DragonBot Maze Project Spring 2021
RFID Antenna Testing
Author: Matthew Hillsman
Table of Contents
Introduction
For the RFID sensor to work it requires a very large antenna to be able to detect the cards and tags that are desired. During the process of designing the RFID PCB that could be directly connected to the 3Dot board, a decision needed to be made as to where the antenna should be located. The initial iterations of the RFID PCB had the antenna sticking out of board, and out of the chassis of the robot. Professor Hill had an idea however, to possibly place the antenna of the RFID sensor underneath the 3Dot board, so that the card could be detected when the robot drives over them. This would require placing the RFID’s antenna very close to the ground pane of the 3Dot board. Another idea that Professor Hill had was to pace the antenna of the 3Dot board on the shield itself and have the antenna detect the card through this ground plane. Testing was needed to be done to see whether or not these ideas were a viable option.
Testing detection through the 3Dot board
For the first test that I preformed, I took the RFID breakout board and placed it on top of the 3Dot board, where the top shield connectors are located. I placed an RFID tag underneath the 3Dot board, approximately where it would be when the robot was moving. No detection of the card was made by the sensor. I tried this set up several times and at different angles to confirm but concluded that placing the RFID antenna on top of the robot, and have it detect the cards through the board would not work.
Testing detection near the 3Dot’s ground plane
I then took the RFID board and placed it near, but not touching, the ground plane on the bottom side of the 3Dot board. The distance from the 3Dot board and the RFID’s antenna was approximately 3mm. I then turned on the RFID board and moved a tag near it to attempt a detection. Nothing happened, and no communication between the two devices were made. I tried again several time at various ranges and angles to verify, however, I did come to the conclusion that the antenna could not be mounted to the bottom of the board, underneath the paperbot chassis.
Conclusion
In conclusion, because there is a large antenna that is required for the operation of the RFID sensor, a practical location to place said antenna needed to be decided. While the ideas that Professor Hill had in mind for the placement of the antenna were a good idea, the operation of the antenna would not work with this set up due to the effects that the ground plane of the 3Dot board have. It was hypothesized that the reason the RFID sensor did not work with this set up is because the ground plane was acting as a faraday cage and preventing the EMF signal of the RFID sensor to have the range needed to make a proper detection of the cards. It was decided then, to just have the antenna hanging off the board and outside the paperbot chassis, as was originally considered in the first iterations of the design.