This post describes a project to place an Embest LCD8000-70T 7-inch display in an aluminum enclosure suitable for use with a similarly enclosed RIoTboard SBC.
References
Metal Enclosure for RIoTboard
Motivation
The Embest LCD8000-70T touchscreen display ships as a bare board with no enclosure. A thin ribbon cable is used to connect the display board to an included small interface board (LCD-EX) which connects directly to the GPIO pins on the RIoTboard. The link above describes a metal enclosure for the RIoTboard itself, and this enclosure has sufficient space to permit installation of the LCD-EX interface board. A metal enclosure can provide the LCD8000-70T display with physical protection and (hopefully) a measure of RFI shielding in a similar fashion.
Materials
Embest LCD8000-70T 7-inch Touchscreen Display
Hammond 1550Z124 Diecast Aluminum Enclosure
#4-40 x 1/2 Inch Zinc Machine screws and nuts (4)
Results
This photo shows the almost finished product with the exception of a binding post for connection to a suitable ground:
This image shows the top view of the enclosure with the sole ribbon cable interface (note that the display is elevated above the enclosure surface to provide unhindered access to the touchscreen):
The interior of the enclosure:
Note that the ribbon cable interface is offset to the left of center on the display board, and the display board itself is mounted as far as possible to the left within the enclosure. This is done in order to minimize the interference of the central pylon containing the screw shaft in the upper side of the enclosure. The following closeup shows that it was necessary to cut slightly into the central pylon in order to create a slot for the ribbon cable interface:
Connecting the LCD8000-70T to the RIoTboard
The following photo shows how the LCD8000-70T can be connected to the RIoTboard when the LCD-EX module has been mounted on the RIoTboard GPIO pins and a suitable slot has been created for the ribbon cable interface in the RIoTboard enclosure:
Note that the LCD8000-70T is upside-down and the RIoTboard is right-side up.
The next image shows a closeup of the two devices after the cover of the RIoTboard has been properly restored and both devices have been flipped over:
The slots in the two enclosures for the ribbon cable interface have been cut to be at the same height above the surface on which the two devices rest. The devices can now be moved together as shown below:
The two enclosures can now be mechanically and electrically connected if desired, although there are a couple of considerations to bear in mind. First, the Hammond enclosure is tapered from bottom to top (where the display protrudes) on all four sides. This means that if corresponding holes are drilled in both enclosures to bind them together with machine screws, the RIoTboard enclosure will actually tilt slightly toward the LCD8000-70T enclosure and only the edge nearest to the LCD-8000-70T on the surface underneath the RIoTboard will remain in contact with that surface. Second, the top part of the RIoTboard enclosure wraps a short distance around the lower part all along the side adjacent to the LCD8000-70T enclosure as seen in the above photo. There is then a gap between the two enclosures on the adjoining sides. If the holes to bind the two devices are drilled through the lower part of the RIoTboard enclosure (the half to which the RIoTboard is actually mounted), and nothing is placed between the enclosure surfaces, then any overtightening of the joining screws will likely result in deformation of the RIoTboard enclosure in the vicinity of the screw holes due to the gap between the surfaces. In cases of extreme overtightening, the LCD8000-70T enclosure might become slightly warped as well. For this reason, it is advisable to use metal washers or some sort of metal shim between the two enclosures to prevent any warping during mechanical attachment.
Binding posts can be installed on both enclosures to permit connection to a common ground.
Construction Considerations
The side of the LCD8000-70T circuit board which contains the display has a white rectangular boundary which is apparently used to define where the display itself is to be mounted during manufacturing. I have four LCD8000-70T displays for use with my RIoTboards, and after examining them, I have realized that there is considerable variation in exact placement of the displays on the circuit boards with respect to the white rectangular boundary. In one instance, the display is parallel to and evenly spaced with respect to the rectangular boundary. In the second case, the display is parallel to the rectangular boundary, but the display is shifted to one side. In the third case, the display is centered more or less correctly, but the display is rotated slightly with respect to the rectangular boundary. In the last case, the display is mounted in such a way as to be both slightly rotated and shifted to one side. Therefore, extra care should be taken when trying to gauge where to cut the aperture for the display.
The four-wire touchscreen interface that is mounted on the display surface protrudes a bit along the bottom edge of the lower left quadrant (see the first photo in this post). Although it isn't obvious from the photos, I made a point of cutting a small slot to accommodate the full width of the interface and prevent unnecessary abrasion.
Conclusion
The Hammond enclosure makes a sturdy case for the LCD8000-70T. While there is nothing wrong with this:
this setup does have its advantages:
