[IEEE 2012 1st International Conference on Emerging Technology Trends in Electronics, Communication...

Wireless Smart Power Saving System For HomeAutomation

Jalpa Shah,Lokesh Pathrabe,Brijesh PatelInstitute of technology,Nirma university,Ahmedabad,Gujarat,India

[email protected][email protected]@nirmauni.ac.in

Abstract—Mostly in home and office appliances like lightand fan are manually controlled which leads to powerwastage. They are left ON even if there is no usage andeven when the appliances are in use their operation isnot controlled by environmental conditions like daylightand temperature variation. By making a smart automatedcontrolling system for appliances we can save the power byhuge amount. In this paper we are providing a solution forpreventing the wastage of power in a comfortable and costeffective way. Our system consists of an electronic door lockand power saving module. When the person enters the correctpassword in door lock the power saving module is switchedon. The power saving module switches the appliances in theroom based on the presence of the person. It also controls thepower delivered to fan and light according to temperature ofroom and natural daylight intensity.

I. INTRODUCTION

Fig. 1. Power consumption comparison

Work in home automation system is still underdevelopment phase and we have not come across anyeffective and low cost home automation system. As theFig. 1 shows the amount of power that can be saved bysmart control. The comparison of power consumptionat home with and without a smart control system areshown in Table I[2] . With smart control the total powerconsumed can be reduced by about 18%. A ZigBee based

TABLE IENERGY CONSUMPTION COMPARISON

Scenario Without smart With smart Difference Costcontrol(kWh) control(kWh) (kWh) saving($)

Living 4044.596 2780.448 1264.148 227.55RoomDining 183.553 123.841 59.712 10.75AreaKitchen 2087.024 2061.820 25.204 4.54Bed 3366.062 2736.425 629.637 113.33Room

home automation system and Wi-Fi network integratedthrough a common home gateway have been developedearlier [8]. A remote controlled home automation systemhave been developed using bluetooth technology[3]. Asmart door lock home automation system [1] in which theappliances of home can be controlled and monitored fromthe door lock connected with Zigbee network. Most of thesystems developed earlier are dependent on the motionsensing of the user in the room which can fail if usersmovements are minimum (sitting or sleeping). Anotherproblem is the cost of wireless network. The use of Zigbeeand other protocol devices increases the cost of the system.The system we propose is free from these problems.Instead of just sensing the motion, the system also countsthe number of persons in the room and decides theroom occupancy status to prevent any errors. Insteadof just ON-OFF switching, it also monitors theirintensity through a power control drive according tothe daylight availability and temperature of the room.For creating a wireless network we have used low costRF modules that are easy to use and easily available.

The user can enter the house by entering the correctpassword in the digital door lock. It unlocks the door andenables the power saving module by turning the powersupply ON. Thus when the user is not present in thehouse the power saving module is switched OFF and turns

2012 1st International Conference on Emerging Technology Trends in Electronics, Communication and Networking

978-1-4673-1627-9/12/$31.00 ©2012 IEEE

Fig. 2. Block diagram of system

ON only when a correct password is provided. Once thepower saving module is active the two transmitters sendtheir respective sensor readings to the main receiver. Onecircuit has temperature sensor LM 35 and light sensorOPT101 and a RF transmitter we call it Node2. Thesesensors are used to decide the environmental conditionsand requirement of the user. The other circuit has a pair ofPIR sensors and RF transmitter we call it Node1. Node1decides whether the room is occupied or not. The readingsfrom both the nodes are transmitted to the Base stationwhich contains RF receiver and power control circuit.The reading from the two nodes is used to calculate thefiring angle. By changing the firing angle we can not onlyswitch the appliances ON and OFF but can also vary thepower delivered to them. So if the temperature is low thepower delivered to the fan will be lowered, similarly if thenatural light intensity is low i.e. during evening the powerdelivered to the light will be increased.

II. HARDWARE ARCHITECTURE

A. Wireless RF module

Fig. 3. 433MHz RF Transceiver module

These RF modules[7] are easily available implementedat low cost compared to Zigbee based devices. Transmit-ter and receiver modules are tuned to work correctly at433.92MHz. Transmitter can be powered from 3 to 12V

power supply while receiver accepts 5V. 5V is commonfor AVR microcontrollers so no problems with interfacing.Modules do not require addition components just applypower and connect single data line to send informationto or from. For better distance we can put 30 35cmantennas. Modules use Amplitude-Shift Keying (ASK)modulation method and uses 1MHz bandwidth. The datais serial send and received through these modules frommicrocontrollers. This makes the system cost effective.The range as tested in free space is:

At 7000bps, Range about 90mAt 5000bps, Range about 100mAt 2000bps, Range over 150mAt 1000bps, Range over 150m

For sending data through these transmitters and receiversVirtual Wire library[9] for Arduino IDE is used. Thedetails about the data packet is given below. Each messageis transmitted as:

• 36 bit training preamble consisting of 0-1 bit pairs• 12 bit start symbol 0xb38• 1 byte of message length byte count (4 to 30), count

includes byte count and Frame check sequence (FCS)bytes

• n message bytes• 2 bytes FCS, sent low byte-hi byte

B. Electronic door lock

The door lock uses a 4 digit password to open. The 4digit password entered by user is stored in the EEPROMof the microcontroller. Atmega 328 provides 1KB ofEEPROM. The 4x4 keyboard and 16X2 LCD display isused to enter the password, when the password is correctthe door lock can be unlocked by rotating a servo motorconnected to a rack and pinion structure.

