Sunday, February 20, 2011

§ LDR+555: Dark Sensor


Component used:

1)        9v Battery with cap

2)        ON/OFF Switch

3)        L.D.R (Light Depending Resistance)   

4)        I.C 555 with Base

5)        L.E.D (Light Emitting Diode) 5 pieces.

6)        Variable Resistance of 50K ohms

7)        P.C.B (Printed Circuit Board)

This circuit uses the inbuilt comparator of 555.LDR is a special type of resistance whose value depends on the brightness of light which is falling on it. When light falls on the LDR then its resistance decreases which results in increases the voltage at pin2 comparator compares between the input voltage from pin2 and 1/3rd of the power supply voltage. When input falls below 1/3rd then output is set high otherwise set low. When light falls on LDR its input voltage rises so we get 0 volt at pin 3, besides in poor light we get positive output at pin3 to drive LEDs.

Circuit Diagram : design the circuit using PCB-WIZARD.


PCB:
normal


real world


artwork


unpopulated

NOTE: We can also use LM358 or LM324. These are comparator ICs.
LM358 pin details


Circuit Using LM358




real world

artwork
                                                                                                                                              ~pg

1 comment:

  1. Hey buddy, LED1...LED4 need each one a limiting resistor(4!). Otherwise they will blow up. Or 555 will blow up. Or the battery. You never know.

    ReplyDelete

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