Transcript
SIMS:
Smart Inventory Management System Group 37 Masaki Negishi & Anthony Fai ECE 445 Senior Design April 27, 2005
Introduction
SIMS provides a cost effective solution for the management of inventory which leverages RFID technology. Combines an antenna array to a single RFID reader to map out an area for inventory detection
Features
PC serial interface Compatible with RFID Readers and Antennas Up to 8 outputs per unit Expandable, modular design
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Format Picture -> Compress
The SIMS System
System Overview
Hardware:
Power Supply, PC Interface Processing Unit, RF Switching Unit TI HF RFID Reader, TI HF RFID Antenna, TI HF RFID Transponders
Software:
PC control for antenna switching
System Overview
Hardware Overview (In House Manufactured)
Power Supply
PC Interface Processing Unit
Takes 6Vdc from AC/DC wall converter and converts to stable 5Vdc PC communication with system
RF Switching Unit
Switching of RF signal from reader to selected antenna
PC Interface Processing Unit
PIC Microprocessor RS232 Serial Communication with PC Sends output to RF Switching Unit
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PC Interface Processing Unit (Schematic)
RF Switching Unit
Takes in input from RFID reader Four outputs per board (expandable) Relay switching
RF Switching Unit (Schematic) RF input from Reader Normally Open SPDT Relay Switch
5Vdc
Input from PIC
RF OUTPUT TO PIC
PIN Diode Switching Unit (Eliminated)
Employ PIN Diodes for Switching Great performance for small peak to peak AC signal (low power) Poor performance for large peak to peak AC signal (high power) Introduce impedance mismatch
Power Supply (Main Idea)
Supplies +5 Vdc and GND to switch and control units Maximum current: 1A
More stable compared to 5V from the wall
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Power Supply (Schematic)
We always like to see measured data (especially with waveforms)!
Power Supply (Results)
Vmax: 5.023 V Vmin: 4.975 V Max. Ripple: 48.44mV Freqnency: 95.057KHz
Hardware Overview (Outsourced)
TI RFID S6500 HF Reader TI RFID HF Transponders TI RFID HF 13.56 MHz Antenna (RI-ANT-T01A)
TI RFID S6500 HF Reader
RFID Reader
Necessary to read and write to transponders Can be connected to PC through RS232 Operating Frequency of 13.56 MHz (HF) Output voltage of 48 V peak-to-peak Power output of 4 W
TI RFID HF Transponders
Transponders
Receives 13.56MHz of the signal from the reader, and sends back a signal to the reader Consists of a loop antenna and a chip microprocessor
Factors Influencing Communication with Tags
Orientation of tag with respect to antenna Environment around tag (e.g. metals, liquids) Background Noise
Recommendations for Tag Placements
Parallel to antenna Away from metals Within reading range of antenna (~25 cm)
TI RFID HF 13.56 MHz Antenna
Used to transmit and receive signals. Used for Magnetic Tuned at 13.56 MHz Input Impedance of 50 Ohms
Loop Antenna (In House)
Followed Texas Instruments’ Antenna Cookbook 50cm x 50cm Made of copper tape and wooden board T-matching network Reading range of 1 mm (SWR ~ 2.2)
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Loop Antenna (Self-Made)
Measurement Results (SWR = 60.832)
Loop Antenna (RI-ANT-T01A)
Dimension: 337mm x 322mm x 38mm Matched to 50 Ohms Maximum Reading Range: 50cm
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Loop Antenna (RI-ANT-T01A)
Measurement Results 1: Vertical, Away from Metal SWR = 1.004
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Loop Antenna (RI-ANT-T01A)
Measurement Results 2: Horizontal, Sitting on Lab Table SWR = 1.636
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Loop Antenna (RI-ANT-T01A)
Measurement Results 3: Close to Lab Equipments SWR = 5.111
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Overall Z-Parameters
SIMS System + Antenna Results During Operation SWR = 1.349
Factors Influencing Antenna Impedance
Orientation Environment (e.g. metals, liquids) Noise
Antenna is operating always in near field since wavelength is 22 meters!
Just about the maximum amount of text on a slide
Antenna Recommendations
Antennae must be placed first, then tuned. May need multiple antennae at one station for more complete coverage (and avoid nulls from environmental factors) Larger antennae for longer reading range Do not completely trust antenna cookbooks because they are unreliable! Buy one antenna first and analyze it.
Software
PERL software
Takes in user input and sends out two HEX digits through RS232 serial port (I/O)
PIC software
Takes in input from RS232 serial port and sends logic high to corresponding pins
PERL Software
Serial.pl
Takes in keyboard inputs in HEX
Must read header “AF” followed by two HEX digits (e.g. AF06)
Send out input from COM 2 to PIC Checks to see if PIC received correct signal
PIC Software
Switch0331.hex
Takes input from RS232 and sends logic high to corresponding outputs Will only respond if header “AF” is seen Sends back to PC its output
Room Setup
Map out room and give coordinates to each antenna For example, antenna B-2 can correspond to the secretary’s desk
Future Hardware Development
Improved Switching Unit for longer lifetime and higher signal isolation Increased number of antenna outputs Improved Antenna Design
Larger loop antenna More stable impedance matching network and BALUN
Future Software Development
Friendly user online interface (HTML) Information processing on transponder data Network with central server
Laptops
Workstation
Server
Workstation
Workstation
Workstation
RFID Frequency Comparison Frequency
Pros
Cons
LF (100 – 140KHz; ~2.5 km) Read Range: ~100 cm MAX Magnetic Inductive Transponders
Less susceptible to environment Longer reading range than HF
Only usually one transponder can be read at a time Tags bulkier and more expensive than HF ones and less memory capacity
HF (13.56MHz; ~22m) Read Range: ~50 cm MAX (current antenna ~25 cm) Magnetic Inductive Transponders
Anti-collision intelligence allows multiple of tags to operate concurrently Well defined magnetic field
More susceptible to environment Short reading range
UHF (860 – 960MHz; ~33 cm) Anti-collision detection Read Range: ~9m MAX Long reading range Electric (but passive tags) Capacitive Transponders
Not well defined electric field Field nulls near antenna requires complex anti-collision intelligence Tags have less memory capacity
SWOT Analysis of SIMS Strengths:
Weakness:
Modular design Supports LF and UHF Minimize number of readers Cost effective
Short range Susceptible to environmental factors Relay power consumption and lifetime
Threats:
Opportunities:
Smart Shelves RTLS
Inventory Management UHF implementation Software Expansion
Credits
Mr. Richard Martin Cantzler, II Professor P. Scott Carney Mr. Nicholas Soldner Professor Jennifer T. Bernhard Professor Steven J. Franke
Thank You
