1. SMART CART Group 20 Ciju Francis, Tom Rosengrant

2. Idea  A system that transforms a shopping cart into a point of sale device

3. Benefits  Paying without waiting in line  Lowering labor costs for grocery businesses  Lowers the cost of products sold

4. System Overview

5. RFID Module  Parallax RFID Reader Writer Module  Read and write to passive, 125kHz RFID transponders  Power Requirements:  5 V  200 mA (Active mode)

6. RFID Module Requirements 1. Module is able to power a transponder within 1 foot Verifications 1. Check if serial data is being sent back to the microcontroller from the module

7. RFID Module  Challenges  Multiple implementations explored  Building transmitter from scratch Time constraints, Lack of background in RF  Using a TI Chip Only surface mounted packaging available  Parallax RFID module Limited range up to 3 inches

8. RFID Module  Induced voltage V 0 in a tuned loop coil of RFID tag  where f = frequency of arrival signal N = number of turns of coil in the loop S = area of the loop in square meters Q = quality factor of circuit B0 = strength of arrival signal ⍺ = angle of arrival signal

9. RFID Module  Calculation of B Field in a Tag Coil

10. RFID Module  Number of Turns and Current Necessary  where a = radius of coil r = read range µ = 4π x 10 -7

11. Microcontroller  Arduino MEGA board  Based on ATmega 1280 microcontroller  4 UARTs (hardware serial ports)

12. Microcontroller Requirements  Able to send tag ID to Bluetooth module Verifications  Check the assigned hardware serial pin for correct ID number

13. Microcontroller  Challenges  Software Serial library issues  Hardware Serial Uno 1 UART interface available Able to easily remove Atmel microcontroller MEGA 4 UART interfaces available Atmel microcontroller is surface mounted to Arduino

14. Microcontroller  Hardware Serial Implementation  Serial1.available()  Arduino is unable to read serial data from RFID reader

15. Bluetooth  Roving Networks RN41XV Bluetooth Module  UART data connection interface  Power requirements:  3.3 V  30 mA (connected mode)

16. Bluetooth Requirements  Transmits a signal containing RFID tag ID Verification  Android application is able to detect tag ID through Bluetooth connection

17. Bluetooth  Challenges  Needed to solder together a PCB adaptor to use on a breadboard  Electrical connections between the headers and PCB were not soldered on properly  Difficulty in testing module due to poor soldering

18. Bluetooth

19. Power  DC-to-DC Converter  Charge Indicator

20. Power  DC-to-DC Converter

21. Power  DC-to-DC Converter Output (Simulation)

22. Power  DC-to-DC Converter Output (Experimental)

23. Power  DC-to-DC Controller Circuit

24. Power  Charge Indicator

25. Power  Charge Indicator

26. Ethics  Impact on labor  Electrical safety

27. Summary  Successes  Power Circuit  Android application  Challenges  RFID reader  Soldering issues with PCB adaptor for Bluetooth

28. Further Work  Create a custom RFID detection circuit  Extend range to cover whole shopping cart  Use a stand alone microcontroller, such as the PIC18F87XA, to create a smaller footprint  Finish enabling Bluetooth capability  Polish Android application