solar energy based automated and secured smart home using

Solar Energy Based Automated And Secured

Smart Home Using DTMF Technology

Pratyush Kumar Panda

UG Student School of Electrical and Electronics Engineering

Reva University, Bengaluru, Karnataka, India

Email- [email protected]

Adithya Ballaji

Assistant Professor School of Electrical and Electronics Engineering



Sujo Oommen

Assistant Professor School of Electrical and Electronics Engineering



Abstract- In this 21st century of modern human civilization when each and everything is becoming automatic and wireless

at a gradual pace and everything getting done in just a touch of a button of our smart phones, our society is still trying to

improve in all aspects of our day to day life. Home is the place where we spend much of our needed time to sooth ourselves

from all day of hectic work and again the high energy demands at homes to run most appliances consuming high energy

makes it one of the foremost essential areas in high energy consumption. This paper introduces Solar Energy based

automated smart home and security system for the much needed good of our society which will not only provide green

energy for running the appliances on the touch of a button but also security for the safety of the user and his/her family.

For the management of this entire module we will use the solar power to charge battery with help of solar charge controller

and this energy would be passed through an inverter to obtain a usable source of power for our home appliances and the

security system.

Keywords – Renewable Energy, PWM Charge Controller, DTMF(Dual Tone Multiple Frequency)Technology, Smart

Home Automation, Home Security, Arduino Uno.

I. INTRODUCTION

The non-renewable sources of energy are major source of power in the entire world. In India most of the power is

being generated by non-renewable sources of energy such as thermal and nuclear power plants and the renewable

sources of energy such as solar, wind, ocean being used less. Most of the villages in India still have long power cuts

and many still don’t receive proper electricity [1]. Here the solar panels can be used which can at least power certain

basic appliances such as fan and lights. A charge controller is always coupled with these solar panels for better battery

life and safety of the entire system. This gives a constant voltage and hence the load voltage doesn’t vary even at

different sunlight levels. Home automation is a system or technique which helps the user control all the appliances

inside or outside the home using certain methods which minimizes the intervention of the humans with the conventional

switch boards. The demand of homes being automated is increasing in a rapid manner and it opens plethora of ways for

the user to control the appliances. This method is not only very efficient but also economical at the same time. In this

Journal of Xi'an University of Architecture & Technology

Volume XII, Issue IV, 2020

ISSN No : 1006-7930

Page No: 4585

mailto:[email protected]

mailto:Email-%20%20%[email protected]




paper we have used the DTMF (Dual Tone Multiple Frequency) technology because it allows the user to control all the

appliances from a touch from any part of the world [2].

When both the home automation and the solar energy is implemented together, the system provides much better efficiency of power and also reduces the effort which needs to be carried by a person. This not only reduces the risk of getting electric shock since there are no conventional switch boards because of which there is no direct contact between the user and the supplied electricity but also everything becomes automatic and can be controlled seamlessly just by giving a call and control the desired appliances on the press of a button.

Figure 1. Block diagram of the Solar Energy based Automated and Secured Smart Home

II. PROPOSED SYSTEM OF SOLAR ENERGY BASED AUTOMATED AND SECURED SMART HOME

2.1 Proposed System-

This project aims to develop a system which can be used in home by everybody which will provide automatic and

simple control of the various home appliances and also provide security to the entire home using different security

methods which have been implemented. All of this works on green energy which produced by converting the solar

energy into electrical energy with the help of solar panel. A charge controller is also used to control the solar energy

which varies from time to time and is coupled with a battery which is charged during the day and the energy is used

during the night. The energy hence stored in the battery is passed through an inverter to produce the required ac voltage

at desired frequency for the appliances to run as expected at home.This two systems when integrated i.e., Smart and

Home and Security along with the Solar Energy leads to system which can be used by all and can be implemented

everywhere for betterment of not only human but also the environment.

