• The Conductive Ink Challenge


    I was recently asked if I wanted to take part in a competition organised by Newark Canada and presented with VHS ( Big thanks to Tom :-) ); a challenge that focused on a very interesting and versatile product, conductive ink. I received a pen in the mail and started to investigate what I could do with it. The Conductive Ink Pen essentially allows you to easily draw lines or tracks that you can pass electricity through. Here is the project that I decided to submit for this challenge. I’ll also explain how I went about building this project and how these concepts can be applied to other projects.

    Rudolph the Conductive Nosed Reindeer

    When constructing this project I wanted to make the conductive ink the star, really show off what it could do but also make it a little out of the norm. From an artistic point of view I really like the way that the silver conductive ink is highlighted on the white stone, even more so when it is lit, beauty in simplicity. I also wanted to bring people closer and connect with this piece so I created a touch interface that starts the sequence.


    Building the Project

    The piece is made up of 4 main parts:

    1. Base Model
    2. Surface mounted lights
    3. Microcontroller
    4. Conductive Ink


    The Base Model:

    As Christmas is nearing there are many ornaments being stocked at local craft shops. After an afternoon looking for just the right subject I came across a reindeer and the idea was obvious. I glued it to a base and that was all I needed to start going.


    Surface mounted lights:

    Surface mount devices or SMD’s for short are components used on the surface of a circuit board as opposed to the traditional through hole method. I decided to use these tiny lights because I didn’t want to drill holes into the reindeer and I wanted to keep the process simple. I mounted one red SMD LED (Light emitting diode, essentially a Light) on his nose and 2 on either corner at the front of the base giving some mood lighting to the model.


    The Microcontroller:

    To control the whole sequence I used a small microcontroller called an Arduino. It looked after detecting the touch, animating the lights and triggering the audio to play on the computer. The code I used for this project is based on the code that I wrote in my experiments with capacitive sensing with Conductive Ink with the addition of the light animation.


    Conductive Ink:

    The main star of this show is the Conductive Ink, it was used to connect all the parts together. There are many great things about this product; the pens are easy to use, they can be applied to almost anything and any shaped surface but the best thing is you can use it as part of the artwork. Conductive ink used to light the nose runs down the left and right side of the reindeer’s face and front legs and out to the sides of the base. For the touch sensor I used a single line from the antlers, down its back and across the background of the base.


    Other Applications

    Conductive Ink is such a versatile and easy to use product, from educating basic electronic concepts to complex circuits, flexible boards and interactive projects. Capacitive sensing as I have used in this project can be applied to many application from detecting a user’s touch or proximity to creating paper thin controls as I have shown in a previous post. The potential uses for conductive ink are vast, grab a pen and start experimenting with making switches, sliders interactive circuits and great looking art.

  • Conductive Ink – Capacitive Sensing Test

    Earlier this week I got a conductive ink pen for a competition that I am currently entered in. I had a bit of a muck around with what I could do with it and the first test that I tried was a capacitive sensing control. The control is a simple slider that drive an LED’s brightness. Capacitive Sensing is a technology that uses the capacitance of the body to alter the charging time on an input pin. The larger a contact surface is the faster the charge time will become; Knowing this we can map the surface charge time to a scale and thus the LED brightness.

    Capacitive sensing circuit using conductive Ink surface with 1 Megaohm resistor and a 100pf capacitor.

    The code below was based on the CapSense tutorial from the Arduino Playground with some additions. I’ve added in 3 sample smoothing and some low end noise reduction. The LED is then mapped to the values coming directly out of the CapacitiveSensor library included in the tutorial.

    #include <CapacitiveSensor.h>

    CapacitiveSensor cs_3_4 = CapacitiveSensor(3,4);
    int led = 9;
    long total;
    long total_01;
    long total_02;
    long holdValue;
    void setup()
        // turn off autocalibrate on channel 1 - just as an example
        pinMode(led, OUTPUT);
    void loop()
        long start = millis();
        //Buffer Samples
        total_02 = total_01;
        total_01 = total;
        total = cs_3_4.capacitiveSensor(30);
        // Average (Smooth values over 3 Samples)
        total = (total + total_01 + total_02) / 3;
        // Remove Bottom end noise
        total -= 300;
        if(total < 0)
        total = 0;
        else if(total > 11000)
        total = 11000;
        //Update LED Brightness
        analogWrite(led, total/43);
        // check on performance in milliseconds & Print Total (Debug)
        Serial.print(millis() - start);
        // arbitrary delay to limit data to serial port

    The Conductive Ink Pen worked quite well and was easy to apply, I didn’t need a lot to get a good surface down on the paper to act as a contact. You can see in the video that I made the conductive surface in the shape of a triangle, this provides the variation in charge time. As the finger is in constant contact with the paper, you need to vary the amount of contact surface to drive the change.

    I have a couple more sensor ideas that I need to try out in the next few weeks and I’ll keep you posted. If you want to try some out yourself head over to Newark and pick yourself up some, there are some pretty freakin’ cool circuits you can make.