原创 Building a BADASS display (Part 4)

Many diverse aspects have to be reviewed with regard to a project like my Bodacious Acoustic Diagnostic Astoundingly Superior Spectromatic (BADASS) display. In my previous blog on this topic, I showed a pencil sketch illustrating my first-pass thoughts for the front panel of the display. As you may recall, I'm going to use a large piece of plywood stained to look like dark, old wood. Inlayed in this is going to be a piece of pressed board, which I'm going to paint to make it appear to be antique brass.

Before I actually start building something like this, I'm a great believer in creating a prototype using cheap-and-cheerful materials like paper and cardboard. This allows me to play around with different placements and proportions and suchlike without actually spending a lot of my hard-earned dosh. It also tends to save a lot of time, effort, and money in the long run.

Several days ago, my realtor wife (Gina The Gorgeous) had to go into work. As soon as she left the house, I whipped out a bunch of rulers and protractors and pencils and paper and card, and set to work. One of my first tasks was to use Visio to create some "birds-eye" drawings of things like washers and acorn nuts and momentary pushbuttons.

 

Why washers? Well, I'm going to have a 16x16 array of LEDs. I'm planning on having a disk of translucent white film in front of each LED. Also in front of each LED (sitting on top of the translucent film) will be a brass washer, which I will artificially age. I don’t know why, but I think this could look rather tasty.

One useful tip, should you ever do anything like this yourself, is to include faint vertical and horizontal lines in your Visio drawings as illustrated below, because this will save you a lot of messing around downstream. All you have to do is use scissors to quickly cut between the images (you don’t have to precisely cut around them). Later, you can use these lines to quickly and easily line things up on the main piece.

One thing I really wish is that I'd had some sort of training in industrial design (I wonder if anywhere local to me offers night-school courses in this sort of thing). Unfortunately, I pretty much have to make things up as I go along. My first decision was that the white translucent disks (and the holes behind them) would be 10mm in diameter. Why did I pick 10mm? Well, I'm using Adafruit's tri-colored NeoPixels. These NeoPixels are 5mm x 5mm square, which means they are 7mm across the diagonal. The NeoPixels I'm working with are mounted on a strip, so using 10mm diameter holes will give me a minimum of 1.5mm of "wriggle room" on either side.

When it comes to the washers, we know the diameter of the hole in the middle will be 10mm, so the next step is to decide on the outer diameter. The image above reflects an outer diameter of 20mm, which means the width of the brass band will be 5mm (i.e., half the diameter of the hole in the middle).

My initial gut feel was that a 20mm outer diameter was what I wanted, but I wasn't 100% certain, so I created a couple of alternatives as illustrated below. The four columns on the left show "washers" with a 20mm outer diameter; the next two columns have a 17.5mm outer diameter; while the two columns on the right have a 15mm outer diameter.

 

Based on this simple experiment, I decided that my original plan of 20mm was the correct way to go. Now, as I already mentioned, I'm using Adafruit's NeoPixel strips. The type I've opted to use boast 30 NeoPixels per meter. I'm going to mount these strips vertically to form the columns on my display, which means that the vertical distance between adjacent pixels will be 1000mm/30 = 33.3333mm.

I decided that I didn’t want to arrange my 16x16 as a perfect square. Making it rectangular will give it more visual appeal. I believe that the human brain spots subtle ratios and relationships at an unconscious level. I also believe that if things are in proportion as obvious multiples of each other, they tend to be more pleasing to the eye than if their proportions are random. I may be wrong on this -- as I say, I've not had any formal training so I just muddle along as best I can.

In this case, I decided that the spacing between adjacent columns should be 1.5X the spacing between adjacent rows, which means 33.33mm * 1.5 = 49.99mm, which I rounded to 50mm. Following this decision, I marked out the full matrix and affixed my paper "washers" in place using Elmer's all-purpose glue, as illustrated below.

