SIMS: Smart Inventory Management

System

Group 37Masaki Negishi & Anthony Fai

ECE 445 Senior DesignApril 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

The SIMS System

The images in this presentation have been reduced to screen quality (saves space)

Format Picture -> Compress

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

Takes 6Vdc from AC/DC wall converter and converts to stable 5Vdc

PC Interface Processing Unit 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

PC Interface Processing Unit (Schematic)

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RF Switching Unit Takes in input

from RFID reader Four outputs per

board (expandable)

Relay switching

RF Switching Unit (Schematic)

5Vdc

Input from PIC

RF OUTPUT TO PIC

RF input from Reader

Normally Open SPDT RelaySwitch

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

Power Supply (Schematic)

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Power Supply (Results)

Vmax: 5.023 V Vmin: 4.975 V Max. Ripple:

48.44mV Freqnency:

95.057KHz

We always like to see measured data (especially with waveforms)!

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)

Loop Antenna (Self-Made) Measurement Results (SWR = 60.832)

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Loop Antenna (RI-ANT-T01A)

Dimension: 337mm x 322mm x 38mm

Matched to 50 Ohms

Maximum Reading Range: 50cm

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

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Factors Influencing Antenna Impedance Orientation Environment (e.g. metals, liquids) Noise

Antenna is operating always in near field since wavelength is 22 meters!

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.

Just about the maximum amount of text on a slide

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

Workstation

Server

Laptops

Workstation Workstation

Workstation

RFID Frequency Comparison

Frequency Pros ConsLF (100 – 140KHz; ~2.5 km)Read Range: ~100 cm MAXMagneticInductive Transponders

Less susceptible to environmentLonger 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)MagneticInductive Transponders

Anti-collision intelligence allows multiple of tags to operate concurrentlyWell defined magnetic field

More susceptible to environmentShort reading range

UHF (860 – 960MHz; ~33 cm)Read Range: ~9m MAXElectric (but passive tags)Capacitive Transponders

Anti-collision detectionLong reading range

Not well defined electric fieldField nulls near antenna requires complex anti-collision intelligenceTags have less memory capacity

SWOT Analysis of SIMS

Strengths:Modular designSupports LF and UHFMinimize number of readersCost effective

Weakness:Short rangeSusceptible to environmental factorsRelay power consumption and lifetime

Threats:Smart ShelvesRTLS

Opportunities:Inventory ManagementUHF implementationSoftware Expansion

Credits Mr. Richard Martin Cantzler, II Professor P. Scott Carney Mr. Nicholas Soldner Professor Jennifer T. Bernhard Professor Steven J. Franke

Thank You