ELECTRONICS STREET LIGHT SWITCH

Circuit Description of Electronics street light switch 

As electronics street light switch is a switching circuit so, for more detail we can divide this circuit into two section i.e. power supply and switching circuit.

In this power supply section the work of step-down transformer is done by register R₁ and further rectification to change into 9.1V dc is by diode D₁ and zener diode ZD₁. The output voltage across zener diode is further filtered by capacitor C₁ and c

 The another section  of street light is switching section built around light-dependent register LDR₁ with the help of transistor T₁ through T₃ and timer IC NE555 (IC₁), where LDR₁ is used as sensor of this switching circuit.As in day time the resistance of LDR₁ remain low but it is reverse in night time i.e. high resistance is offered by LDR₁. For this property of LDR₁ the timer IC used in this circuit is as inverter. So, high input at pin 3 is provided by low input at pin 2 and vice-versa. Lastly, this inverter is used to turn street bulb B₁ on with the help of triac (triac is activated).

The transistor T₁ and T₂  is remain cut-off to make pin 4 and pin 8 of IC₁ low due to light fall on LDR₁ during day time. Due to this transistor T₃ is also cut-off and trigger voltage is not received by IC₁ through pin 2. As a result the output voltage at pin 3 is low which does not activate triac and the street bulb does not glow.

     Automatic street light switch

PARTS LIST

Resistors (all ¼-watt, ~+mn~ 5% Carbon)

R₁ = 10 KΩ/10-watt

R₂ = 33 KΩ

R₃ = 39 KΩ

R₄, R₆, R₇ = 10 KΩ

R₅ = 100 Ω

Capacitors

C₁, C₅ = 0.1 µF

C₂ = 1000 µF/25V

C₃ = 10 µF/25V

C₄ = 0.01 µF

Semiconductors

IC₁ = NE555 timer IC

T₁, T₃ = BC548

T₂ = 2N2222

ZD₁ = 9.1V/0.5V

D₁ = 1N4001

Triac₁ = BT136

LED₁ = RED color

Miscellaneous

LDR₁ = light-dependent resistor

F₁ = Fuse, 5A

B₁ = 100W/ 230V AC

SW₁ = On/off Switch