Tiny Cube Satellite

ATtiny85 based solar powered satellite circuit sculpture.

The schematic is very straightforward. We use the internal 1MHz oscillator of the ATtiny85 microcontroller, thus eliminating the need for any external oscillator circuitry. The solarcells are connected in series and fed to the system via a reverse current blocking diode. The diode also helps bring down the voltage to safely charge the super capacitor. In bright sunlight, the solarcells generate enough current to charge the capacitor and power the system. A fully charged super capacitor should be able to keep the system running for a couple of days on it’s own. You can further modify the circuit to make the behavior nocturnal, by measuring the voltage across the solarcells, and only blinking the LED when it crosses a low threshold.

The key to getting a long run time out of the system is to utilize the low power modes of the ATtiny microcontroller. You can do this by disabling all the unnecessary internal peripherals, and putting the device in deep sleep mode inbetween the blinking. You can bring down the average current consumption from 10mA down to 230uA. The device only consumes about 4.84uA (at 3.8VDC) when in sleep! You can further bring down the average current by using longer time periods inbetween blinks, modifying the blinking pattern, and increasing the current limiting resistor value for the LED.

Arduino IDE code: