When I leave home for a few days, feeding my cat is always a huge challenge. I have to ask friends or relatives to take care of my cat. I looked for a solution on the internet and I found a lot of food dispenser products for pets, but I did not like them. Firstly, they are very expensive. Secondly, they are suitable only for handling dry cat food (my cat eats wet food most of the time). Lastly, they are too big, I do not have so much space in my flat. So I decided to build a compact, automatic, wet food optimized cat feeder. The problem with wet food is, that it goes bad very quickly. I realized, that after I open a canned cat food, I have maximum 1 day to use it. To save space and keep the food quality and make this project as cheap and simple as possible I designed a machine, which can give only one meal to the pet. It will give to me two days absence from my cat feeding duties (freedom:)).
The feeder operates very simply. I fill up the food container (empty yogurt box) with food, close the door of the container, and plug the cable with an outlet timer to the 230VAC network. I set up the timer so that after a day it will power up the feeder. When the instrument is powered on, the food container will be opened by a servo motor. After a day the door will open and the cat can have a good meal. When I arrive home, I remove the food container and clean up any leftover and fill up with fresh food, then I put it back and, close the top of the box and the cycle can start again.…
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Step 1: BOM List
I collected and bought the following materials. The total cost of this project is under 30USD:
-24-Hour Mechanical Outlet Timer 1 pc $6,19
I used this Outlet Timer to power up for a short time of period and power down the complete electronic. Time delay can be calculated by the microcontroller, but I not recommend it. During the time I am not at home the cat can play with the machine, and it is better if there is no electricity at all.
-Stepper Motor 1 pc $6,21
This stepper is strong enough for moving the top of the box. And it can work from a 5 V power supply, perfect for the task.
The L9110S driver is a small and cheap driver without any cooling. I use it only for the door opening time period. If it is continuously turned on it get very hot. The disadvantages of turning of the driver after every usage are that the stepper will no longer hold the actual position. I can move the door with my finger. If my cat gets cleverer she can simply push the door with her nose, or paw. Fortunately, at the moment, I have no problem with this.:)
-Linear Shaft Support SHF8 1 pc $3,18 This shaft connecting the stepper shaft to the top of the box. I used rubber rings to fill out the gaps.
-Plastic enclosure for holding the yogurt box 1 pc
-Yogurt box for food container 1 pc
-Plastic Enclosure for the electronics 1 pc
I found these enclosers at home. Any encloser can do. Important: The yogurt enclosure should fit into the plastic encloser. The plastic enclosure is part of the machine should stay clean, the yogurt box will be dirty every time the cat eats, it has to be cleaned regularly.
-USB Wall Charger 1 pc $2,36
Any phone charger will do. It should have a 5V USB output at least 1A.
Arduino mini pro processor module 1 pc $1,89
I choose this Arduino module because it is the cheapest and smallest one. Other Arduino modules can be used as well. Make sure that you set the right board at Arduino IDE software Tools->Board
USB Male Connectors to DIP Adapter 1 pc $0,16
This adapter makes it possible to convert the USB connector into separated wires. I connected the Arduino and the stepper driver power cables at this adapter.
USB Extension Cable 1 pc $0,77
The cable between the electronics and the phone charger. It should be longer than mine. The 230VAC connection should be at least 0.5 m from the ground.
This will give weight to the whole structure. Every component is mounted on this.
Optional push-button 1 pc $0,96
Optional. If it pressed the door will step a few mm to one direction. It can be used to check the operation of the system.
Step 2: Assembly
First, I did the cabling of the electronics. I used only twice my soldering iron to connect the power cables to the USB adapter PCB. Before connecting to the 230V network I recommend using a laboratory bench power supply with current control and current measurement. if you cabled something wrongly, this checking could save you any damage on the adapter or at another component. The whole consumption should be less than 1 Amper at 5 Volt.
Secondly, I assembled the corner braces, then modified the box and fixed to the structure of the machine. All major steps can be seen in this video:
Step 3: Arduino Programming
The code is simple. In the setup, it will turn the stepper than in the main loop it waits until the button is pressed then it will move once again.
Step 4: Conclusion
I made a very compact unit. The price is more than acceptable. It takes approximately 3 hours to build it. This project is perfect for education purposes, it is simple to build and understand how electronics and robotics work. Does not need any special tools.
I finished this project a week ago, now it is in the test period, my cat is still satisfied so I am too.
Have a nice day.