Figure 2. Proposed System of Solar Energy Based Automated and Secured Smart Home



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2.2 PWM Charge Controller –

The intensity of the PV solar radiation is variable with respect to time and hence will produce different voltages

which might damage the load or the battery which is being used for being charged due to fluctuations [3]. A device

which regulates the voltage and current coming from the solar panel in such a way that the battery is always supplied

with constant current and voltage is called as Solar charge controller. One of the main objectives of the charge controller

is to supply a constant voltage and current to batteries. Even in case of high voltage generation from the PV panel, the

controller regulates the voltage such that battery is not supplied with overvoltage which may damage the battery and

the system. The Fig.1 shows the circuit diagram of the PWM charge controller. The PWM (Pulse Width Modulation)

signals is basically used to have a constant output voltage, this is done by varying the Duty cycle from 10% to 95%

which depends on the intensity of the Solar PV radiation or intensity of the light. It is one of the most effective methods

of getting a constant voltage for battery charging by Duty variation using the MOSFET switches. The current from the

solar panel is adjusted according to the battery’s condition and recharging needs with the help of solar charge controller.

In case the battery voltage reaches the regulation set point or the over current region, the charging current is reduced

using the PWM algorithm to avoid heating and gassing of the battery, yet the charging continues to return the maximum

amount of energy to the battery in the shortest time.

Figure 3. PWM Charge Controller Circuit

Figure 4. Working Circuit of PWM Charge Controller



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2.3 Voltage Sensing –

Figure 5. Potential Dividers for Voltage Sensing

There are two potential dividers used in the charge controller circuit. These dividers are used to sense the incoming

voltage from the solar panels at all time. The Arduino Uno has 6 analog pins which are restricted to 5V only, hence the

voltage coming from the solar panel must be reduced to less than 5V so that the voltage sensing function implemented

could work properly. It is very important to change the values of resistors in the potential divider according to the

applications which might require higher power applications. The value of resistors must be kept high so that there is a

minimum power loss due to less current. If the value of the resistors is kept low then the current would be high and so

the power loss since P=I2R.

2.3.1 ADC Calibration –

The Arduino Uno ADC is of 10-bit resolution; hence it means that it will map all input voltages from 0-5V between

210 (that is 1024) digital values. Thus, volt per ADC count is given by,

1 𝐴𝐷𝐶 = 5

1024= 0.00488 𝑉 (1)

Now since the voltage output of the solar panel is reduced to within 5V by the potential divider, the constant ratio is,

𝑥 =𝑆𝑜𝑙𝑎𝑟 𝑉𝑜𝑙𝑡𝑎𝑔𝑒

𝐷𝑖𝑣𝑖𝑑𝑒𝑟 𝑜𝑢𝑡𝑝𝑢𝑡 (2)

Hence, in Arduino the solar voltage can be obtained by using the formula,

𝑉𝑜𝑙𝑡𝑎𝑔𝑒𝑆𝑜𝑙𝑎𝑟 = 0.00488 × 𝑥 × 𝑠𝑎𝑚𝑝𝑙𝑒 𝐴𝐷𝐶 (3)

where ‘sample ADC’ is the output ADC by Arduino analog pin.

2.4 Protection of Charge Controller –

Figure 6. Protections provided in the Charge Controller



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2.4.1 Reverse Current Protection –

A reverse current protection has been given by using a diode after the solar panel. During conditions such as night

when the battery voltage is higher than the solar panel output a reverse current might flow in such conditions resulting

to damage of the circuit.

2.4.2 Over Current Protection –

Two fuses of appropriate rating have been used at the beginning and near the load so as to provide protection from

over current. Under such circumstances the fuse will break isolating the circuit from any further damage.

2.4.3 Over Charge Protection –

This protection has been implemented in the Arduino software which immediately disconnects the battery from the

circuit when the battery voltage exceeds the specified value given in the software. This extends the battery life so that

battery provides the desired performance throughout its life.

Figure 7. Shutting down battery charging when Solar voltage is very less (DSO Showing Duty cycle 0%)

2.4.4 Filter Protection –

A capacitor is implemented at the input of the circuit to protect the components from any unwanted noise or ripples

from the solar panel.

2.4.5 Automatic Disconnection of Load –

The load is disconnected automatically when the battery voltage falls below the rated voltage so as to avoid total

discharging of the battery or when solar voltage is less than battery voltage. This protection has been implemented via

the software.

