Integrated Electronic Window

1. Integrated Electronic Window Stephen Stec Tom Ludwick Steven Silverman Betrework Tizazu Dr. NatarajanNarasimhamurthi Advisor John Finch, Masco Advisor

2. Project Purpose • Home Automation • ‘Neat’ Factor • Assist the aging population • Energy Reduction • Save on Heating and Cooling

3. Window Functionality • Provide an integrated solution for different electronic components that could be added to a home window • temperature sensor • H2O sensor (rain sensing) • motor drive (to open and close) • controlled light transmission/privacy • an intuitive user interface to control each solution • Certain systems of this window would work together to provide automated control as well.

4. Tint Technology Driving Electrochromic Windows

5. Electrochromic Windows • Chemical reaction initiated by an electric charge • Oxidation Reaction • Window Layers • Ion Storage Layer (green) • Ion Conductor Layer (yellow) • Electrochromic Layer (gray) • Reverse the polarity of the charge, reverse the direction of the reaction • This causes the window to become transparent or opaque • Reaction is very slow (~3 minutes light to dark)

6. Electrochromic Windows • Benefits • Low Voltage (3.3V) • Uses little or no power when reaction is complete • ~10mA @ 3.3V = 33mW • Current sense resistor to indicate when reaction has completed • Drive System • Zetex ZXMHN6A07T8 N-Channel H-Bridge • Microcontroller to control switching • Light sensors to help with tint level control

7. Light Sensors • Choice • Tested both LX1972 Ambient Light Detector and Photoresistor • Chose LX1972 because of low IR sensitivity, very repeatable output current, and an easily scalable output.

8. Light Sensors • Testing: • Voltage divider configuration • 10 K resistor used to scale • Prototypes • Soldered onto SURF Boards and measured in parallel with light meter

9. Light Sensors • Closed loop system: • Outer sensor is sampled by ADC and stored at the PIC • Inner light sensor is sampled by ADC and stored • The difference between the two sensors is the present level of tint • This tint level is read by the tint controller and the output is adjusted accordingly

10. Temperature Sensors • Determines tint level in conjunction with light sensors • Placed on the inside as well as outside to measure difference (ΔT) • Cold and sunny outside-make opaque to let in warming sunlight • Hot and sunny outside-tint to keep warming sunlight out • ΔT will determine a set level of tinting

11. Temperature Sensing • Resistance Temperature Device (RTD) • Most stable • Most accurate • Linear relationship • Vishay Platinum SMD Chip Temperature Sensor • R0 = 500 Ω at 0˚C • Automotive, Aviation, and Industrial applications • Temperature Range: -67˚F to 311˚F (-55˚ C to 155˚C) • Only need ~ -40˚F to 150˚F (-40˚ to 66˚C) • ΔR for this range is ~250Ω (400Ω to 650Ω)

12. Temperature Sensor Design • Current Source to minimize error • Current-Sourcing Current Mirror • Choose Rbiaswith a low Temperature Coefficient • RTD measurements made with low source currents • 100μA to 250μA • Rbias≈ 20kΩ to 50kΩ

13. Temperature Sensor Calculations • ϑ = Temperature in ˚C • Ro = Resistance at 0˚C • Rϑ = Resistance at Temperature • A and B – Part specific coefficients

14. Window Automation Motorized Drive System

15. Motor Functions

16. Motor Controller Selection • N-channel MOSFET H-bridge • N-channel MOSFET and P-channel MOSFET H-Bridge • Zetex ZXMHN6A07T8 • SN754410 • Decided on L298 because it can handle the 24V and 400ma load with ease

17. Motorized Operation Here’s how it’s laid out:

18. Water Sensing • Detect H20 and send signal to microcontroller • Consists of interweaving copper tracks on a PCB board • Uses rain droplets to complete circuit • Send “rain” or “no rain” respectively

19. Block Diagram

20. Water Sensing Test • Performance Testing • 1/8” spacing between tracks • 1/12” spacing between tracks

21. Water Sensing Performance • Resistivity • Varies by track spacing • Sensitivity • Varies by track spacing • Repeatability • Consistency of Result

22. Water Sensing Performance • Sensor with 1/12’’ spaced sensor with copper chosen • More sensitive • Repeatable and consistent • Takes less space

23. Water Sensor Design • Drop down Resistor provide current path to ground • 50Kohms chosen as the drop down resistor • Determines input to Comparator circuit • After a drop of rain

24. Water Sensor Shematics

25. Sensor Performance

26. Motor Overdrive Protection • Detects if something is blocking the window • Stops operation • Receive signal from current sensor on the H-bridge • The output voltage targeted at 150mv

27. Window Control Processor and User Interface

28. Microprocessor • Firmware in C • PIC C CCS Compiler • Microchip’s PICkit 2 Development Board • PIC16F887 • 8-bit • Each window component described above will have its own code module • This allows for parallel development

29. Microprocessor (cont.)

30. Graphical User Interface • Created in Visual Studio . • Uses RS-232 serial communication to send commands and display current conditions. • Messages are one byte long in each direction. • Baud rate is 9600 • Decided not to use a parity bit.

31. Graphical User Interface • The computer’s and the PIC’s serial ports operate at different voltages. • Computer: 8V for 0 and -8V for 1 • PIC: 0V for 0 and 5V for 1 • The MAX232 IC translates these voltage levels.

32. Graphical User Interface

33. Graphical User Interface • Five LEDs • Displays desired tint level. • One LED is on for 0% tint. • Five LEDs are on for 100% tint. • Three Pushbuttons • Cycle through tint levels • Open/close window • Turn on/off rain sensing feature

34. PIC Programming • In the main loop • Check for a new serial byte. • Set desired conditions. • Set LEDs if the byte represents tint. • In a timer overflow interrupt every 65 ms • Check for buttons pressed. • Set desired conditions. • Set LEDs if the tint button is pressed. • Set LEDs if the tint button is pressed • Set LEDs if the tint button is pressed. • Wait for the button to be released before setting desired conditions again.

35. PIC Programming • Other functions in the main loop check desired conditions, do their job, and set current conditions. • After 45 interrupts (every 3 seconds) • Place current conditions in a 5 byte array. • Send each byte with a 10 ms delay to allow the computer display to update.

36. Acknowledgements • Masco (John Finch) • Funding • Workspace • Equipment (EE Department) • Encouragement • Dr. Natu • Project Advisor

37. Questions and Comments?