About a year and a half ago, I started work on a fun little project. I’ve been dabbling with it on-and-off, and now it’s finally finished. So I thought I’d post a retrospective, as the process and challenges along the way were just as enjoyable as the end result.
It all began with a tweet that randomly popped into my head one day:
Sean Martell replied with a classic GIF, and something about the combination of tweets made me start itching to build a real, physical version. The basic plan came together quickly, but I didn’t realize that it would be a long and meandering path through researching GIFs, vintage electronic hardware, nitpicky laser printer output, metalwork, 3D modeling/printing, and more.
I think the finished result is pretty good:
Here’s a bit more about the process of building it.
Research and Foundation
The first thing I had to do was some due-diligence: what are the essential qualities of meme-meter? After extensive research on every such GIF I could find, I knew exactly what I wanted. A meter with a retro feel, a realistic face that was scientific and precise, and a needle that jittered around the bottom of the scale to indicate approximately “zero fucks given”. In metric.
The next day, I jumped on Ebay to scope out some vintage analog meters, and got unbelievably lucky: a pair of Triolab voltmeters from the early 1960s for just $16 (plus shipping). One was rather ugly and worn, but the other was absolutely perfect. Retro, with just enough wear to be authentic, yet in excellent condition. A compact 4-inch cube with a hefty weight makes it perfect for desktop display. And, oh, the details – industrial black crinkle-paint finish, sturdy knobs, brass and stainless steel screws, and a classic aluminum product nameplate.
The insides are equally amazing. Lots of colorful antique components (even a vacuum tube!) on a wire-wrapped board, complete with that distinctive “old electronics smell” that may or may not be known to the state of California as causing cancer. Even the cabling just oozes quality, neatly bundled with lacing that’s rare to see today outside of aerospace applications.
As an added bonus, there’s an instrument calibration label on the top from “Martin Marietta Corporation, Aerospace Division,” certifying that it’s within 2% of manufacturer’s specs as of November 1963. Plus an earlier ink stamp from June 1961. They help make it feel like it fell into a time warp straight from a mid-century laboratory. (I’d love to know what this meter was originally used for – Martin Marietta was probably best-known for the Titan family of rockets and ICBMs, so something involving them might be a good guess.)
Unfortunately, the paper sticker was in desperate need of conservation; it was starting to degrade and was very fragile. One corner was missing, and another was barely hanging on. Not too surprising, as it was a simple tag meant to be replaced after 6 months, and not designed for a 50-year lifetime. To fix it I used some adhesive to fasten the loose edges, and a clear “Ultra Matte” polyurethane paint to stabilize the surface. I was pleased with the result, which maintains the appearance of plain (unpainted) paper. [Aside: the tech who originally applied the label was very sloppy with the glue, if you look closely that’s what you see around the edges, not my work!]
Face Time
My first major undertaking was to design a new faceplate for the meter. I used Acorn to draw the scale using vector lines and circles; most of the work was tedious but straightforward. One handy trick was to scan the original faceplace at 600dpi on the office scanner/copier, and use that as a template for accurate physical sizing.
I spent a disturbing amount of time in the vintage typeface rathole. My first thought was to use Futura, which is commonly used in aerospace instrumentation (notably, the flight controls on Apollo and the Space Shuttle). But it didn’t feel quite right – ironically(?) too modern. I also looked through piles of other typefaces, named and unnamed, from hobbyists who recreate flight controls on vintage aircraft. In the end, I just used the modern Avenir Next Condensed font that comes with OS X for the main text. It’s a faithful nod to the original meter faceplace. I also matched typefaces as best I could for the smaller labels, and redid the “triolab” logo to make it sharper than the original scan.
Once printed, I carefully disassembled the analog meter, flipped over the original aluminum faceplate, and affixed my version with some spray mount.
Laser Printer Resolution
Attention to detail was important to me on this project, but one issue I didn’t catch until too late (and never fully resolved) was print quality. Despite my work being in resolution-independent vector format, I consistently got suboptimal output when printing. Here’s an example of a 10pt capital letter “K” printed 3 different ways, photographed through a USB microscope:
On the left is output from Acorn, as printed on my 10 year old home HP LaserJet 1012 (600dpi), and in the middle as printed on a new Ricoh C2503 (1200dpi). The rightmost is the same letter “K” printed on my HP, but using TextEdit instead of Acorn. I tried myriad combinations of printing to intermediate formats, source bitmap resolutions, and printer settings, but the results were always the same… Anything coming from Acorn or Photoshop came out with bumpy edges, while output from a text editor was crisp.
My assumption is that something in the pipeline was rasterizing everything, and the printer was just doing it’s best to blithely print a greyscale bitmap with halftones. Eventually I got slightly better, but not great, output by printing to an absurdly high-resolution PDF, filtering to B&W and downsizing with ImageMagick, and then printing the final 1-bit depth image. I’m curious if a dedicated vector program like Adobe Illustrator would have made this Just Work, or if there’s even any good way to do this. Back in the day one could have hand-crafted some PostScript/PCL for this, but I’m not sure exactly how modern printing pipelines work.
Who knew that 1200dpi wasn’t enough for good black-and-white output?! (This guy, apparently.)
Electronics
The electronics on the new meter are slightly overkill, but are what I had sitting around. At the core is a Digispark (basically a tiny Arduino clone), with an IO port expander and a custom protoboard for gluing everything together.
The Digispark controls the meter through a PWM output. Analog meters are driven by rather small currents, and I needed just 206 microamps to drive it full-scale, which is trivial for the microcontroller to provide directly. At 4.65v that needs about 22kΩ (thanks, Ohm’s Law!), so I used a couple resistors summing to 20kΩ and a 4kΩ trimpot for fine-tuning… That lets the software simply use the PWM pin from 0-100% without having to worry about overdriving the meter. Doing so can actually make the needle stick at the over-100% point, and I didn’t want to risk having a software bug cause hardware damage. This meter does not go to 11.
