ECE 477 Final Presentation Group 8 Fall 2004. Outline Project overviewProject overview Block diagramBlock diagram Professional componentsProfessional

ECE 477 Final ECE 477 Final Presentation Presentation Group 8 Group 8 Fall Fall

20042004

OutlineOutline

• Project overviewProject overview• Block diagramBlock diagram• Professional componentsProfessional components• Design componentsDesign components• Success criteria demonstrationsSuccess criteria demonstrations• Individual contributionsIndividual contributions• Project summaryProject summary• Questions / discussionQuestions / discussion

Project OverviewProject Overview

• Objective: To design and build a shopping Objective: To design and build a shopping cart capable of following a shopper around a cart capable of following a shopper around a storestore– Shopper carries an ultrasonic beaconShopper carries an ultrasonic beacon– Cart follows beacon by maintaining fixed Cart follows beacon by maintaining fixed

signal strength (within a small range)signal strength (within a small range)– Infrared sensors mounted on cart enable it Infrared sensors mounted on cart enable it

to avoid obstaclesto avoid obstacles

Block DiagramBlock Diagram

Atmel ATMega32L

Motor1

Sharp GP2D15

Sharp GP2D15

Ultrasonic Receiver 1

UltrasonicReceiver 2

Motor2

PWM

PWMIRQ

IRQ

A/D A/D

Professional ComponentsProfessional Components

• Constraint analysis and component selection Constraint analysis and component selection rationalerationale

• Patent liability analysisPatent liability analysis• Reliability and safety analysisReliability and safety analysis• Ethical and environmental impact analysisEthical and environmental impact analysis

Constraint AnalysisConstraint Analysis

• Microcontroller Constraints:Microcontroller Constraints:– Moderate clocking speed (1 – 4 MHz)Moderate clocking speed (1 – 4 MHz)– Modest space constraintsModest space constraints– Peripheral requirementsPeripheral requirements

• A/D ConverterA/D Converter• RTI/Timer module and PWMRTI/Timer module and PWM• External InterruptsExternal Interrupts

– Power and cost efficientPower and cost efficient


• Microcontroller Candidates:Microcontroller Candidates:– Rabbit / PIC:Rabbit / PIC: Did not offer required Did not offer required

combination of peripheralscombination of peripherals– HC05 / HC11:HC05 / HC11: One-time programmable One-time programmable

memorymemory– MC9S08GT32 / ATMega32L:MC9S08GT32 / ATMega32L: Identical Identical

feature set – Atmel chip was chosen feature set – Atmel chip was chosen

due to ready availability of due to ready availability of

development toolsdevelopment tools


• Infrared Proximity SensorInfrared Proximity Sensor

– Prime candidates were Sharp GP2D12 and Prime candidates were Sharp GP2D12 and Sharp GP2D15 (analog vs digital)Sharp GP2D15 (analog vs digital)

– Chose GP2D15 – digital output was more Chose GP2D15 – digital output was more convenient and did not tie up A/Dconvenient and did not tie up A/D

• DC MotorDC Motor

– Fast enough to keep up with a personFast enough to keep up with a person

– Sufficient torque to power 6lb. cart Sufficient torque to power 6lb. cart

– Jameco 10:1, 600RPM,12V DC Jameco 10:1, 600RPM,12V DC

geared motorgeared motor

Patent Liability AnalysisPatent Liability Analysis

• Using Sensors to track / locate objectsUsing Sensors to track / locate objects– US Pat # 5,165,064 US Pat # 5,165,064

• Uses array of ultrasonic transducers to locate a beaconUses array of ultrasonic transducers to locate a beacon

– US Pat # 5,491,670 US Pat # 5,491,670 • Uses multiple ultrasonic beacons to triangulate positionUses multiple ultrasonic beacons to triangulate position

– US Pat # 6,567,044US Pat # 6,567,044 • Uses sensors to determine locationUses sensors to determine location

