I am an experienced sewer but had never worked with LEDs or electrical circuits before. I'm still bitter that I was forced to take Home Ec in high school, but was not allowed to take shop class. I could not find any instructions on the web that answered by very basic questions, so I've written this Instructable with others like me in mind.
Basically, I built the circuit, placed the LEDs into holes in a vinyl strip, and then covered the back of the strip with Velcro (TM). I sewed the other side of the Velcro onto the pants, pulled the wires out the top of the LED strip, connected them to a 9-volt battery and stuck the battery in the front pocket.
Be sure to review the circuit diagram for an overview of what's to come!
Step 1: Materials
Pants - be sure there are no pockets covering the side seams
1/4 yard vinyl - pick a color that matches the pants or consider getting a shiny silver vinyl to act as a reflector for your LEDs. Here is one example (scroll to the bottom of the page)
2 yards 2" wide sew-on (Non-adhesive) Velcro (TM)
1/4 yard woven cotton fabric- any color will do, I used a medium weight black
22 gauge stranded wire - this is from Radio Shack .
I got 22 gauge because that's all they had. I got stranded wire instead of solid since it's less rigid.
30 LEDs of your choice - I got these ultra-bright white LEDs because I wanted as much light as possible.
Two 9-volt batteries
Wire stripper and wire cutter
Single-edge razor blade
Rotary punch - available at sewing, crafts, and leather stores. You can use pretty much any tool that will cut 5 mm holes in the vinyl.
Soldering iron or gun
Cutting board - I used this old cutting board as a work surface when soldering.
Webpage to calculate the size resistors and batteries you'll need LED Series/Parallel Array Wizard
Appropriate resistors for your circuit - I used six 82 ohm 1/4 volt resistors and one 220 ohm 1/4 volt resistor in each circuit (for a total of twelve 82 ohm resistors and two 220 ohm resistors). Radio Shack does not carry these exact resistors so I bought these on-line. If you can't find the right ohm resistor, go up to the next one. Do not use a resistor with too little resistance because you could blow out the LEDs.
Yardstick or tape measure