Thursday, January 17, 2019

DSKY substitute laser cutting and 3D printing sent to manufacturing


Keyboard construction

I drilled holes in the aluminum case and test fitted the keyboard stack for both orientation and height. The top of the honeycomb sidewalls touch the underside of the faceplate and they can be centered under the opening. I had previously tested the adhesive to install the keycaps on the plungers, using acrylic glue.

The only process uncertainty remaining is the way I will install shims in the honeycomb cells. This has to be done after I have snapped the plungers into place in the honeycomb since I can't insert the plungers unless the excess clearance exists. The shims minimize side to side rocking of the plungers to make the key movement smooth and accurate.

Display construction

I drilled holes in the aluminum case to test fit the display board for both orientation and height. The board fits well. I can't bolt it down yet because I have to build connectors and cable exits on the box, since those have to be connected to this PCB from the underneath.

The cover plates arrived today from the 3D printed service. These hold a frosted plastic panel atop the display board, as well as providing a more realistic appearance to the DSKY substitute. I tested their fit inside the aluminum case and made a slight modification required for fit.

The cover plates are a three piece construction, with the frosted plastic enclosed inside the cover which consists of a top plate and a bottom flat plate which get glued together. I have to trim one edge of the bottom plate and of course I have to wait for the frosted plates to be done before gluing this up.

Top plate covers, not yet glued together, awaiting frosted plate
The top plates are slightly distorted, one long side of the rectangular shape is bent inwards, but the frosted plate will force this out to shape.

Frosted plate and other light cosmetics

I have to build two plastic plates, one that simulates the electroluminescent display from a real DSKY and the other that simulates the 14 incandescent lamps of the indicator panel. These will be built of thin acrylic, with custom transfers and spray paint on the underside to complete the look.

The indicator panel is the easier of the two - it is simply divided into two columns of seven rows each, with white LEDs illuminating the left column and yellow LEDs for the right side. I need to install some light dams, material that will keep light from one of the fourteen sections from spilling over to adjacent areas. I am still designing this; it may be 3D printed plastic or I can go with foams or other materials I can shape and install myself.
Plastic light dam to separate lights on the indicator panel
The EL panel requires text and other features to be installed, plus light dams for all the areas that are illuminated by individual LEDs. What complicates this is the use of 21 seven-segment displays as their faces are up close to the panel while the individual LEDs are recessed down on the PCB.

I decided that I need some diffusers to even out the light from individual LEDs - for example the illuminated lines that separate the three register areas of the EL display. Another issue is the plus/minus sign, where I need the minus to be a continuous bar with the two spots above and below that convert it to a plus, but I formed it with just four discrete LEDs.

The diffuser has to channel the light from the two minus sign LEDs to form a continuous bar. I believe that I can build a sandwich of a black laser cut form with a thin frosted plastic on top, which will blur the light sufficiently to meet my artistic goal. This in turn is recessed below the top panel with its own diffusing coating.

A similar diffuser is needed for the rectangular lighted areas under the text for Noun, Verb, Program and Comp Acty, which should be as smooth and even as possible from a small number of point source LEDs. These will also need light dams to keep the illumination from any one rectangle from spilling over to the other areas.

Any remaining exposed areas of the PCB might be covered with flat black paper. The combination of the diffusers, black paper and other treatments underneath should render the best appearance up at the plastic panel.

I whipped up the light dams using Fusion 360 and submitted the designs to my 3D printing service provider. I then designed the diffuser plastic that will clean up the shape of the plus/minus sign, using
Inkscape, then submitted that to a lasercutting service provider.

Connector design and construction

The display board has all the external connections to the DSKY substitute - main 5V power, 31 input channels, 10 output channels, 'spacecraft' 28V power and switchable AGC 14V power. The connections on the underside of the board are set, based on the .100" spacing headers and barrel power connectors I built onto the PCB.

What needs to be determined is the way the wires run out of the aluminum case. I need openings to be cut, at a minimum. I believe it will be cleaner and more rugged to provide some form of connector in the wall of the case, thus allowing disconnect and connect of external cables as I move the DSKY substitute and hook it up to the AGC.

A related question is the placement of the opening or connectors on the case. Should the wires exit the bottom? If a side, which one? Using the bottom would allow the DSKY substitute to be fitted to a larger control panel structure for realism, but adds a need for rubber feet or other standoffs when the unit is sitting flat on a table in order to allow the cables to exit underneath.


  1. For the AGC memory X-Ray, there looks to be a very sharp bend in the wire as I've highlighted. This would be a high stress area and there might be a break at the very corner of the bend. We could also be seeing the wire turning vertically. It still looks strange though.

  2. There are a few of these odd looking bends among all the images we have. Higher resolution and CT would help us determine if they are gentle bends, curves or indeed a bent-over wire.