SIMS:
Smart Inventory Management System
Group 37
Masaki Negishi & Anthony Fai
ECE 445 Senior Design
April 27, 2005
Introduction
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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
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PC serial interface
Compatible with RFID Readers and
Antennas
Up to 8 outputs per unit
Expandable, modular design
The images in this presentation have been reduced to screen quality (saves space)
Format Picture -> Compress
The SIMS System
System Overview
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Hardware:
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Power Supply, PC Interface Processing Unit, RF
Switching Unit
TI HF RFID Reader, TI HF RFID Antenna, TI HF
RFID Transponders
Software:
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PC control for antenna switching
System Overview
Hardware Overview
(In House Manufactured)
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Power Supply
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PC Interface Processing Unit
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Takes 6Vdc from AC/DC wall converter and
converts to stable 5Vdc
PC communication with system
RF Switching Unit
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Switching of RF signal from reader to selected
antenna
PC Interface Processing Unit
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PIC Microprocessor
RS232 Serial
Communication with
PC
Sends output to RF
Switching Unit
Black will have better contrast on a projector
PC Interface Processing Unit
(Schematic)
RF Switching Unit
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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)
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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)
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Supplies +5 Vdc and
GND to switch and
control units
Maximum current:
1A
More stable
compared to 5V
from the wall
Black will have better contrast on a projector
Power Supply (Schematic)
We always like to see measured data (especially with waveforms)!
Power Supply (Results)
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Vmax: 5.023 V
Vmin: 4.975 V
Max. Ripple:
48.44mV
Freqnency:
95.057KHz
Hardware Overview
(Outsourced)
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TI RFID S6500 HF Reader
TI RFID HF Transponders
TI RFID HF 13.56 MHz Antenna
(RI-ANT-T01A)
TI RFID S6500 HF Reader
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RFID Reader
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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
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Transponders
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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
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Orientation of tag with respect to antenna
Environment around tag (e.g. metals, liquids)
Background Noise
Recommendations for Tag
Placements
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Parallel to antenna
Away from metals
Within reading range of antenna (~25 cm)
TI RFID HF 13.56 MHz Antenna
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Used to transmit
and receive
signals.
Used for Magnetic
Tuned at 13.56
MHz
Input Impedance
of 50 Ohms
Loop Antenna (In House)
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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)
Black will have better contrast on a projector
Loop Antenna (Self-Made)
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Measurement Results (SWR = 60.832)
Loop Antenna (RI-ANT-T01A)
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Dimension: 337mm
x 322mm x 38mm
Matched to 50 Ohms
Maximum Reading
Range: 50cm
Black will have better contrast on a projector
Loop Antenna (RI-ANT-T01A)
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Measurement Results 1: Vertical, Away from Metal
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SWR = 1.004
Black will have better contrast on a projector
Loop Antenna (RI-ANT-T01A)
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Measurement Results 2: Horizontal, Sitting on Lab Table
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SWR = 1.636
Black will have better contrast on a projector
Loop Antenna (RI-ANT-T01A)
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Measurement Results 3: Close to Lab Equipments
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SWR = 5.111
Black will have better contrast on a projector
Overall Z-Parameters
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SIMS System + Antenna Results During Operation
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SWR = 1.349
Factors Influencing Antenna
Impedance
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Orientation
Environment (e.g. metals, liquids)
Noise
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Antenna is operating always in near field since
wavelength is 22 meters!
Just about the maximum amount of text on a slide
Antenna Recommendations
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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
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PERL software
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Takes in user input and sends out two HEX digits
through RS232 serial port (I/O)
PIC software
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Takes in input from RS232 serial port and sends
logic high to corresponding pins
PERL Software
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Serial.pl
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Takes in keyboard inputs in HEX
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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
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Switch0331.hex
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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
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Map out room and
give coordinates to
each antenna
For example,
antenna B-2 can
correspond to the
secretary’s desk
Future Hardware Development
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Improved Switching Unit for longer lifetime
and higher signal isolation
Increased number of antenna outputs
Improved Antenna Design
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Larger loop antenna
More stable impedance matching network and
BALUN
Future Software Development
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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
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Mr. Richard Martin Cantzler, II
Professor P. Scott Carney
Mr. Nicholas Soldner
Professor Jennifer T. Bernhard
Professor Steven J. Franke
Thank You