DragonBot Maze Project Spring 2021
RFID Trade off Study
Author/s: Matthew Hillsman
Table of Contents
Introduction
The DragonBot needs the ability to detect and identify many different card types that are placed throughout the maze. It was decided that an RFID sensor would be the best way to do this. Research was required to determine the best hardware to effectively complete the task of reading the RFID tags that are on the maze. There were 2 critical hardware components that needed such consideration, the RFID IC and the RFID tags to be used.
RFID IC
During the selection for the RFID IC, the following criteria was used:
First, the IC must accept a voltage in the range of 3.3V – 5V. This requirement is because that is the range of the voltage that can be supplied by the 3Dot board.
The IC must support either the I2C, SPI, or UART communication protocol. This requirement is because we need an IC that can be easily connected to the 3Dot board for communication purposes, and these are the communication protocols supported by the 3Dot board.
There must be libraries available for this device that work with Arduino. The reason for this requirement is that because we are limited on time for the project, we want an IC that will not be overly complicated to program with the 3Dot board. Having the ability to use an already functioning library will save much valuable development time.
The frequency that the IC uses to communicate with the RFID tags must be 13.56MHz. The reason for this requirement is that there is a very limited amount of RFID tags available at 125KHz. The tags available are considerably more expensive. Thus, having a frequency of 13.56MHz was a requirement in my selection.
The price must be reasonable. This requirement is somewhat subjective, but we wanted to find an IC that will work for our application and not have to break the bank for it, therefore, much consideration was taken into the comparison of the prices of the different ICs compared.
Figure 1: RFID IC comparison
As can be observed in figure 1, two different ICs were taken into consideration. Both ICs satisfied all the requirements specified. It was ultimately decided to go with the RC522 IC since the price was less than half that of the PN532.
While considering the selection of the RFID tags, the following criteria was used to come to a decision on which one to use.
The communication frequency of the tag must be 13.56MHz. The reason for this requirement is that the RFID tags and the RFID IC must have a matching frequency.
The tag must have both read and write ability. The reason for this requirement is that we need to be able to write some unique data to the tag so that the robot will be able to tell the difference between one card type and another.
The tag must support the MIFARE transmission protocol. The reason for this requirement is that the transmission protocol must be the same for both the IC and the tag that it is reading.
The size of the tag must be no larger than 76.2mm x 76.2mm x 1mm. The reason for this requirement is that the RFID tag must be able to fit within the dimension of the room on the maze.
The cost for one individual tag is to be no more than $1 per a unit. The reason for this requirement is that because there will be so many tags needed for the maze, we wanted to put a limit on how much money can be spent per a card.
Figure 2: RFID tag comparison
As can be seen in figure 2, there where 3 RFID tags that were considered. Only one of the tags considered however, satisfied the required criteria. It was decided that the sticker tag would be used since neither the key fob and smart cards satisfied the size requirement.
Conclusion
In conclusion, a decision was made on the critical hardware components used in the project, after performing a side-by-side comparison. The MFRC522 was decided on for the IC due to its lower cost than the PN532. The sticker tags were decided on for the RFID cards due to them being the only part considered that met the size requirements to fit in the rooms of the maze.