In this ible, I use a washable battery pack and some LEDs to sew a soft circuit into cuff for riding your bike at night.
Step 1: Make a Sketch of Your Circuit
Draw in the battery with the ( + ) and ( - ) holes marked, and add a line of LEDs beside it.
First draw a line (orange here) to show the flow going out of the positive end of the battery and through all of the positive ends of the LEDs.
Next draw a line (green here) to show the negative flow going from the negative ends of the batteries back into the battery on the negative hold.
Step 2: Cut and Mark Your Webbing
Take your webbing or stiff fabric and cut it to length. You want the approximate circumference of your calf here, but later you can add velcro for adjustability.
Next, count how many LED lights you have. Divide the length of your webbing by the number of LEDS + 1 (for the space for the battery pack) . Mark off equal increments on the webbing to show where you will sew the LEDs in place. I used a silver pen so that you could see the marks on the black webbing.
Step 3: Sew the Battery Pack in Place
Cut a length of conductive thread that is about 1.5x the length of your webbing. Tie a knot in your conductive thread and use it to sew the battery pack in place though ONLY ONE HOLE (either one positive or one negative).
To make things easier to follow in this tutorial, I recommend starting with the positive hole.
Make sure to sew around the hole several times in order to secure a strong electrical connection.
After the thread is thoroughly wrapped around the positive hole in the battery pack, sew a line up towards the first second silver mark. Use small stitches and pull the thread tight with every stitch. This helps prevent short circuits later on.
Place you first LED on the second silver mark and sew it to the webbing through the positive hole on the LED.
Next repeat the process for the negative side with a new thread. Make sure to establish a solid connection with the battery pack and use small stitches to sew toward the first LED.
Step 5: Test Your LED and Battery
It's better if you have alligator leads to test the LEDs and Battery packs before you get started, but since I didn't have them, I wanted to check to make sure it was working ASAP.
As you can see in the first picture, my light shone very dimly. Luckily, as you can see in the second picture, replacing the battery fixed the problem.
This first LED will be the brightest of all because of it's proximity to the battery pack.
Step 6: Sew in the 2nd LED
Using the same process as the first LED, sew in the second one. Again, make sure that the LEDs are in the correct orientation so that the positive mark on the battery connects to the positive mark on the First LED and every LED after that. Same goes for negative - Negative connects to negative.
As you can see in the first picture, if you like you can save time by sewing several stitches at once.
Step 7: Finish Off the Light Strip
The back side doesn't have to be pretty, but it should resemble your sketch from the first step.
When you've reached the end of your webbing or run out of LEDs, it's time to tie off each end of the thread. I flipped over the webbing and sewed several knots into the back side.
If you have it available, drop a drop of clear nail polish onto your knot. When the nail polish is dry, trim off the excess thread. Repeat for the other thread.
As seen in the last picture, your finished strip should glow quite brightly.
Step 8: Begin Making the Outer Band
Lay the webbing with the circuit side down along the edge of your semi-transparent fabric. Pin it down and sew along the edge of both.
Step 9: Wrap the Fabric Around the Webbing
After you've sewn the webbing to the fabric, fold the side of the fabric back over itself twice. What you are doing is forming a small tube of fabric around the webbing.
Next I pinned my reflective strip on top of the tube and sewed it all together one one side.
Sew as far down the strip as you can without running into the battery pack.
Step 10: Finish the Tube
This step depends on how you're constructing your tube.
Here, I trimmed the fabric so that it ended underneath my reflective strip. Then I sewed the other side of the reflective strip down. It didn't come out super clean looking, and in retrospect, I wish I'd used grey thread or something that would blend in better with the reflective strip.
Step 11: Start Sewing Velcro
Next, I lifted up the reflective strip and cut away the tube below it to expose the battery.
Then I pulled back the fabric to sew a piece of velcro to the webbing. Then I sewed a tiny piece of velcro in the opposite orientation on the back of the reflective piece.
Now, there is a little velcro door for accessing the battery pack.
Step 12: Attach the Velcro to the Back of the Strip
Now you want to close off the end of the strip near the battery pack with a row of stitches. You also want to sew a strip of velcro behind the battery pack.
I actually wish I'd done this sooner so that I could sew on a bigger piece of velcro, but right now the battery pack was in the way.
Step 13: Add Velcro to the Other End.
Cut a piece of velcro that will fit the opposite end of the strip and sew it into place.
Step 14: Check Out How It Looks
Your finished band should look some thing like this.
Step 15: Test It Out
Turn it on, make sure that the battery pack is still accessible.
Step 16: Ride Your Bike!
Step 17: Gather Your Supplies
Small battery pack (Lilypad works well ) https://www.sparkfun.com/products/10730
At least 5 LEDs (Lilypad Red work well) https://www.sparkfun.com/products/10044
Conductive thread https://www.sparkfun.com/products/10867
Piece of webbing about 2" wide and 15" long. Stiff fabric can work here too
Fabric that is semi-transparent (doesn't have to be fancy outdoor fabric. Most cotton scraps are thin enough for light to shine through)
Reflective tape (http://solutions.3m.com/wps/portal/3M/en_US/ScotchliteNA/Scotchlite/Products/~?N=4621+8696059)
About 4" of velcro
Clear nail polish