Design Considerations

Outer Housing

The first design choice was to use off-the-shelf 6" PVC pipe for the housing of the device. The 5/16" thick walls of the pipe meant components could be fastened securely.
Relatively cheap and readily available. PVC is workable with standard tools which made cutting certain sections very easy.
A hinged latching lid keeps your pet from accidently gaining access to the hopper. This also makes refilling the device simple.
3D printed parts make up the bowl bottom and the motor cover. The motor cover is secured with two screws and can be removed when servicing the motor.
The device incorporates a removable stainless steel food dish. This allows the user to clean the food dish if/when it gets dirty.
A load cell is incorporated into the design underneath the food dish. Accurate weight readings are taken and plotted on the users phone app.

Several dispensing mechanisms were considered (auger, rotating plate, paddle), but a 3D printed auger screw was chosen because when combined with a 1-1/2" PVC Wye, the risk of input jams could be minimized.
A 1-1/2" PVC Wye was used to create a novel, gravity-fed Archimedes screw solution to precisely control the output amount of food.
NEMA 17 68oz.in. Stepper Motor provides excellent control. A motor driver allows for the selection of input current, thus limiting the output torque from the motor. This prevents accidentally breaking the auger in the event of a jam. The stepper motor will "skip steps" if the maximum torque is exceeded.
An adapter was 3D printed with an internal 1-1/2" NPT thread to allow the main stepper motor to be securely attached to the PVC Wye. A shaft coupler joined the auger screw to the motor output shaft.
Mounted to the hopper funnel, a second stepper motor provides agitation to the feed input. This motor is powered by a separate 12V-5V buck converter and motor driver. Eliminating any possible electrical interference with the Arduino.

An Arduino Mega 2560 provides ample IO ports for the various components. A protoshield was used to provide a soldered base for the main stepper motor driver, WiFi module, and load cell amplifier. Pin headers were used to allow for faulty components to be swapped out.
ESP8266 WiFi module was used to communicate with the Blynk cloud server. An ESP-01 adapter board was utilized to simplify power delivery and data transmission between the Arduino and ESP.
3D printed mount can be removed using one screw. Shaped to the inside diameter of the housing permitting study installation.
12V supply allows the main motor driver board to receive the necessary voltage to drive the stepper motor via the Vin pin on the Arduino.

Blynk was used to create a widget-based phone application. The pre-built libraries made communicating with the Arduino using a phone very simple.
Storing the WiFi network credentials on the Arduino allowed the device to connect to the internet and begin communicating with the user's phone after being powered on.
The application allows for complete control over the device. Everything from setting feeding schedules, to manually dispensing food. An amount-over-time chart was added to the application later in the project and proved to be very useful in monitoring food levels.