Solar pocket light
A fast and easy, project build for fun. A solar cell charges a single micro NiMH battery. A step-up converter provides 4V. The ATtiny13 powers a red, green, blue and ultraviolet LED. Normal operation of the button is to toggle the red, green and blue LEDs on and off. If pressed longer, there can be switched between each possible combination of LEDs being on. Material bill is approx 18€. Low battery warning is done by flashing the LEDs, oh and there is a disco mode too. Because the reset pin is used as I/O pin, a HV programmer might be required.
Software and schematicsAs always, use at your own risk.
Charging per dayOut of curiosity, the charging performance of the solarcell was measured. The cell (30mm x 30mm, 3V, 35mA) laid flat behind a window, directing to the south. There were some cloudy days and some with clear view.