For this version of the headband, you'll be sewing a wire light onto the headband. The wire light is all one piece -- all you have to do is stitch around it to hold it in place. And it's waterproof, so it's OK to wear in damp weather (as long as the battery pack is tucked away inside the headband).
Since the stitches will be showing, you might as well make them part of the design! To do that, you will use embroidery floss -- a thick, shiny thread made up of six strands that can be separated or used all together.
And since the lights are pretty bright, you can also use embroidery floss stitches to cover the LEDs and diffuse the light. That reduces the intensity and spreads the light around to cover a slightly larger area.
You don't need to know any official stitches for this project -- it's perfectly OK to just make them up as you go along.
If you need help with the basics, The Hand Sewing Class on Instructables can help you get started, and give pointers on the stitches mentioned here. The Instructables Embroider Class also has tips for sewing with embroidery floss.
Since you're limited by the length of the wire, start by putting the battery holder near the back of the neck.
Open up the headband and on the inside layer, mark and cut a slit a little further away from the bottom of the back seam than the length of the battery pack. Make it wide enough for the battery pack to fit through.
Put the battery pack inside the pouch formed by the headband, about where you want it to sit when you are wearing it. On the outside layer, mark and cut a small slit just big enough for the wire to fit through.
Pull out the wire and position it around the outside of the headband.
Make sure to leave enough extra wire to let you take the battery pack when needed.
Hold the wires in place with tape. Now you're ready to sew them on! The technique you will use is called couching.
Anchor your thread or floss on the inside of the outer layer (inside the pouch). Wrap the thread around the wire three or four times, just before the first light. Then make tight little stitches around the wire, evenly spaced, to hold it in place against the fabric. Remove each piece of tape as you come to it.
When you get to an LED, make a stitch right before and after it. And make sure the bulb is pointing out!
Keep going to the end of the wire, then anchor the floss just past the last LED.
You can sew any kind of design to cover the LEDs and diffuse the light. Here they are covered with messy stars. Each star starts out with three criss-crossing stitches of thick embroidery floss.
Then go back in and make shorter stitches between the long ones. Turn the light on from time to time to make sure you are covering the glare.
Do the same on all the lights. If you use different color floss, you will get the effect of multi-colored lights.
The final step is to close the top of the headband. Starting at the bottom of the back seam, sew through all the layers of fabric, gathering them together in the stitch.
When you reach the top edge, go all the way around.
A simple whip stitch works just goes over the top, around and around. It's good for holding the edges of the opening together.
A blanket stitch creates a line of thread or floss across the top of the opening, which gives you a nice finished look.
There are also more elaborate variations. This example uses a stitch called a crossed buttonhole. It takes a little practice to get it right!
If you make a mistake in your embroidery, you can take out the stitches with a seam ripper and start again. Just be careful not to damage the wire or electronics.