 

The next step was to determine the placements for the brass acorn nuts, which I'm going to use to hold this panel in place. The easiest solution would be to have one nut for each row and column, but that would look like total overkill. Last week, when I was bouncing ideas around with my chum Willie -- the mechanical design engineer whose office is in the next bay -- he made the very good point that the function of the acorn nuts was totally divorced from the function of the washers. Based on this, Willie had suggested that the spacing between the acorn nuts should reflect this difference in function. A close up view of one of the corners is shown below.

 

The distance between the center of the acorn nuts and the center of the nearest washer is the same as the vertical separation between adjacent pixels; that is, 33.33mm. The distance between the center of the acorn nuts and the edge of the board is half of this value; that is, 16.66mm. At this point, I ran into a bit of a conundrum. Consider the following image.

 

Let's start with the seven nuts on the left-hand side. I started by placing an acorn nut in each corner. I then placed one in the center of the left-hand side. I then played with my nuts for a while (stop smirking, it doesn’t become you) and eventually decided that adding two nuts between the center and each corner resulted in the effect I was looking for. The end result was a vertical spacing between nuts of around 91mm.

Now consider the bottom side of the above image. Again, I started by placing a nut in the center of the bottom side, because this matched my having nuts in the center of the left- and right-hand sides. In this case, I tried adding four nuts between the center and each corner, but that resulted in a horizontal spacing between nuts of 80mm. The difference between the vertical spacing and the horizontal spacing just didn’t "feel right."

As you can see, there are eleven nuts on the bottom edge with ten "gaps" between them. Now look at the top edge. In this case there are ten nuts, with nine "gaps" between them. Although this means there isn’t a nut in the center of the top edge, it does mean that the horizontal gap between nuts is now 88.88mm, which is close enough to the vertical gap of 91mm on the edges to fool the eye. The end result is that -- when I come to construct the real display -- I will be using the 10-nut arrangement for the top and bottom edges.

In the fullness of time, I will be experimenting with a variety of different display modes, so I'll need some way to switch between them. Originally I was thinking of embedding an LCD display in the front panel (I was thinking of using a black-and-white display, and making it look like a CRT-type unit). But my chum Ivan, who also has an office in the next bay, gave the opinion that this was a waste of time, effort, and money. As he pointed out, I can actually use my 16x16 LED array as the option/menu display -- all I need to do is add is a small control panel with some momentary push buttons as shown below.

 

This panel will also be formed from pressed board painted to look like antique brass. The red button is the "Reset" button; the green button is the "Menu/Select/OK" button that will allow you to enter and exit the menu system and select amongst the various options; and the four black buttons will allow you to scroll "Up," "Down," "Left," and "Right" between the various options. Below we see a closer look at this control panel.

 

Putting this all together, below we see the main LED array and the control panel glued on to a piece of cardboard. In the real display, the cardboard will be replaced with the plywood stained to look like dark, old wood.

 

In this case, I started by making the distance between the edge of the LED array panel and the edge of the cardboard on the left- and right-hand sides 10cm (2X the horizontal distance between NeoPixel Elements). Similarly, the gap between the top-edge of the LED array panel and the top of the cardboard is 10cm. In the case of the control panel, we have a 5cm gap above and below it, which means that the total width at the bottom is 20cm (i.e., 2X the width of the sides and the top).

As you can see from the final image below, the end result is a tad larger than I had originally envisaged, but I think it's going to look outrageously tasty. Can you imagine this little beauty lit up in all its glory? I cannot wait!

Yours truly in his 'Kilroy was here' pose.

 

So, why have I just spent so much time waffling on about all of this? Well, there are several reasons, actually. First, I thought you might be interested to hear the mental process behind my decision-making. Second, these directions will hopefully come in handy if you decide to create such a display for yourself. Third, if you have any industrial design experience or knowledge, I would really welcome any feedback as to the decisions I've made. Do they make sense? Is there anything I should change? Are there any "rules of thumb" of which I should be aware? And are there any good books on industrial design you would recommend?

Building a BADASS display (Part 5)