There was recently an article in the Christian Science Monitor about the launch of a cracker-size satellite. The article says that the satellite has, "power storage in capacitors, and switching circuitry to turn on the microprocessor when the stored energy is enough to create a single radio-frequency emission — a digital beep." The power is collected from a solar cell.
I'm interested in creating an earth-based device which would do just that, collect power from a solar cell and only turn on the device to transmit when it's got enough power. I recently purchased an arduino, but have little experience with this kind of engineering. Any suggestions about how to get started? Thanks!
Best Answer
That satellite will presumably use "energy harvesting" (EH) to store the energy provided by the solar cell in a super capacitor. Both TI and Microchip have just started suppling evaluation kits using EH with a solar cell to power an MCU and a wireless transceiver. Advanced Linear Devices makes the EH300 energy harvesting module, which can charge a pair of super capacitors from a variety of sources, including solar cells. I've been experimenting with one, and it can provide 1.8V - 3.3V from very low voltage sources, and is capable of delivering 25 mA for 68 ms, which is more than enough for an MCU such as an MSP430 or XLP PIC and a low-power transmitter. The EH300 has two super capacitors. They cost about £34, I bought mine from Farnell.
The Arduino isn't suitable for this application, as it won't work from such low voltages, and takes too much power. XLP PICs typically use 20 nA in deep sleep mode, and 50 uA/Mhz when active.