• All cause problems under doctrineAll cause problems under doctrineof equivalents. First is also literalof equivalents. First is also literal

Patent Liability AnalysisPatent Liability Analysis

• Other Patent Liability issuesOther Patent Liability issues– US Pat # 4,751,658 US Pat # 4,751,658

• Uses sensors to avoid obstaclesUses sensors to avoid obstacles

– US Pat # 5,911,767 US Pat # 5,911,767 • Has a central control that uses sensor data to determine Has a central control that uses sensor data to determine

future actionfuture action

– US Pat # 4,710,020 US Pat # 4,710,020 • Uses sensors to determine distance of a transmitterUses sensors to determine distance of a transmitter

• The first is a literal infringementThe first is a literal infringementrest are infringements under the rest are infringements under the doctrine of equivalentsdoctrine of equivalents

Reliability/Safety AnalysisReliability/Safety Analysis

• Reliability Drivers:Reliability Drivers:– Heat : Increased heat increases unreliabilityHeat : Increased heat increases unreliability– Component Derating: Prevents wear outComponent Derating: Prevents wear out

• Product Specific Drivers:Product Specific Drivers:– Low power microcontroller, good ventilation, Low power microcontroller, good ventilation,

lowers unreliability caused by heatlowers unreliability caused by heat– High current through motorsHigh current through motors

and IR leads to non-derated and IR leads to non-derated

power chipspower chips


• Components have failure rates of the order of Components have failure rates of the order of 10E-6 or better 10E-6 or better

• Acceptable for a non-critical applicationAcceptable for a non-critical application• Components analyzed for failure:Components analyzed for failure:

– ATMega32L – 4.29E-6 failsATMega32L – 4.29E-6 fails– Max663 – 3.336E-6 failsMax663 – 3.336E-6 fails– IRL530N – 4.795E-6 failsIRL530N – 4.795E-6 fails


• FMECA- FMECA- – 5 major blocks: U/S transmitter, U/S receivers, IR 5 major blocks: U/S transmitter, U/S receivers, IR

sensors, Motor drive circuitry, Power circuitrysensors, Motor drive circuitry, Power circuitry– Critical reliability problem - potential collision Critical reliability problem - potential collision

with user:with user:• Motors stuck onMotors stuck on• Defective IR sensorsDefective IR sensors

– Both components well derated, Both components well derated,

and should not fail, leading to highand should not fail, leading to high

overall safety of cart. overall safety of cart.

Ethical/Environmental AnalysisEthical/Environmental Analysis

Environmental ImpactEnvironmental Impact• Manufacture of semiconductors Manufacture of semiconductors

– Environmentally unfriendlyEnvironmentally unfriendly• Soldering on PCBsSoldering on PCBs

– Exposure to leadExposure to lead• Plastic casingPlastic casing

– RecyclableRecyclable


Environmental ImpactEnvironmental Impact• ElectricityElectricity

– Precious resource usedPrecious resource used• Battery DisposalBattery Disposal

– Careful and correct disposal neededCareful and correct disposal needed


Ethical ImpactEthical Impact• SafetySafety

– Warning labelsWarning labels– DocumentationDocumentation– Safety mechanismsSafety mechanisms

• ReliabilityReliability– Perform as stated in user manualPerform as stated in user manual

Design ComponentsDesign Components

• Packaging design considerationsPackaging design considerations• Schematic design considerationsSchematic design considerations• PCB layout design considerationsPCB layout design considerations• Software design considerationsSoftware design considerations

Packaging DesignPackaging Design

• Board mounted on bottom trayBoard mounted on bottom tray• Board dimensions - 4” x 6Board dimensions - 4” x 6””

• Motors with wheels attached mounted at Motors with wheels attached mounted at bottom – front wheel drivebottom – front wheel drive

