1 / 30

Smart Window

Smart Window. By Josh Karr & Greg Kupiec ECE 445 Senior Design November 30, 2005. About Smart Window. Smart Window is designed to control the position of the window for temperature control

mayes
Télécharger la présentation

Smart Window

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Smart Window By Josh Karr & Greg Kupiec ECE 445 Senior Design November 30, 2005

  2. About Smart Window • Smart Window is designed to control the position of the window for temperature control • Temperature sensors provide information so that a window can be positioned in order to adjust the indoor temperature closer to a target temperature

  3. Features • The remote temperature sensor is battery powered and uses RF signals so that it may be placed in various places outside of the house. • Manual control allows you to override the automated controls • Multiple target temperatures may be selected

  4. Smart Window

  5. Control Unit • Local temperature sensor • Target temperature setting • RF receiver • Manual override • Motor control

  6. Control Unit

  7. Remote Unit • Remote temperature sensor • RF transmitter • Battery powered

  8. Remote Unit

  9. Hardware Overview • PIC 16F877A • Receive, process and send data • Respond to user input • Control motor • Temperature sensor (TC74) • Measures temperature in degrees Celsius and transmit this data to the PIC

  10. Setting up the PIC • Enabled the PIC to create a clock signal from an RC oscillator We chose the value of the resistance and capacitance based on the RC time-constant that gave us our desired clock frequency Fosc = 1/ τ = 1/(R*C) = 1MHz We aimed for a clock frequency of 1MHz and also knew from reading the data sheet that R must be at least 100kΩ We then chose R = 100kΩ and found that a value of C = 10pF would give us the desired clock frequency

  11. Setting up the PIC (cont.) • The I²C bus pins, SDA and SCL, both required pull up resistors in order to function properly • After researching different values for the resistors we found that others had the most success using R ~ 2kΩ • A pull up resistor of 1kΩ was also needed on the MCLR’ pin

  12. I²C Communication • I²C communication is a two-way serial communication system that we used to obtain temperature data from our temperature sensors • I²C has the ability to either send or receive information in 8-bit increments • I²C uses start, stop and acknowledge sequences to ensure successful transmission of data between devices

  13. Problems With The PIC’s • I²C Communication (unfamiliar with the process and built in functions within the compiler) • Correctly setting fuses (NOLVP) • Correctly using certain ports (Port C)

  14. Temperature Sensors (TC74) • Outputs temperature as an 8-bit digital word in 2’s complement form • Temperature given in degrees Celsius and accurate to within +/- 2ºC • Uses I²C communication to transmit data • Low power consumption (200μA)

  15. Manually Controlled Window

  16. Temperature Controlled Window

  17. Software int read_temp() { int ret; i2c_start(); i2c_write(0x90); i2c_write(0x00); i2c_start(); i2c_write(0x91); ret = i2c_read(1); i2c_stop(); return ret; } main() { init_pic(); while(1==1) { delay_ms(150); update(); check_disp(); control_motor(); } }

  18. Hardware (cont.) • RWS-434 & TWS-434A • Transmits signals via RF • Uses a binary encoder and decoder • Motor Controller • Bidirectional controls using a H • Power and direction defined by the control unit PIC

  19. RF (TWS-434A) • The PIC of the remote node sets the 8 bit input into the HT-640 encoder • The information is then sent to the transmitter • The signal is transmitted at 433MHz

  20. RF (RWS-434) • Signal is received at 433MHz • The signal is then sent to the HT-648L Decoder • The binary output of the decoder is then sent to the control unit PIC

  21. RF Functionality • Tested the ability to send through multiple walls and over moderate distances(<50ft) • There was a slight lag which is acceptable • Transmitter strength can be increased if needed (up to +12V)

  22. Motor Controller • Bidirectional DC controller using an H driver • Originally built with transistors • Caused unusable voltage drop • Very noising signal • Later built with reed relays • Solved voltage drop problems • Much cleaner signal

  23. Controller using transistors Transistor H with no load Motor turned on Motor turned on Transistor H with load

  24. Controller using relays Motor turned on Relay H with no load Motor turned on Relay H with load

  25. Motor Controller

  26. Motor Selection • We picked multiple motors to test and use • The first motor was from a cordless drill • The second motor was a hobby size motor • The third motor was similar to those used in printers

  27. Motor Problems • The motor from the drill drew too much current (2-3A) • Was also very noisy • The small hobby motor caused a large voltage drop • The final motor was the one we selected • Caused the least voltage noise • Seemed to have the least current spike

  28. Controller problems • The transistor circuit had some problems • Voltage drop across transistors • The relays seemed to burn up because of a possible current spike • They are specified to handle 500mA

  29. Recommendations • Find different relays that would be better suited for our motor controller • Possibly use a stepper motor for increased flexibility • Use a potentiometer and the internal A/D converter to set the target temperature

  30. Thank You Greg Kupiec & Josh Karr November 30, 2005 ECE 445, Senior Design

More Related