Copper Tape – Sensor Report

Copper foil tape is made from thin pure copper and is sold in different widths and lengths. Just like copper metal, copper tape is extremely flexible and can be formed into shapes and can be soldered to. The tape itself can carry electricity just like a wire. It can be used to carry electricity between a battery and components like LEDs, buzzers, and motors. Copper tape can be used as a switch or wire and works well in paper circuits. We will also see below how it can be used as a speaker!

Copper itself conducts both heat and electricity very well. Perhaps learning more about the metal and how it is used can prompt more inventive uses of the copper tape form of the metal. Learn about the compound itself on wikipedia as well as the common uses of copper.

[photo credit: Adafruit.com]

There are two types of copper tape: with conductive adhesive and with non-conductive adhesive. Copper tape with non-conductive adhesive is more common. This type of tape is practically used as a garden animal repellant and is generally found in the hardware. For physical computing, copper tape with conductive adhesive is used. This is the form that I will explore in this report.

On the back is an electrically conductive adhesive. The adhesive can’t carry significant current but it is very handy for sensing applications where you don’t want to solder the copper tape (see the labs below).

Photo credit: adafruit.com

Conducty.com nicely highlights the features of some commercially available copper tapes. These tapes are also available for purchase through the website.

This Makezine article outlines pros and cons of using the above mentioned types of copper tape. The con of tearing at the crease can be solved by using nylon backed copper tape.

Links to sources for purchase

Copper tape can be purchased in different widths and lengths. Here are some hobby stores where it can be purchased.

https://www.adafruit.com/products/1128 – 6mm width
https://www.adafruit.com/products/1127 – 25mm width
https://www.sparkfun.com/products/10561 – 5mm width
https://www.sparkfun.com/products/11081 – 2” width

Datasheet

I found a few different datasheets for copper tape with conductive adhesive from Adafruit, 3M and Sparkfun.

Using Copper Tape

When using copper tape, it is important to ensure solid connections in your circuit. That also means making sure the tape is flat! Bubbles or folds can cause interruption in connectivity and the flow of current. Below, I’ve experimented with addressing connectivity issues with paper circuits. Just like with a wired circuit, make sure ground and power tapes don’t intersect. Using masking tape or scotch tape works well as a barrier. This tutorial provides some tips for using copper tape.

Materials:

• LED sequins (purchased from Adafruit)
• 6mm width copper tape with conductive adhesive
• a 9V battery
• index cards
• alligator clips

LED sequins: showing their positive and negative leads

• Lab 1: Creating a Copper tape circuit

Here, a simple circuit was created to turn on an LED. In this lab, the leads of the LED are connected by placing a strip of copper tape over each lead. This proved to be an unstable connection. In figure 1 you can see that the surface of tape covering each LED lead is not flat or flat enough. In the video below, you will notice that when the LED is pressed, the light turns on. This indicates that there is insufficient contact between the copper tape and LED leads.

figure 1

Creating a larger conductive surface
A base layer of copper tape was added to the index card for both ground and power. The LED was secured to the circuit with additional copper tape strips (added to the surface of each lead). This was done ensuring smooth contact between the two sheets of tape. The LED was pressed firmly to secure contact with both top and bottom layers.

figure 2

Observation: The circuit with copper tape on both the back and front of the LED leads (figure 2) worked better to conduct electricity.

Conclusion: Connectivity matters. While the adhesive back is conductive, it is best to reinforce connectivity by ensuring connection to the copper tape’s surface. Also, it is very important to establish a flat surface of connection. Eliminate any folds or bubbles when laying the tape to establish a flat surface. A smooth flat surface ensures an uninterrupted flow of current.

• Lab 2: Controlling two LEDs with a copper tape switch

With this experiment, I ensured the copper tape lined the back and front sides of each LED lead (as in the successful lab above). Ensuring the power and ground connections did not cross to create a short circuit was important. I used masking tape to cover intersecting layers.

Photo showing copper tape circuit with 2 LEDs. Masking tape was used to cover areas where ground and voltage connections intersected.

Examples using Copper Tape

• Here is an example I found where copper tape is used as a speaker. As speaker was created using an analog paper circuit, coiled copper tape and a magnet.
• This Instructables tutorial explores the technical, design, and aesthetic possibilities of 2-D, flexible audio speaker technology.
• For my NIME performance (previewed below), I created a pop-up book and used copper tape for my circuitsand as a switch. I used the Makey Makey as my microcontroller and programmed each sound using MAX/MSP and Kontakt Player – essentially creating a MIDI-controller.

The Makey Makey attached to me (as ground) and to items connecting to it as power. In the case of the diagram, when the apple is touched the circuit is closed and the desired reaction occurs. In the case of my MIDI-controller, when I touched respective drums on the pop-up book, corresponding sound played. photo credit: dhmakerbus.com

When the drum is touched sound is played. The drum’s surface is made with copper tape (with conductive adhesive)

A closer look at the drum. You can see the surface with layers of copper tape, when touched acting as a switch. The single piece of tape to the right continues the circuit to the Makey Makey connection. Conductive fabric was added at the crease to ensure a steady connection was achieved. Necessary as elements in pop up books are folded.

Lessons learned from using copper tape for this NIME project:

Benefits of using copper tape

• The flat thin material worked well for this application as I needed a flat seamless circuit.
• Simple to use once the circuit design was mapped out.

Weaknesses of copper tape

• It tears easily where the tape is folded. I resorted to enforcing these folds by adding a backing of conductive fabric.
• Long pieces get tangled quite easily rendering the piece of tape garbage.
• I experienced some connectivity issues with my switch. I added more lengths of tape but should have also created a weaved pattern to create a wider conductive surface (think how fabric is weaved – the conductive fabric did an excellent job at conducting electricity).

Citations

Makezine.com
Conducty.com
Copper Tape Tutorials
Sparkfun
nikitahuggins.com
thebalance.com
Wikipedia
Instructables