Case

The outer case of the machine had various functional and non-functional requirements:

• Usability requirements
  • Should be usable
    • Should include a user interface
    • Should include coin intake and ejection spaces
    • Should have space for the power intake
  • Should not bother the user
    • Should encase all the components
    • Should neatly integrate all the components, so they are safely attached
    • Should facilitate cable management
• Configurability requirements
  • Should allow different configurations for different coin systems
    • Different amounts of coins (4 coin types for US currency, 5 coin types for EUR currency, etc…)
    • Should provide adjustable positions for all the components inside it

Proof of concept

Integration with User-Facing features

Touchscreen

The case will need to contain the touchscreen so the user can interact with it.

It should be sturdy enough to sustain the weight of the entire assembly:

• the touchscreen, facing upwards
• the touchscreen driver board, hanging right below it
• the primary raspberry pi board, hanging below that
• and any other lightweight appliances that might be attached to it:
  • USB dongle for mouse
  • USB keyboard cable
  • power supply jack
  • etc..

Creating subjection points for the touchscreen

References:

• Raspberry Pi Touchscreen
  • Datasheet
  • Mechanical drawings
  • Product info page
  • Purchase page on Sparkfun

Coin Acceptor

The coin acceptor data sheet has some hard-to-understand dimensions.

This proved to be a problem in the end, because the position and size of the hole had to be guessed and adjusted during manufacturing.

Manufacturing

CAM for Laser cutting in Fusion 360

The DXF for Laser plugin for Fusion360 has received both positive reviews and nice tutorials that explain how to use it.

This plugin is exactly what I wish I had discovered during week 02:

• It can export directly from Fusion360 to DXF
• It accounts for laser kerf
• It splits the operation into layers to make sure that the outer cut is always performed last
  • 
• And it detects problems with the design where there might be overlapping geometries
  • 

Validating sizes are correct for kerf

$117.703 - 117.55 = 0,153$

Dimensions in Design

Dimensions in Exported File

The finished case

Configurability

The other requirement that the case had to fulfil was allowing various configurations and positioning of the elements.

This was accomplished by having three different types of holders, and lots of small holes on the sides of the case, where they could be attached to.

A few of each will be enough to allow us to subject and hold any elements at the right place.

These components allowed the different ejection funnels to be placed at different positions and heights, to fit the needs for the ramps (their angles, positions, etc…)

System Integration and Cable Management

The wiring and cable management in the case went over various iterations and changes to keep it clean and organised.

Iteration 1 was the first draft wiring and was only needed to make sure all the connections and servos would work

After replacing a couple of defective servos for working ones, I created a small servo driver board that would take a 5V, GND and the 5 control pins as input, and would create some type of cartesian product and output five 3-tuples of outputs, one for each servo: (GND, 5V, control-1) + (GND, 5V, control-2) + (GND, 5V, control-3) + …

Assets

Assets: Assets in gitlab