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This deluxe solar-powered light  uses a battery and solar cells salvaged from a solar lamp with a four-cell battery (4.8 V nominal terminal  voltage).

The schema can operate from any  DC voltage around this value and  its current consumption, at 20 mA,  is low. This means that the battery  can give up to five days of operation. The schema consists of an Atmel  ATtiny microcontroller which drives  a red, a green and a blue LED directly  from three port pins. Series resistors are of course included to limit  the LED current. The microcontroller  drives the LEDs in sequence to produce an  RGB running light effect. The microcontroller  is also responsible for ensuring that the light automatically switches on when it gets dark  and off when it is light. The light sensor is  made from one of the solar cells from a bro-ken solar lamp (it is more common  for the battery to fail rather than  the solar cells). 

The power output of this cell is not  important, as the microcontroller  only measures its output voltage  using its internal A/D converter  connected to pin PB4. The project is  ideal for beginners, as a ready-programmed microcontroller is avail-able from the Elektor Shop (order  code 100581-41).