Hardware - plastic parts and assembly

Development and Prototyping

The 3D printed parts were developed using OpenSCAD and evolved over a number of prototypes.

The first parts to be developed were the buttons and direction pad. I tried a number of different arrangements before settling on a setup where the button sits on top of a miniature push switch which in turn sits in a recess in another printed part. This part, which I refer to as the backplate, has small holes in the back to allow for the switch connections. The end result is a sandwich of the case front, with a hold for the button, the button itself with a lip around the edge to hold it in the case, the switch and the backplate. In between the pairs of buttons and in the centre of the direction pad a piece of foam is used to hold the button against the case and stop it rattling. The backplate is attached to the case with screws which self tap into printed support posts. This arrangement worked well, giving good tactile feedback and responsive buttons but it was awkward to wire up. If I were to build another one I would replace the printed backplate with a PCB or stripboard and solder the switches straight to that.

Button prototype 3 - Parts Button prototype 3 - Assembly Button prototype 3 - Front Button prototype 3 - Side Button prototype 3 - Back


The next part to be done was the part of the case front that holds the screen. This was fairly straightforward, bacially a rectangle with a hole in it and four posts at the corners for screws to hold the screen. Note that the Adafriut screen module that I used is now discontinued and its replacment is physically different meaning this part would have to be redesigned to accept a newer screen. There are an additional four posts around the screen that are taller and hold the part the holds the Teensy and battery box.

The Parts

The outer case is made up of seven parts:

  • Upper front - holds the screen, teensy and batteries.
  • Lower front - holds the buttons, directon pad, power switch, speaker, amplifier and switch pcbs.
  • Upper back - Has a hole in the back for a removable access panel and a space in the bottom for the connector plate
  • Lower back - Has a hole in the back for a removable access panel.
  • Connector panel - slots into the lower back and holds the USB connector, voltage regulator, and low battery circuit.
  • Back covers - two of these fit into the upper and lower back and can be removed without tools to access components and change batteries.

Top Front Buttom Front Top Front Buttom Back Connector Panel Back Cover

The internal parts are:

  • The direction pad, control and option buttons.
  • The back plates for the direction pad, control, and option buttons.
  • The speaker clamp.
  • The holder for the Teensy and the batteries.

Direction Pad Control Buttons Option Buttons

Direction Pad Back Plate Control Button Back Plate Option Button Back Plate

Speaker Clamp Teensy Holder

Assembly

To assemble the complete device:

  • The upper and lower front are screwed together.
  • The low battery LED and wiring are fitted and hot glued into place.
  • The speaker and speaker holder are attached.
  • The amplifier PCB is fitted and connected to the speaker.
  • The screen is screwed into place.
  • The power switch is attached.
  • The diode board and switches are assembled with the back plates for the buttons and direction pad.
  • The buttons and direction pad are placed in positon and the back plates and diode board fitted.
  • The Teensy, battery holder and associated wiring is assembled with the Teensy holder.
  • The Teensy holder and associated electronics are fitted.
  • The voltage regulator, USB connector and low battery circuit are assembled to the connector plate.
  • The upper and lower backs are screwed together.
  • The connector panel is fitted and to the lower back and the back screwed to the front.
  • The back covers are fitted. These press into place and can be removed by pushing the sides of the case together slightly and lifting them out.

Assembly 1 Assembly 2 Assembly 3 Assembly 4 Assembly 5 Assembly 6 Assembly 7 Assembly 8 Assembly 9


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