Servo-based Fish Feeding Mechanism

For our accessibility project, we designed a fish feeder that can allow the students to have more control over feeding their pet fish in the nurse's office. The inspiration for the project came from one of the students who wants to be able to feed the fish, but cannot reach the tank or unscrew the fish feed container.

There are two main components: one component is the delivery system which actually transfers the feed (placed by a teacher who is accompanying the student) into the fish tank. The other component holds a button that the student can press. The idea behind the button is that it can be moved anywhere and also has a connection for a 3.5mm audio jack, meaning any student can control it using whatever interfaces are available to them. This will also allow for the connection of other buttons or mechanisms more suited to a student's needs.

The entire system is designed to be compact, requiring very little desk space, since space is at a premium for the campus school. The entire feeder is compact enough to live on top of the feeder itself and it is easy to move around and resilient to being knocked into.

Briefly, the supplies:

10 LEDs

Wire

Wire Strippers

Pico

Breadboarding wires

Button

3d printer (if you want to use our designs)

Non-continuous Servo

Hot glue gun

Your mileage may vary if you want to use more or less than 10 LEDs. Wire and wire strippers are used for the fish as well, and are very helpful in connecting the positive and negative ends of the LEDs flexibly.

The delivery mechanism works by using a servo that is mounted in a 3d designed & printed mount. There is a chute that the food can be placed into. The chute has a space that you can connect or glue one of the one sided arms that comes with many servo kits. It is designed this way so that an easily replaceable part and easily findable part is used as the connector to the servo, since they are designed to fit snugly with the gearing on the servo itself.

Both the chute and the stand are 3d printed. The only specifications that are out of the control of the builder is the connection from the chute to the servo itself, which is standardized to the plastic arms. However, if a better connection exists, feel free to modify the .stl files as such.

Steps for construction:

1. Print the motor holder and food holder on a 3D printer
2. Super glue a motor leg to the food holder
3. Screw in the servo to the servo holder
4. Cut the female holders off of the end of the servo and solder wires to the stripped ends
5. Connect the data wire to GP15 and the power and ground to 5v and ground respectively

The button is a singular large button connected to the Pico. This serves the singular purpose of when it is pressed, the servo motor rotates by 180º, pauses for a short time, and then rotates back to its original position. The large and easy to press button allows for nothing more than a light touch to operate the mechanism in its entirety.

Steps for construction:

1. Clip and strip two wires
2. Solder the ends of each wire to the brass ends of the button
3. Assuming you are using a breadboard connect one wire (does not matter which) to GP16 and then the other wire to ground

The decorative fish light is a small ambient addition with the purpose of entertaining and indicating status to the user. We 3D printed a template for the positioning of lights with a small divot added for visual cohesion. We ran the lights in parallel to allow for singular indexing of the lights.

Steps for construction:

1. Print the fish model on a 3D printer
2. Grab 10 led lights and separate the legs 90º from one another
3. Solder each of the positive legs to a shared brass wire
4. Solder each of the negative legs to a shared brass wire
5. Connect the positive ends to GP18 and the negative ends to GP14

Customizability was very important for this project, since we do not know what the use cases of the Campus School will be in the future. Therefore, we included a female 3.5mm connector to allow the school to connect whatever accessibility devices they need to to the feeder.

Steps for construction:

1. Strip the ends of the 3.5mm connector
2. Find two wires, preferably with breadboard pins on the other sides. Strip if needed
3. Solder the two wires to the two ends of the 3.5mm connector, and connect to breadboard as needed