December 26, 2000 Thank you for your interest in the pet door project. Feel free to read our project report below. We never did fully develop and market our design. However, I have seen some other quality automated pet doors at the following link. If you decide to buy one, please use this link to do so, as I will get a commission on the sale.Buy Pet Care Michael Sprague, Jr. |
Our design group at Michigan State University developed an automated pet door. This project was undertaken with the intent of addressing and ultimately solving the problem of unintended creatures (e.g., wild animals or stranger's pets) gaining entrance into the homes of pet owners. The pet door would use discriminatory tactics to distinguish the owner's pet from other creatures. The system would include a microprocessor to provide the capability of logging pet activity as well as provide practical functionality that has not been addressed by current pet door systems.
The main goal of this project was to design a system that would give one's pet access into one's home through discriminatory tactics lest others' pets or any other creatures would be allowed access into that home. Various means of discrimination were investigated: electronic article surveillance as used in libraries and shopping markets, optical detection using a reflective collar, inductive loop proximity sensing, piezoelectric tactile sensing, infrared imaging, invisible fencing, and cow identification systems used on dairy farms.
While all of these discriminatory tactics have worked for various applications, none were perfectly suited to our application. Instead of using any of these means, we decided to implement a hybrid infrared and radio frequency communications system that would allow a collar that the pet would wear to communicate with the pet door. This communication system will be discussed in more detail in the following sections.
Many pet doors on the market today do not allow for recognition of one's pet from another owner's pet. For the most part, pet doors on the market today are not electronic, and are just mechanical fixtures which allow the pet to enter and leave a pet owner's home by means of a flapping door. The problem with this current design is that it does not provide a great deal of protection from other creatures (humans, as well as animals) entering into the owner's home. There are electronic pet doors on the market today; however, these have very limited capabilities. Most use magnets as their means of detecting the presence of a pet in order that the door would open. As far as the limitations in performance are concerned, it would be beneficial to have pet doors that would operate independently of other pet doors that may be used in the immediate vicinity. The current electronic design using magnetic keys does not provide this capability.
Our proposed design provides a remedy for the problems experienced with existing pet doors. Through the use of an electronic collar that uses a hybrid infrared and radio frequency communications system we have developed a way to provide for the independent operation of many different pet doors in a given vicinity. By interfacing this communications system to a microcontroller (Motorola M68HC11) there are additional features that can be implemented in this system. Some additional capabilities include various modes of operation, timing features, data logging, and light activation. In addition, this IR/RF system will permit multiple pets within the same household to have different permissions in the use of the door.
The automated pet door is an electronic system that allows one's pet access through a door by means of communications with an electronic collar that has an active IR sensor and an RF transmitter. When the animal is within two feet of the door mounted IR transmitter, the IR sensor on the collar triggers the collar RF transmitter to send a signal of 300 MHz to the RF receiver located on the pet door. When the RF receiver on the door obtains a signal from the collar the door opens (sliding up as in a garage door system); otherwise, the door remains closed.
On each side of the door there is an IR transmitter. Each of these is monitored by the microcontroller. This enables the system to determine whether the animal is inside or outside. The system also has a sensor that detects the presence of pets within the threshold of the door to determine when it would be appropriate to close the door. This sensor consists of another IR transmitter and a phototransistor. This creates a beam across the opening of the door that is broken when any part of the pet is in the plane of the door. This beam sensor was implemented as a safety precaution to insure that no pet would be in the door's way while closing. In addition to this sensor, it is feasible to include a contact sensor along the bottom edge of the door to determine whether or not it comes into contact with any object during the closing operation.
Various modes of operation can be implemented for the system through the use of the microcontroller. Some examples are: one way operation (in only, out only), two way operation, and keeping the door locked. A timer that would allow the door to be in operation only during a certain time of day could be implemented as well. The owner could also keep track of information such as, the number of times the pet enters or exits the house each day. Features that could be interfaced external to the system would include a switch on one's yard gate to disable the pet door if the gate was open and the pet was inside the house. This would prevent the pet from having the opportunity to run away. Also, the door could activate exterior lighting if the pet goes out when it is dark. Some of these different capabilities will be added later to our operational prototype system.
The door itself is constructed of a high-tech polymer that effectively provided a means to construct a prototype of the door mechanism. The door is driven by a 4 V DC motor. Limit switches allow the microprocessor to determine when to turn the motor off during the opening and closing cycles. The motor is reversed for these cycles using a DPDT relay which is actuated by the M68HC11. Also, the motor is connected to the door by means of a gear train and pulley system, thus providing vertical actuation. A diagram of the door can be seen in Figure 1 below.
A representation of the communications system between the door and the collar is shown in Figure 2 below.
The collar makes use of an IR detector module that outputs a logic signal based on the detection of infrared light modulated at 40 kHz. Each of the IR transmitters on the door use a 555 timer set to output a 40 kHz signal. This 40 kHz signal is then used to switch a IR LED on and off by means of a transistor. The schematic for the two IR transmitters is shown in Figure 3 below.
The radio transmission and reception was implemented by modifying a commercially available wireless door chime (Radio Shack) and interfacing it to the system. This provided us with a radio transmitter and receiver operating at a frequency of 300 MHz. It was necessary to probe the existing circuitry of the door chime in order to determine the appropriate signals to interface to since the schematics were not available. We decided to use this door chime because it was already in our possession and it was the most feasible way to get the compact transmitter required for the project.
As far as the functionality of the prototype is concerned, it is working in a minimal fashion and as stated previously, additional features will be added later. However, the pet door does have the two-way operation as desired, with the ability for one to select one-way operation. It has the IR sensor to determine if the pet is still in the door before it is closed. This also will reopen the door if something gets in the way while it is closing. A contact sensor would also be beneficial as an extra precautionary measure, however. The prototype also has the ability to determine which side of the door the pet was on when it received the signal. This is done by having the microcontroller alternate the operation of the two IR transmitters. When the RF signal is received from the collar the microcontroller can then determine which IR transmitter was active at the time. This information is then displayed with two LEDs.
It is noteworthy to recognize that there could be a potential problem with the IR door beam sensor as it operates currently. The problem is that ambient light can affect sensor performance and thus cause false alarms. To avoid this the IR should be modulated at a frequency of around 10 kHz. This frequency would prevent any cross-talk with the main IR system used in the communications system with the collar and the door which operates at 40 kHz. The flow chart for the prototype's software executed on the microprocessor is shown in Figure 4 below.
We realize that various improvements can be made to the operational system. One is to reduce the bulk of the pet's collar device. The current device is relatively large and uses three AA batteries. A suitable battery that is compact and durable is desirable. One battery that looks promising is the 6 volt Lithium type used in many cameras that would allow the device to be packaged appropriately. We also foresee making the door in varying sizes, and using metal such as aluminum or stainless steel in its manufacture. Some of the other features mentioned earlier will also make the system more commercially viable.
We believe that our Automated Pet Door design is a significant improvement in the design of mechanical and electrical pet doors on the market today. Not only does it provide protection for the home owner and the pet alike, but it allows for more capabilities than any existing pet door systems. Overall, the design is inexpensive and solves problems experienced by home owners who have pets.
The Automated Pet Door is a one of a kind product. To our knowledge, there is no product that uses such a communications system to effectively detect the presence of a homeowner's pet in the efficient manner that ours does. We realize that there are some alterations that will have to be made, but the Automated Pet Door promises to be the trailblazer and the pioneer of pet door systems of the future.
During the course of this project we prepared weekly progress reports. Here they are.