Transcript Smart Cart
SMART CART Group 20 Ciju Francis, Tom Rosengrant Idea A system that transforms a shopping cart into a point of sale device Benefits Paying without waiting in line Lowering labor costs for grocery businesses Lowers the cost of products sold System Overview RFID Module Parallax RFID Reader Writer Module Read and write to passive, 125kHz RFID transponders Power Requirements: 5 V 200 mA (Active mode) 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 RFID Module Challenges Multiple implementations explored Building transmitter from scratch Using a TI Chip Time constraints, Lack of background in RF Only surface mounted packaging available Parallax RFID module Limited range up to 3 inches RFID Module Induced voltage V0 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 RFID Module Calculation of B Field in a Tag Coil RFID Module Number of Turns and Current Necessary where a = radius of coil r = read range µ = 4π x 10 -7 Microcontroller Arduino MEGA board Based on ATmega 1280 microcontroller 4 UARTs (hardware serial ports) Microcontroller Requirements Able to send tag ID to Bluetooth module Verifications Check the assigned hardware serial pin for correct ID number 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 Microcontroller Hardware Serial Implementation Serial1.available() Arduino is unable to read serial data from RFID reader Bluetooth Roving Networks RN41XV Bluetooth Module UART data connection interface Power requirements: 3.3 V 30 mA (connected mode) Bluetooth Requirements Transmits a signal containing RFID tag ID Verification Android application is able to detect tag ID through Bluetooth connection 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 Bluetooth Power DC-to-DC Converter Charge Indicator Power DC-to-DC Converter Power DC-to-DC Converter Output (Simulation) Power DC-to-DC Converter Output (Experimental) Power DC-to-DC Controller Circuit Power Charge Indicator Power Charge Indicator Ethics Impact on labor Electrical safety Summary Successes Power Circuit Android application Challenges RFID reader Soldering issues with PCB adaptor for Bluetooth 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