Group 32Watts The Matter?

Home Power Consumption Monitor

CpE: Daniel AllenEE: Jonathan NguyenCpE: Richard Velez

Motivation

Many people are aggravated at the end of the month when they see their electric bill and have no idea why it is so high

There is a curiosity as to what consumes the most power in a house or apartment and while many people have a good idea as to what devices do, they do not know the exact numbers

In an effort to reduce power consumption in a reasonable manner it would be useful to have a system in place that can report in a familiar measurement (kW/h) as to how much is being used

Goals & Objectives

Measure and report power consumed by each device plugged into an outlet

Give users the ability to set goals that can be met during a month or longer period

Forecast power consumption and turn off offending devices (with permission) that will prevent the user from reaching previously set goals

Accurately predict the users bill given the kWh rate by the user as well as their billing cycle

Record a users history for long term storage so that it can be reflected on in the future through the use of graphs and other analysis

Block Diagram

Microcontroller

Parallax P8X32A-Q44

44-Pin Quad Flat Package (QFP) Chip (32 GPIO)

8 Independent Cores running on same system clock

System Clock Speed: DC to 80 MHz

32 KB Ram + 32 KB ROM

Up to 40 mA per I/O

VDD 3.3 V

Capable of producing VGA/NTSC/PAL signal

Can run assembly and C within the same program, support for other languages as well

MSRP $7.99

How Efficient?

EEPROM

Microchip Technology IC EEPROM

512K (64K x 8)

400kHz

Interfaces with I²C

Requires 2.5 ~ 5.5V (will use 3.3V)

8 pin SOIC package

Will be used for holding the main program and the users history

Programming the Microcontroller

There were two routes that could be taken and those include USB or serial

The option selected was a 9 pin D Sub connector to allow programming over a serial connection

Programming is completed upon booting the microcontroller if serial connection exists

Displaying Content to User

The use of a DE-15 connector will be needed to output a VGA signal to an LCD screen

Requires 5V on pin 9

8 resistors will be used to get the appropriate timings for the RGB signals

LCD Screen

7” Resistive Touch LCD panel

Inputs include HDMI, VGA, and 2 AV sources

Driver Board Included

640x480 Resolution

Touchscreen used to eliminate the need of a mouse or keyboard

4 Pin FFC Connector

Flat flex cable connector is needed to obtain the input from the resistive touch film from the LCD panel

Analog signal will need to be converted to digital using two 1nF capacitors, a 100kΩ resistor, and two pins on the microcontroller in conjunction with the cog counters

Sigma Delta conversion will be used

Quad 1-2 Demultiplexer

Used to change inputs on the touch screen

Supply voltage: 4 - 5.5V

Less than 0.25ns max delay through switch

No circuit bounce

Close to 0 standby current

Real Time Clock

Maxim DS1302

Accept to voltage inputs from battery and power source

Selects the greater of two sources

Use with 32.768 kHz crystal

Trickle Charger

2.0V to 5.5V

CR1220 Battery used

3 wire serial interface

Power Source

CUI Inc Barrel Power Connector (SMT)

Rated for 16VDC and 5A

2.1mm ID, 5.5mm OD

CUI Inc Wall Adapter

Can accept 90-264 VAC

Outputs 12V and 2A

2.1mm ID, 5.5mm OD

Power Regulation

Step down from 12VDC 2A to 5V 2A and with slight modification 5V to 3.3V 2A

Power Regulation Cont

Texas Instruments TPS54331 Switching RegulatorCapable of handling 3.5V to 28V input

Transient voltage protection

Small Outline Integrated Circuit (SOIC) 8 package

Supported by SwitcherPro software

Includes PowerPAD technology for better cooling

High Efficiency at Light Loads

Initial Startup

Program Flow

Schematic (Main Board)

Kilowatt Hour Meter

Determine power drawn from appliances

Transmit data back to central hub

Correctly read in Voltage and Current

Capable of cutting off power to an outlet

Kilowatt Hour Meter

Connects directly to live and neutral wires of outlet

Break in both the live and neutral line for the design

Location will be between outlet and device being monitored

Microcontroller

Name Frequency GPIO ADC Flash

ATMega32 16 MHz 32 8 32 KBytes

ATMega382 20 MHz 23 8 32 KBytes

MSP430AFE 12 MHz 11 3 8 KBytes

Parallax Propeller

80 MHz 32 0 64 KBytes

Microcontroller

Parallax P8X32A-Q44

Same microcontroller as VGA Board

Working knowledge

Uniformity between device and VGA

Voltage/Current Measurement

HCPL-7800

Isolation Amplifier

Ignores High CMSR (at least 10kV/ms)