2.5 PWM Signal Generation –

PWM stand for Pulse Width Modulation. This technique is used to control the width of a particular waveform or

otherwise duty cycle of the output voltage so as to have a control on voltage which would appear across the load. This

method has been implemented in this is done by simply controlling the time for which the output voltage will be

appearing across a load. If Ton is the time period for which the output waveform appears across the load and Toff is

the time period for which the output waveform is prevented to appear across the load, then the expression for duty cycle

is given by,



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𝐷𝑢𝑡𝑦 𝐶𝑦𝑐𝑙𝑒 =𝑇𝑜𝑛

𝑇𝑜𝑛+𝑇𝑜𝑓𝑓× 100 % (4)

When Ton+Toff is called the total time period of the waveform.

If Vin is the solar input voltage then the voltage at which the battery will be charged is,

VBat = Duty Cycle × Vin (5)

Since an Arduino’s analog output pin is 8 bits therefore the duty cycle of 0-100% can be mapped between 28(256) or

0-255 digital values. Hence digital value 0 would means 0% duty cycle whereas the digital value 255 would mean 100%

duty cycle.

Figure 8. Battery Charging at PWM Duty Cycle 10%

Figure 9. Battery Charging at PWM Duty Cycle 90%



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2.6 Driving of MOSFET –

There are two MOSFET drivers used in the circuit. These drivers give the appropriate gate pulse to drive the

MOSFET. The signal generated by an Arduino is very small and is not sufficient as to drive the MOSFET, hence the

Arduino signal is given at the base of the transistor Q1 & Q2 and at the collector we obtain an amplified signal sufficient

enough to give the required gate voltage to the MOSFET. There are two drivers used in the circuit,

Figure 10. MOSFET Gate Driver Circuit

2.7 Smart Home Automation using DTMF –

The switching on and off of the appliances can be done very easily using a smart phone. Since there is use of the

DTMF technology in the home automation system it gives an upper hand over other systems by providing very long-

range connectivity in terms of controlling the appliances. Any old phone with ‘auto receive’ option set ‘on’ needs to be

connected to the circuit via the auxiliary cable provided in the circuit. The phone thus connected is called via any smart

phone from any part of the world and can easily control all the home appliances.

Features of the DTMF based Home Automation System-

2.7.1 Extremely long-range connectivity –

The DTMF based home automation systems gives extremely long connectivity in terms of tens of thousands of

kilometers making it extremely versatile in terms of connectivity.

2.7.2 Less cost of installation –

Installation cost of a home automation system is reduced if DTMF is used since it requires almost negligible cables.

Early access to all appliances.

2.7.3 Early access to all appliances –

If a person needs his room to be cool before he reaches home, he/she can turn on the Air Conditioner in his home

while being in office.

2.7.4 Access to security –

The owner has all access to home security 24/7 hrs. even when he is far away from his home. The security can be

turned off or on and all the updates regarding the security of the home can be accessed through the security system even

when the owner is not present in his home.



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Figure 11. DTMF Based Home Automation System Circuit Diagram

Figure 12. Working Circuit of a DTMF Based Home Automation System

2.8 Smart Home Security System –

Proposed system has home security solutions such as laser security system, fire security system, door security system.

These systems have been included so as to protect the user and his home from any thief or any person the user deems

unwanted.



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2.8.1 Laser Security System –

The laser security system has been placed across the perimeter of the house. Mirrors are used to reflect back the laser

rays into the sensing circuit which is made such that as soon as the laser light is blocked by any means and it does not

fall on the LDR sensor the buzzer starts to beep indicating intruders. This proves extremely beneficial to keep the

burglars away.

Figure 13. Circuit diagram for Laser Security System

2.8.2 Fire Alarm System –

In case of any fire accidents the fire security system immediately gets activated at the very initial stage of fire. When

the fire security system gets activated the buzzer beeps along red indicating light showing emergency. The

potentiometer provided in the circuit needs to be adjusted according to the ambient room temperatures so that the alarm

goes off even at a slight change of 5-10° Celsius change is temperature. This fire alarm system can be synchronized

with a water sprinkler system to stop the fire as soon as alarm goes off. This system becomes a must in homes, offices

where there is always a potential threat of fire.

Figure 14. Circuit diagram for Fire Alarm System

2.8.3 Door Security System –

The door security system keeps away any unwanted intruders inside the house if the system has been activated. The

siren goes off whenever the door is opened without the permission of the owner and immediately notifies about any

unwanted or uninformed people trying to enter the house. There are two metal contacts installed on the either side of

the door which is supplied with a small 5V supply. Suppose the door is closed the circuit is completed which triggers

the relay and the movable contact moves to the normally open position where there is not component connected on the

other hand if the door is opened the relay is not triggered and the movable contact remains same in the normally closed



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position due to which the circuit for the triggering of the buzzer is completed which gives a siren notifying the owner

of the house.

