0 Solar Street Light circuit

Same with the normal street light, this one automatically turns on when environment is dark (night or gloomy rainy days) and off during bright day. An advantage of this lighting system is very easy to build since uses minimal and very common electronic parts. Another advantage is it uses solar power as main source of energy, thus no more 220V supply is needed and environment friendly. It has a built in battery that is charged during the day and supplies power during the night.

Street light circuit

Part List:
R1 - any light dependent  resistor (LDR)  2k to 1Meg
R2 - 50 kilo ohms 1/4W
R3 - 120 ohms 1/4w
R4 - 1 kilo ohms 1/4W
D1 - 1N5817, 1N5818 or any diode with low voltage drop
Dz - 2.7V zener diode rated 1W
Q1 - 2N2907, 9012, or similar PNP transistor
Q2 - 2N2222, 9013, or similar NPN transistor
Lamp - 1.5V to 2.5V rated flashlight bulb 30mA to 75mA
Bat - 2 NiCd cell rated 1.2V @ 800mAh or higher
Solar cells - MPT3.6-150 Flexible Solar  or any  3.6V @ minimum 100mA cells

If you plan to use LED instead of  lamp, just follow the diagram below. The resistance is equal to 10 ohms rated 1/4W. Use only red or orange LED to make it work. Other LED like white or blue requires higher forward voltage (see LED forward voltage table for more info ) and our source is around 2.4V only.

Replacing buld with LED

White , blue and other high intensity LED requires 3V to 3.6V forward voltage. Our battery can supply only 2.4V, thus impossible for us to use these LEDs using the same circuit above. But if you want to use these LEDs, try modifying the circuit above and add the joule thief circuit.