Electronic Textiles How To: Sew a Light Up Wristband with Four Twinkling LEDs (computer chip circuit)

Wednesday, May 10, 2017

If this were a fancy place, that image above would be animated and you'd see that the lights twinkle at different rates. This is the very beginning of the fancy computer-processing portion of eTextiles. It uses the same concepts as our previous tutorials - all the negative connection points connected to each other/the negative end of the battery holder. But now all the positive ends of the LEDs are connected to different pins on the little computer chip. The computer chip can be reprogrammed to have the lights/pins do different behaviors, but I just used this cheap little pre-programmed LilyTiny that gives some preset behaviors.

The diagram included in the tutorial below shows what I'm talking about with the positive/negative threads.




Supplies for Four Twinkling Lights Wristband
As always, SparkFun.com is a great source for most of your supplies.

• 1 CR2032 Coin Cell Battery (PRT-00338)
• 1 sewable battery holder (DEV-08822 or DEV-13883)
• 4 Lilypad LEDs (DEV-13903)
• 1 LilyTwinkle or 1 LilyTiny - they have different sparkling behaviors (DEV113-64 or DEV-10899)
• ~1 yard+ conductive thread - actual number depends on how far apart all your components are! (DEV-10867)
• 1 sewing needle (small enough to fit through the connection point/hole) (TOL-10405)
• craft scissors
• felt wristband (or textile of some sort).

Before we begin...
It's usually wise to prototype your electronic circuit design using paper first: http://byov.blogspot.com/2017/04/etextiles-paper-prototype-before-you-do.html. Just cut out the pieces you'll be using from the paper (i.e., a battery holder, 1-4 LEDs, and 1 LilyTiny/LilyTwinkle), tape them down onto a piece of paper that resembles the necessary circuit layout, and then draw lines connecting the positive connection points. And then a line connecting the negative connection points. These represent two separate pieces of thread, and remember, they should not intersect!

I like to test out my designs with alligator clips first, so I can ensure that all the pieces are working as they should. Below, I'm trying out two LEDs and a LilyTiny chip. Once I got rid of the dead battery, it worked!

1. Make your felt wristband / whatever textile you're sewing to
   If components (i.e. battery holder) are going on the inside of the wristband, you'll want a little extra length. Maybe an extra 0.75" or 1" extra to accommodate the size of the battery holder. I also find that using sewing thread, rather than embroidery floss, makes it easier to sew Velcro to the felt.
   
   
   
   
2. Figure out approximate placement of battery holder and LilyTwinkle (I'm putting mine on the back of the wristband)
   
   
   
3. Figure out approximate placement of the LEDs (subtly mark their spots with a marker)
   
   
   
4. Follow diagram to connect appropriate points.
   
   1. Using 4-5 overcast stitches to secure each connection point, sew a running stitch from the positive connector of the battery holder to the positive connection point of the LilyTwinkle. Secure and trim threads.
      
   2. Do the same for the negative points of the battery holder and LilyTwinkle, but instead of trimming thread, continue to connect all 4 of the negative sides of the 4 LEDs with the same thread. Trim threads after all 6 components' negative connection points are connected via running stitch and overcast stitches.
      
   3. Connect each positive side of each of the 4 LEDs to one of the numbered points on the LilyTwinkle. Do not sew these threads across any other threads! Each of these lines needs to be cut & trimmed in between connecting another LED.
      
   
   
   
   
5. Insert battery, matching positive end to positive side of holder. Lights should twinkle on an off.
   
   
   
6. Remove battery before attaching wristband decorations with non-conductive sewing thread.
   I used stars and a moon. Maybe you could do flowers? Or an Xmas tree or Menorah?
   
   
   
7. Done!