• Two ultrasonic sensors mounted at front endTwo ultrasonic sensors mounted at front end• Two infrared sensors mounted atTwo infrared sensors mounted at

front cornersfront corners


• Cart only moves forward Cart only moves forward – IR sensors only needed at front two IR sensors only needed at front two

cornerscorners– Ultrasonic sensors placed strategically to Ultrasonic sensors placed strategically to

allow determination of beacon bearingallow determination of beacon bearing• Back wheels are freely rotating caster wheelsBack wheels are freely rotating caster wheels

– Provides for smaller turning radiusProvides for smaller turning radius


• Beacon carried by shopperBeacon carried by shopper– Small and lightSmall and light

• Circuit may be damaged/tampered withCircuit may be damaged/tampered with– All circuitry hiddenAll circuitry hidden

• Storage space must be maximizedStorage space must be maximized– No components placed in cartNo components placed in cart

• Batteries must be accessibleBatteries must be accessible– Batteries not hiddenBatteries not hidden

Schematic DesignSchematic Design• Main Main

SchematicSchematic– Headers Headers

for all for all sensorssensors

– Motor Motor control control MOSFETsMOSFETs

– IR input IR input invertedinverted

Schematic DesignSchematic Design

• Cart Power Cart Power SupplySupply

– Power: Power: 9.6V9.6V

– 6V rail6V rail

– -6V rail-6V rail

– 3.3V 3.3V railrail


• TransmitterTransmitter– Max 663Max 663– 12 V 12 V

batterybattery– 555 timer555 timer


• ReceiverReceiver

– LF353 op LF353 op ampsamps

– Gain of 90Gain of 90

– Filter for Filter for noisenoise

PCB Layout DesignPCB Layout Design

• 5 PCBs – 1 U/S Transmitter, 3 U/S Receivers, 1 Main 5 PCBs – 1 U/S Transmitter, 3 U/S Receivers, 1 Main Board. Board.

• Need modular layout to enable cutting of single Need modular layout to enable cutting of single board. board.

• Noise immunityNoise immunity::– Bypass capacitors close to microcontroller and Bypass capacitors close to microcontroller and

noise suppression capacitors between power and noise suppression capacitors between power and ground at intervalsground at intervals

– Need wide, short traces to reduce Need wide, short traces to reduce

inductance, thereby reducing current inductance, thereby reducing current

spikes and noise. spikes and noise.

PCB Layout DesignPCB Layout Design

• Noise ImmunityNoise Immunity::– No 90No 90oo angles minimize wave reflections angles minimize wave reflections

which lead to noise and radiationwhich lead to noise and radiation– Reduce interference between sub-circuits, Reduce interference between sub-circuits,

by placing individual power and ground in by placing individual power and ground in parallelparallel

– High current motors need to be isolated High current motors need to be isolated from rest of circuit, powered from rest of circuit, powered

directly from battery directly from battery – Copper pourCopper pour

PCB Layout DesignPCB Layout DesignReceivers Transmitter Main board

Software DesignSoftware Design

• 32Kb flash, 2Kb SRAM – EEPROM not used32Kb flash, 2Kb SRAM – EEPROM not used• Application code is organized in a command-Application code is organized in a command-

driven fashiondriven fashion– Ultrasonic receivers are polled periodicallyUltrasonic receivers are polled periodically– Infrared sensors generate interrupt Infrared sensors generate interrupt

requestsrequests– Main loop reads voltage samplesMain loop reads voltage samples

and adjusts motor speedsand adjusts motor speeds


Main loopMain loop

FlowchartFlowchart

Start

Initialize on-board peripherals

Enable global interrupts

Read the last sampled front left, and front right voltages

Is left or right voltage non-

zero?

