For the personal semester project, I chose to create a machine that will load and compact the coffee grounds holder in an espresso machine. To load the machine manually, first you remove the holder (which we will call the “pot”).
Afterwards, the coffee grounds are scooped in until the pot is filled to the appropriate height (either 2 or 4 shots of espresso). The grounds are then compacted using a flat surface. The loaded pot is then secured in the espresso machine in order to begin the process.
The aim of the machine is to automate the process, while adding the flexibility of selection from three different coffee flavors.
The machine will need three hoppers to hold the three different flavors of coffee grounds. Each of these hoppers will be controlled by some type of valve. The machine will also include some type of mechanism to compact the grounds afterwards. To take the selection, some type of user interface will also be provided, and a microcontroller to run the show.
Step 1: The Machine
The machine I created revolves around the Parallax Propeller MSR1 board. The board includes handy features to interface with accessories (i.e. Servos, LCD, etc) that use the standard 3-pin connection (power, ground, signal). It also includes an on-board H-bridge to control external DC motors. And of course, it comes with voltage regulation.
To use the machine, the pot is first secured in the pot holder. The clip is used to secure the pot in the circle on the base (made of hot glue). After the pot is secured, the machine can be turned on using the red power button underneath the keypad. The screen will then prompt the user for the flavor (1-3) and the number of espresso shots (2 or 4). The user then presses OK, which starts the dispensing sequence.
The machine first moves the chute into position on top of the pot, and then the appropriate valve is opened depending on the flavor selected. The valve is held open for a pre-determined amount of time, depending on whether the user selected 2 or 4 shots. After the pot is full, the chute is moved out of the way of the compacter. The compacter then comes down onto the pot, compacting the coffee grounds. The sequence is then complete, and the user takes out the pot to be used in the espresso machine. Refer to the detailed subsystems below for more information.