LIGHT SENSOR / DARK INDICATOR

A light sensor is a module which can sense the presence of light or in other words we can say that it is a dark indicator.


Means in the dark it gives us a output as 1.

Concept :-

LDR

                   In light sensor or in a dark indicator the sensing device is LDR. LDR is stands for Light Depended Resistor. In the presence of light LDR gives very high impedance up to 1M ohm so we get 0 output and in the presence of dark LDR gives very low impedance(negligible) so we get the output 1. A LDR is shown in figure below:-

LDR symbol

List of components :-

•                  330ohm resistor - 1
•                 1M ohm resistor - 1
•              100k ohm resistor - 1 
•                                 LDR - 1
•                         NE555 IC - 1
• 1000 pf ceremic capacitor - 1
•                            Red led - 1
•                       5V battery - 1

Circuit of light sensor :-
                                         We use 555 timer IC in astable multivibrator mode for this purpose.

After making this circuit you can test your output by applying a led with the resistance of 330 ohm.

PCB layout of light sensor :-

print this layout as it is and make your own pcb

m1 and m2 are male connectors M1=5V.

Images :-

                      

top view and 0 output in the presence of light

bottom view

1 output in the presence of dark

                    

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