Old quarantined technology

The old design expression says: "The device should not work in principle, but in the case." And the process of finding, buying or creating a housing of a new design is one of the main for those involved in amateur radio. It seems that recently there have been no problems with the first two points in the aforementioned process, and the third, given the low cost of 3D printers, too, however ...

... however, no, no, yes these posts appear in forums and chat rooms:




But we had the urge to collect a calculator. No, not just like that, but taking into account old desires and physiological necessity, because what is being sold now is designed for people with at least normal eyesight. But we will not talk about it now (specify in comments, if that), talking about something else ...

So, the device was assembled, debugged by hardware and software, it remains to hide it in the case for beauty and usability. But inappropriately, the quarantine crept up and found something, and even more so to buy, it became somewhat difficult. There is a printer, but at the other end of the city, experience in creating a model for printing is missing a little more than completely, and I did not want to puzzle an outsider for five hours with a stinky print. I had to turn on a thinker, refresh the memory of a long-forgotten one, look around in search of suitable material and create;)

Our calculator was assembled on two boards inserted one into another so that the keyboard and display occupied the usual position for us. Accordingly, all used parts have already been arranged so as to be as compact as possible. It looked something like this:





The limiting sizes, I think, are understandable, this is the width-length of the main board, the height along the top of the display board, the height of the keys (so that they do not stick out above the case and are not deeply recessed), the dimensions of the indicator and the field of keys. That is, there are already a lot of parameters. Next, we decide that the assembled board will simply be inserted into the finished case, relying on some side stops, while the installation process should be simple, without any bending / pressing and other non-technological trash. Thus, for the initial design of the case, we need to know the internal volume occupied by the finished board. After, taking into account the material used, it is possible to pre-calculate the dimensions of the finished structure.

Putting the sideways on a sheet of checkered paper and armed with a ruler, we draft a draft of the case. Then, having previously selected the material, we “assign” it to the outlined volume in millimeters, obtaining a draft version of the drawing, according to which it is already possible to calculate some details.

In one of its designs ( habr.com/en/post/248379 ), 10 mm plywood was chosen as the body material. But there the sizes were larger, and the keyboard is larger, and the calculator should not be monstrous. Therefore, it was decided to cut out only the bottom of the case from plywood, but to create the rest using the technology rarely used by modern lovers, called papier-mâché.

So far we have only a rough drawing, with the planned use of plywood on the sides and a sheet of PCB around the keyboard and indicator. We need to use only internal dimensions from the figure.



Some polystyrene, pieces of plywood, small screws and cloves, newspapers, paper towels, gauze in the form of bandages, and PVA glue were removed from the apartment. Instead of the latter, it would be better to use an epoxy, but it was not available (I remind you - quarantine), and it is not comme il faut to do epoxy in an apartment.

In terms of internal volume, we cut a foam plastic block, divide it along the line of installation of the construction board - in this place we make mortgages from plywood, on which the board will rest. The size of the mortgages is made so that when you install the board, the keycaps do not touch them. Glue the volume block under the indicator so that it does not hang.



We screw / drive in small screws and carnations into the mortgages so that their heads stick out for a couple of millimeters. Subsequently, these heads will be walled up in the "meat" of the body and will keep the mortgages in the right position.



Now we glue the blockhead with slightly soaked newspaper strips and paper towels, alternating every three layers of paper with a layer of gauze. We do it slowly, well smearing with glue and squeezing out air bubbles from under the paper. They made three layers with gauze - they dried it a day. Made three more layers - still dried. It will be enough 12 layers, this is about 3 - 3.5 millimeters of the thickness of the future case. We finally dry it, preferably in a warm place, and we get such an unpretentious creation:



Then we scratch the polystyrene from the inside and dry it for another day, until we stop feeling with our fingers the minimal crushing of the composite material inherently. Polyfoam may stick in some places, but this does not bother us.



Well, the case is almost ready, we cut off the excess with a knife, and in order to fix it a little for further processing, we cut the bottom out of plywood, adding several rubber plugs from medical bubbles to it as legs.



Once again, having checked the initial drawing and armed with a carpentry knife, we cut out the holes for the keyboard and indicator. We make the first fitting:



Since everything went smoothly, we take a rubber and metal spatula, and begin to putty the body.



After the first layer, we dry, grind, look for the jambs, wipe them with the second, or even the third layer (with intermediate drying and grinding), try on the board again, grind the excess, finally grind and grind. Then we paint from a spray can in two or three layers.

For the indicator light filter, we cut out a piece of thin transparent plexiglass (from a new CD box, for example), pasting it on both sides with a transparent red self-adhesive film. We fix the filter in the body with hot glue.

The inscriptions on the keys are made in the simplest way - on the matte self-adhesive paper on a regular laser we put the key notation, and on top, for wear resistance, we stick a regular thin adhesive tape. If there were buttons with collapsible caps, it would look prettier, but we only have old domestic buttons. It would be possible to turn to the "nails" or tokens and get also a voluminous font, but again, quarantine ...

In general, we got such a handsome man:



The case is lightweight, durable, the board inside holds on to the case with “teeth” (mortgages stand really like a glove, allowing even a little mechanical processing), the bottom plywood adds some weight, not allowing the calculator to crawl around the table. Yes, the technology is only for a single production and requires accuracy, care and some time-consuming, but how much is needed for a finished construction for personal use?

If someone is interested about the calculator itself, then the rest of the technical information is here .

All health and do not cough;)