Project CSCE488 Proposal "RFID Pet Door"
Team #2 Andrew Parr Conner Rocole Ben Peetz Eric Sturm
Prepared for Dr. Sharad Seth
October 30, 2006
Introduction
The objective of the project is to develop a secure system to regulate a domesticated animal's movement through an entryway. The system will be automated by utilizing Radio Frequency Identification (RFID) technology. RFID technology will make it possible to associate a pet with a set of initial parameters determined by the user. The hope of the design team is that the final version will be a basis for a manufacturable product. The motivation for this project is to increase security from a regular pet door. A locking mechanism that requires a pet to have a unique identification tag to open the door will ensure that unwanted animals cannot get through the door. This will allow pets in and out of a building without constant human supervision. A pet owner can choose which times the pet has access through the door and will not have to worry about stray or wild animals getting into the house. The RFID pet door will give the pet and the pet owner more freedom without sacrificing security. The basic design will include a locking door, microcontroller, RFID reader, antenna, RFID tags, and a simple user interface. System implementation begins by attaching an RFID tag to a pet's collar. Embedded in each RFID tag is a unique identification code. The code and initial parameters will be entered by the user into the system via a user interface consisting of an LCD with buttons to interact with various menus. When a pet is in the vicinity of the RFID Pet Door, its tag is scanned. If the scanned tag is found to be valid, the initial parameters associated with that tag are evaluated to determine the appropriate action. If the pet is allowed to pass through, the door will unlock until the pet passes through. Then the door will return to a rest position where it will lock again. This report will cover the project specifications and the approaches that will be necessary to meet the objectives of the project. The specifications are broken down into many components which will aid in determining the feasibility of the project. Every design is confronted with numerous complications in addition to various design issues that affect its feasibility. Acknowledging these concerns early in the design process is tremendously beneficial to the team and the overall success of the project.
Main Components and Their Functions
Microcontroller The microcontroller is responsible for the information processing of the project. It communicates with the RFID reader, controls the pet door lock, stores individual pet information, and interacts with the user. The Atmel STK500 development board will be used to develop the code for the Atmel ATmega16 microcontroller. Antenna A large amount of time was invested in pricing RFID antennas. It was concluded that their exorbitant price would make the product uneconomical. The basic RFID antenna was valued at over $100. The design team determined that building a custom antenna would greatly reduce cost. The antenna needs an inductance of 47H, a Q factor less than 20, and a resonance frequency of 125.0 kHz or 134.2 kHz. RFID Reader Selecting the reader proved difficult since the team had little experience with RFID technology. Samples of three different readers were obtained: Texas Instruments' (TI) Series 2000 micro reader, Philips' HTRC11001T IC and Atmel's 2207B IC. Using the TI component ensured a functional reader would be used to test the antenna. Once the antenna is tested and functional, work will begin with the Atmel or Phillips components. These readers are basic RFID ICs (Integrated Circuit) and will require numerous passive components to achieve functionality. Door The door will be a standard pet door that will utilize a locking solenoid. When a valid pet ID is read, the solenoid will unlock the door and allow the pet to go through. Eventually the system will implement a way to determine which side of the door the pet is on. This will allow for control of whether the pet is permitted to exit only, enter only, both, or neither. The door design has yet to be finalized. User Interface The user interface is a large portion of the project. It will consist of a fourline LCD (Liquid Crystal Display) screen, multiple push buttons, and a tri-position switch. The LCD will display a menu system that allows the user to add and remove pets and manage the times they can access the pet door. Board Layout A major objective of the project is to layout a professional PCB. The board will include the microcontroller, RFID reader, power supply, user interface, and various passive components. The team has yet to determine which software application will be used to generate the board layout.
RFID Pet Door Design
Microcontroller The first issue addressed for designing the "RFID Pet Door" was selection of a microcontroller. The microcontroller would need a sufficient amount of memory to store pet information, user interface information, and the main program. It must also have at least 16 I/O pins to interface with the RFID reader, pet door, and user interface. After many considerations, the group decided to use an Atmel AVR microprocessor. Next was choosing the correct AVR to fit the scope of the project. The range of AVR 8-bit RISC microprocessors was narrowed down to the ATmega16, ATmega32 and ATmega168. The ATmega16 and ATmega168 have 16 kilobytes of Flash memory, whereas the ATmega32 has 32 kilobytes of memory. The group decided that 16 kilobytes of memory would be adequate for programming commands, pet information, and user interface purposes. The ATmega16 has 32 I/O pins while the ATmega168 has only 16 I/O pins. Although 16 I/O pins may be enough for project, the group decided that 32 I/O pins would allow the project to take on greater complexity if time permits. Price difference between the processors was negligible; therefore, the ATmega16 microcontroller was chosen for the RFID Pet Door. RFID Reader RFID systems use low, high, or ultra-high frequencies. Low frequency RFID uses frequencies between 125 kHz to 148.5 kHz and has a range generally no farther than 10-15cm. High frequency RFID uses 13.56 MHz and has a typical range of 1 meter. Ultra-high frequency RFID uses 902 MHz-928 Mhz and has a potential range of 10 meters. Ultra-high frequency RFID will not work with objects in the path of the transponder and reader. The range is also more than necessary for the pet door. Low frequency can travel through objects better but has a limited range. For a pet door scenario, it is more feasible to use low frequency readers and transponders in order for the signal to pass through the pet's body or the door; however, range becomes an issue. If an effective range cannot be obtained, high frequency RFID readers may need to be used. A complete RFID reader costs over $200 dollars and seems to have more features then what is necessary for the pet door. RFID ICs that require passive components to be added and assembled on a PCB are only $2 to $6. Hence, the group decided RFID IC's would work well for the project. This cost difference is a major factor in creating a more economical product. Antenna RFID antenna prices ranged from $150 to $600. Like the RFID reader, this seems overpriced for what is actually needed. This led to building a custom antenna for the pet door. The antenna had to be designed to transmit and receive a signal of 134.2 kHz. No group member had a background with antenna design; therefore, Ben and Eric went to multiple professors to research antenna
