Smart Home Temperature System with Spinning LED Display Group 49: Jianxi Lu, Jia Shi, Xingchang Cheng May 4th, 2016 ECE445

Problems  1. Energy waste when no one in room  2. Have to go to thermostat to adjust temperature  3. ‘Dull’ Thermostat

Design  Control room temperature based on environment temperature and room occupancy status  User able to control AC system remotely  Display room temperature with spinning LED

Objectives  Energy saving: Stepped output based on temperature difference, turn off AC when no one in room  Convenience: Mobile app shows room temperature and allow user to set temperature  Cool factor: Spinning LED display

Block Diagram

Power Unit  Utilize wall outlet power: 10:1 Transformer  AC convert to DC: Rectifier

Voltage Regulators Component Required Voltage Verification Number Used Maximum Current Maximum Power Consumption Temperature Sensor 5±0.2V4.98V250 μA0.5 mW PIR Motion Sensor 8±0.2V7.97V45 mA0.16 W ATMega 328P Module 5±0.2V4.98V120 mA0.1 W DC Motor12±0.2V11.94V10.5 A6 W HC-06 Bluetooth Module 5±0.2V4.98V150 mA0.25 W Total ~ 0.59 A~ 6.51 W

Sensing & Control Unit  We use ATmega328 as our microcontroller

Temperature Sensor  TMP36 (Input voltage: 5V)  Use Analog Input pins to read the output voltage

PIR (Passive Infrared) Sensor  Input Voltage: 8V  Generate a pulse when a person enters the detect area  Use Analog pins to read the output voltage

Occupancy by PIR Sensors  Set up and Finite State Machine

Alert for Mobile App  Cooling Mode: Room is occupied && Preset – Real < -2 degree  Heating Mode: Room is occupied && Preset – Real > 2 degree

Output Unit  Spinning LED Display  Pulse-Width Modulation (PWM) Output  Mobile App

Spinning LED Display  Composed by 10 LEDs and a DC Motor(12V, <0.5A, 500RPM).  Using POV (Persistence of Vision) effect.  Controlled by microcontroller.  Display temperature & Reflect Alert.

 Each number is decomposed into 15 segments (5*3 Matrix).  Display numbers column by column.  Delay time for each column: 2150 microseconds.  Spinning LED Display

Pulse-Width Modulation (PWM) Output Output with stepped duty cycle depending on temperature difference. Output to Variable-Frequency Drive (VFD) in air conditioning system

Mobile App Flow Chart

Bluetooth Connection  HC-06  Paired up in the system, first time use need to click on the paired-up list to build the connection  Automatic connections in the future use  The working range: it covers every room of the chosen apartment

Bluetooth Connection  onItemClick(): Build the connection to the paired up Bluetooth unit  runOnUiThread(): Jump to an error page indicating connection failed  InputStreamReader() & BufferReader() Contains a buffer of bytes read from the source stream. The buffer size is 8K.

App Interface  Mode Switch Heat/Cool Mode  Count Display Number of people in a certain room  Temperature Display Current temperatures of different rooms  Setting and Buttons

Successes  Temperature detected correctly by temperature sensors.  System correctly detects when person enters/leaves.  Spinning LED correctly displays room temperatures and color changes responding to temperature change.  Mobile App correctly displays room temperatures and pops out according to occupancy status and temperature difference.  System correctly conduct Pulse-Width Modulation (PWM) depending on temperature difference.

Challenges  Temperature sensor may be over sensitive.  Slip ring has large resistance.  PIR Motion sensor cannot distinguish multiple people.  System sometimes breaks down.  Aesthetic design could improve.

Future Work  Industrial Design, more integrated system  Smaller, more compact PCB design.  Feedback mechanism for spinning LED to stabilize display

Thank you!  Questions?