Sigma Delta / Analog Digital Converters

Voltage/Current Measurement

Voltage Divider (1001:1)• 1 MOhm : 1 kOhm• Used to step down AC voltage to a safe level from

170V to 0.17VPP

Vline = 1001*Vdivider

Current Sensing Resistor (0.2 Ohm)

I = Vcurrent/(0.2)

Voltage, Current, Power Calculations

VI=Voltage across current sensory = sample size (1000 in this case)

COM-10924 Relay SPDT

Used to manual and automatically turn off power to an outlet

Located inside outlet casing

Feed 5VDC signal to trigger relay

Single Pole - Double Throw

Rated up to 2000VAC @ 20A

GFCI Outlet

Ground Fault Circuit Interrupters

Used as a safety hazard

Will cut power in the event of a ground fault

Reacts within as little as 1/40 of a second

Reacts when a difference of 5mA is detected between current and entering and leaving device

KWH Schematic

Software Process

Foreground and Background process

Foreground will initialize all hardware and software components

UART, ADC, Clock, I/O, Timer, etc

Background will handle the data/sample collection

Radio Communication

In order for this system to operate, it needs to communicate between each of the microprocessors and the central hub to relay the data to be displayed.

Since we will be tracking multiple outlets in different parts of the room, it becomes necessary to use radio transmitters to accomplish this.

Choosing A Transmitter

The XBee Series

LINX NT Series

Atmel RF

Multitudes of choices on Amazon/Ebay

Attributes vary, but so too does the quality and reliablility.

Name Frequency Power Output Max Range RF Data Rate

Xbee Pro 900 HP

900 MHz 250 mW 15.5 km 200 Kbps

Linx TRM 900 NT

900 MHz 18 mW 914m 56 – 300 Kbps

Atmel AT86RF212B

769- 900 MHz 10 mW 1 km 1 Mbps

MX-05V RF (eBay)

433MHz 10mW 200m 4Kbps

Choosing A Transmitter

Xbee 802.15.4 Series 1

Can handle supply voltages up to 2.8-3.4 VDC

Has a range of up to 100m line-of-sight

Frequency Band of 2.4 GHz

Tiny and easily programmable

Uses Universal Asynchronous Receiver Transmitter (UART) @ 250 Kbps

Power Down adjusts power levels to extremely low levels • (< 10.0uA)

Operates on 2.8-3.4V

Data_IN• Logic Low: 0.3V to (0.2V*Vcc)• Logic High: (0.7V*Vcc) to 5.5V

Data_Out• Logic Low: 0.3V to 0.4V• Logic High: (0.5*Vcc) to (Vcc-0.4V)

Absolute Max voltage: 3.4V

Max Temperature: 85° C

Specifications for LINX 900NT

Interfacing

Possible Bluetooth capability

Ability to transmit to smartphone devices able to pick up the signal

An app could then be created to simulate the same display and touch capabilities of the main screen.

Environments

Paralax Propeller development to be used for main system

Eclipse equipped with Android tools would be used for the development of the app if that option is taken• Both chosen for familiarity with language and

convenience.

Product Quantity Price Budget($1433.12)

LCD Screen (1) $78.55

Xbee Series 1 (3) $54.00

HCPL-7800 (4) $5

Parallax (2) $15.00Voltage Regulator

(DC-DC)(4) $6.88

PCI Serial Port Card

(1) $16.95

Real Time Clock (1) $3.05

24LC512 EEPROM (8) $12.48

AC/DC Adaptor (3) $38.89

Misc: Resistors, Capacitors, Diodes

~$90

PCB Fabrication ~$300Total Spent ----- ------ ~$800

Distribution of Work

Jon Daniel Richard

VGA Display X X

RF Transmission X X

Circuit Breaker X X

kWh Meter X X

Questions?