design. A TI RFID reader datasheet gave a detailed description of how to build an antenna that resonates at 134.2 kHz. The information seemed suitable for all of the readers purchased. While the construction method provided was sufficient, a few adjustments had to be made. In order for the antenna to work with the various readers, it needed to have an inductance between 46.0 H to 48.0 H and a series impedance close to 2.2 ohms that would produce a Q factor of 20 or less. After constructing the antenna according to the datasheet, testing using a spectrum analyzer confirmed the antenna resonates best at 134.2 kHz. It also transmits frequencies within 20 kHz above or below 134.2 kHz, but the strength of the signal was clearly strongest at 134.2 kHz according to the spectrum analyzer. Reader Microcontroller Integration The antenna must be within specifications for proper operation with the RFID reader ICs. The TI microreader was purchased for this purpose. This component has an RFID IC and a built-in microcontroller but no antenna. The microreader will allow for testing to make sure the antenna is built correctly. The TI microreader will not be used in the final design because it would make the product too expensive. It has a read mode specifically for testing functionality. the If antenna reads in a signal from a transponder, the microreader will output a high signal. Using the microreader should ensure the antenna is working correctly and could actually work as a backup plan to replace the RFID ICs if they do not work or cause problems in the design. The goal for the end of this semester is to interface the RFID reader with the microcontroller. To complete this objective, communication between the microcontroller and RFID reader must be clearly defined. Code will have to be developed to make the RFID reader routinely poll for a tag in range. The microcontroller will need to interpret this data and execute the appropriate course of action. 6User Interface The user interface will be designed to provide easy programmability for the user. If this project is to be marketable, the interface needs to be simple and user friendly. It will require an LCD and a few buttons to interact with a menu system developed for the screen. Members of the group compiled different ideas for a user interface implementation. Andrew's design was determined to be the most logical. Pet Door The electronics may be the most important aspect of the project, but the final product comes down to a mechanical door that needs to open and lock at specific times. There are multiple ideas the group has for a door and how to open it. The intent is to start with a basic design, and if time permits, make the door motorized or detect if the pet came in or out. The first idea is to have a swinging door with a latch or lock. The hinges to the door could be on the side or on the top as long as the pet could push
through the door. It would be locked until the pet came within range of the reader. The door would then unlock with a valid pet in range. Consequently, this would require a force from the pet to open the door, which may be undesirable for the user. The way in which the door swings could also determine whether the pet is coming in or out, but the pet would always have to push (or pull) in order to tell which way it is going. This idea is basic and might be the easiest way to let pets in and out, but tracking them would be difficult. Another idea is to have a motorized door. When the pet steps in range of the reader the door would automatically open using a motor. This way the pet does not actually have to push on the door. Also, the door would need a sensor to see if the pet went through the door in order to know when to shut. With this added sensor it would be easier to track the direction of the pet as well, but with this design there are complications that could arise. For instance, if the pet decides to not go through the door, the door would stay open unless programmed otherwise. And like with any project, more complexity could lead to more flaws in the final product. In conclusion, it is probably in the best interest of the group to start with a swinging door and latch. If time permits or if the swinging door does not work very well for the project, other ideas could be implemented.
Experience
The design team members are Andrew Parr, Ben Peetz, Conner Rocole, and Eric Sturm. All team members are senior Electrical Engineers from the University of Nebraska at Lincoln. In addition to majoring in Electrical Engineering, Andrew and Conner are also pursuing a degree in Computer Engineering. Their knowledge in embedded systems will be utilized in the setup of the microcontroller and interfacing with other components. Ben and Eric will be responsible for the functionality of the RFID scanner. Their experience in communication systems will prove to be valuable in the implementation of the RFID scanner. The combined talents and ingenuity of the design team should result in completion of all miniature projects this semester and a successful final project completed in the spring. In only two months the team has derived the project idea, specifications, and initial design. For the first time the team is performing functions on a project in addition to design. For example, the team investigated which interface would be most comprehensible to a user. In addition to non-engineering functions, the team is also assuming managerial responsibilities. In order to develop an end product that operates to specification, the team has to be properly motivated and held accountable when deadlines are not met. It has been determined that equally dividing managerial assignments is the most effective method for the group. Essentially, the team is experiencing the full design process of a real product condensed into a few months with the team as the only labor resource. In addition to witnessing a complete design process the team members are also becoming versed in business mannerisms. The team discovered in the first few weeks that meetings can become lengthy and arduous while accomplishing little. An effective meeting format was rapidly established to maximize the team's time. Development of a project timeline helped to ensure that milestones were being completed in a timely manner. Adherence to this project timeline will ensure that the group finishes the project on time. Cooperation and equal distribution of labor make the project progress smoothly. A team member who is weighed down with a large portion of the project will likely harbor resentment and ill feelings against the rest ...