AUTOMATIC NIGHT LAMP WITH MORNING ALARM

ABSTRACT:

Automatic Night Lamp with Morning Alarm System is a simple yet powerful concept, which uses transistor as a switch. By using this system manual works are 100% removed. It automatically switches ON lights when the sunlight goes below the visible region 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 the sunlight comes, visible to our eyes and activates the morning alarm. 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. The resistance of light dependant resistor (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. This project uses regulated 12V, 750mA power supply. 7812 three terminal voltage regulator is used for voltage regulation. Bridge type full wave rectifier is used to rectify the ac out put of secondary of 230/18V step down transformer.

COMPONENTS REQUIRED:

S.NO	COMPONENTS	RANGE/TYPE	QUANTITY
1	IC	IC 7806,IC NE555,UM66	1,1,1
2	Transistor	BC 548	2
3	LDR	-	2
4	Diode	IN4007,IN4001,Zener diode(3.3V,0.5W)	4,2
5	Resistor	1K,150K,120K,220Ω,580Ω,560Ω	2,2,1,1,1,1
6	Capacitor	1000µF,0.01µF	1,2
7	LED	white	1
8	Transformer	230/18V	1
9	Power supply	230V  ac,50Hz	1
10	Battery	9V	1
11	Loudspeaker	-	1

COMPONENT DETAILS:

555 TIMER:

The 555 Timer IC is available as an 8-pin metal can, an 8-pin mini DIP (dual-in-package) or a 14-pin DIP.

This IC consists of 23 transistors, 2 diodes and 16 resistors. The explanation of terminals coming out of the 555 timer IC is as follows. The pin number used in the following discussion refers to the 8-pin DIP and 8-pin metal can packages.

UM 66 :

It is the simplest melody generator circuit you can make using an IC.The  UM66 series are CMOS IC’s  designed for using in calling bell, phone and toys. It has a built in ROM programmed for playing music. The device has very low power consumption.The melody will be available at pin3 of UM66 and here it is amplified by using Q1 to drive the speaker.

IC 7806:

7806 is a 3-terminal positive voltage regulator designed with built in internal current limiting, thermal shutdown and safe-area compensation for maximum flexibility and safety .

With adequate heat sinking provided, USM 7806 can deliver up to 1.5A output current. USM 7806 can be used as fixed voltage regulator in a wide range of applications where local voltage regulation is preferred for elimination of noise and distribution problems associated with single-point regulation. USM 7806 can also be used (by adding external components) to obtain adjustable output voltages and currents.

ZENER DIODE:

A Zener diode is a type of diode that permits current not only in theforwarddirection like a normal diode, but also in the reverse direction if the voltage ilarger than the breakdown voltage known as "Zener knee voltage" or "Zenervoltage". The device was named after Clarence Zener, who discoverethis electrical property

BC548:

 The exact specs of a given device depend on the manufacturer. It is important to check the datasheet for the exact device and brand you are dealing with. Philips and Telefunken are two manufacturers of the BC548.

CIRCUIT DIAGRAM:

click here to download circuit diagram

CIRCUIT EXPLANATION:z

This circuit automatically turns on a night lamp when bedroom light is switched off. The lamp remains ‘on’ until the light sensor senses daylight in the morning. A super-bright white LED is used as the night lamp. It gives bright and cool light in the room. When the sensor detects the daylight in the morning, a melodious morning alarm sounds.

The circuit is powered from a standard 0-9V transformer. Diodes D1 through D4 rectify the AC voltage and the resulting DC voltage is smoothed by C1. Regulator IC 7806 gives regulated 6V DC to the circuit. A battery backup is provided to power the circuit when mains fails. When mains supply is available, the 9V rechargeable battery charges via diode D5 and resistor R1 with a reasonably constant current. In the event of mains failure, the battery automatically takes up the load without any delay. Diode D5 prevents the battery from discharging backwards following the mains failure and diode D6 provides current path from thebattery. The circuit utilises light-dependant resistors (LDRs) for sensing darkness and light in the room.

 The resistance of LDR is very high in darkness, which reduces to minimum when LDR is fully illuminated. LDR1 detects darkness, while LDR2 detects light in the morning. The circuit is designed around the popular timer IC NE555 (IC2), which is configured as a monostable. IC2 is activated by a low pulse applied to its trigger pin 2. Once triggered, output pin 3 of IC2 goes high and remains in that position until IC2 is triggered again at its pin 2. When LDR1 is illuminated with ambient light in the room, its resistance remains low, which keeps trigger pin 2 of IC2 at a positive potential. As a result, output pin 3 of IC2 goes low and the white LED remains off. As the illumination of LDR1’s sensitive window reduces, the resistance of the device increases. In total darkness, the specified LDR has a resistance in excess of 280 kiloohms. When the resistance of LDR1 increases, a short pulse is applied to trigger pin 2 of IC2 via resistor R2 (150 kiloohms). This activates the monostable and its output goes high, causing the white LED to glow.

Low-value capacitor C2 maintains the monostable for continuous operation, eliminating the timer effect. By increasing the value of C2, the ‘on’ time of the white  LED can be adjusted to a predetermined time. LDR2 and associated components generate the morning alarm at dawn. LDR2 detects the ambient light in the room at sunrise and its resistance gradually falls and transistor T1 starts conducting. When T1 conducts, melody-generator IC UM66 (IC3) gets supply voltage from the emitter of T1 and it starts producing the melody. The musical tone generated by IC3 is amplified by single-transistor amplifier T2. Resistor R7 limits the current to IC3 and zener diode ZD limits the voltage to a safer level of 3.3 volts. The circuit can be easily assembled on a general-purpose PCB. Enclose it in a good-quality plastic case with provisions for LDR and LED. Use a reflective holder for white LED to get a spotlight effect for reading. Place LDRs away from the white LED, preferably on the backside of the case, to avoid unnecessary illumination. The speaker should be small so as to make the gadget compact.

ADVANTAGES: 

Highly sensitive

      Works according to the light intensity

        Fit and Forget system

   Low cost and reliable circuit

           Complete elimination of manpower

           Can handle heavy loads up to 7A

          System can be switched into manual mode whenever required

APPLICATIONS

  Bed Rooms

          Hostels and Hotels

          Balcony / stair case / parking Lightings

          Street lights

          Garden Lights

CONCLUSION:

        Thus the working of the automatic night lamp with morning alarm was explained in detail.