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Watt Smart
Wireless Single Phase Power
Monitoring System
(WPMS)
• Kamyar G. Osgoei
• Glen Nogayev
• Titus Cheund
• Wenqi Sun
• Babak Sobhani
Outline
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Introduction
Motivation
Existing Products
System Overview
Product Design
Test Measurements
Budget and Timeline
Business Opportunities
Problems Encountered
Future Development
Introduction
Watt Smart Inc.
• Kamyar: CEO
– R&D, HW, Documentation, Wireless
• Titus: CFO
– Funding request, R&D, Documentation, Wireless
• Glen: COO
– Documentation, Wireless, R&D, HW
• Wenqi: CSO
– HW, SW, PC Interface, Q/A
• Babak: CTO
– HW, SW, R&D, Q/A
Motivation
• Improve the efficiency of your home
• Consumers: save energy and money
• Average household power consumption in
BC is 11,000 kWh/year
• BC Hydro to become energy self-sufficient by
2016
Existing Products
• Some devices perform only basic
measurements
• Most products don’t have wireless option
• Not accurate!
• Eg. Kill-a-Watt and Blue Planet
Our Solution
• Low cost, portable power monitor
• Measure power/energy/power factor
• High accuracy
• Wireless capability
Power Background
• Average power calculations
• Current and voltage both
sinusoidal waveforms
• Power factor (pf) phase
difference between the two
waveforms
– Reactive loads (pf = 1)
– Inductive loads (pf < 1)
• Consumers charged for real
power (P) consumption
System Overview
– Consists of sensing and PC interface units
– Easy to install and maintain
– Wireless communication with PC
– Capable of monitoring several units
– Provides kW, kWh, and electricity cost
System Overview
– High level
system design
– Current and
voltage inputs
– Power, energy
and power
factor outputs
System Overview
– Sensing unit design
• Current transformer
(CT)
• PIC microcontroller
• XBee wireless module
System Overview
– PC interface unit design
• XBee receiver
• Data acquisition software
• Graphing application
What is measured?
Why?
What?
Power, measured in kW.
Why?
It gives us a sense of the rate at which we
are consuming energy (J/S).
What is measured?
Why?
What?
Power Factor
Why?
It a measure of real power consumption
to reactive power flow.
What is measured?
Why?
What?
Real time energy consumption cost,
shown in Canadian dollars.
Why?
You tell me!
Power Theory and Technical
Implementation:
1-Theory behind calculations
2-Hardware (Sensing Unit)
3-Software (PC Interface Unit)
Theory
Process of calculating power factor, power and
real time cost:
1-Data acquisition (Voltage and Current).
2-Filtering voltage and Fourier transforming
current.
3-Calculating THD factor.
4-Calculating PF.
5-Calculating Power.
6-Calculating real time cost.
Theory (Data Acquisition)
Theory (Data Acquisition)
Theory (Filtering Voltage)
Theory (DFT of Current)
Theory (DFT of Current)
True Power Factor or Not So
Much True Power Factor, That Is
The Question!!
Theory (Calculating
Power)
P=Vrms*Irms*PF
Theory (Calculating Real
Time Cost)
• Real time cost=(Power in kW)*1h*($ per kWh)
Hardware – Sensing Unit
1-Power Supply Unit
2-Signal Conditioning Unit
3-MCU Board
4-RS232 Unit
Sensing Unit
UART
Wireless Unit
To PC
(Optional)
MCU
RS-232 Module
ADC
Power
Supply
Unit
Input Signal Conditioning
Unit
To Appliance
From Outlet
CT
Hardware (Power Supply
Unit)
• Supplies +12V, -12V to Opamps
• Supplies +5V to MCU, RS232 and Signal
Conditioning Unit
• Real Scenario
Hardware (Signal
Conditioning Unit)
• Converts voltage and current’s range to 0-5V.
Hardware (MCU Board
& RS232)
• MCU ADC (12 bits) unit performs the sampling
and send them off to RS232 unit.
• RS232 unit sends data to the laptop.
PC Interface Unit
Data Acquisition
Power
Calculation
XBee
802.15.4
Receiver
Graph Plotting
PC Interface
• Why we choose PC Interface
– Easy Accessibility
– Easy to use
– Faster calculation
– Database support available
– More functionality
– High compatibility with industry
PC Interface
• How to make a good Interface
– User’s need is the first thing we consider
– Structure Principle
– Simplicity Principle
– Feedback Principle
– Tolerance Principle
– Reuse Principle
PC Interface
• MDI (Multiple-document interface)
PC Interface
• RS232 and Wireless connection
PC Interface
• Main Monitor Panel
Software Implementation
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Communication via RS232(Serial Port)
Communication via Xbee
Discrete Fourier transform
Inverse Discrete Fourier transform
Plot Graphs
Results (From 2007
Similar Project)
Results (Watt Smart)
Device
Power
(Watt
Smart)
Power
(Fluke)
%Error
PF (Watt
Smart)
Old
Computer
42W
43W
2.3%
0.71
Laptop 1
31.45W
29W
7%
0.98
TV
60.6W
65W
6.7%
0.71
Coffee
Maker
767W
770W
0.3%
0.99
Possible Improvements
• Investigate and include the phase shift caused by
circuit components.
• Voltage Regulation for all power supplies.
• Quality of voltage signal capture.
• Not base everything on Fluke power meter.
• An alternative way of measuring real power
• And the last and the most important:
Continuous Research on Power
Analysis!
Budget
Component
Expected
Actual
Wireless Module
150
170.93
Current Transformer
50
250
Voltage Probe
50
0
MCU-development
board
200
242.63
Enclosure
50
0
AC/DC transformer
30
0
10% contingency
53
68
Total required
583
731.56
0
500
ESSEF Funding
Timeline
Business Opportunities
– Replace manual meter reading from
utility companies.
– Introduce two-way communication with
utilities companies
– Integration with home automation
systems.
Problems Encountered
– MCU replacement
• TI MSP430 MCU too complex to implement
• Insufficient information in data sheet
• Replaced with PIC MCU
– Wireless module
• Zigbee features not critical in project
• Higher costs for Zigbee
• Replaced with XBee module
Future Development
• Home Automation
– Control appliances from PC
• Internet Connectivity
– Remote monitoring/controlling
– Data collection by Hydro companies
• Business/Industrial monitoring
Conclusion
•Great project
•Great Team
•Home electricity usage
can be reduced
•Goals met
Questions?