Whether prototyping an eletronics project, making an art piece, or even giving a friend a birthday card, there are countless ways to incorporate DIY electronics into your life. For a novice or intermediate tinkerer though, these techniques generally fall into one of two rather frustrating categories: those that are too expensive and/or complicated (like PCB etching) and those that are too simple (like conductive ink). Luckily, there is an option that bridges the gap between these two extrema: vinyl cut copper circuits!
To demonstrate the value of vinyl-cut circuitry, I put together two projects that would have been difficult, if not impossible to make with other techniques. More in depth descriptions of each project are at the end of this post.
The robo-cup project is a great example the unique possibilities for copper foil. I adapted this circuit from a water-level sensor I made a couple years ago to create a light up cup/mug! The design, inspired by the MakeHaven robot, uses an NPN transistor as a switch to turn on the LED roughly where the robots eyes would be when a small current can travel between between two leads inside the cup. Because of this, when the cup has water (or any other mildly conductive liquid) in it, the LED will light up when the cup is tipped! To make a more finished version of this, you can place your circuit inside a DIY travel mug like this one (although you may need to find smaller button cells to fit inside the cavity).
DIY 14 segment display
This project is an example of some of the more complex, multimedia applications of vinyl cutting copper foil. Using just LEDs, resistors, and 12V 1A power adapter, I was able to make a reasonably attractive 14-segment alphanumeric display. This project could be easily expanded by implementing multiplexing and attaching to a driver IC of your choice. One could make a clock, scoreboard, or pretty much anything you choose!
The MakeHaven vinyl cutter is a Vinyl Expres R-Series II vinyl cutter and uses LXi cutting software, which reads EPS files. Luckily, nearly all vector graphics software is capable of exporting to this format. The MakeHaven computers have InkScape installed, which is a free, open-source vector graphics editor. I recommend choosing whatever software best suits your skills and the needs of your project. (For instance, the robo cup required mapping the circuit onto a 3d surface and the 14 segment display required cutting CNC molds, so I chose to use Rhinoceros3D).
The example designs on this post use a few of the simplest and most important components in electronics: resistors, LEDs, transistors, and DC power supplies. I've compiled some of my favorite resources for beginners using any of these components
- capacitors (I haven't used any in my examples, but they come up a lot and it's a good thing to understand)
For basic circuit design, it's also important to understand components working in series and parallel and Kirchoff's Laws. These can be a bit confusing at first, but there are a number of resources out there for circuit design, so I recommend doing a bit of research to try to find resources that fit your taste and learning methods.
Finally, I 100% recommend checking out the electric circuits guide from hyperphysics (my favorite resource for pretty much everything), which has information on everything you need for analog circuitry.
designing around the cutter
I found the vinyl cutter to be a bit finicky when cutting copper, so you want to design your circuit to limit the chances of failure. The most problematic details are sharp corners and small details in close vicinity to each other. These properties will cause the blade to pull the copper from its backing, which will ecentually ruin the entire circuit. I found the best way to fix sharp corners was to use a fillet or chamfer when I hade the space. And when it comes to fine details, I recommend spacing components at least 0.05" away from each other when possible.
cutting your copper
Copper and vinyl are very different materials, which means they also behave differently in the vinyl cutter. Copper tends to peel up, so I recommend using the lowest speed and lowest possible pressure while still shearing the metal when cutting.
The best pressure is sensitive to the copper foil being used, but is generally somewhere between 70g and 90g. You can see the copper pressure test behind the vinyl cutting computers as a guide, which was used on the Tapes Master copper foil in MakeHaven
It may not be the most time efficient method, but it's better to have to retrace some cuts with an X-ACTO blade than jam the vinyl cutter and ruin your material
There are two issues I've run into when cutting copper: either the blade doesn't make it through the material or it peels the copper right off the backing. I've run into this with vinyl as well, but the middle ground, producing a perfect cut, is much more narrow with copper
not cutting through
- increase blade pressure
- Use multiple passes
After cutting your circuit, I recommend waiting to weed until after its application. Since the adhesion between the foil and its backing isn't nearly as strong as that between vinyl and its substrate, it is very easy to damage your circuit while weeding. This is especially true if you have small, standalone closed curves in the circuit. The ratio between surface area and perimeter of these shapes means even a small weeding mistake can pull them off the backing. The workflow should instead be as follows
- Cover the entire circuit with contact paper and either use a squeegee or the palm of your hand to rub out any spots without adhesion
- Carefully peel off the copper foil backing
- Press the foil onto your substrate. Unlike vinyl, I haven't had any issues with air bubbles when depositing copper, but I would still try to lay it onto the substrate starting one corner at a time and using my palm to work out any air bubbles while depositing
- Use an X-ACTO blade and dental pick to carefully weed
One of the great things about most copper foil as that it's very easy to solder components onto. I kept the soldering iron at a pretty low temperature to avoid mess up the foil, but since the melting point of copper is 1984°F, you'll be hard pressed to damage the foil too badly. Most copper foil adhesives are acrylic-based though, so it will melt. You can avoid any problems associated with this by holding the foil in place. It will resolidify and become sticky quickly after removing the iron tip.
When I was still prototyping and not ready for soldering, I just placed a bit of electrical tape on top of the components, which worked fairly well. I definitely recommend keeping a multimeter with you anyway.