EE2031 Mini Project Report

8/10/2019 EE2031 Mini Project Report

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EE2031 Mini-Project Report

Energy Saving Light System

LAB DAY: FRIDAY

GU JUNCHAO A0105750N

XIE KAI A0102016E


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Introduction

In Singapore, many of us might have noticed that some light bulbs are turned on for 24 hours

every day. During the sunny day time, this kind of lights are not helping with lighting at all except

for wasting the energy away. Moreover, a more general case is that we may notice that some

lights are turned on for the whole night. When it is around 2AM~6AM, actually there is almost no

activity in some places but the light bulbs there keep being on. These two cases result in large

consumption of electricity, which should have been saved a lot if the light bulbs can apply certain

energy saving functionality.

Project Idea

Therefore, our project idea is to build an energy saving light system that has the following

features: basic brightness is provided based on the environments luminance, and maximum

brightness is provided if there are some activities.

There are two set of lights in our system: 1. Smart Luminance-Sensitive Lights for basic

brightness 2. Light-Sound Controlled Lightsfor additional brightness.

For the first function, when the sunlight is shining, our energy saving light should be off to save

energy when the sky is cloudy or dark, Smart Luminance-Sensitive Lights are turned on to

provide necessary brightness and their brightness is controlled by the luminance of the

environment. If the environment is dark, some lights are turned on to a certain brightness if the

environment gets darker, those lights will be on with more brightness.

For the second one, when its in the evening (dark enough) and someone passes by(a human

activity), Light-Sound Controlled Lights will be fully on for some time. There is a threshold of

luminance for this set of lights and once it is below certain value and somebody walks by (sound

detected), our system will provide more light for people at night.

As whole system, Smart Luminance-Sensitive Lights will work with Light-Sound Controlled

Lights and we want to achieve:

1. When the environment is very dark, Smart Luminance-Sensitive Lightswill be on to provide

basic lighting and people will still be able to see the environment--so that they are not afraid ofthe darkness

2. When the environment is very dark and people walk by, Light-Sound Controlled Lightswill

be on for some time to provide more light so that people walking under the lights will be able see

the environment more clearly.


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3. When the environment is not very dark, Smart Luminance-Sensitive Lights will not be fully

on to save energy. But they will still be functioning for people to get a glimpse of the area under

lights and provide basic lighting compensation of environment lighting.

4. When the environment is not dark at all, two kind of lights will not be on at all to save energy.


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Components List

Opamp LM358 x 4, Quad 2-input NAND 74LS00 x 1, Quad 2-input NOR 74LS02 x 2, Up/down

binary counter 74LS191 x 1, LED x 9, Light Dependent Resistor (LDR) x 1, Microphone x 1,

some wires, resistors and capacitors.

Circuit Description

General Description: the circuit of our project can be divided into 2 parts. The first part of the

circuit refers to our Smart Luminance-Sensitive Lights, which deals with the analog input and

output. For this part, we built a Pulse-Width-Modulation (PWM) control circuit, in which the

duty cycle produced is controlled by LDR. By using this PWM control circuits output to drive

LEDs, we can adjust lights brightness based on the environments luminance. For the other part,

which is Light-Sound Controlled Lights, an oscillator (timer) of ~1 Hz is built by Opamp in orderto drive the counter, and a detector is made to detect sounds and luminance. In addition,

some logic gates are used as supplement for Light-Sound Controlled Lights. Thus, the second

circuit can achieve that it will turn on LEDs for some time (using counter), if the environment is

dark enough and theres sound detected.

PWM control circuit using Opamp and LDR


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Below is one screenshot about our PWM circuit output. The yellow curve is the voltage of C1

against time, and the blue curve is the voltage of PWM output against time. Noted that the duty

cycle of the PWM output (blue color) is 74.0% on the bottom right corner. Further details about

its characteristics can be found in LDR Characteristics section.


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Oscillator (timer) that drives counter

According to T = 2CRln(3), the period of this timer is ~0.5s


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Sound and Brightness detection


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Logic circuit that enables counter

The condition that enables counter is (sound detected AND very dark) OR (counters output not

equal to zero). Hence, when there is sound and its dark enough, the counter is enabled to

count when it starts to count, its output becomes non zero and this also enables it to continue.

However, if the environment is bright, theres no sound and outputs still zero, the counter cannot

be enabled.

General Output Circuit

LED1, LED3, and LED5 refer to Smart Luminance-Sensitive Lights LED2, LED4, and LED6

refer to Light-Sound Controlled Lights.


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LDR CharacteristicsLab Procedures:

0.Place LDR right below the bright light bulb with constant luminance the resistor in series with

LDR is 8.2K ohm. Then power up the circuit with voltage 6.8v.

1.Place an A4 hard-cover black paper above the LDR and ensure its parallel to the ground here

we use papers vertical distance to the LDR to simulate the luminance of the

environment.

2.Starting from 100cm height from LDR, we decrease the vertical height of the paper gradually

until the distance reaches 0cm.

