Automatic Street Light
Automatic Streetlight needs no manual operation for switching ON and OFF when there is need of light. It detects itself weather there is need for light or not. When darkness rises to a certain value then automatically streetlight is switched ON and when there is other source of light i.e. day time, the street light gets OFF. The sensitiveness of the street light canal so be adjusted. In our project we have used four L.E.D for indication of bulb but for high power switching one can connect Relay (electromagnetic switch) at the output of pin 1 of I.C LM358 Then it will be possible to turn ON/OFF any electrical appliances connected all the way through relay.
This circuit uses a popular timer I.C LM 358. I.C LM358 is connected as comparator with pin-6 connected with positive rail, the output goes high(1) when the trigger pin 3 is at lower then voltage level at pin no 2. Conversely the output goes low (0) when it is above pin no 2 level. So small change in the voltage of pin-2 is enough to change the level of output (pin-1) from 1 to 0 and 0 to 1. The output has only two states high and low and can not remain in any intermediate stage. It is powered by a 12V power supply. The circuit is economic in power consumption.
Pin 4 is ground and pin 8 is connected to the positive supply and pin 1 is grounded. To detect the present of an object we have used LDR and a source of light. LDR is a special type of resistance whose value depends on the brightness of the light, which is falling on it. It has resistance of about 1 mega ohm when in total darkness, but a resistance of only about 5k ohms when brightness illuminated. It responds to a large part of light spectrum. We have made a potential divider circuit with LDR and 10K...
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