Designing Interactive 3D Printed Things with Tinkercad Circuit Assemblies

What happens when 3D printed parts become more than just plastic?

Tinkercad Circuits (tinkercad.com/circuits)

So many devices we rely on every day can only come about through the careful combination of mechanical, electrical, and software design — from using our smartphones to connect with friends, to setting our toaster timer to prepare our bread just right, to pushing a button to request to cross the street.

Learning how mechanical, electrical, and software design integrate not only helps us better understand how interactive systems work today but also empowers us shape how they will function tomorrow. What happens when we create design tools that start to bridge these domains, and can we do it in a way that engages new audiences to explore them in the process of designing their own creations?

This opportunity is what I’m excited to contribute to as part of the Autodesk Circuits team, where we’re closing the gap between electrical and mechanical design tools to support integrated product design.

We recently brought circuit design to Tinkercad, expanding the free browser-based 3D modeling tool to become a hub for tinkering with electronics too. As part of this initiative, I’m leading a design effort on a feature called Circuit Assemblies that enables anyone to incorporate real electronic parts to create interactive 3D-printed things.

Circuit Assemblies: Glow (left) and Move (right)

Here, I’ll share some of the thinking, prototyping, and design details around the creation of Circuit Assemblies — and provide a sneak peek of some upcoming modules! If you’re a maker educator just getting started with your school year, I hope you’ll check out Circuit Assemblies and share how your students are using them to design their own interactive creations (I wrote step-by-step lessons for how to use them that you can find here: https://www.tinkercad.com/learn/)

Learning about Electronics in the Classroom

Right at the start of the project, I wanted to gain insight into how teachers today introduce electronics to their students. I talked with several elementary and middle school technology teachers in the United States to learn about the types of circuit activities they facilitate in their classrooms. In the process, the teachers revealed examples where circuits and 3D printing combine in interesting ways:

Examples of 3D printing with Electronics (Clockwise from top right: Copper tape + plastic 3D prints for interfacing with the Makey Makey, drilling holes into prints for wire channels, and 3D-printed mounts to hold sensors and breadboards).

The interviews uncovered several trends about circuits in the classroom:

Examples of laser-cut lights, all using the same fundamental internal circuit. From Jaymes Dec at the Marymount School.
  1. Personalizing simple circuits
    All of the teachers spoke about the power of using simple circuits that are infinitely customizable. It was common for educators to introduce fundamental concepts such as series and parallel circuits in the context of lighting up LEDs, and then students would fabricate their own custom designs around these basic circuits. As one educator stated, “All the kids make the same circuit, but if they get to customize their own housing around it, it becomes more personally meaningful.”
Using flexible materials like hot glue and rubber bands for securing electronics. From Ken Hawthorne at St. Raymond School.

2. Rubber bands, hot glue, and tape (in lieu of solder)
Especially in elementary and early middle school classrooms, students used flexible materials like hot glue and rubber bands to secure connections between components. This eliminated the need to introduce soldering, which requires its own set of safety training and procedures. Removing soldering for beginners both speeds up prototyping and makes circuits more accessible.

Component selection for small hands

3. Big components for little hands

Teachers took careful consideration to ensure electrical components were ergonomically appropriate for small hands. This can be especially important as there are an overwhelming number of options for basic components like switches and buttons, many of which are optimized to be as small as possible for professional product design. For little hands, the opposite is usually a priority: Ensuring that components can be easily handled and wired requires larger components.

Electrical Components

4. Components over kits

While several of the educators did have access to electronic prototyping kits in their classrooms, they also spoke of the power of introducing real electronic components that cost several dollars per student as opposed to hundreds of dollars per kit. They spoke of the authenticity of handling parts that real electrical engineers work with as a way for students to more easily transition into breadboarding and potentially even PCB design.

(My Own) Prototyping

To put myself in the mindset of a middle school student, I experimented with my own set of 3D printed parts, incorporating large switches and hot-glue connections.

3D printed dino with hot-glued wire connections

This made me acutely aware of the complexity of the design task at hand — ultimately, it would be awesome to have the capability to wire components directly in the 3D modeling environment, and doing so has its own unique set of challenges, both on the technical- and UI-fronts.

Around the same time, a colleague of mine shared a fantastically simple video that a Tinkercad YouTube user named Eunny shared on decorating a flickering LED module:

Tutorial on designing around an LED candle

This was a lightbulb (or LED?) moment for me, as I realized that just as teachers expressed the power of basic circuits, we could have our own set of basic modules in Tinkercad for integrating common interactive behaviors. This was the seed that helped launch Circuit Assemblies!

Circuit Assemblies: Glow

Glow Circuit Assembly

The first Circuit Assembly that was prototyped was a light-up LED throwie, combining a coin cell battery and LED along with a 3D-printed holder. The holder (shown in red in the GIF) is designed to hold the electronic modules securely in place but also be easily embeddable into many different 3D designs.

In the Tinkercad editor, the Circuit Assemblies are available in their own category of Shapes, along with a special new part we call a Cutout. The rationale behind the Cutout is we want it to be as easy as possible for users to embed Circuit Assemblies into their 3D-printed designs, which means that providing a way to carve out the space needed for the Circuit Assembly would be critical to user success. A Cutout, then, is a special version of a Hole: By grouping your design with the Cutout, you create the cavity needed to press-fit a printed Circuit Assembly into your design!

