DrgonBot Maze Project Spring 2021
RFID and LDC Interference Testing
Author/s: Matthew Hillsman & Muath Almandhari
Table of Contents
Introduction
One of the main concerns that we had in terms of the robot’s design was the potential for interference between the RFID and LDC sensors. Both the RFID sensor and the LDC sensor work by outputting an elector magnetic frequency in order to detect or communicate with their respective counterpart on the maze. The RFID sensor operates at a frequency of 13.56MHz, while the LDC sensor operates at a frequency of around 10MHz, so these two frequencies are close enough to cause concern. The RFID tags and copper tape are to be placed next to each other and used simultaneously to read the card type and the room configuration in front of the robot, so with these two frequency outputting devices so close to one another, we had concerns for interference. In this test, the Card Design Engineer and the Navigation Design Engineer met to test whether or not the possibility of interference between the RFID and LDC sensors would be an issue for our robot.
Testing the RFID Sensor
In order to test whether or not the LDC sensor or the copper tape would interfere with the RFID sensor and the RFID tags, the following tests were performed.
Interference with LDC Antennas
First, the antenna of the LDC sensor was placed within close proximity of the RFID sensor’s antenna. Both devices were turned on and transmitting their signals. The RFID tag was moved within range of the RFID sensor’s antenna, and a reading of the tag was observed on the serial monitor. This test was repeated several times to test the reliability of this. The RFID was repositioned and set at different angles, ranges, and locations. The LDC sensor’s antenna was also moved around to see if the positioning of the LDC made any difference. The results were the same for all, the RFID tag was read without any perceived disruption or change in reliability.
Testing RFID and copper tape in contact
For the next test that I performed, I took a strip of the copper tape, and placed it underneath one of the RFID tags. I moved the RFID sensor’s antenna within range of the RFID tag while viewing the serial monitor output and attempted a reading. No reading was made from the RFID tag. I then slowly moved the copper tape out from underneath the RFID until a reading was made. The RFID would not make a reading while the copper tape was directly underneath the RFID tag, but once the copper tape was not in direct contact with the RFID tag anymore, a reading was possible. From this, I was able to conclude that an RFID reading was not possible while the copper tape was in direct contact with the RFID tag, however, a reading was possible with the copper tape near the tag but not touching.
Copper Tape and RFID Tag in Close Proximity
I then wanted to test the reliability of the RFID reading while the copper tape was near the RFID tag, but not in contact with it. I stuck the adhesive back of one of the RFID tags and placed in on a sheet of cardboard. I then cut two strips of the copper tape, removed the film that protects the adhesive back of the tape and placed the tape on both sides of the RFID tag on the cardboard. I then moved the RFID’s antenna within range of the RFID tag while viewing the serial monitor and was able to successfully detect the tag. I moved around the antenna several times to test if this reading was reliable, and attempted readings at varying distances and all gave successful readings.
I then attempted readings after moving the copper tape around at varying distances and locations relative to the RFID tag. The results were the same for all, the RFID readings were reliable as long as the RFID tag was not in contact with the copper tape. I was able to conclude that the copper tape would not interfere with the RFID readings when the tags was near the copper.
For the final test the was conducted, I took the described setup above with the RFID tag within close proximity of the copper tape. I turned on the LDC sensor and placed it within close proximity of the RFID antenna and positioned it such that a reading was being made of the copper tape by the LDC sensor. I then attempted a reading with the RFID sensor and was successful. I retired this test at varying distances and angles in which I would get a reading under normal circumstances. All the tests of this type were successful.
Testing the LDC Sensor
Because Dragonbot’s design requires having LDC and RFID sensors to be placed next to each other, we performed some tests in order to examine if there will be any interferences between the two sensors. Therefore, we performed the following tests on the LDC sensor:
LDC Interference with the RFID
At the beginning of the LDC and RFID interference testing, we performed a test on the LDC by itself. Therefore, we placed copper tape in a piece of carton and recorded the outputs from different distances from 0cm to 3cm. We recorded these output results in order to compare it to the second test and see if the readings would change on the same settings. Then we placed the RFID sensor between the copper tape and the LDC sensor for the same distances and recorded the output results of the LDC.
The result was that the LDC did not interfere with the RFID and the outputs remained the same as the initial test. The LDC did not interfere with the RFID because the frequency that the LDC is using which is about 10 MHz is much less than the RFID is using which is about 13.56 MHz.
RFID Tags and Copper Tape in Contact
The goal of this test is to examine the reliability of the LDC sensitivity while having a tag that is close or covers the copper tape. Therefore, we started by placing one RIFD tag close to the copper tape and examined the readings of the LDC in the same settings we performed in the first tests. We realized that the LDC output did not get effected with having the tag next to it.
For the next test, we placed a tag on top of the copper tape while having the LDC in same settings of the first test. By examining the output of the LDC, we realized that the LDC readings changed because the RFID tag covered the copper tape. This test helped us understand the behavior of the LDC readings in order to plan the best positioning of RFID tags in the maze in order to have the best LDC readings.
Conclusion
In conclusion, we studied the behavior of both solutions, RFID, and LDC when they are placed next to each other and were able to conclude that the two devices would not interfere with each other while performing their operations on the robot. We believe that the different operating frequencies are far enough apart, which we believe is why there is no interference between these two devices while operating near one another. Furthermore, these tests would help us to create design requirements that would fit with this experiment’s results.