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Night Lamp using 555

Summary

By: 
Himanshu Choudhary

Ever imagined how the street lights get turned ON automatically in the evening and gets switched OFF in the morning? Is there anyone who comes early morning to turn off these lights? The following circuit can perform this job properly. This project uses the output from a simple light/dark activated circuit known as LDR (Light Dependent Resistor) and drives a relay in its output which can be further coupled to switch on/off an electrical appliance in a household.

An appliance can be made dark or light activated by slightly changing the circuit’s configuration.  This idea finds numerous applications such as, automatic watering of gardens in evening, automatic night lamp, dark activated siren and so on. 

Description

 

In this project, a variable resistor is used to set the sensitivity of the LDR since LDR the resistance of LDR changes in response to the ambient light. The resistance decreases as the intensity of incident light increases and vice versa. In the absence of light, LDR exhibits a resistance of the order of mega-ohms which decreases to few hundred ohms in the presence of light.

An IC 555 timer is also used. When the light falls on LDR (Light Dependent Resistor), its resistance becomes very low and as a result IC1 doesn’t work. So the voltage at PIN2 becomes zero. Due to this there will be no output at PIN3 as a result the lamp remains switched OFF.

When the LDR is not lighted, its resistance becomes high. As a result voltage across LDR becomes high enough to make IC1 work. Due to this PIN2 of IC1 receives a positive pulse or a high output that could be enough to activate the relay. So PIN3 receives high voltage and drives the lamp in ON state. 

Circuit Diagram

Components

Resistor Image
Resistor

Resistor is a passive component used to control current in a circuit. Its resistance is given by the ratio of voltage applied across its terminals to the current passing through it. Thus a particular value of resistor, for fixed voltage, limits the current through it. They are omnipresent in electronic circuits.

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Capacitor image
Capacitor

 

 

Capacitor is a passive component used to store charge. The charge (q) stored in a capacitor is the product of its capacitance (C) value and the voltage (V) applied to it. Capacitors offer infinite reactance to zero frequency so they are used for blocking DC components or bypassing the AC signals. The capacitor undergoes through a recursive cycl...

Potentiometer, Variable Resistor Image
Potentiometer

Potentiometer (Pot) is another class of variable resistors and is used as an adjustable voltage divider. It consists of a fixed resistance track having connections at both ends and a sliding contact, called wiper, which moves along this track by turning the spindle. If only one of the connections and wiper are used, it behaves as a variable resistor or rheostat. In case wiper is not used, it will offer fixed resistance across th...

DPDT | Double Pole Double Throw Relay Image
DPDT relay

DPDT stands for double pole double throw relay. Relay is an electromagnetic device used to separate two circuits electrically and connect them magnetically. They are often used to interface an electronic circ...

555 Timer | IC 555 | NE555
555 Timer IC

555 is a very commonly used IC for generating accurate timing pulses. It is an 8pin timer IC and has mainly two modes of operation: monostable and astable. In monostable mode time delay of the pulses can be precisely controlled by an external resistor and a capacitor whereas in astable mode the frequency & duty cycle are controlled by two external resistors and a...

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