ECE 477 Design Review – Spring 2010Team 15

Team Members

OutlineProject MotiveProject OverviewProject-Specific Success CriteriaBlock DiagramsComponent Selection RationalePackagingSchematicPCB LayoutPreliminary Software DesignSoftware StatusProject Timeline

Project Motive

Green Energy Management System aims to conserve electric power by facilitating remote

management of household appliances through a web interface and a touch screen.

Project OverviewAdapter

Connects to two appliancesMonitor usage of power over timeCommunicates with a base-unit using R/FCan turn devices on/off on receiving

appropriate command

Project OverviewBase

Touch-Screen InterfaceCommunicates with adapter using R/FStores appliance usage dataUsage based alerts , modes and statisticsHosts server and web-services for remote

access

Project-Specific Success CriteriaAn ability to measure power consumption of

plugged-in devices over timeAn ability to communicate with a base unit using

RF and to upload recorded information on a web server using the Ethernet interface

An ability to turn devices on/off remotelyAn ability to set up intelligent power plans to turn

off devices either after a fixed amount of time or after fixed power consumption

An ability to use touch screen interface to control operating parameters of the power management system

Block Diagram

Current Sensor

AC in

AC out

MC9S12A512(uC)

ATDATD

Solid State Relay

Current Sensor

AC in

AC out

Solid State Relay

Transceiver

TRM315LT

ATD Rx

Tx

RF

Transformer (steps down voltage for

voltage sensing)

Adapter Unit

Block Diagram

Transceiver

TRM315LT

MC9S12A512(uC) Intel Atom Board

LCD

Tou

ch s

cree

n

RS232 VGA

USB

Tx

RxRF

Base Unit

Component Selection RationaleCurrent Sensor - Must be able to tolerate huge amounts of

current (up to 25A). - Must be able to measure alternating current - Muse be cheap and easy to use. Solid State Relay Opto 22 – 120D25 Carlo Gavazzi – RA

2410LA

Optical Isolation Yes No

Zero Switching Yes Yes

Control Voltage 3-32 3-32

Price $26.50 $36

Component Selection Rationale Solid State Relay - Optical Isolation for protecting the rest of

the circuit from current surges. - Zero crossing for switching inductive loads. - Control voltage should be low enough to be

produced by microcontroller. Current Sensor

Tamura - L18P***D15

Allegro - ACS710

Output Voltage 4V 2.5V

Accuracy +-1% +-2.2%

Price $12.50 $22.00

Component Selection RationaleMicrocontroller

- Low power consumption - Multiple ATD channels. - SCI interface or built-in RF interface - Cost effective (Must be cheap as it would

have to be installed in every power adapter.)

Component Selection RationaleMicrocontroller ATMEGA128RFA1 Freescale

mc9S12A512

# of pins 64 112

# of I/O pins 38 54

Program Memory (kB) 128k(Flash) 4k(EEPROM) 14k (RAM), 4K(EEPROM)

Flash (kB) 16k 512K

ATD resolution 8 bit 10 bit

Power Consumption 16mW 25 mW

Documentation Yes Yes

Price Sample Available Sample Available

Availability Shipping Delayed Available

PackagingSolid State Relay Plug point

Fuse box and switchPCB

4 cm 7.5 cm

2.5 x 3.5 cm

6 cm 18 cm

7 cm

3.3cm

Adapter Unit

Packaging

Base Unit

Schematic & Theory of Operation

Main ComponentsPower Supply Circuit

Voltage Regulator circuits

Microcontroller Circuit Current Sensor Circuits Voltage Sensor Circuits

120 V AC voltage stepped down to 25V using simple center – tapped step down transformer

3 sets of rectifier circuits connected to specific voltage regulators to generate a regulated DC supply +/- 15 V (7915,7815)+/-5V (7905,7805)+/-2.5V (2937,2837)

Power Supply

SchematicPower Supply

SchematicVoltage Regulator Circuit

Voltage Sensors

Stepped down voltage to 5VppV out shifted up by 2.5 V to get accurate

value on ATD of microcontrollerVoltage shift is done using adder circuits

using 741 operational amplifiers

SchematicVoltage Sensor

Current Sensors work on hall effect principleSmall in sizePCB mountableKeeps direct line current away from PCB

The output voltage varies between +/- 4 Vpp based on amount of current

The output voltage is shifted up by 2.5 V to get accurate reading on the ATD.

Current Sensors

SchematicCurrent Sensor

Solid State Relays

The solid state relays work on DC control which varies between 3V – 32V

Allows current to flow above 3.5 V Provides optical isolation to rest of the circuit

when switched off

MicrocontrollerSample the voltages from current sensor and

voltage sensor circuitsTransmit the collected data to the base

stationReceive control signals from the base station

and control the appliances accordingly

Schematic Microcontroller Circuit

PCB Design Considerations2 PCB boards

Power Adapter: Small, narrow to allow for portability.

Base Unit: Must be able to fit a small LCD display (10”)

Microchip Transceiver close to PCB edge.Current Sensor must be close to PCB edge.High Electromagnetic Interference from the

power lines and most electric lines.

Microcontroller Layout

Decoupling capacitors must be placed as close to the IC as possible.

Voltage regulators must be used to ensure that maximum input voltage of ATD is not exceeded.

The supply voltage to the microcontroller must be satisfied from the power line voltage. This requires the use of current rectifiers and regulators to supply DC voltage.

Tri-state buffers are required for the Tx/Rx pins

Microcontroller Layout

• Bypass filters placed close to micro controller

•Pierce oscillator circuit for generating clock

•Regulated 2.5 V power supply

Power Supply

The following voltage supplies are needed for different circuit components - +15,-15,+5,-5,+2.5V

The power supply needed by most of the components is DC thereby requiring the use of rectifiers and voltage regulators.

Requires circuit components which can tolerate high amounts of current(0-20A) and voltage fluctuations.

Power Supply• 3 sets of regulated voltage supply ( +/-15V,+/-5V, 2.5V)

•Rectifier circuits placed at the edges

PCB Layout

PCB Layout

Voltage Regulator +/-

15V

Voltage Regulator +/-

5V

Voltage Regulator +/-

2.5V

MC9S12A512

RF transceiv

er & tristate buffer

Current Sensors BD

M

Preliminary Software DesignPower Adapter Unit

Decided on TCP/IP like protocol to communicate with base station.

Used Real-time interrupts of the microcontroller to initiate the ATD conversion.

Multi-Channel ATD conversion carried across three channels. (2 for current sensor and 1 for voltage sensor)

Send the recorded values using Serial Communication Interface to the RF transceiver.

Check for incoming commands from the base station at regular intervals

Preliminary Software DesignBase Station

Receive data sets from the RF transceiver using the serial port

Buffer any on/off signals for devices and transmit them at regular intervals

Send the data sets to the Intel Atom Board using the COM port

Host a web-server on the Intel Atom board so that it could be accessed using a web-browser

Software StatusAdapter Unit

Majority of software complete except for interface with R/F module and network protocol

Base UnitXP has been installedApache Servers installedTouch Screen interfaced (Drivers, etc.)

Project Timeline 

Week 8

Week 9

Week 10

Week 11

Week 12

Week 13

Week 14

Week 15

Week 16

  1-Mar 8-Mar 15-Mar 22-Mar 5-Apr 12-Apr 19-Apr 26-Apr 3-May

Design Review                  

Finalizing PCB design                  

ATD module                  

Setting up RF interface using SCI                  

Debugging data transmission errors                  

Configuring firmware and web-server on Intel Atom Board                  

Setting up RF interface on base station                  

GUI development for base station                  

Writing Web Services

Packaging

Debugging