Design of a Sensor-Based Adaptive Smart Home System

Using NXP ARM Cortex-M3

M. I. U. Haque1, D. Valles1 1Ingram School of Engineering, Texas State University, San Marcos, Texas, USA

Abstract - This paper discusses a project of designing a

smart system which is user-defined and adaptable for

different environments such as home, offices, and

classrooms. By using the values received from temperature

sensor and motion sensor some electrical appliances such as

fan and light may turn on or off. Moreover, the user can

define fan speed, brightness of lighting, as well as, time to

gradually increase the brightness of a light to its full

capacity. Also, other electrical appliances chosen by the user

may turn on automatically. All current statuses of appliances

will be shown on an LCD. Same scenario can be applied to a

bedroom, kitchen, toilet, office, etc. configurations. In short,

this project aims to build a smart system which is user defined

and adaptable to every possible indoor environment.

Keywords: Embedded, LPC1768, Sensors, Adaptive, Smart

1 Introduction

Smart systems have proven to facilitate automation for

different applications for home and office environments. The

impact and presence of embedded systems is felt directly in

our daily walk of life [1]. The applications of an embedded

system vary from cellular phones, digital cameras,

biomedical and home appliances up to ubiquitous and sensor

networking [2]. For this paper, we introduce an embedded

solution that can provide a form to automate room

environments.

Embedded solutions provide many forms of facilitating

many aspects of living and are being applied for smart-living

concepts. Figure 1 is the basic input/output system diagram

of the proposed project. This project uses NXP Cortex-M3

LPC1768 microprocessor as the main processing unit along

with a temperature sensor and motion sensor. The

temperature sensor will measure the temperature of the room

and there will be a predefined temperature value in the

processor. If the measured temperature is equal or larger than

this predefined value, then the fan will automatically turn on.

Additionally, the user can control the speed of the fan by the

‘Fan mode selection’ input and this will be done using PWM

technique and DIP (Dual In-line Package) switch. The fan

can also be turned off if the user wants. Similarly, the motion

detector will detect any human presence in different

environment selections. When detected, the light will

automatically turn on to pre-defined configurations.

Now, it is surely not convenient and not pleasant for the

eyes when someone enters a dark room and suddenly a light

is on with its full brightness. Also, the brightness of light

depends on different environment and configured by the user.

For this project, there is an additional option for the user to

select the right light mode by the ‘Light selector’ input in

other words how bright the user wants the light as well as how

much time the user needs to gradually increase the brightness

to the selected level. This will also be done using the DIP

(Dual In-line Package) switch and PWM technique.

Fig.1. Basic Input-Output design of the project

Depending on the environment, a user can define which

light or fan to be turned on. Each personalized setting

mentioned here may vary by different users and they can be

changed accordingly which shows the flexibility of this

system. As the whole project will be demonstrated using

breadboard and microcontroller, LEDs will be used as the

light and small cooling fan as the fan. The project will be

completed using NXP LPC1768 microcontroller, TMP36

temperature sensor, passive infrared motion sensor, LCD,

DIP switch, LEDs, cooling fan, n-channel MOSFET, diode,

jumper wires and resistors.

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ISBN: 1-60132-475-8, CSREA Press ©

The following sections are organized as: Section 2

discusses background and motivation of this project. Section

3 gives whole procedure. Section 4 discusses outcomes of the

project. Conclusions and scope for future work are included

in Section 5.

2 Background and Motivation

Different mini sensor-based projects have been done

using LPC1768 such as temperature measurement, humidity

measurement, angular/linear velocity measurement etc. [1].

Also, previously temperature controller system for LED

lighting has been designed where according to the ambient

temperature obtained by sensors, the designed system can

adjust the glow color automatically to provide a pleasant

lighting environment [3]. Another project done is about

weather monitoring and controlling system [4]. The proposed

project in this paper combines all the ideas above and an

additional feature to the system.

It is well known that smart systems are typically made

possible by network-enabled sensors/actuators and intelligent

computational algorithms. Most smart systems are designed

to be used directly by general consumers which we refer to

as human-centered smart systems. Smart technologies,

including smart-healthcare, smart-home, smart-grid, as well

as smart vehicles and intelligent transportation system are

transforming our society and have enormous economic

impact [5]. This proposed project is in the area of smart-home

and will surely be impactful upon successful completion.

