09-02-2013, 03:30 PM
AUTOMATIC NIGHT LAMP WITH MORNING ALARM
AUTOMATIC NIGHT .pptx (Size: 2.53 MB / Downloads: 205)
INTRODUCTION
By using Automatic night lamp with morning alarm system manual works are 100% removed.
It automatically switches ON a night lamp lights when the sunlight goes below the visible regions of our eyes. This is done by a sensor called Light Dependant Resistor (LDR) which senses the light actually like our eyes. It automatically switches OFF lights whenever sunlight comes, visible to our eyes and activates a melodious morning alarm sound.
Components required:
LDR and transistor are the major components.
This project uses regulated 12V power supply.
IC NE555 & LM UM66 is used.
some of resistors, capacitors & LED are used.
Transformer
A step down transformer is used.
Contains 12 v.
Connected with main AC supply.
Output voltage – 28.5v(p-p) ac.
Light Dependent Resistor
A Light dependent Resistor is a device which has a resistance which varies according to the amount of light falling on its surface.
LDR is made of a high resistance semiconductor.
LDR is a resistor whose resistor decreases with increasing light intensity.
If light falling on the device is of high enough frequency ,photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band. The resulting free electron conduct electricity, thereby lowering resistance.
SWITCHING REGULATOR NE555
555 is a very commonly used IC for generating accurate timing pulses.
Two modes of operation:
> MONOSTABLE
> 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 capacitor.
MONOSTABLE
A mono stable multivibrator (MMV) often called a one-shot multivibrator.
It is a pulse generator circuit in which the duration of the pulse is determined by the R-C network, connected externally to the 555 timer.
In such a vibrator, one state of output is stable while the other is unstable.
The time taken in storage determines the pulse width.
TRANSISTOR AS A SWITCH
The LDR varies according to the light falling on it. This LDR is connected as biasing resistor of the transistor.
According to the light falls on the LDR, the transistor is operated in saturation and cut-off region. This transistor switches the relay to switch on/off the light.
CONCLUSION
Manual works are 100% removed.
By using this system energy consumption is also reduced because nowadays the manually operated street lights are not switched off even the sunlight comes and also switched on earlier before sunset. In this project, no need of manual operation like ON time and OFF time setting. LDR and transistor are the main components of the project.