C. Occupation sensor node

Fig. 4. Passive Infrared Sensor(PIR)

A Passive Infrared (PIR) is a sensor detects the presenceof a nearby objects without any physical contact. PIRsensors are used as proximity sensor. A proximity sensorgenerally emits an electromagnetic or electrostatic field, or


978-1-4673-1627-9/12/$31.00 ©2012 IEEE

a beam of electromagnetic radiation and looks for changesin the field or return signal. The object being sensed isoften referred to as the proximity sensor’s target.

Fig. 5. PIR range

The maximum distance that this sensor can detect isdefined nominal range which in this case is up to 3-4 m.The sensor has three terminals. Vcc, GND and OUT theoutput is analogue. When the sensor detects any motion itprovides +5V output otherwise 0V.

Fig. 6. PIR occupation sensor

The sensor usually used for sensing motion hasbeen used here for detecting the direction of mo-tion. By using two PIR sensors suitably and inter-rupt programming in microcontroller the number of per-sons entering and leaving the room can be counted.Fig. 6 shows how the two PIR sensors are placed at adistance of few centimetres. The PIR sensor encounteredfirst is shown by bigger size and the sensor encounteredlater is shown by smaller size. Phase difference betweenthe readings of the two sensors can be used to detectthe directions of the movement. The microcontroller iscontinuously reading the sensor pair. User while movingin or out of the room will pass through these sensorsone by one. Both the sensor will give HIGH signal tothe microcontroller. If PIR1 sensor, as shown in the Fig.6 gives +5V before the PIR2 sensor then the person ismoving IN the room. If PIR2 sensor gives +5V before thePIR1 sensor then the person is moving OUT of the room.Whenever a person is detected entering or leaving the roomthe count is incremented or decremented respectively. Thuswe can know number of persons available inside the room

at any moment and whether the room is empty or occupied.Accordingly we can switch on or off the lights and fan.

D. Temperature and light sensor node

Fig. 7. Sensor node

Fig. 7 shows the circuit of sensor node and itscomponents. This node transfers the temperature andlight intensity information to the receiver through the433MHz transmitter. The light sensor used is OPT 101it provides analogue output proportional to the lightintensity which is converted to digital by analogue todigital converter (ADC) available in the microcontroller.Similarly temperature sensor LM 35 also gives analogueoutput that is converted to digital by ADC. The measuredanalogue value is compared to some preset value insoftware. After analysing the sensor readings signal issent to the receiver for changing the power delivered tothe load.

E. Base station

Fig. 8. Base station

Fig. 8 shows the circuit of base station. The sensorreading from the two sensor nodes is received by the


978-1-4673-1627-9/12/$31.00 ©2012 IEEE

receiver. The microcontroller compares the received sensordata to a preset values to decide the amount of powerto be delivered. The AC control circuit obtains signalfrom the microcontroller for changing the firing angledelay of the triac circuit. Fig. 9 shows the block diagram

Fig. 9. Power control circuit

of AC control circuit. The zero-crossing detector(ZCD)gives high pulse whenever the AC supply signal crossesthe x-axis. The ZCD circuit consists of 4N35 and 12Vtransformer. The signal from the ZCD is used to interruptthe microcontroller. After getting interrupted it waits fora period of firing angle. After a delay of firing angle(α)the microcontroller triggers the triac through opto-couplerMOC3010.

Fig. 10. Change in AC supply

The Fig. 10 shows how the power is changed by chang-ing the firing angle of the triac through a microcontroller.The shaded region of the waveform is delivered to theload and unshaded region is blocked by the triac. Thus thepower can be varied from zero to maximum value.

III. SOFTWARE ARCHITECTURE

This section contains software details of all the modulesin the system.

A. Electronic door lock

start

ReadPassword

fromKeypad

Readpassword

fromEEPROM

Display”Incorrectpassword”

ComparePassword

Readkeypad

commands

Execute thecommands

end

Incorrect password

correct password

Fig. 11. Electronic Door lock algorithm

Above flow chart shows the algorithm of door lock. Thepassword is entered in a 4x4 keyboard. The entered pass-word is compared with the password saved in EEPROM.If password matches the door lock is opened by rotatingthe servo motor, which is fixed with a rack and pinionstructure that locks the door. The password can be changedafter entering the correct current password so only theauthorised user can change the password. Once the doorlock is unlocked it enables the power saving module.


