Simple Automatic Fish Feeder by bicx

Last crawled date: 3 years ago

This is a simple automatic fish feeder built using some cheap components I originally had lying around from previous projects. This design works well with food pellets, but feel free to try it with other forms of food. The feeder should be a perfect fit for aquariums with rimless 4mm glass walls. If you have this 5-gallon aquarium like I do, you should be golden.
(Demo video: https://youtu.be/mi4jcUzdbd0)
Servo
The center slot is designed to friction-fit an SG90 servo that spins the food rotor, but I would recommend some sort of extra anchoring (I used hot glue since it can be removed). As far as servos go, I had the 180-degree-limited servo left over from my first Arduino Uno kit from Vilros. To convert it to a continuous servo, I performed some modifications. However, if you can spare $7.50, just get the purpose-made continuous servo in the same form factor. The final modification you need to make for this project is to cut a 1mm-wide and 2mm-deep slot into the servo's nylon gear connector in order to connect to the feed rotor. I just used an Xacto blade. This isn't ideal, but it allows for decent leverage. Before permanently affixing your servo, do a test run with your rotor to make sure everything is lined up for full successful rotation.
Microcontroller
The outer screw mounts are spaced to accommodate an Adafruit Trinket microcontroller to run the servo. I only had the 3.3V Trinket available, so I had to power the servo via the USB power pass-through pin since the servo requires 5V. You can do the same, but you should carefully select the USB power source since this power is unregulated on the board. I personally chose a 500mA 5V wall wart that was lying around, and it seems okay so far. As far as programming goes, the biggest challenge with this feeder is timing the servo correctly. In my demo video, you can see I'm not quite there yet. I've since improved, but a lot of factors come into play depending on your servo and power source. This is where a purpose-built continuous servo will really help you (rather than a modified standard 180-degree servo).
Screws
All screw holes (2x for connecting the wall and base and 2x for the board mount) are designed for M2 x 4mm screws.
(Small note: since doing the renders and my first version in the photos, I added an additional millimeter to the height of the walls to allow for some minor fluctuations in vertical movement of the rotor since, like my print, yours may not be 100% perfect.)