Solar recharging LED system PUBLIC

Circuit to support solar powered house number system

This circuit allows a set of NiCd batteries to be charged by day and used to illuminate a set of high brightness LEDs by night. The circuit is intended to light up a set of house numbers.

When the solar panel is exposed to light, it generates up to 280 mA at about 12V under load. Diode D2 prevents reverse current through the solar panel. The TIP125 darlington pair is switched off when the solar panel output voltage is above about 11V and switches on when the solar panel output voltage drops. Thus, the panel drives recharges the batteries by day, and allows the LEDs to be driven by the batteries at night.

The suggested components are about $25 from All Electronics, depending on the number of LED sets used.