What with this being a music themed project, the build deserves a soundtrack. I put together a YouTube playlist to get things started: https://www.youtube.com/playlist?list=PLrfzNWfDo0A6ByuWI65fHsNAxutBXIJEi

I picked up a automatic cat feeder with audio on Amazon a while back. They are advertised as "pet feeders" but don't work very well with a lot of dog food + there is a picture of a cat on the box + "cat feeder" amuses me so "cat feeder" it is. I had originally thought this project wouldn't require any hacking at all: the feeder comes with the ability to record and playback sound. However, the sound quality is beyond redemption and I ended up wanting to live stream video. Projects grow, you know how it is.

There are four screws that attach the top half of the enclosure (motor, PCBs, display, buttons) to the bottom half (batteries, speaker). 

The white tube contains what is essentially an Archimedes screw for cat food. Gravity drives cat food into the end of the tube underneath the cat food reservoir. The motor rotates the screw, which drives the cat food horizontally towards the other end of the tube where it falls out and onto the ground (or whatever the outlet happens to be above). The whole  contraption can be powered by a 5V external power supply or 6 D (alkaline 1.5v) batteries  in the battery housing at the bottom of the feeder. 

There is a plastic retainer that holds in the two PCBs. Unscrew it and the PCBs slide right out.

Functionality is split between two PCBs. The rear yellow PCB handles power, motor and audio. The front green PCB handles the buttons, LCD and control functions.

There are a number of ICs....

Titan Micro TM1723: LCD driver (green PCB - https://lcsc.com/product-detail/LCD-Drivers_TM1723-TM0607_C89186.html)

ISD 1820: voice recording a playback module (yellow PCB - https://www.allelectronics.com/mas_assets/media/allelectronics2018/spec/ME-63S.pdf)

MC96F8316: General purpose 8-bit microcontroller from ABOV semiconductor (green PCB - http://www.abov.co.kr/en/index.php?Depth1=3&Depth2=1&Depth3=1&Depth4=1&Item=MC96F8316A)

The green PCB logic runs at 1.5v. All I am really interested when it comes to these PCBs is motor control. There is a manual override button which turn the motor on and distributes food as long as you keep the button pressed. Bingo. I solder wires to the manual override button contacts on the green PCB. These will be attached to the Raspberry Pi GPIO with appropriate drop down resistor so we can control the feeder motor via Raspberry Pi.

I added a 5v regulator so I don't have to feed the battery directly into the Pi. In the long run though I want to find places I can put this that have AC outlets handy so I can use an external power supply. Maybe strategic places in subway stations? Maybe also make good use of free subway station WiFi? I micro USB cable plugs into the power supply USB plug for the Pi.

Since this contraption is going to be left in public places I decided some camouflage would be a good idea. It will still have to be hidden to one degree or another but black paint is a good first step. Also, it looks cool.

Since there is plenty of room inside the cat feeder enclosure I decided to mount the Pi and other electronics inside. I wanted easy access to the Pi, so I decided to mount it on the inside of a door which I can swing out. This keeps the wires and electronics away from the ravenous jaws of hungry rats.

I wanted to mount the Pi in a fashion that would allow for easy removal. I had an old Raspberry Pi A+ case lying around and with a little modification I made it fit the 3b I'm using for this project. How you attach the Pi isn't important to the project.