HCIN 720: Prototyping Wearable and Internet of Things Devices

Introduction

In Assignment 1, you learned about online data and visualizations. In Assignment 2, you took your skills further and incorporated some hardware for some basic interaction. Now in this assignment, you’ll take the final step in your basic learning and learn how to integrate electronics with physical structures.

Goals

The main goal for this assignment is to become comfortable with designing for 3D printing and laser cutting and to learn how to use the equipment. The learning goals for this assignment are as follows:

• Learn how to use TinkerCAD, 123D Design, or another app for 3D modeling
• Learn how to evaluate the printability of 3D models
• Learn how to use a 3D printer
• Learn how to use Inkscape or Adobe Illustrator for 2D design for laser cutting
• Learn how to use the laser cutter
• Learn how to measure existing objects and incorporate those measurements into models

What to do/Evaluation

Basic: 75% credit

Design and fabricate a case for your electronics for IA 2. Do this via either 3D printing or laser cutting. It should enclose the components and expose the interaction elements (and you may want to include a way to easily get to the buttons).

Enhanced: 10% credit

Do the basic work; then do it again for the other fabrication method. That is, if you made a case with the laser cutter, make another one on the 3D printer; if you made one on the 3D printer, make another with the laser cutter. Alternately, make a single case that combines in some interesting way elements from both the laser cutter and the 3D printer.

Make one of your cases work with an existing physical object in the environment. For example, you might add a part to your model to allow your Photon to attach to a light switch cover.

Fancy: 15% credit

Do the basic and/or enhanced work. On one of the cases, incorporate into your case an extra input or output element not previously existing in your IA 2 project. For example, add a servo for motion or an LED for output. Some part of the case must be involved in the I/O mechanism: a servo might move some piece, an LED could side light something.

Deliverables

You’ll turn in your model files via your Github repository. Along with your files, upload a Readme.md file, which Github will then display with your repository. Include a description of your case, the techniques you used, and any special features (in the case of A-level). Also include a photo or a short video.

You will also show your work in class.

Setup and learning

Laser cutting

Install Inkscape or use a lab machine with Adobe Illustrator on it. If you have another 2D design program you really like, you are welcome to use it instead.

Inkscape

1. Create a new document
2. Go to File -> Document Properties
3. Under the Page tab, change Default units to “in”
4. Under “Custom Size” on the Page tab, change Units to “in”, Width to 32 and height to 18
5. Close the Document Properties window
6. In the toolbar, find the set of icons that look like . Click the leftmost icon to turn it off, so it looks like . This operation disables the defaul behavior of scaling the width of an object’s line when you change the size of the object.

Illustrator

1. Go to File -> New
2. In the New Document window, change the Units to “Inches”, Width to 32 in and Height to 18 in
3. Open the Advanced area
4. Change Color Mode to RGB

Selecting cut vs raster

The laser cutter works via a print driver. This is good, because it means that you don’t have to use a particular program. This is bad, because you have to set strange settings in your programs.

The laser cutter’s default behavior is to raster, or engrave. Even vectorized lines will be in raster mode by default. For every line in your design that you want to cut rather than raster, you must do two things.

1. First, you must set the line color to 100% red. It must be exactly RGB (255, 0, 0). This is why in Illustrator you must set the color mode to RGB instead of CMYK.
2. Second, you must set the line to be equal to or less than 1,000th of an inch thick, or <= .001 inches.

When the laser cutter gets a line that looks like this, then it will cut it with the power level you instruct in the print control panel.

3D printing

Visit TinkerCAD and create an account (or login with your existing Autodesk account). If you have another 3D modeling program you like that can export STL files, you are welcome to use it.

Resources

Here are some useful links:

• A good guide for using a laser cutter very similar to ours.
• The manual for the laser cutter in the FETLab.
• My Tips Trello board with more useful links for laser cutting and 3D printing.

There are many, many, many other sources of information for laser cutting and 3D printing. Here are a few:

• Laser Cutting Tutorials Tips
• So you’ve opened Inkscape for the first time ever