This crusty hunk of metal was retrieved from an old Soviet submarine rusting in a dock in Vladivostok. It was scavenged by black market scrap metal dealers and eventually smuggled out of the country in a shipment of goat sausage. When I eventually ended up with it, the first thing I did was make sure it was not contaminated with radioactivity. It now resides in my kitchen. 







OK, here is the real story...



This is something I made for my kitchen. It is a central control box for all the various lights in my dining room. The front has a rotary switch with 4 positions, a separate single switch, and a large knife switch mounted on the side. It also has some purely decorative elements as well. The large dial was purchased through ebay, shipped from a former Soviet republic (I forgot which one). I bought it cheap, not knowing what operated it, purely because it looked fancy and mysterious, with strange lettering on it. When I finally got it I realized that it was some sort of pressure gauge; the back of it had two ports that were actually labeled with a "+" and a "-", and I could make the needle fully deflect by literally blowing into the "+" port! I came to the conclusion that it measured air pressure variations of a relatively minor degree. The dial also glowed in the dark, another bonus. I really wanted it to be functional to the degree that it would move in response to the state of the switches on the front. All the switches on the box are connected to an Arduino microcontroller, with the exception of the large knife switch. The Arduino controls the lighting, either directly or through relays, and controls the servo that moves the needle on the gauge. The large knife switch only has 5 volts running through it, and it controls some LED lights.  





The box pieces were cut from 1/8" plywood with a BlackTooth laser cutter.


The weathered and rusty look was achieved by using the techniques in this video.



The labels and insignia are all made on a Printrbot Simple 3-D printer (a marvelous machine in its own right). Here are the labels being printed.

The labels were designed in Google Sketchup and the resulting file was sent to the Cura printer software for rendering.


The labels were surprisingly easy to make in Sketchup; here's how I did it. I first needed some Russian words. What the words meant was not important, I just wanted words that had lots of those exotic Cyrillic characters in them. I simply used Google Translate and entered in random words and if the Russian translation looked "fun" enough, I cut and pasted the Russian spelling into a Word document. Surprisingly, Microsoft Word retained the spelling, complete with Cyrillic characters! Then in Sketchup, using the "extruded lettering" function, I cut and pasted the foreign word into the dialog box of the lettering function and it would make an extruded version of the word that I could literally set onto the flat base of the label. It was that easy! When the file was saved as a .dfx, Cura would import the file and print it perfectly, amazing!


How did I get the needle to move? Simple. (actually, not so simple) As stated previously, it was essentially an air pressure gauge. My first thought was to connect the air pressure inlet to a simple rubber bulb via a silicon tube and mechanically squeeze the bulb with a simple hobby servo. That did work, but I eventually decided that such an arrangement was way too "clunky". The final method involved some surgery on the gauge. I managed to take it completely apart buy unscrewing the retaining ring that held the glass face in. The mechanical guts of the gauge then came out the front of the casing intact. As I suspected, the heart of the gauge was an aneroid, a flexible metal bellows, which literally expanded or shrank in response to changes in air pressure. 

Here is the internal frame of the gauge. The dial face has been removed, and a mounting bracket (white) was printed with my Printrbot to hold the servo.

I decided to completely remove the aneroid and replace it with a servo that had a simple direct mechanical linkage to the needle mechanism. 



"I waited until he had the whole thing glued together and mounted on the wall and then I burned out one of the LED bulbs so he had to take all back apart again to replace it. And that was after I broke two wires on his 3D printer when he was trying to make the labels!"