Mini Solar Light. Home Utility Circuit 5

IMAGEYou can make this Solar light using only a few components. You need a 3 V Solar panel, two 1.5 V Rechargeable Pen cells and few other components. It is a miniature Portable Solar light that can be placed anywhere like garden, porch or even in an outing place. During day time battery charges from Solar panel and at Sunset, White LED turns on for around 6 hours.

Working of the circuit
Small 3V 100 mA Solar panel is available which costs around Rs.80 only. It delivers around 100 mA current in bright Sunlight to charge the battery. Diode D1 prevents the backward flow of current from the battery to the Solar panel during night. Capacitor C1 acts as a Buffer during charging. During day time, D1 forward biases and current flows from the Solar panel to the battery. At the same time, PNP transistor remains cut off since its base is held high by the current flowing from the solar panel through R1. The 0.5 W White LED connected to the collector of T1 remains off. When the sunlight ceases, base of T1 turns low and it conducts to light the White LED. Thus the solar panel acts like a charger as well as a switch to control T1. You can use any PNP transistor that handles more than 400 mA current.
Solar Light
You can convert the same circuit for 6 volt or 12 volt operations to light 1 W and 3W LEDs. For this use 6 or 12 volt panel and 6 V or 12V Battery. SK 100 can handle up to 800 mA current and 1W and 3W LED consumes around 300 mA current. You can replace SK 100 ( Bel 100 P or CK 100 ) with any Medium power transistor like BD140.