illuminator

1. INTRODUCTION:

The INTELLIGENT ILLUMINATOR-2 is an automatic battery backed emergency light system on upgraded version of the earlier project named INTELLIGENT ILLUMINATOR. It is being designed to plug & forget, in a sense that once plugged to ac mains; no human intervention is required except for unconditional switching.

Comprising of discrete and integrated components, this system is capable of sensing the surrounding light, battery voltage, and presence of ac mains and take action accordingly.

The need for design and development of the project arises from the frequent black-outs familiar these days. The smartness of the system alleviates the problem and provides a better solution over candle sticks and other commercially available lighting products.


2. BACKGROUND:

As of our knowledge, our Nepal, the second largest country for water resources, has a potential of lighting every house in Asia, but a matter of unfortunate ness, we and most of our citizens face a power shortage and stay in darkness. The development of this project has been undertaken to tackle the problem and eliminate the darkness. It has been designed to power enough smartness to replace contemporary illumination equipments.

3. OBJECTIVES:

· To design and develop a domestically applicable project for illumination.
· To apply the knowledge gained in classroom.
· To design a project to tackle practical problem.


4. PROJECT FEATURES:

4.1 High power:
The system can handle power rating up to 2A at 12V safely.

4.2 Continuous Power:
As far as available the power derived from ac mains wall outlet is provided (in case of larger power requirement the battery acts as a power-buffer) and upon its failure backup battery is brought into use.

4.3 Ambient Light Sensor:
If the locality under sensor coverage is lighted, even manual switching can't switch on the light. As soon as darkness is sensed light is switched ON but for a fixed short interval of time in order to save power. During the time interval, a beep tone and indicator is also made active. The time interval can be changed externally.

4.4 Manual Switch:
After darkness has been sensed, the manual switch is used to switch ON and OFF the light. During this time, the manual switch overrides the sensor and other control circuits.

4.5 Battery Charging Regulator:
To ensure longer battery life, this section doesn't allow discharging the battery below safe level and if such is the case , starts charging on availability of ac power ; an indicator also indicates the voltage state. The charging is controlled by IC and once full the battery is maintained in float state.


5. BLOCK DIAGRAM: DESCRIPTION:
The projects consists of two sections
5.1 charger and battery section
5.2 timing and control section

5.1 Charger and battery section :-
As shown in fig no: 1, the charger and battery section comprises of eight blocks.

The first block is STEP DOWN TRANSFORMER that lowers the higher ac voltage to suitable lower one. The conversion is from 220V to 18V ac.

RECTIFICATION AND FILTERING block takes in the lower ac voltage, rectifies it so that it has an average value and makes it ripple free by filtering process; the output is a smooth (unloaded condition ) dc voltage.

Voltage regulation is required for the ripple free voltage during loaded condition. The VOLTAGE REGULATION block provides a constant output voltage. It is also responsible for limiting the voltage in order to limit the maximum current that can flow during low resistance conditions.

The next block is REVERSE CURRENT PROTECTOR which stops the battery from discharging through circuit ahead when ac line fails.

The CURRENT SENSING block lies on the path that connects the mains source and the overall load and keeps an eye on the charging current and provides a proportional voltage to the regulation block.

The RECHARGABLE BATTERY is the store house of energy in chemical form from which electrical energy can be put in or taken out as per requirement.

The voltage state of the battery is monitored by the COMPARISION block and provides outputs that are fed to indicators.

The INDICATORS are simple on\off devices that make it possible for us to see the voltage state of the battery.

5.2 Timing and control section:-

The timing and control section consists of six blocks as shown in fig: 2. this section is used for automatic switching of light bulbs and thus comprises of sensors and control units.

The AMBIENT LIGHT SENSOR senses the light in the surrounding it is placed in and gives either high or low output based on light intensity.

The TIMING AND CONTROL CIRCUITS receives signals from the sensor as well as manual switch and generates control signal to be used by power switching block as well as indicator and buzzer block.