3. Then we records the duty cycle of PWM output and the voltage across the LDR for every

~10% changes in duty cycle.

4.Repeat step 2~3 until the vertical distance of paper reaches 0cm.

Below is the collected data and the graph generated from the data:

Vertical

Distance(cm)

Duty Cycle Voltage(v)

across LDR

LDR Resistor(K

ohm)

Ln(LDR

Resistor (K

ohm))

100 2.10% 1.20 1.76 0.563689113

19.1 10.10% 1.52 2.36 0.858918391

8.8 19.80% 1.92 3.23 1.17131412

6.6 31.00% 2.40 4.47 1.497998351

4.2 40.10% 2.78 5.67 1.735303179

2.7 50.00% 3.25 7.51 2.015841547

0.7 61.30% 3.88 10.90 2.388385692

0.5 70.20% 4.47 15.73 2.755654295

0.3 80.11% 5.51 35.02 3.556056559

0 100% 6.72 688.80 6.534950953


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ApplicationAssumption 1: the lights are all of 18 W

Assumption 2: the energy consumed by the controlling circuit can be neglected compared to 18

W

Function 1: Smart environment lighting sensitive lights

It is very difficult to quantify the energy saved by smart environment lighting sensitive lights

compared to lights that are on for 24 hours a day as the variables for this kind of lights are too

many. So we will have to make many assumptions here.

Assumption 3: During daytime, most of the time environment is bring enough not to turn on the

smart environment lighting sensitive lights. On average, there will be only about 0.5 hour when

lights will be 5% on(PWM duty cycle is 5%) (For this assumption we did not do any statistical

experiment at all so this is just for the convenience of calculation. In reality, we can control the

value of resistors in series with LDR though to control the system)

Assumption 4: During 18:00 - 20:00, the lighting condition of the environment varies and it follows

a linear change such that PWM duty cycle of smart environment lighting sensitive lights will havelinear change from 0% to 100%. And the same principle applies to time during 6:00 - 8:00 but the

PWM duty cycle is from 100% to 0%.

Assumption 5: From 20:00 to 6:00 in the next day, smart environment lighting sensitive lights will

be fully on.

Normal lights that are on for 24 hours Smart environment lighting sensitive lights

18W*24Hour = 0.432kw*h 18W*10%*0.5Hour + 18W*(100% +

0%)/2*2Hour*2 + 18W*100%*10Hour =0.216kw*h

Energy saved per light: 50%

Function 2: Light-Sound Controlled Lights

For this function, we are also assuming about human activity and the real time system but the

assumptions are simpler.

Assumption 6: Normal lights during night will be on from 18:00 - 6:00 in the next day. For

Light-Sound controlled lights in our system though will only be on from 20:00 - 6:00 in the next

day when human activities are detected.Assumption 7: Light-Sound controlled lights will be mostly on from 20:00 - 1:00 in the next day as

we assume human activity are rather frequent during this time interval. But for 1:00 - 6:00 in the

next day the system will be only be on for about 0.5 hour.

Normal lights for lighting at night Light-Sound controlled lights


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18W*12Hour = 0.216kw*h 18W*(5Hour + 0.5Hour) = 0.099kw*h

Energy saved per light: 54.17%

Conclusion of the whole system in energy saving

Normal lights that are on for

24 hours(6 lights)

Normal lights for lighting at

night(6 lights)

Energy-saving light system(6

lights)

0.432(kw*h)*6=2.592kw*h 0.216(kw*h)*6=1.296kw*h 0.099(kw*h)*3 +

0.216(kw*h)*3=0.945kw*h

100%(reference) 50% 36.46%

Clearly, the comparison shows that our system is very effective in saving energy and besides

that, our system is context-sensitive and therefore will be able to provide enough lighting when

people need it.

Possible improvementsFor this project, we are just doing a showcase of the idea. To install the system and make sure

the system will be able to work in real life, many improvements and extensions can be done to

the current design.

1. One deficit in our current simulation, the LEDs simulating lights are not powerful enough to

influence the LDR. Therefore, the real time feedback effect of lighting controlled by LDR to LDR

sensor itself cannot be simulated. This effect is very important and therefore we need more

experiment on this aspect.

2. Currently we are using counter to provide a short amount of time for Light-Sound Controlled

Lights to be on. However, from our observation, counter heats up very fast and therefore cannot

continuously function. Also, the idea of using counter needs to be revised.

Conclusion

This experiment shows that we can save a large amount of energy with balance between savingenergy and providing enough light based on peoples need by realizing context/environment

sensitivity and flexible output format. Though some deficits remain in the experiment but we can

see the potential of this application in energy-saving and improving smartness of lighting system.

Also, academically this experiment also means a lot as it makes use of different kinds of

sensors, applies analog input/output, digital input/output in parallel and makes use of opamp to

form comparators and oscillators.

Documents

EE2031 Mini Project Report