I have been researching these days on the possibilities to use ultra low power sources for the Funky sensor. I started my research with the idea to power a Funky from a CT wrapped around a power line. This is entirely possible, and there are commercial products that utilize this idea, but then during my research I found a more appealing solution based on Linear Technology’s LTC3108
The LTC®3108 is a highly integrated DC/DC converter ideal for harvesting and managing surplus energy from extremely low input voltage sources such as TEGs (thermoelectric generators), thermopiles and small solar cells. The step-up topology operates from input voltages as low as 20mV
So basically it is a small charge pump that will take 20mV input and gradually charge a super capacitor or a battery to a preset voltage, 3.3V being one of the options. The datasheet states that it can build a 3.3V charge for around 2 minutes from 20mV power source such as Peltier cell, a chip solar cell, a piezo generator or whatever low voltage DC power source.Probably a good solar cell will output that much voltage at moonlight, so here is moonlight powered solution 🙂
The chip provides a 2.2V output to power a processor, that is well within the specs for Attiny84V running at 8Mhz on internal oscillator, What I like, is that it also provides two MCU controlled 3.3V outputs for powering up a RF module and a sensor, that means the MCU can start independently of the RF and sensor, then issue a command to power them up.There is a “Power Good” pin that can be used to wake up the MCU as well. Lovely little chip.
It turns out that these are available as a break-out from FemtoGen:
Here is another project with the same chip, this time it is Open Hardware and the Eagle schematics and board files are available.
Yet another Open Hardware project that utilizes similar techniques is the Mosquino.