ECE 477 Design Review – Spring 2010 Team 15. Team Members.
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Transcript of ECE 477 Design Review – Spring 2010 Team 15. Team Members.
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