Figure 15. Circuit diagram for Door Security System

III. WORKING OF THE PROPOSED SYSTEM

The connection of the PWM charge controller circuit is done as shown in the figure. The solar panels are connected

at the solar input of the solar charge controller. Now the battery is connected as shown in the Fig.3 and it is charging is

varied by the charge controller depending upon the environmental conditions. The load part of the charge controller is

connected to a suitable inverter which produces an AC supply of 230V, 50Hz. The output of this inverter is given as

the mains supply to the house so that all the appliances give the output as expected.

The DTMF technology is the heart of the entire proposed system. It is the basic working principle of our working

project. DTMF technology is widely used by the service providers for taking any input from the consumer at the other

end. Customer care helplines might have asked you to type your bank account number and then press 1 to confirm or

while asking to select language to press 1 for English, 2 for Hindi, 3 for going to main menu and 9 to talk with customer

care executive or when retrieving your bank account balance. All these inputs which are taken from the consumer is

sent the service provider where it is then decoded using the DTMF technology. Whenever we press a button of the

keypad of our smart phone the DTMF Encoder IC(like CD22859E) present in our phone sends two frequencies

corresponding to that button, one low tone frequency and one high tone frequency. These two frequencies are then

superimposed on one another to obtain one final sinusoidal waveform which is transmitted to the desired location. For

this very reason this method is known as Dual Tone Multiple Frequency. At the receiver’s end one DTMF Decoder IC

(like MT8870 or HT9170B) receives the superimposed frequency and then decodes it to obtain the corresponding digit

in the keypad which was pressed. This information is now got to known by the service provider. The DTMF keypad is

given below [4],

Figure 16. DTMF Keypad

1 2 3 A

4 5 6 B

7 8 9 C

* 0 # D



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Below is the table for DTMF frequencies for the Keys of the DTMF Keypad [4],

Table -1 DTMF Frequencies for Respective Keys

Key

Pressed

Low DTMF

Frequency

(Hz)

High DTMF

Frequency

(Hz)

Binary Coded Output

Q1 Q2 Q3 Q4

1 697 1209 0 0 0 1

2 697 1336 0 0 1 0

3 697 1477 0 0 1 1

4 770 1209 0 1 0 0

5 770 1336 0 1 0 1

6 770 1477 0 1 1 0

7 852 1209 0 1 1 1

8 852 1336 1 0 0 0

9 852 1477 1 0 0 1

0 941 1209 1 0 1 0

* 941 1336 1 0 1 1

# 941 1477 1 1 0 0

In our proposed system the signal from the DTMF encoder is send via the auxiliary cable connected to the headphone

jack provided in the smart phone. The other side of the cable is connected to the circuit. The auxiliary cable usually

offers four wires, one for left stereo, one for right stereo, one for microphone and one for ground. The left and right

stereo wires are twisted together (usually red and green in color) to obtain the live wire whereas the microphone wire

and ground wire are twisted together (usually blue and golden in color) to obtain the ground. The live wire so obtained

is connected to the 0.1µf capacitor and the other wire is grounded. Now the signal thus received to phone which has

been connected to the system send the superimposed frequencies to the DTMF decoder where it is decoded to obtain

the binary output. Suppose that key 1 is pressed from the smart phone available with the user which then produces two

frequencies 697 Hz and 1209 Hz respectively corresponding to the binary 0001. This is then received by the decoder in

the automation system which then decodes the frequencies to obtain the binary 0001 and hence generates the

corresponding output and sends to the ULN2003A which is an IC is containing 7 Darlington pairs which produces an

active low output for an active high input. Now one part of the relay coil is supplied with DC 5V and the other terminal

of the relay coil is connected to respective outputs of the IC which completes the circuit. The moving contact is supplied

with 220V supply and the load is connected to the normally open of the relay. So when the Darlington IC supplies a

current return path for the relay coils the circuit gets completed and then movable contact slides from normally closed

position to normally open position which allows the respective appliance connected to that relay to obtain the required

supply to run.

