Home Energy Management System Sponsor: Progress energy

1. Dennis Kilgore Zineb Heater Ryan Jones Home Energy Management System Sponsor: Progress energy

2. Project Motivation • Power bills only give consumers a look at • Monthly power usage • Power usage for the entire house • How much power does your home entertainment system use? • What if you could turn your water heater off when you don’t need it?

3. Standby Power • All electronics that are powered by DC power have an AC to DC converter • These converters draw power even when they aren’t in use • Entertainment systems consume power when off, cable box, gaming system, almost every other modern device • Research in leading G8 countries shows that Standby power consumes 8 to 12 percent of a home power bill • France – 7% • US – 10% • Japan – 12%

4. Goals • A system that measures the power consumption of various household appliances • A system that allows the user to shut the power off any household appliance • A system that monitors the power usage and display it on an LCD screen • A system that can be accessed wirelessly • A system that will save more energy than it uses

5. Project Overview • Build a circuit to measure both the current and voltage used by an appliance • Build the circuit to control the power on and off an appliance • Write a program to calculate the power and transmit it wirelessly • Display the results on an LCD touch screen

6. Requirements and Specifications • Measure currents varying from 0 Amps to 15 Amps • Measure voltages up to 120V • Control the relay and shut the power off an appliance • Power measured must be within 10% error

7. Block Diagram

8. Hardware

9. Current Sensing Methods • Current measuring Shunts • Current transformers • Hall Effect current sensors • Magneto resistive Field sensors

10. Pros and Cons

11. Our Decision • AMP25 Hall Effect Linear sensor • Linearity 1%, Accuracy +/-2% • 25 Amps rating • -55ºC to +125ºC • Voltage supply Vs 4.5VDC to 10VDC • Offset voltage of Vs/2 +/-2% • Output voltage proportional to Vs

12. AMP25

13. Voltage Sensing Methods • Voltage sensor, expensive, configuration required • Voltage divider, cheap and easy

14. Power Measurement • What are we calculating: Real Power (P) in Watts or Apparent Power (S) in VA? P=V*I*cos(θ) S=V*I

15. Power measurement Error vs. PF

16. Power Relay • TRIAC switch, expensive, large • Solid state relay switch, small and reliable

17. CX240D5 SSR • Ratings of 5A • AC or DC control • Zero-crossing (resistive loads) or random-fire (inductive loads) output

18. SFH620A, Optical Isolator • Isolation test voltage, 5300 VRMS • High collector emitter voltage • Low saturation voltage • Fast switching times • Temperature stable

19. SFH620A, Optical Isolator

20. Schematic Layout

21. Schematic layout

22. Schematic Layout

23. Schematic Layout

24. Schematic Layout

25. Schematic Layout

26. PCB layout

27. Testing

28. Testing • Output of Vcc/2 when there is no current • Vcc=4.86 V • 100W@120V • I=P/V=833mA • The sensor has an output of 37mV/1A • Sensor should have an output of 30.821mV for this load • 30.821mV*7 loops = 216mV RMS

29. Testing

30. Testing

31. Testing

32. Testing

33. Testing

34. Testing

35. Microcontroller • 2-3 analog inputs • High accuracy D/A conversion • 2 digital outputs • 1 serial i/o

36. Microcontroller • Arduino Pro Mini • Small Size: .7 x 1.3 inches • Easily Programmable through FTDI • Development Environment

37. Accuracy • Accuracy is a major concern • Any inaccuracy in the measurement circuit will multiply with microcontroller inaccuracies. • Need to measure and confirm accuracy of the chip.

38. Voltage vs Integer Calculation

39. Measured vs Calculated; Error %

40. Measured vs Calculated; Error %, correction

41. Error Correction

42. Microcontroller Programming • Setup • Main Loop • Read Serial Data Function • Print outputs

43. Setup • Initialize serial communication • Set digital pin 10 to digital output • Set the pin to high • Turns on the relay

44. Main Loop • Take Measurements • Find high and low of the waveform over 1 sec period • After 1 second, print the values to serial • If switch is off, wait to turn back on

45. Read Serial • Read the incoming serial data and decide what to do • Incoming data will be the on/off command • Be able to respond immediately to commands • Microcontroller is always looking for incoming serial data

46. Print outputs • Determine the height of the waveform • Correct for innacuracies • Hall effect sensor floats at 1.5 mV(integer of 5) when powered • Subtract 1 from the voltage measurement • Print the output as comma separated values to the serial comm, to be processed by the screen • N#,vol,cur,

47. Wired Communication • Powerline Communication • No range or attenuation issues • Requires Bulkier Parts • Increases size of end unit PCB • Requires modifications to home circuitry depending on the house

48. Wireless Communication • Zigbee • Mesh Networking • Excellent range • Better supports many nodes • Protocol and parts are a mess

49. Zigbee -> Xbee • Xbee is not Zigbee • Xbee is based on the Zigbee stack • It is however a more stable alternative to Zigbee

50. AT Command Structure • The Xbee units use AT commands for control • This allows direct control of the addressing, and node address discovery • Changing the address to a specific node requires the address to be known