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Off-The-Shelf Hacker: Finishing the Low Cost Conference Badge

11 Jul 2018 12:00pm, by

As I speed toward OSCON, there are a million things to do to get ready for the trip. Just like deadlines for articles, design decisions for projects you’re going to demo have a way of working themselves out as your date with an airline seat gets closer and closer. Don’t worry, the badge I’m using in my official tech talk session is pretty well ready to roll. I’ll actually use three different steampunk badges while at the conference.

We talked about the plans for my “simple, low cost and low-key” physical computing badge, a few weeks back. Since then I’ve found a “crystal” for the badges three-color LED nuclear power source and went forward with my home-kitchen method of aging paper for the nameplate.

This time, we’ll cover those topics and wrap things up, so I can take it with me to Portland.

Make a Decision Already

I don’t know about you, but I frequently suffer from overthinking most parts of a project. It’s a common affliction. Engineering geeks visualize endless possibilities in function, features and capabilities. We want our design to be the coolest, most sophisticated and most Earth-shattering gadget ever, in the history of the universe.

From a practical standpoint, you just have to build something, that mostly works before you hit your deadline.

I puzzled for weeks trying to come up with a “nuclear power source crystal” to stand in for the “ozone tube,” that I used on my much larger fourth-generation steampunk badge.

While rummaging through one of my kid’s art drawer, I found a handful of round plastic crystals. Some were silver, some were smooth and some were clear. The smallest one turned out to be the perfect size for the “low-cost” badge.

Nuclear power crystals

I clamped the crystal in a piece of towel cloth and slowly drilled out the hole, using the drill press, to accommodate the three-color LED. I actually used two slightly different sized bits so the LED fit snugly and then used a dab of hot glue to hold the assembly together.

Next, I wired up the three resistors and the four connections to the Arduino Pro Mini. The blue LED lead went to pin six, the green to pin five and the red to pin three. The common lead on the LED went to ground. I used a simple four AA battery holder hardwired to the RAW pin and ground for power. It’s easy to pull one of the batteries out to turn the device on an off. No need for a switch. The power cord is about 24 inches, so I can just put the battery pack in my pocket.

I grabbed this code from GitHub and changed the pins to suit my Pro Mini setup. It fades through all the colors on about a 20-second cycle. Upload it to the Pro Mini with the standard Arduino IDE and a USB-to-serial cable from the Linux notebook.

const int redPin = 3;
const int greenPin = 5;
const int bluePin = 6;

void setup() {
  // Start off with the LED off.
  setColourRgb(0,0,0);
}

void loop() {
  unsigned int rgbColour[3];

  // Start off with red.
  rgbColour[0] = 255;
  rgbColour[1] = 0;
  rgbColour[2] = 0;  

  // Choose the colours to increment and decrement.
  for (int decColour = 0; decColour < 3; decColour += 1) {
    int incColour = decColour == 2 ? 0 : decColour + 1;

    // cross-fade the two colours.
    for(int i = 0; i < 255; i += 1) {
      rgbColour[decColour] -= 1;
      rgbColour[incColour] += 1;
      
      setColourRgb(rgbColour[0], rgbColour[1], rgbColour[2]);
      delay(40);
    }
  }
}

void setColourRgb(unsigned int red, unsigned int green, unsigned int blue) {
  analogWrite(redPin, red);
  analogWrite(greenPin, green);
  analogWrite(bluePin, blue);
}

The brass frame ended up being 4-1/8 inches x 2-1/2 inches in size. The inside of the frame made a great template for cutting a piece of lightly tanned leather to serve as the nameplate. The leather fits flush with the back of the frame so I just used hot glue to secure it on all sides.

Hot glued leather nameplate to the brass frame

Mounting the Arduino Pro Mini was also easy with a 1/2″ x 3/4″ strip of leather hot glued to the back of the board, then onto the front of the nameplate. The power cord and programming pins are at the bottom. I used a couple of 3/8-inch long, 1/4 inch x 1/16 inch brass flat stock as LED cable retainers at the bottom of the brass frame.

Arduino Pro Mini mounted on leather nameplate

I still haven’t decided on how exactly to mount the 3-color LED, nuclear power crystal assembly yet. That will happen between now and when I head to Portland.

Vintage Antique Paper

One thing I like about steampunk is its aesthetic of the “old” and the “vintage.” I want to emulate that look-and-feel on my badge.

Aging paper is pretty straightforward and in this case, I used it for the nameplate on the badge.

The first step is to find some period looking printing in LibreOffice. I’m fond of the Penshurst font. Since this badge is much smaller than the generation 5 model, I printed the “Dr. Torq” on two lines at size 66, in bold and center aligned. The printing has to fit between the Arduino and the crystal, so a vertical layout made sense. Print the name on standard laser-jet paper.

Next, tear around the letters so it fits onto the leather nameplate. You could smoothly cut the paper with scissors, but that won’t give you the right late 1800’s look.

Roll the paper up into a ball, then carefully unfold it flat again. Soak the paper under a faucet and then flatten it back out on a paper towel. Sprinkle a small amount of common, everyday instant tea onto the paper. Work the tea into the paper slightly with your finger, then rinse the paper very carefully under a weak stream of water. You can again crumple the paper and unfold it, depending on how old you want it to look.

Don’t worry if it tears slightly. When you have the desired amount of stain, spread the paper out again on a dry paper towel. The printing should look weathered. If not, crinkle and flatten the paper as needed. You can either let the paper air dry or use a hair dryer to speed up the process.

Use Elmer’s glue to stick the paper to the leather badge. I had used clear nail polish over the paper on the generation five badge, but on this one, I’m just going to leave it plain.

Antique paper on the nameplate

Since the badge is pretty light, I’ll use a stick-on rubber magnetic sheet on the back of the badge. A second badge-sized magnetic sheet will secure the badge to my shirt on the inside.

Wrap Up

The low-cost conference badge is just about ready to go. I plan to wear it around the show floor and maybe during some of the social events. I may put a couple of copper loops on the top so I can hang it with a lanyard.

Look for me at OSCON.


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