Our growing ability to sense physical phenomena from a distance allows us better control over our activities: By monitoring temperature, pressure, motion, humidity and position, for example, our farms, factories and homes can be made more productive, efficient and safer.
Remote sensing usually requires the “harvesting” of minute amounts of energy from the environment: Solar cells, piezoelectric and thermo-energy generators, even human muscles, can provide batteryless power to a transducer and a wireless transmitter. But, remember: This is the realm of microwatts and nanoamps; the fewer the components, the lower the power.
At minimum you need a harvester, a transducer, an energy storage element (capacitor, super-capacitor or battery), a step up (“boost”) or step down (“buck”) converter that provides usable voltage levels and a microcontroller with a low power mode and integrated transmitter.
The “Solar dice” reference design from Texas Instruments is a simple sensor node that combines all those components: An onboard accelerometer detects the orientation of the dice and wirelessly transmits this to a host, such as a USB dongle or smartphone.
A tri-axial accelerometer from Bosch detects the cube’s face; six thin-film solar panels from Sanyo power a DC/DC step down converter and an ultra-low-power microcontroller with an integrated RF transceiver core, running power-optimized code. The energy buffer is a 330uF low impedance capacitor.
It’s an easy way to experiment. And, potentially lucrative; applications for such sensing nodes, as part of the Internet of Things, are limited only by your imagination.