Sewable Wrist Cuff with Metal Snap Switch

Sewable soft circuits are a unique way to explore electronics and fashion. Using conductive stainless steel thread, you can sew circuits that power lights in unique ways. When you add a metal snap, you can create a switch to turn the circuit on and off, which conserves battery power and can also create unique interactive effects. This tutorial is inspired by Leah Buechley’s e-textile activities located in Sew Electric.

GATHER MATERIALS: (Vendors – Sparkfun, Adafruit, Amazon)

  • LED lights with resistors
  • battery (3 volt CR2032 coin size)
  • conductive thread (stainless steel thread)
  • scissors
  • sewing needle (self-threading needles work best)
  • felt fabric
  • sewable metal snaps (male and female ends that fit together)
  • assorted sewing notions (fabric pencils, buttons, scrap fabric, sequins, regular sewing thread, etc.)

PART ONE – PLAN THE CIRCUIT:

  1. Draw on paper to plan your design. Indicate placement for the battery and LED light and where the conductive thread will connect the components.
    1. Remember you will use one piece of conductive thread to connect “+” sides and a separate piece to connect “-” sides. Think about the metal snaps as being “+” and “-” components as well because when they touch they will complete the circuit path in order to power the LED light.
    2. Do not cross the positive and negative lines of conductive thread.
    3. Consider how you can use regular thread to complete non-conductive aspects of your design.
  2. Lay out your materials.
  3. Test batteries and LED light to ensure they work.

THINK ABOUT: How can the design use as little conductive thread as possible and still maintain a balance of conductivity and aesthetics?

PART TWO – MAKE THE FABRIC BATTERY POUCH: (*Note: You can purchase battery holders but they are usually too expensive to use for large group activities.)

  1. Cut two squares of fabric (slightly larger than battery).
  2. Sew a small circle of conductive thread in center of each square (about ¼ or ½ size of battery).
  3. Use regular thread to stitch three sides of squares into a pouch (leaving one side open for access).
  4. Test to make sure battery fits. Make sure battery is accessible for replacement. Used batteries cannot be thrown in regular trash and must be disposed of properly.

THINK ABOUT: How much conductive thread is needed to ensure maximum power from the battery pouch? Will the battery pouch be placed on the inside (non-viewable) side of the cuff or appear on the outside (viewable) side of the cuff?

PART THREE – SEW THE CIRCUIT:

  1. Mark the longer “+” lead of the LED light(s) with Sharpie marker.
  2. Coil resistor ends of LED light(s) into sewable circles.
  3. Sew components onto fabric. Remember to use separate pieces of conductive thread for “+” and “-” connections. Don’t forget that the metal snaps will act as your on/off switch and one will need to be sewn on the outside visible side of cuff and the other sewn on the inside hidden side of the cuff.
  4. Secure ends with hot glue.

THINK ABOUT: How can you insulate the conductive thread without compromising the aesthetics of the design? Is the cuff comfortable and functional for everyday wear?

EXPERIMENT CONSIDERATIONS:

  • How many LEDs can you power with one battery? What other types of circuit designs can you use to power more than one component?
  • What other conductive materials can you use to make the sewable circuit interactive or modular?