In the circuit shown in the Fig.8 Light, Fan and TV have been connected to Q4, Q3 and Q2 respectively through the

relay. The Q4 is left open. When key 1 is pressed with the dial pad of the phone the decoder receives the frequency and

decodes this tone to produce the output corresponding to the frequency given in the table. So when key 1 is pressed its

sets Q1 low, Q2 low, Q3 low but Q4 high and hence the Light is switched on. If we want to turn off the light then we



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need to press 8 from the keypad of the phone because when 8 is pressed it sits Q1 bit high and all other bits Q2, Q3, Q4

low. Since we have not connected Q1 none of the other loads are affected and also the light connected to Q4 is switched

off. Suppose we want to switch on the fan which is connected to Q3, then we need to press 2 which will set the bit Q1

low, Q2 low, Q3 high and Q4 low, thus the fan gets switched on. If the user wants to turn on both light and fan then he

needs to press 3 which will set the bits Q3 and Q4 high and rest all low. If we want to switch on the TV and fan with

light turned off then we need to press 6 which will set the TV on since the bit Q2 is set high and also the fan on since

bit Q3 is set high and bits Q4 and Q1 set low. If all the appliances of the room including TV, light and fan must be

switched on then key & is pressed which sets all the bits high except the bit Q1 which otherwise is not connected.

Suppose the user is going out of the house and wants to switch off all the appliances the key 8 is pressed which sets Q2,

Q3, Q4 low and Q1 high. Since none of the appliances are connected to Q1 no appliances are switched on.

The home is secured with multiple security systems which have been implemented both inside as well as outside the

home. The fire security system implemented inside the house is triggered immediately when then fire is at its very initial

stage. The laser security outside the house when activated protects the house from any intruders. When the door security

system is activated it triggers an alarm whenever an unauthorized person opens the door without the owner’s permission.

All these systems work together to overall make a smart and secured home works on the green energy which reduces

the hazardous emissions to the atmosphere even if it is minute in quantity and helps the society to move towards a better

future.

IV. EXPERIMENT AND RESULT

Figure 17. Working model of Proposed system of Solar Energy Based Automated and Secured Smart Home using DTMF Technology



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Figure 18. Experimental Setup for PWM Solar Charge Controller and verifying of PWM waveforms.

( Figure depicting the battery charging at maximum speed of Duty Cycle 95% when battery voltage is less)

Figure 19. Experimental Setup for PWM Solar Charge Controller and verifying of PWM waveforms.

( Figure depicting the battery charging at lowest speed of Duty Cycle 10% when battery voltage is near full charge)



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V.CONCLUSION

As the demand and awareness for renewable energy is on a rise, the paper presents a new Solar based Automated

Smart Home and Security System. This being achieved by coupling a PWM charge controller along with the solar

panels and using the DTMF technology to satisfactorily control all the home appliances. PWM charge controller has

been used because it is an easy and cost effective solution to many villages in India which are yet to receive the luxury

of electricity. The proposed system not only provides electricity to their home via solar energy but also provides a cheap

and effective module to fulfill the daily demands of the people of the society. It overcomes the drawbacks such as high

cost of PV system as well as the complexity in operation, cost and risk of using conventional switch boards in our home.

REFERENCES

[1] Banerjee, Sudeshna Ghosh; Barnes, Douglas; Singh, Bipul; Mayer, Kristy; Samad, Hussain. 2015. “Power for All: Electricity Access Challenge in India”. World Bank Study. Washington, DC: World Bank. © World Bank.

https://openknowledge.worldbank.org/handle/10986/20525 License: CC BY 3.0 IGO.

[2] Vaishnavi S. Gunge, Pratibha S. Yalagi, “Smart Home Automation: A Literature Review”, IJCA, RTDM 2016.

[3] Bishwajit Swarnakar , Anupama Datta, “Design and Implementation of PWM Charge Controller and Solar Tracking System”, IJSR, Volume

5 Issue 5, May 2016.

[4] CH. Sreeja Reddy , S.Durga Bhavani2, M.Bhavani Marati, C.Divyani , NAGARJUNA.T, “DTMF Modem with Tone Generation and

Detection Using Goertzel Algorithm with MATLAB”, IJCSMC, Vol. 6, Issue.4, April 2017, pg.78 – 89.



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