3 Procedures

In this project, the smart system will be demonstrated

for five different environments. Those five different

environments include an office and different rooms of a

house: bedroom, living room, kitchen, office, and toilet. For

the bedroom, the light will glow gradually to its full capacity

in 5/10/15/20 seconds depending on the user whereas for

living room, the brightness of the light will be half of its full

capacity. For the kitchen and toilet, the light will glow to its

full glow instantaneously. In the office, the light will be the

desk lamp and the time and brightness can be adjusted as

well. The fan speed and status for all the environments can

also be varied by the user. These settings can be selected via

the keypad used for input ‘fan mode selection’ and ‘light

selector’ and the environment can also be selected via the

DIP switches. So, there will be enough options for different

inputs. All of the statuses will be shown on the LCD screen.

Figure 2 shows these features and adaptability of the

proposed design.

For temperature measurement, the TMP36 sensor is

used. It is a low voltage, precision centigrade temperature

sensor. It provides a voltage output that is linearly

proportional to the Celsius temperature. It also doesn’t

require any external calibration to provide typical accuracies

of ±1°C at +25°C and ±2°C over the −40°C to +125°C

temperature range. The design decision to utilize this sensor

is due to the ease of utilization and implementation: provides

the device a ground and 2.7 to 5.5 VDC in providing the

required power source. The output voltage can be converted

to temperature easily using the scale factor of 10 mV/°C [6].

Fig. 2. Environment adaptability(Home)

For motion sensing, PIR Motion Sensor (SEN-08630)

is used. The PIR Motion sensor (SEN-08630) is a small, low

cost proximity sensor user to detect motion. The specified

operation voltage is 12V, but the sensor works just fine off of

the 5V from the bed. A pull up resistor is needed since the

output pin is open collector. This can be done with an

external resistor or in software with internal pull-ups [7].

The main and only microcontroller unit used for this

project is NXP Cortex-M3 LPC 1768. It includes 512KB

FLASH, 32KB RAM and lots of interfaces including built-in

Ethernet, USB Host and Device, CAN, SPI, I2C, ADC, DAC,

PWM and other I/O interfaces. The pinout above shows the

commonly used interfaces and their locations. One of the

main advantages of this board is its’ low power consumption.

It consumes power in the range of 0.2885 - 1.103 Watts [8].

The maximum power consumption occurs when all of its’

peripherals are turned on. For this useful feature this board is

really a good choice to use in an embedded system project.

The NXP LPC1768 board is shown in Figure 3.

Fig. 3. NXP LPC1768 board [9]

The main working principal flow diagram is shown in

Figure 4. The whole algorithm for this program will be

decoded and compiled using Mbed online compiler.

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ISBN: 1-60132-475-8, CSREA Press ©

Fig. 4. Flow chart of working principal

The algorithm will look first for an environment to be

selected. When one is selected, the two sensors will supply

data to the board. When temperature data is equal to or

greater than a predefined value for that specific environment,

the fan will turn on. Similarly, when motion is detected by

the motion sensor the light will turn on. Both light and fan

can be turned off by the two-selector named as fan mode

selection and light selector. Also, these two selectors have

some more functionalities which have been discussed earlier.

All of the selections including environment selection will be

executed using the keypad. All of the statuses of on/off, fan

mode, light brightness will be shown on the LCD. A 16×2

LCD panel will be used. Finally, the outcome is a sensor-

based smart system adaptable for every possible

environment. For this project the outcomes will be shown

through LCD, LEDs and cooling fan. In other words, this

project is a small size of implementation to high level

comfortable environment.

4 Outcomes

This section discusses different outcomes from

different environments. The Outcomes are based on small

scale demonstration of the project using a project board and

different components discussed earlier.

Figure 5 shows the outcome of toilet environment.

When the motion is detected by the motion sensor,

LED(Yellow) turns on with its full brightness. Environment,

temperature and light status is shown on the LCD. For kitchen

environment, the exact same thing happens and this time a

red LED turns on when motion is detected. Figure 6 shows

the outcome for kitchen environment. Again, all statuses are

shown on the LCD.

