Dennis Kilgore

Zineb Heater

Ryan Jones

HOME ENERGY MANAGEMENT SYSTEM

SPONSOR: PROGRESS ENERGY

Project Motivation

Power bills only give consumers a look atMonthly power usagePower 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?

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%

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

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

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

Block Diagram

Hardware

Current Sensing Methods

Current measuring Shunts Current transformers Hall Effect current sensors Magneto resistive Field sensors

Pros and Cons Pros Cons Price

Shunt High Accuracy Heat Dissipation Moderate

Transformer Isolation Large size Moderate

Magnetic High Accuracy Temperature dependency

Moderate

Hall Effect IsolationHigh AccuracyHigh LinearityRepeatable operation

Small Output Voltage

Moderate

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

AMP25

Voltage Sensing Methods

Voltage sensor, expensive, configuration required

Voltage divider, cheap and easy

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

Power measurement Error vs. PF

Power Relay

TRIAC switch, expensive, large Solid state relay switch, small and

reliable

CX240D5 SSR

Ratings of 5A AC or DC control Zero-crossing (resistive loads) or

random-fire (inductive loads) output

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

SFH620A, Optical Isolator

Schematic Layout

Schematic layout

Schematic Layout

Schematic Layout

Schematic Layout

Schematic Layout

PCB layout

Testing

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

Testing

Testing

Testing

Testing

Testing

Testing

Microcontroller

2-3 analog inputsHigh accuracy D/A conversion

2 digital outputs 1 serial i/o

Microcontroller

Arduino Pro Mini

Small Size: .7 x 1.3 inches

Easily Programmable through FTDI

Development Environment

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.

Voltage vs Integer Calculation

00.

203

0.40

70.

605

0.79

91.

007

1.20

51.

399

1.60

71.

803

2.00

22.

204

2.40

12.

62.

798

2.99

93.

202

0

200

400

600

800

1000

1200

Series1

Measured vs Calculated; Error %

00.

203

0.40

70.

605

0.79

91.

007

1.20

51.

399

1.60

71.

803

2.00

22.

204

2.40

12.

62.

798

2.99

93.

202

0

2

4

6

8

10

12

Series1

Measured vs Calculated; Error %, correction

00.

203

0.40

70.

605

0.79

91.

007

1.20

51.

399

1.60

71.

803

2.00

22.

204

2.40

12.

62.

798

2.99

93.

202

-2

0

2

4

6

8

10

12

Nominal

Addition

Error Correction

00.

203

0.40

70.

605

0.79

91.

007

1.20

51.

399

1.60

71.

803

2.00

22.

204

2.40

12.

62.

798

2.99

93.

202

0

0.5

1

1.5

2

2.5

3

3.5

Series1

Microcontroller Programming Setup

Main Loop

Read Serial Data Function

Print outputs

Setup

Initialize serial communication

Set digital pin 10 to digital output

Set the pin to highTurns on the relay

Main Loop

Take MeasurementsFind high and low of the waveform over 1

sec periodAfter 1 second, print the values to serial

If switch is off, wait to turn back on

Read Serial

Read the incoming serial data and decide what to doIncoming data will be the on/off commandBe able to respond immediately to

commands Microcontroller is always looking for

incoming serial data

Print outputs

Determine the height of the waveformCorrect 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 screenN#,vol,cur,

Wired Communication

Powerline CommunicationNo range or attenuation issuesRequires Bulkier PartsIncreases size of end unit PCBRequires modifications to home circuitry

depending on the house

Wireless Communication

ZigbeeMesh NetworkingExcellent rangeBetter supports many nodes

Protocol and parts are a mess

Zigbee -> Xbee

Xbee is not ZigbeeXbee is based on the Zigbee stack

It is however a more stable alternative to Zigbee

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

Control Board

Future Designs DK-57VTS-LPC3250

ARM926EJ-S processor 256KB of Internal SRAM 512MB NAND Flash Micro SD (up to 16GB) Ethernet, USB, RS232 Embedded Linux 5V or 3.3V

LCD Touch Screen 5.7” VGA LCD Screen 4 Pin Resistive Touch 1024x768 resolution 18 bit color

User Interface MiniGUI

GNUPlot for graphsMuch of the support is in Japanese

Qt for Embedded LinuxQwt for graphsMore support in English

GUI Mock-Ups

GUI Mock-Ups

GUI Mock-Ups

Software Block Diagram

Integration Receive data from Xbee

Process dataStore dataUpdate graphs

Respond to touchNavigate Menus

Administrative

ResearchParts Acquisition Design Prototype Test0

20

40

60

80

100

120

BudgetItem # Unit Cost ($) Total Cost ($)

Arduino Pro 3 19.00 57.00

Xbee 4 19.00 76.00

PCB 3 20.00 60.00

LCD Screen 1 515.00 515.00

Xbee Adapter 4 11.00 44.00

Hall Effect sensors 4 11.90 47.60

Power Relay 4 13.18 52.72

Resistors, capacitors, etc. 12

Total 863.72

Questions?