A. PROGRAMMING BOARDWe designed a programming board to program the MSP430 Launch pad microcontroller. This consists of JTAG in Spy-Bi-Wire mode . The power supply was connected with fuse blow protection. Additionally, the port pins were attached with a single pole single thrown (SPST) switch and LED for testing the code visually.
B. IR PROXIMITY SENSOR An IR transmitter/LED is a device that emits infrared light outside the visible spectrum. It emits the light near-infrared energy at about 880nm. The device that detects or receives the IR light is called infrared sensor which sense aspects of its surroundings to show fig 3. In our example, the IR sensor is used to detect arriving vehicles.
The SE555P Timer by Texas Instruments is used in the monostable mode. When IR radiation is received (“no vehicle ” condition) triggering occures, resulting in a high output. When a vehicle arrives at a toll plaza,the IR ray are blocked by the vehicle,and the output of the timer to toggle to low. The change in output of the timer is sensed by the microcontroller,which is programmed to turn on the IR transmitter. The IR sensor at the entry and exit check is used to make the controller wait until it receives the acknowledgement signal and to block the vehicle when automatic transaction failed. Code Shoppy
C. RADIO-FREQUENCY IDENTIFICATION (RFID) Radio-frequency identification (RFID) is a technology that uses radio waves to transfer data from an electronic tag, called RFID tag or label, attached to an object, through a reader for the purpose of identifying and tracking the object. Some RFID tags can be read from several meters away and beyond the line of sight of the reader. The application of bulk reading enables an almost-parallel reading of tags. RFID tags can be either passive, active or battery assisted passive. Passive RFID does not use a battery, while an active has an on-board battery that always broadcasts or beacons its signal. A battery assisted passive (BAP) has a small battery on board that is activated when in the presence of a RFID reader. Most RFID tags contain at least two parts: one is an integrated circuit for storing and processing information, modulating and demodulating a radio-frequency (RF) signal, and other specialized functions; the other is an antenna for receiving and transmitting the signal . D. DATA TRANSMISSION The vehicle code is transmitted through RFID communication between the vehicle and toll plaza. An RFID module, in combination with a modem, is used to transmit and receives a electromagnetic signals . We used is the EM41000 family RFID module in our project. It has ability to transmit and receive data with a 2 to 4m range. In addition to the 4-digit vehicle number, three additional nibbles are transmitted –two at the start and one at the end of the vehicle number. The frequency of operation of the RFID Reader module is in UHF band from 125 kHz to 928MHz, operating at 5V supply .They are referred to as passive tags because the only time at which they are actively communicating is when they are within relatively close proximity of a passive RFID tag reader or interrogator.This onboard power source allows an active RFID tag to transmit information about itself at great range, either by constantly beaconing this information to a RFID tag reader or by transmitting only when it is prompted to do so.
The transmit enable triggered low by the controller to handle transmission of data by RFID module. The code for handling the RFID module is developed for the MSP430G2553 microcontroller using assembly language. Initially, the watchdog timer of the microcontroller is turned off and the directions of the ports are set and all the outputs are initialized. When an input is received, the RFID reader is is used for transmission and detection. A delay function is used with two different delay values – a higher delay is used between “end of one transmission” and the “start of transmission”. A smaller delay used between “start of transmission”. This is to avoid the transmission of the same data more than once.The RFID module at the toll plaza is configured with some reading capability. The reads also operated at 928MHz, and has a sensitivity of 3V.
E. TOLL GATE OPERATIONThe toll gate need to be operated fast to increase the traffic throughput. In our demonstration version, we used the motor present in the Compact Disk (CD) players as they operate at very small voltages (~3V)as shown in figure 6. The motor used is connected with gear to reduce the speed of the motor and to open and close the gate attached to them. Once the negative acknowledgement signal from the computer is received by the microcontroller or the microcontroller is timed out then it gives a pulse to the gate which makes the gate close. A manual switch is used to open the gate circuit are given using the Relay Mate Cables (RMC) as the gate is a separate structure.
F.SWITCHING INPUT TO MICROCONTROLLER As the microcontroller needs only 3.3V to operate, the board was designed for 5V operation. The inputs to the microcontroller were given through a transistor switch as shown in figure 7.