Fig. 5. Outcome for toilet environment

Fig. 6. Outcome for kitchen environment

For office environment, a desk lamp automatically turns

on whenever user enters the office room. And to display the

lamp, a red LED is used and a variable resistor to control the

brightness of the LED. PWM technique is used here to

control the brightness of the LED. Outcome for office

environment is shown in Figure 7. Here, on LCD ‘Lamp’ can

be seen instead of ‘Light ON’.

As written in the procedures section, the LED

brightness for the living room will be half of its full capacity.

After motion is detected by motion sensor, whenever the

temperature in the room measured by temperature sensor

exceeds a predefined value of 20°C., the fan turns on. Also,

TV turns on when motion is detected. This is shown on LCD

with ‘TV’. Here, a small 5V DC brushless fan is used to

demonstrate the fan output. Figure 8 shows the activation of

the fan.

The last environment is bedroom. For bedroom, three

different settings are implemented. For first setting, the LED

increases its brightness to full capacity in 5 seconds and Fan

speed will be 100 percent. PWM technique is used here to

drive the fan and LED. For second setting, time to reach the

full brightness is 10 seconds and fan speed is 75 percent. For

third setting, time to reach the full brightness is 15 seconds

and fan speed is 60 percent. Fan and light statuses along with

temperature reading are shown in Figure 9.

24 Int'l Conf. Embedded Systems, Cyber-physical Systems, & Applications | ESCS'18 |

ISBN: 1-60132-475-8, CSREA Press ©

Fig. 7. Outcome for Office environment

Fig. 8. Outcome for Living Room environment

Fig. 9. Outcome for Bedroom environment

5 Conclusion and future scope

This paper proposes an embedded solution that

provides an automation and configuration for smart-living

environments. This sensor-based project will be useful for

learning embedded systems deeply and preparing for

industrial work. The main work is to measure analog data

provided by the temperature sensor and motion sensor and

then use those data for driving some outputs. There are also

some other inputs, controlled and defined by the user to make

the system more useful and user-friendly. The whole project

is adaptable to every possible environment such as home,

classroom, office, etc.

As this is an adaptable project for every environment, it can be extended to other extended functionalities that can adapt to different environments. For example, if someone wants the Xbox, speakers, video game consoles, Bluetooth speaker, etc. to be on as soon as user enters the room, it can be done by extending this project. Similarly, for each environment different outputs can be added as per user choice. The goal is to design an embedded system that doesn’t require switch interaction and utilizes wireless communication through smartphone devices. To implement the project in real life, each output should have a WI-FI module and then all of them will be connected to a main server through LAN (local area network). So, wireless communication part will play the vital role to implement it in real life. This embedded design is scalable and adaptable for every possible environment.

6 References

[1] A. Kommu, N. K. Uttarkar, and R. R. Kanchi, “Design

and development of sensor-based mini projects for

embedded system laboratory using ARM Cortex-

M3(LPC1768),” in International Conference on

Information Communication and Embedded Systems

(ICICES2014), 2014, pp. 1–6.

[2] “Human-Centered Smart Systems and Technologies,”

IEEE Access, 01-Jun-2017.

[3] L. Xin, S. Ling, S. Quan, C. Changzhu, and C.

Xiaoqiang, “Temperature controlling system for LED

lighting based on ARM,” in 2013 3rd International

Conference on Consumer Electronics, Communications

and Networks, 2013, pp. 649–652.

[4] P. Susmitha, Design and Implementation of Weather

Monitoring and Controlling System.

[5] H. Mitsui, H. Kambe, and H. Koizumi, “Use of Student

Experiments for Teaching Embedded Software

Development Including HW/SW Co-Design,” IEEE

Trans. Educ., vol. 52, no. 3, pp. 436–443, Aug. 2009.

[6] “Temperature Sensor - TMP36 - SEN-10988 - SparkFun

Electronics.” [Online]. Available:

https://www.sparkfun.com/products/10988. [Accessed:

19-Mar-2018].

[7] “PIR Motion Sensor (SEN-08630) | Mbed.” [Online].

Available: https://os.mbed.com/components/PIR-

Motion-Sensor/. [Accessed: 19-Mar-2018].

[8] “mbed Power Control/Consumption | Mbed.” [Online].

Available:

https://os.mbed.com/users/no2chem/notebook/mbed-

power-controlconsumption/. [Accessed: 19-Mar-2018].

[9] https://www.switch-science.com

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