Of course, no Arduino project is complete without some LEDs! I mounted an I2C-controlled RGB BlinkM LED inside the meter, behind a small sheet of milky-white plastic sheeting to diffuse the light. I have it set to generate an warm orange glow reminiscent of a vacuum tube, but it can be changed to other hues with the front-panel knobs (as read by the Digispark). The BlinkM has 24-bit color resolution, which really turns out to be inadequate. The exact color of orange I want (a mix of red + green) is tricky for it to reproduce — the human eye is very sensitive to green, and there is a single 8-bit level that looks about right. One level less and it’s too red, one level more and it’s too green. Next time I’d probably just use a dedicated monochrome orange LED at the right wavelength, or an RGB LED with ADC levels I can control better.
I also tossed in a couple extra white LEDs, just because I could. These have a higher power draw, and are switched by transistors. But they ended up not really working well for illuminating the meter at night, because they’re too far behind the faceplate. Oops.
The components I used were quite small – 0805 surface-mount resistors, 5mm×5mm PLCC LEDs, and 30-awg wire for connections. Some people hate working with stuff smaller than standard 0.1″ PTH parts, but I like the compactness and challenge. However, it’s essential to use a good soldering iron and wire strippers that can handle tiny wires. Also highly recommended: a steady hand, and a magnifying loupe or USB microscope for inspection.
When I was adding the control electronics, I didn’t want to totally gut the existing voltmeter components because they are so beautifully vintage. So they’re simply disconnected and left in-place. Similarly, I wanted to be respectful to the existing layout by carefully routing and weaving my new wiring harness. It’s completely hidden without the case being opened, but it was important to me, knowing what was inside.
Software
There’s not much to say about the software running on the Digispark, since it’s fairly simple. You can view it here. To make the meter’s needle jitter, it outputs a semi-random value near zero, with a rare outlier to make it bounce a bit more on occasion. I can’t make it twitch as hyperactively as the original GIF (there are physical limitations on how quickly the needle will move), but it’s still satisfactory. I also added some debouncing on the selector switch, using a small state machine and timeout. Probably over-engineered, but it was fun to write.
I did have to do some debugging with an oscilloscope, that was also fun! The code for adjusting the BlinkM LED color would sometimes fail to work — I’d tell it to change color, but nothing would happen. The interface to the BlinkM is an I2C bus, and so I used my oscilloscope to see what was happening. It’s got a built-in I2C decoder, but it was more enjoyable to learn how I2C works and decode the signaling by hand. The problem ended up being that the BlinkM device would sometimes fail to acknowledge a command. I’m not really sure why, but happened rarely enough, and was detectable in software, so I just added a retry for when a failure occurred.
Connections
The most stress-inducing aspect of the project was adding a micro-USB connector to power the whole thing. None of the existing holes in the Triolab case were big enough to accommodate a connector, so I’d have to make a new – and permanent – hole. Further, I wanted a nearly-invisible connector, but none of the commercially available panel-mount connectors I could find were suitable. They were all designed to bolt on top of a large hole in the mounting surface, as a large protruding lump of plastic.
So, I ended up designing a custom assembly for mounting a micro-USB connector and 3D-printing it. A little bit overkill, but it was a fun process to go through.
I’ve previously used Google’s SketchUp, but found it limiting. It seems well-suited to freeform artistic design, but less so for CAD-like design where one needs specific dimensions and layout. After looking at a number of options, I settled on OpenSCAD. It’s both free and Free, has some good tutorials, and allows for precision synthesis . Based on constructive solid geometry, it’s great for someone with a programming background, and reminds me a lot of playing with the POV-Ray raytracer years ago.
The connector I designed basically mounts to the back of the mounting panel, and is thus flush with the outside. I had it printed in Frosted Extreme Detail from Shapeways (16 micron resolution!) for just $15. I soldered my connecting wiring to a splashproof micro-USB connector, epoxied it into my 3D-printed connector, and then mounted that onto the meter’s case with silicone. The silicone gave a solid connection, but one that I can easily replace in the future when micro-USB is obsolete. This meter is over 50 years old, and USB format changes won’t be the death of it!
Why a splashproof connector? I wanted to pot (encase) my connector in epoxy for reliability, but from previous experience had learned that epoxy has a tendency to seep though any openings, and foul up the ability to insert the connecting cable. I hoped this connector type would be sealed and avoid that. As it turned out, even a “splashproof” connector still has tiny openings, and I had to spend an hour scraping out partially-cured epoxy from the insides. In the future, I would make my soldered connections, lightly seal up any superficial openings, and only then glue it into its final resting spot.
Another lesson learned is that it’s a pain-in-the-butt (A HUGE PAIN-IN-THE-BUTT!) to solder connecting wires to an extremely tiny micro-USB connector. (I suppose it’s still a good challenge and builds character. Or something.) The connector I used was really designed for surface mounting, but I manged to make it work with patience and plenty of flux. If I did it again, I’d reflow it to a tiny PCB adapter, which would make connecting the wires trivial.
It all worked out pretty well, the connector is flush with the case and mounts perfectly into the hole I drilled for it. I thought about painting it black to blend in a bit more, but the fit looks so good that I was concerned that painting could just make it worse. It’s also easy enough to do later, or maybe if I eventually redo it as a USB-C connector…
Conclusion
This was a really fun project for me. It was stretched over a long period of time, but the end result was something that I was happy with, something that I learned from, and something that I hope others might find interesting too.
Ironically, I really gave a fuck about this zero-fucks-given meter!
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