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ECE 477 Design Review – Spring 2010 Team 15 Team Members Outline Project Motive Project Overview Project-Specific Success Criteria Block Diagrams Component Selection Rationale Packaging Schematic PCB Layout Preliminary Software Design Software Status Project 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 Overview Adapter Connects to two appliances Monitor usage of power over time Communicates with a base-unit using R/F Can turn devices on/off on receiving appropriate command Project Overview Base Touch-Screen Interface Communicates with adapter using R/F Stores appliance usage data Usage based alerts , modes and statistics Hosts server and web-services for remote access Project-Specific Success Criteria An ability to measure power consumption of plugged-in devices over time An 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 remotely An 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 ATD MC9S12A512 (uC) Rx Tx Transformer ATD (steps down voltage for voltage sensing) Solid State Relay Solid State Relay ATD Transceive r TRM315LT AC in AC out Current Sensor AC out Current Sensor RF AC in Adapter Unit Block Diagram RF Transceive r TRM315LT Tx MC9S12A512 (uC) RS232 VGA Intel Atom Board Base Unit USB L C D Touch screen Rx Component Selection Rationale Current 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 Rationale Microcontroller - 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 Rationale Microcontroller 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 Packaging Solid State Relay PCB Plug point Fuse box and switch 2.5 x 3.5 cm 3.3cm 4 cm Adapter Unit 7.5 cm 7 cm 6 cm 18 cm Packaging Base Unit Schematic & Theory of Operation Main Components Power Supply Circuit Voltage Regulator circuits Microcontroller Circuit Current Sensor Circuits Voltage Sensor Circuits Power Supply 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) Schematic Power Supply Schematic Voltage Regulator Circuit Voltage Sensors Stepped down voltage to 5Vpp V out shifted up by 2.5 V to get accurate value on ATD of microcontroller Voltage shift is done using adder circuits using 741 operational amplifiers Schematic Voltage Sensor Current Sensors Current Sensors work on hall effect principle Small in size PCB mountable Keeps 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. Schematic Current 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 Microcontroller Sample the voltages from current sensor and voltage sensor circuits Transmit the collected data to the base station Receive control signals from the base station and control the appliances accordingly Schematic Microcontroller Circuit PCB Design Considerations 2 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 RF transceiver & tristate buffer Voltage Regulator +/-15V Voltage Regulator +/5V MC9S12A512 Voltage Regulator +/2.5V Current Sensors BDM Preliminary Software Design Power 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 Design Base 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 Status Adapter Unit Majority of software complete except for interface with R/F module and network protocol Base Unit XP has been installed Apache Servers installed Touch Screen interfaced (Drivers, etc.) Project Timeline Design Review Finalizing PCB design ATD module Setting up RF interface using SCI Debugging data transmission errors Configuring firmware and webserver on Intel Atom Board Setting up RF interface on base station GUI development for base station Writing Web Services Packaging Debugging 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 Questions