POWER SWITCHING block switches the lights on and off based on the signals received from timing circuits and manual switch.

The block named BUZZER AND INDICATORS show the light condition in the locality.

On precedence base, the MANUAL SWITCH resides at the top. It can override all the automation and on/off the light unconditionally provided that light is gone.

The LIGHT can be one of various types of light like LED, CFL bulb’s, inverter coupled fluorescent tubes.


6. CIRCUIT DIAGRAM:

7. CIRCUIT DESCRIPTION:

The overall circuit is built from discrete components as well as integrated packages. The fore mentioned two sections require the following components:

7.1 Charger section:

Component name: Part no: No:

Transformer 9 -0- 9, 1 AMP 1
Diodes 1N4007 6
Capacitor 1000mF, 25V 1
Voltage regulator LM317 2
Resistors
¼ W 220 W 1
2.2 kW 2
100 W 2
10 kW 3
1.5 kW 2
1 W 1 W 1
Transistors BC548 1
Preset 200 kW 2
Comparator unit LM324 1
Diode 5402 1
Indicators LED’s 3 mm 3
Battery 6 V Sunca batteries 2(Series)

Wires, plugs, clips and board

7.2 Timing and control section:

Component name: Part no: No:

Comparator units LM324 1
Timer ic NE555 2
Capacitors 10 mF electrolytic 1
100 mF electrolytic 1
0.1 mF ceramic disc 3
Diodes 1N4007 4
LDR 1
Resistors
¼ W 10 KW 4
68 kW 1
3.3 kW 1
1 kW 1

Transistors BC548 1
SL100 1
Preset 200 kW 2
Variable resistor (Volume) 470 kW 1
Indicator LED’s 3 mm 2
Switch DPDT (Double pole double terminal) 1
Buzzer Suitable 1
Light 10 mm LED array 1(up to 5)

Wires, plugs, clips and board

8. OPERATION:

8.1 Charger section:
The basic idea lying behind the charger section is charging a lead acid battery by regulated voltage, which makes sure that the battery doesn’t over charge. Current limiting is also employed in order o prevent the battery from drawing excessive amount of current which eventually degrades its life.

The transformer steps down the ac voltage to 18 V ac (9 and 9 terminals). (18 V ac is taken in consideration that the local line supply is very poor voltage source). This small ac voltage is rectified by four diodes, B1, that are configured in full bridge mode. The output is a pulsating voltage that has some dc value. The ripples are filtered by the capacitor C1.A LED indicator connected through 2.2 kW (R1) indicates the availability of line power. The voltage is now ready to be regulated by IC1.The resistor network (R2 and R3) configured around IC1 determines the output regulated voltage which charges the battery. If the battery is discharged too much and tries to draw large current, it is sensed by R4 and generates a proportional voltage at point B. This voltage turns on T1 which diverts some of the current flowing through R3. The result is decrease in the voltage across terminals A and B.

D3 protects battery discharge through the circuit ahead and D4 saves IC1 from damage due to backward current.

The other part is used to monitor the voltage state of the battery. IC1 and the network around it generate almost a constant voltage to be used by comparator (IC2) and reference generating presets. Two presets P1 and P2 each generate about one third of discharged and charged battery voltages which are then fed into IC2.

The battery voltage is sampled using three resistors of 10 kW each. The sample is also about one third of the battery voltage and is fed into remaining inputs of IC2. According to the configuration shown in figure, D2 (green color) turns on when battery voltage reaches around 13.2V (13.05 to 13.3V) and D1 (red color) turns on when battery voltage gets down to 11.5 to 12V.

Now as long as ac line power is available the battery is kept in full charge in standby mode. Power is taken from points A to B. Because the power output is taken from battery terminals, continuous dc power is obtained.

