PowerPoint Presentation

RFID Technology Comparison

Cost is referring to the tags, however for a single receiver/scanner combo, LF was much cheaper.RFID Receiver Overview

4 PinsVCC (+5V)GND/ENABLE (input)SOUT (output)

Small size, efficientAllows for convenient placement on the wheelchairLow power use when scanning, and almost-zero power use when not scanning.RFID Receiver Overview/ENABLE Flag (input)HIGH = Scanner is off, power consumption is down.LOW = Scanning actively for keys and passing them out serially to the SOUT lineSOUTData is transmitted at 5V over serial communication.RFID Receiver OverviewSOUT (continued)Transfer protocol

CommunicationSerialData bits8Stop bits1ParityNoBit OrderLeast significant bit firstTransfer speed2400 bpsSignal5V TTL-level, non-inverted asynchronous serial

RFID Receiver OverviewSOUT (continued)12 bytes transferred from a key read

Middle 10 bytes are ASCII charactersStart byte is 0x0A , NewLineEnd byte is 0x0D, Carriage Return

RFID Receiver OverviewLEDAlong with the RFID lock/unlock system will be a simple LED that changes colors based on the current state:

LED ColorMeaningOccurs WhenGREENIdle state - Not searching/ENABLE port is either HIGH or disconnectedREDActively searching for RFID key/ENABLE is LOWBlankNo powerVCC is low or disconnected

RFID Receiver OverviewDC Characteristics of RFID Receiver

RFID Receiver OverviewMaximum Ratings of RFID ReceiverThey are well within the conditions of most human-populated areas of the world

RFID Tag OverviewPassive Key used with Low Frequency RFID technology.ReliableHas no battery requirement, should function well beyond any users needs.FlexiForce A204 SensorSpecificationsThickness0.208 mmLength197 mmWidth14 mmSensing Area9.53 mm diameterConnector3-pin Male Square PinSubstratePolyesterPin Spacing2.54 mmLinearity Error< 3%Repeatability< 2.5% of full scaleHysteresis< 4.5% of full scaleDrift< 5% per logarithmic time scaleResponse Time< 5 microsecondsOperating Temperatures-40C 60CForce Ranges4.4 N, 110 N, 440 NTemperature SensitivityOutput variance of 0.2% per degree

197 mm14 mmFlexiForce A204 Sensor

SpecificationsThickness0.208 mmLength56.8 mmWidth31.8 mmSensing Area25.4 mm diameterConnector2-pin male square pinSubstratePolyesterPin Spacing2.54 mmLinearity Error< 3%Repeatability< 2.5% of full scaleHysteresis< 4.5% of full scaleDrift< 5% per logarithmic time scaleResponse Time< 5 microsecondsOperating Temperatures-40F 140FForce Ranges0 1 lb, 0 25 lb, 0 100 lbTemperature SensitivityOutput variance of 0.2% per degree31.8 mm56.8 mm

Locking MechanismBrakesMotorDriverStandard/Manual Brake LocksReplacing

Piston Driven ActuatorBackup plan/option

Cable Disc Brakes

Product Specifications:Mechanical two piece forged aluminum calipersTri-align caliper positioningSintered padsDual knob pad adjustmentCable disc brakesG2 CleanSweep rotorsWeighs only 329 gramsAdvantagesDurableLight weightCost effectiveLow maintenanceSimple installationTremendous braking powerReliable in all weather conditionsMotor for Locking MechanismServo vs StepperServo pwmGeared Bipolar Stepper MotorSpecificationsMotor TypeBipolar StepperStep Angle0.018Step Accuracy5%Holding Torque48 kg*cmRated Torque48 kg*cmMaximum Torque250 kg*cmRecommended Voltage12 V DCRated Current1.7 ACoil Resistance1.7 OShaft Diameter8 mmWeight568 gNumber of Leads4Gearbox TypePlanetaryGear Ratio99.5:1Maximum Strength of Gears48 kg*cmShaft Maximum Axial Load49.1 NShaft Maximum Radial Load98.1 NL293 H-Bridge motor driverSpecificationsWide Supply-Voltage Range4.5 V to 36 VMaximum Output Voltage 36 VMaximum Switching Voltage36 VPeak Output Current2 ADrivers Per Package4Input CompatibilityTTLDelay Time800 nsPin Package16PDIPPrice$2.20Drive CurrentsBidirectionalOutput Current Per Channel1 APeak Output Current Per Channel2 AMaximum Junction Temperature150CStorage Temperature Range-65 150CL298 Second/Backup OptionBudgetItemUnit PriceQuantityTotal CostInvacare Veranda Manual Wheelchair$991$99A204 FlexiForce Sensor$19.504$78Linx Technologies RXM-GPS-R4-T$21.481$21.48ADH8066 GSM Module$49.951$49.95Quad Band GSM/GPRS 7888 GSM Module$39.951$39.95SIM300 GPRS Development Board w Antenna$31.201$31.20Texas Instruments MSP-EXP430G2$10.991$10.99Texas Instruments MSP430G2553IN20$2.431$2.43Linx Technologies EVM-GPS-R4$27.731$27.73Antenna GPS Embedded SMA$11.951$11.9520-PIN DIP Socket$0.751$0.75SMA Connector$11.901$11.90Basic 20x4 Character LCD Screen$17.951$17.9512v Lithium Ion Rechargeable Battery$89.992$179.98UA7815 Positive Voltage Regulator$0.662$1.32DC Power Connectors$1.262$2.52RFID Card Reader Module$42.991$42.99RFID 54mm x 85mm Rectangle Tag$2.501$2.50RFID Blue Eye Key Fob Tag$1.991$1.99RFID 50mm Round Tag$1.991$1.99Avid BB7 Mechanical Disc Brake$512$102Geared Bipolar Stepper Motor$451$45L293 H-Bridge motor driver$3.501$3.50Total$787.07MSP430Contains all code for the system Low power: 1.8 to 3.6 volts5 power saving modes Low cost: $2.43Supports UART and USCI

GSM ModuleLow power: 3.4V 4.5V (Normally 4.0V)Current consumption as low as 2.5mA Has GPRS capabilities AT Commands used Affordable: $31.20M2M data plan required

GSM Module Task GPS coordinates, battery levels, and error/status messages will be sent SMS message and E-mails Message sent when event is triggered When the wheelchair is moved while it is locked When battery life hits 20% and then again at 10%When failure in componentGSM activity diagramConnect to networkIf data is received then sends message Enters low power mode until woken up for data to be sent GPS ModuleFast TTFF: 32 seconds from cold start Low power: 3.3v and 56 mASupports up to 48 channels Uses NMEA 0183 protocol Small and compact Affordable: $21.48GPS Module Tasks Acquire NMEA 0187 protocol GPS coordinate location is parsed Data is sent to GSM module

GPS Activity Diagram GPS Coordinate acquired Sends data to microprocessor Enters low power mode untilTimer timeoutEvent is triggered

LCD SCREENCharacter typeLow CostNot graphical difficult to ProgramBest type based on Project20 X 4

30LCD Screen Function Provide power levels from circuit Displays if locking mechanism is Locked/ Unlocked

LCD DIAGRAM

Lithium- Ion BatteryExcellent Time DurabilityExcellent Life Durability High Charge efficiency Very Cost Effective12.6V

Battery ComparisonPower

Printed Circuit Board