“The ATtiny85 is a tiny microcontroller (like the Arduino). This project is designed to provide continuous power to the circuit using a solar panel.
A basic solar charging circuit uses a diode to basically “force” the electricity from the solar panel into a battery for later use. I am using an ATtiny instead of a larger board like the UNO because it use less power, so the circuit will be easier to power with a smaller (and cheaper) solar panel.”