Using the Cutout in the Tinkercad 3D Editor

This is the first example of real-world parts in the Tinkercad editor —electronic components have physical dimensions and thus cannot be infinitely scaled like other shapes in the Tinkercad editor. As a result, you may notice in the video above that there is a “Scaling Lock” indicator in the shape inspector for the Circuit Assembly. This means that the Circuit Assembly and Cutout are sized for physical parts and cannot be rescaled.

The lack of scaling leads to an interesting mechanical design challenge in which the Cutout is a fixed size, yet we want our Circuit Assemblies to work regardless of what 3D printer, material, and resolution is used. Tolerances become critical, which means that every Circuit Assembly needs to be carefully designed to ensure a quality fit. As you can see in the image below, many variations on the base of the Glow Circuit Assembly holder were designed and tested on both the Makerbot (top row) and Ultimaker (bottom row), as well as several other printers by our QA team in China!

Test Prints for the base of the Glow Circuit Assembly to account for differences in 3D printing resolution

In the end, I settled on a design that incorporates flexures and tabs along the base, allowing variable compression based on the tolerances of the 3D print.

Flexure design for Glow Circuit Assembly base. The round gaps on either side allow the user to insert their thumb and remove the module if necessary to turn off the LED.

The Glow Circuit assembly was a nice example to start with because LEDs and coin cell batteries come in fairly consistent sizes. But as soon as we start to incorporate other electronic components, the number of possible part variations increases exponentially, which is exactly what happened for the next module I designed: the Move Circuit Assembly!

Circuit Assemblies: Move

Creating a module with a motor was a logical next choice for me, but the trick was doing it in a way that was easy and safe. I initially prototyped a propeller incorporating a DC motor, 9V battery, and switch — but as you can imagine, 3D printed parts + fast moving motors = danger! We pivoted to vibration motors both because they have a safer movement and because they are much more compact to fit into a 3D design.

Original DC motor prototype

Again, channeling the middle-school student that likely does not have a soldering iron, I thought about what a move module might look like that eliminates any need for soldering. I also wanted there to be a switch for this one — the Glow is our quick-win example to get people started, but with a motor, I was sure people would want to turn it off easily without having to take their model apart.

The challenge as hinted earlier is that now, we enter a world where there are many, many switches. Thousands of switches according to Digikey. Choosing a switch that was big enough to be easily turned on and off, yet also had features that remove the need for soldering or breadboarding, was a fun mechanical problem to solve.

Move Assembly steps

In the end, I designed a direct mechanical connection between the bottom pin of a 3-pin slideswitch and a coin cell battery. The ground cable of the vibration motor sits underneath the coin cell battery, making contact with one side of it. The other side of the battery makes direct contact with the bottom pin of the slideswitch. Finally, you thread the positive wire from the vibration motor into the middle pin of the slideswitch to complete the circuit!

The Move Circuit Assembly switched on!

The slideswitch model was deliberately picked because the pins have holes in which you can loop wires directly into — without the need for soldering! This meant that the mechanical design was specifically created around this slideswitch, which introduced another challenge: Where do people actually get this exact switch if they want to build the Circuit Assembly?

Luckily, our friends at Sparkfun have a handy feature where you can create a wishlist of components. We worked with Sparkfun to stock this exact slideswitch and include it in a wishlist with all the other components you need for the Move Circuit Assembly: https://www.sparkfun.com/wish_lists/139225

You can access the wishlist by clicking the “build instructions” in the Circuit Assembly inspector and clicking the link for Sparkfun parts within the lesson viewer.

Accessing Sparkfun Wishlist from Tinkercad editor

Try it yourself!

Now that you’ve gotten a behind-the-scenes look at the design of the first two Circuit Assemblies, try them out yourself! You can find the Circuit Assembly parts in the Tinkercad Editor, or you can go through a step-by-step guide at https://www.tinkercad.com/learn/

Circuit Assembly Lessons at https://www.tinkercad.com/learn/

If you’d like to explore more advanced electronic prototyping, check out the Tinkercad Circuits editor, where you can get started with Starter Circuits and Arduino programming!

Tinkercad Circuits Editor

New Circuit Assemblies Sneak Peak

The Glow and Move are two basic modules designed for beginners to get started with electronics. With these two introductory Circuit Assemblies available, we’re going to level up with new programmable Circuit Assemblies that take advantage of the Tinkercad Circuits editor.

NeoPixel Circuit Assembly

I’ve been working with the awesome educator Erik Nauman on a NeoPixel module, which is essentially a 3D-printed Arduino shield with a snap-and-socket pair you can use to create a rainbow light show with any 3D design, like this crown.

I’m also exploring the use of other microcontroller platforms like the Micro:bit that has a built-in LED array, which opens up a world of expressive character prints!

Experimenting with Micro:bit embedded in 3D prints.

I’d love to hear your feedback about Circuit Assemblies and any suggestion you might have for future modules, so please share below!

Acknowledgments

Thanks to the entire Tinkercad team for contributing to this project, especially Joshua Brooks and Wayne Losey for helping to brainstorm the mechanical design of the Circuit Assembly holders.

Thank you to the awesome educators who have provided feedback throughout this process, including Erik Nauman, Ken Hawthorne, and Jaymes Dec. Finally, a special thanks to The Exploratorium Tinkering Studio and The Cal Academy of Sciences for user testing feedback.

Note: This article is based on a talk I gave at Sketching in Hardware 2017.