Motor speed duty cycles = (255 – Voltage) * 1.5

Y

Turn off both motors

N


Periodic Periodic ExternalExternal

Interrupt Interrupt InterruptInterrupt

Service ServiceService Service

Routine RoutineRoutine Routine

Start

Clear the interrupt flag

Read left receiver

Read right receiver

Store voltage samples in global data structure

Return

Start

Clear the interrupt flag

Turn off opposite motor

Adjust motor on same side

Disable ultrasonic receiver polling

Return

Success Criteria DemonstrationsSuccess Criteria Demonstrations

1.1. Ability to generate a beacon signal - Ability to generate a beacon signal - demodemo

2.2. Ability to identify the bearing of the beacon Ability to identify the bearing of the beacon - - demodemo

3.3. Ability to approximate the distance to the Ability to approximate the distance to the beacon using relative signal strength - beacon using relative signal strength - demodemo

4.4. Ability to follow the beacon - Ability to follow the beacon - demodemo

5.5. Ability to avoid obstacles in theAbility to avoid obstacles in the

path of motion - path of motion - demodemo

Individual ContributionsIndividual Contributions

• Team Leader – Aliasgar PoonawalaTeam Leader – Aliasgar Poonawala• Team Member 2 – Raghuram RamanujanTeam Member 2 – Raghuram Ramanujan• Team Member 3 – Clive LopezTeam Member 3 – Clive Lopez• Team Member 4 – Mohan RokkamTeam Member 4 – Mohan Rokkam

Team Leader – Aliasgar PoonawalaTeam Leader – Aliasgar Poonawala

• Packaging designPackaging design• Ethical and environmental impact analysisEthical and environmental impact analysis• Software debuggingSoftware debugging• Component selectionComponent selection

Member 2 – Raghuram RamanujanMember 2 – Raghuram Ramanujan

• Design constraint analysis and component Design constraint analysis and component selectionselection

• Software design Software design – Wrote diagnostic routinesWrote diagnostic routines– Devised control algorithm and wrote core Devised control algorithm and wrote core

software modulessoftware modules• Hardware design Hardware design

– Microcontroller interfacingMicrocontroller interfacing– Infrared sensor interfacingInfrared sensor interfacing

• Hardware debuggingHardware debugging

Member 3 – Clive LopezMember 3 – Clive Lopez

• PCB layout designPCB layout design• Hardware designHardware design

– Designed (and redesigned) ultrasonic circuitsDesigned (and redesigned) ultrasonic circuits– Microcontroller interfacingMicrocontroller interfacing

• Hardware debuggingHardware debugging• Soldering and population of boardSoldering and population of board• Reliability and safety analysisReliability and safety analysis• Component selectionComponent selection• PackagingPackaging

Member 4 – Mohan RokkamMember 4 – Mohan Rokkam

• Hardware design Hardware design – Ultrasonic circuitryUltrasonic circuitry– Microcontroller interfacingMicrocontroller interfacing

• Created and maintained webpageCreated and maintained webpage• Hardware debuggingHardware debugging• Soldering and population of boardSoldering and population of board• Schematic designSchematic design• Patent liability analysisPatent liability analysis• Component selectionComponent selection• PackagingPackaging

Project SummaryProject Summary

• Important lessons Important lessons learnedlearned– Fuses!Fuses!– Use bypass Use bypass

capacitorscapacitors– Effective time Effective time

managementmanagement– Trust team matesTrust team mates

• Important skills learnedImportant skills learned– OrCAD Capture and OrCAD Capture and

LayoutLayout– Soldering techniquesSoldering techniques– Power supply designPower supply design– Ability to interpret Ability to interpret

datasheetsdatasheets

Project SummaryProject Summary

• Second iteration enhancementsSecond iteration enhancements– Better control algorithmBetter control algorithm– Better noise immunity for sensorsBetter noise immunity for sensors– Ability to send different instructions via Ability to send different instructions via

beaconbeacon– Support for multiple cartsSupport for multiple carts– Better beacon rangeBetter beacon range– Additional sensorsAdditional sensors

Questions / DiscussionQuestions / Discussion

Documents

ECE 477 Final Presentation Group 8 Fall 2004. Outline Project overviewProject overview Block diagramBlock diagram Professional componentsProfessional