8.2 CONTROL AND TIMING SECTION:
This section is for controlling the on and off of the light without human intervention. For this purpose light dependent resistor (LDR) or photodiode senses the surrounding light and generates proportional voltage across R1.This voltage and another reference voltage described by preset P2 are compared by opamp IC1 which is configured as comparator with positive feedback. The reason for positive feedback is to eliminate any additional noise and to compare with two thresholds so that two light conditions can be seen by the sensor. All the inputs and outputs are buffered so that loading doesn’t cause any serious problems.

The output of the comparator is used to trigger IC2 which is configured as one-shot generator. The sensor output is coupled through transistor to get a negative pulse to feed to the trigger input of IC2. The capacitor C1 is used to prevent any false triggering. The one shot period of IC2 can be changed by varying the resistance VR1 or the value of C3. The output of this IC is used to activate or disable IC3 which generates pulse trains with less than 50% duty cycle (the duty cycle can be changed by changing R7 and C4) and to turn on the lights. The output of IC3, which is built as astable multivibrator, drives the indicator LED and buzzer. These indicate that it is dark in the locality the sensor is placed and the light has been turned automatically. The duration is controlled by VR1. The switch SW1 is double pole double terminal and is used for manual control which is the ultimate control after it is dark. It does two things: it can turn on T2 from output of sensor and disable the timing circuits. D2 and D3 OR the signals from manual switch and the output of IC2 and outputs to the base of T2.

Transistor T2 is a medium power npn transistor (which can be changed to power one if more load power is required), and when receives a small current at its base, turns on the load connected to the power and its collector. Thus it acts like an electronic switch.

9. ENHANCEMENTS AND UPGRADES:

The following enhancements are being considered though they may change depending upon time and need.

9.1 Charge meter for battery.
This project can be further upgraded by using charge meter for the battery by which it can regularly and exactly monitor the level of battery.

9.2 Charging through photo voltaic cell ( Solar Panel)
Most of the rural areas are not electrified yet and lighting by kerosene is costlier and unsafe these days. This very project can be modified to suit the situation by using solar panel for charging purpose of battery.

9.3 Clock that shows the time of day as well as the time of battery back-up used.
This is to make this project multipurpose functioning equipment that can replace wall clock and this makes the user to be notice how much time the battery can work safely.

9.4 Multiple blocks of sensor (e.g. one for each room/stairs).
In the specified home there is possibility of having unequal light in rooms. By using multiples block of sensor, room having low light have can be lightened earlier and room having high light have can be lightened a little later. All of these can be maintained with full automation.

9.5 Fully remote control in conjunction with manual switching.
This is for controlling the equipment from a certain distance for user’s convenience.

9.6 Microprocessor control.
The use of microprocessor or a microcontroller can greatly enhance the perforation as well as can add flexibility in modification as they can software controlled by appropriately coding them.



10. CONCLUSION:

The project development is a direct consequence of the current situation of load shedding imposed by NEA and application of the knowledge gained in the course of study. The emphasis has been placed to utilize the locally available commercial components.

As anticipated few customized units has been sold. And it can be inferred that the project is not only a mere fulfillment of course requirements, but a genuine commercially viable product (Mass production can reduce cost per unit).

11. PROJECT OUTPUT:

It’s the expected output that takes on the nerve of the designer and deviate from the actual output. To achieve the goal, redesign and reconstruction of the tentative circuit were frequent and there were frustrating moments. However, there were good results. The charger could charge the battery to about 13 or slightly higher voltage. It was also not necessary to plug off the charger from ac line, instead the battery was kept in standby float charge mode. The indicator indicated the voltage state but slightly unlinear characteristics existed. The other section had problem with sensing part which later worked fine. The timing circuit gave a superb output. Its output caused to indicate the light. The manual switch could override the control circuits.

12. REFERENCES



Books:
Robert L. Boylestad, Louis Nashelsky,
Electronic Devices and Circuit Theory,
Prentice-Hall of India, 2005

The Art of Electronics,
Cambridge University Press