If you are a pet owner, going on vacation can be stressful. Usually, you need a friend or neighbor to come over every day and feed your pets. However, by enslaving robots you can keep your pet happy and enjoy a stress-free holiday. To save money and learn something new, I decided to make my pet feeder out of recycled materials like cardboard and glue sticks. Cardboard is great for rapid prototyping.
I have entered the pet feeder into the Make It Real Challenge because it relies on 3D modelling software for a rapid prototype design. I made this instructable especially for the contest after writing the original article for wonderhowto.com. As much as I love cardboard, I could prototype more precise designs with a 3D printer and build up my design skills for rocketry and robotics mechanisms. Please rate, vote and comment to help make my cardboard dreams a plastic reality!
- Glue stick
- Hot glue
- Continuous rotation servo
- Arduino board
We will be using the glue stick case as a linear actuator. To attach it to our servo, we must first get rid of the glue. Remove the glue from the tube and pry it off of the inner plastic slide. This can get messy so be careful! Remove the circular cap at the base of the glue and set it aside.
Step 2: Make Actuator Arm
The rotational motion exerted at the bottom of a glue stick causes the glue to travel up a spiral rod and out the end of the cap. We are replacing the glue with a brass tube to make it sturdy enough to handle all that pet food.
1. Hot glue the tube into the small plastic cup from inside the glue stick. The hollow tube will fit neatly around the inner corkscrew of the glue stick.
2. Make four notches in the handle of the glue stick and fit them over the servo horn. Use hot glue to secure the connection. It is important to make sure the glue dries while the servo and glue stick are perfectly aligned. This will prevent wobbling.
Step 3: Make an Enclosure
I designed my first ever google sketch up model just for this project. Seeing a model in 3D makes it easy to evaluate your design before you build. While the setup is very simple, I think the 3D model helps in understanding the linear actuator. Open the attached google sketch up file to see the pet feeder sketch up.
Step 4: Attach Arm to Base
There are many methods you can use to attach the moving platform to the actuator arm. I hot glued a circle of cardboard to the arm and then glued the platform onto the circle. You can also use screws and balsa wood if you want a more secure connection.
1. Make the platform slightly smaller than your enclosure to allow the platform to slide inside the box.
2. Glue the bottom of the servo to a cardboard base.
3. Push the actuator arm into the box and seal the bottom with hot glue or tape.
Step 5: Adjust Platform and Cut Exit Chute
Mark where the maximum and minimum heights of the platform are. Cut a circular hole in the side of the enclosure in between the two levels. This is where the pet food will spill from. Set the platform to the maximum height, entirely closing off the chute. Gently pour the pet food until it fills the upper chamber of the feeder.
Step 6: Circuit
Our circuit is very simple. Connect the red servo wire to 5 volts on the Arduino. Connect the black wire to Arduino ground. Connect the white wire to Arduino pin 10. That's it!
Step 7: Code
All our code does is lower and raise the platform every 12 hours. To do this, we need to tell the servo what direction to spin and for how long. This will vary depending on your servo and glue stick.
Continuous rotation servos are programmed differently from regular servos. Instead of being set to a specific angle like 45 degrees, continuous rotation servos are set to a direction at a specific speed. When set to 90 degrees, a continuous rotation servo should stay still. When set to above 90 degrees, the servo will turn right. Set below 90, the servo will turn left. The farther away from 90 degrees, the faster the servo spins.
You can download the code here.
Step 8: Feed!
Time to set up your feeder and hope it doesn't scare your pets! My cat jumped on the opportunity for extra treats when I tested it.
There are a bunch of ways you could use this linear actuator to serve pet food. You could even make a vending machine set up! If you do make a variation of the pet feeder, please add to the 3D model and share with the community!