[tcsullivan]

The tRacket sensor currently depends on wired USB power. It would be massively beneficial if the sensor could be deployed long-term in locations where that isn't available; solar power seems like the most viable solution.

The sensor draws no more than 5V @ 100mA, and a quarter of that if WiFi is not running. Some ideas to look into:

• Solar panel options: USB panels? Solar harvesting circuits? How large of a panel do we need?
• Battery options: chemistry, capacity, size? A battery is necessary since the sensors run 24/7 and need energy when the sun is not out.
• Battery charger for storing excess solar energy into the battery
• PCB modifications: battery and/or solar panel connectors? Low-power microcontroller to minimize energy consumption when WiFi is not needed?
• Enclosure: Do we need a larger enclosure? How will the solar panel secure to it? More drilling for solar and battery connectors? Weatherproofing?
• How much will the solar-powered sensor cost?

I'll share more notes soon on the research I've done, but anyone is welcome to look into any of these points and share their findings here!

[tcsullivan]

Ideally, we would redesign the sensor to be as low-power as possible, which would mean adding an ultra-low-power microcontroller for decibel monitoring as well as a solar harvester chip. Like these:

• Microcontroller: STM32L431KB
• Harvester: BQ25504

We should be able to get the sensor's average current consumption down to the milliwatt range, and the harvester would collect as much power as possible into a battery. We want to be able to charge the battery while also running the decibel monitoring, which would make that milliwatt target essential.

Also considering the solar panel and battery, taking this route would increase the sensor's cost by $20+ CAD.