13. Skin Electronics

References

For this week looking ot previous students work at your own Node is very helpful be cause they are likely using technology that is available to you! I loved the work of Marisa Satsia, how she used the copper fabric forms to create movement and conductivity!

In terms of application of skin electronics I'm most curious about applications of Epidermal Electronics and their ability to extend our senses, possibly supporting people in greater understanding of their hormones, blood sugar levels etc. Finally as a medium, I am curious to see more applications of the conductive liquid eGaln that only becomes liquid when warmed making skin applications particularly interesting.

For this week I built a prototype that worked as a compressive front light knuckle bracelet for when I'm biking around in the dark!

In order to execute this assigment I used the instructions found in the Adafruit Pixel Broach example. This project used the Adafruit Flora V2 board with NeoPixels.

Photo by Adafruit

Design

Neopixels were sewn into place using conductive thread onto felt material. Electronic elements were then connected by copper wire which was tightly secured in order to ensure connectiom (or so I thought). In order to connect to replicate these knuckle lights:

• Starting at VBATT, connect all the "+" side of all of your neopixels together in a chain
• Connect all the arrows in a line leading away from your FLORA 2 starting from digital pin 6
• Starting at GRND, connect all the "-" sides of your neopixels together in a chain,
• Connect your FLORA 2 to a power source of 1300mAh

Photo by Adafruit

Testing

Testing the circuit initially using crocodile clips and then with wire I confirmed that the connections were correct, that the code was operational and that the hardware was operating properly.

I used the code below in order to test and try to get my pixels poppin'!

// NeoPixel Ring simple sketch (c) 2013 Shae Erisson
// Released under the GPLv3 license to match the rest of the
// Adafruit NeoPixel library

#include <Adafruit_NeoPixel.h>
#ifdef __AVR__
 #include <avr/power.h> // Required for 16 MHz Adafruit Trinket
#endif

// Which pin on the Arduino is connected to the NeoPixels?
#define PIN        6 // On Trinket or Gemma, suggest changing this to 1

// How many NeoPixels are attached to the Arduino?
#define NUMPIXELS 3 // Popular NeoPixel ring size

// When setting up the NeoPixel library, we tell it how many pixels,
// and which pin to use to send signals. Note that for older NeoPixel
// strips you might need to change the third parameter -- see the
// strandtest example for more information on possible values.
Adafruit_NeoPixel pixels(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);

#define DELAYVAL 500 // Time (in milliseconds) to pause between pixels

void setup() {
  // These lines are specifically to support the Adafruit Trinket 5V 16 MHz.
  // Any other board, you can remove this part (but no harm leaving it):
#if defined(__AVR_ATtiny85__) && (F_CPU == 16000000)
  clock_prescale_set(clock_div_1);
#endif
  // END of Trinket-specific code.

  pixels.begin(); // INITIALIZE NeoPixel strip object (REQUIRED)
}

void loop() {
  pixels.clear(); // Set all pixel colors to 'off'

  // The first NeoPixel in a strand is #0, second is 1, all the way up
  // to the count of pixels minus one.
  for(int i=0; i<NUMPIXELS; i++) { // For each pixel...

    // pixels.Color() takes RGB values, from 0,0,0 up to 255,255,255
    // Here we're using a moderately bright green color:
    pixels.setPixelColor(i, pixels.Color(0, 150, 0));

    pixels.show();   // Send the updated pixel colors to the hardware.

    delay(DELAYVAL); // Pause before next pass through loop
  }
}

Troubleshooting Soft Connections

Initially I tried to create this prototype using an analog pressure sensor which I created in wearable week. This sensor uses a hamburger method of layering two conductive materials, in this case copper wire and consuctuve thread with Velostat plastic in the middle. The Velostat allows for some current to run through it when compressed but is resistive without pressure.

While the Analog sensor had trouble activating as a switch I decided to move directly to a powered device. Regrettably the powered tests without the soft switch which would have been activate when my hands pressed on the handlebars of the bike were unsucessful - the connections were faulty. We figured this out in two steps:

• We testing that there was voltage running through the Flora using a Volt meter
• we tested the current running through the connections leveraging Crocodile clips.

Here is the final prototype.

Tools

Photo by Adafruit

• Pilers
• Volt Meter
• Copper wire
• Arduino IDE
• Flora V2
• FLora NeoPixels

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Last update: 2023-01-17