I wanted a way to position the Pi camera that is robust, removable and adjustable. I had an adjustable 'helping hand' tool with a magnetic base. The arm has a nice clamp jaw for holding the camera and a strong magnet on the other end. I zip-tied some big steel nuts to the outside of the automatic cat feeder enclosure. The strong magnet on the base of the 'helping hand' tool arm stays firmly attached to the nuts. This provides a detachable, adjustable camera mount. This seems like a solution that could be handy for a variety of projects.

I use a motion sensor to detect rats. If rats come when the Magic Flute of Rat Mind Control recording plays then mission accomplished. "PIR" stands for Passive Infrared. There are tons of tutorials on using these with Pi or Arduino. The primary reason I'm using this one is plug-and-play support from the Cayenne IoT dashboard that I'll be using to monitor and control the automatic cat feeder..

The automatic cat feeder PCB, DFPlayer module and motion detector should be connected to Raspberry Pi as directed above. You don't need to power the feeder PCB and everything else runs on 5v so just connect the motion detector and DFPlayer to the 5v regulator or the 5v pin on the Pi. I had an extra cable with a plug that fits over the Pi pins so I just bundled all the connections into the cable so its super easy for me to switch the Pi in and out - this isn't necessary though, standard bread-boarding wires will work just fine. 

Meet Nicodemus. 

Note: There is a micro USB cord plugged into the 5V power supply for the Pi. I disconnected it for the picture so its easier to see everything.