978-1-4673-1627-9/12/$31.00 ©2012 IEEE

B. Occupancy sensor node

start

Wait forinterrupt

Interruptfrom PIR1

Interruptfrom PIR2

Wait forsignal

from PIR2

Wait forsignal

from PIR1

One personentering inthe room

(increment)

One personleft theroom

(decrement)

calculatenumber ofperson inthe room

storenumberin buffer

send itto master

wait for1 sec

Fig. 12. Occupancy sensor node algorithm

The occupational sensor node contains two PIR sensorsplaced at distance of few centimetres. The signal from PIRsensor interrupts the microcontroller. PIR1 is connectedwith INT0 and PIR2 is connected with INT1 of micro-

controller. Depending upon the sequence of the interruptthe system determines the direction of motion. When theperson enters the room the count of number of persons isincreased and when moves outside, count is decremented.When the count is greater than zero the node sends thereceiver signal to switch ON the appliances and when thecount is zero signal is sent to switch OFF the appliances.The data is send at a delay of one second.

C. Temperature and Light Sensor node

start Read sensorvalue

Compare itwith present

values

Decide themode ofoperation

Buffer

send for1 sec

wait for1 sec

Fig. 13. Temperature and light sensor node algorithm

Above flow chart shows the algorithm for the sensornode which sends light and temperature values to thereceiver. Instead of sending the sensor readings the valueshave been divided in several ranges of light intensity andtemperature for example 30-35, 35-40 centigrade. Thisrange is sent to the base station instead of readings, thisreduces the amount of data to be sent through wirelessnetwork. The microcontroller sends data after every onesecond. The base station changes the intensity of the powerdelivered to the load according to the range of sensorreadings.


978-1-4673-1627-9/12/$31.00 ©2012 IEEE

D. Base station node

start start

Readdata fromReceiver

read sensordata anddecide

firing angle

Zerocrossingdetectorinterrupt

calculatingfiring angle

Firingangle delay

Triggertriac

Return to start Return to start

Fig. 14. Base station algorithm

Above flow chart shows the algorithm of main receiverprogram. The main function of the program receives datafrom both the nodes. The two sensor modes are sendingdata after every 1 second of delay thus both access samechannel to send their readings. After receiving sensorreadings microcontroller compare them with preset valuesto determine the amount of power to be delivered toload. The power can be caried by changing firing angleof the triac in AC drive circuit. TO change the firingangle first the zero-crossing detector (ZCD) interruptsthe microcontroller whenever the supply AC crosses x-axis. After getting interrupted microcontroller waits for aparticular time period corresponding to the current firingangle and then triggers the triac. Before the trigger pulsethe triac blocks the AC supply from reaching to the load,once triggered it acts as a closed switched and allowssupply to reach the load.

Waittime = (α/360) ∗ (1/50)sec.

By changing the firing angle from 0-360 degree the powercan be controlled from zero to maximum. By changing

power based on daylight requirement power can be withoutcausing any inconvenience to the user.

IV. CONCLUSION

The study shows that a lot of power is wasted in homeand offices due to inefficient usage of appliances. Thetransmission of power from power station to the user addsto the loss up to 50 percentage. One unit saved at theconsumer level saves two units of power at the powerstation. Thus the importance of power saving and need of asmart system increases. Such a smart power saving systemis suggested in the paper that can save power and increasecomfort level of the user with minimum expenditure.The components used in the system like microcontroller,sensors and wireless transceivers are readily availableand cheap. With increase in awareness among the usersregarding power saving the need for such smart systemswill go up. In future we will see some more sophisticatedembedded systems monitoring our power requirements andusage.

REFERENCES

[1] Yong Tae Park, Pranesh Sthapit and Jae-Young Pyun, ”Smart DigitalDoor Lock for the Home Automation” TENCON 2009 978-1-4244-4547-9/09/26.00 2009 IEEE.

[2] Dhiren Tejani, Ali Mohammed A. H. Al-Kuwari and VidyasagarPotdar ”Energy Conservation in a Smart Home” 5th IEEEInternational Conference on Digital Ecosystems and Technologies(IEEE DEST 2011), 31 May -3 June 2011, Daejeon, Korea.

[3] Kwang Yeol Lee, Jae Weon Choi ”Remote-Controlled Home Au-tomation System via Bluetooth Home Network” 5th SICE AnnualConference in Fukui, August 4-6,2003 Fukui University, Japan

[4] ”Arduino development board” www.arduino.cc[5] ”voltage controlled AC light dimmer” http://pcbheaven.com/

circuitpages/Voltage Controlled AC Light Dimmer/[6] Lewis Loflin ”Hardware interrupt on Arduino to control AC” http:

//www.bristolwatch.com/arduino/arduino power control.html.[7] ”433MHz RF module with AVR microcontroller”

http://winavr.scienceprog.com/example-avr-projects/running-tx433-and-rx433-rf-modules-with-avr-microcontrollers.html

[8] Khusvinder Gill, Shuang-Hua Yang, Fang Yao, and Xin Lu”AZigBee-Based Home Automation System” IEEE Transactions onConsumer Electronics, Vol. 55, No. 2, MAY 2009

[9] Mike McCauley”Virtual Wire library for Arduino” http://www.open.com.au/mikem/arduino/VirtualWire.pdf


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