Things You'll Need
Standard LEDs (as many as you'd like)
Disappearing ink marker
Garment such as a T-shirt or skirt
Hand sewing needle
Coin-cell or AA battery holder with sewable leads
Coin-cell or AA batteries
Metal sew-on snap
Sewing an LED, or light-emitting diode, into a shirt or other garment is a fun way to make your outfit a bit more festive, and isn't as difficult as it may seem. The process is not unlike most general hand-sewing projects, except you'll need to use a conductive, metallic thread to make the LED light up. You'll also need to attach a battery and a switch to turn the LED on and off. When sewing an LED, keep in mind that you're working with circuitry and electronics and take care to attach positives and negatives properly.
Use the needle-nose pliers to bend the long lead of each LED into a coil. The long lead, or thin metal strand that sticks out of the light, is typically the positive lead or anode.
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Bend the negative lead of each LED into a coil. Make the coil slightly square or triangular to distinguish it from the positive lead.
Arrange the LEDs on the front of the garment in an appealing pattern, then use the disappearing ink marker to draw lines connecting the positive leads of each LED to another. Draw another line connecting the negative leads. Don't let the negative and positive lines criss-cross or touch at any point.
Cut a length of conductive thread and thread the sewing needle. Tie a knot in the other end of the thread.
Push the needle through the garment from the back of the fabric, and bring it up through the positive coil on one of the LEDs. Bring the needle and thread over the coil and push back through the fabric to stitch in place. Keep making stitches around the coil until it is securely attached to the fabric.
Stitch along the line you drew for the positive coils until you reach the next LED. Sew around the positive coil of that LED to attach it to the fabric securely. Continue to sew along the line, stitching the rest of the positive leads of the LEDs in place. Once you've sewn all the LEDs in place, make a row of about five stitches, then place the battery holder next to the stitches.
Sew the positive lead of the battery holder to the fabric the same way you stitched the positive leads of the LEDs. The lead should be labeled with a "+." Trim the excess thread off.
Re-thread the needle with a new length of conductive thread. Stitch the negative leads of each LED down the same way you sewed the positive leads. Don't attach the negative lead of the battery to the fabric.
Stitch one half of the metal snap to the fabric with the conductive thread leading from the negative leads. Sew the other half of the snap to the fabric with the negative thread. Position the second half of the snap so that you can push the snaps together to close the circuit. The snaps will act as an on/off switch for your LEDs.
Stitch from the second snap to the negative lead on the battery. Sew the lead down the same way you sewed the positive lead.
Trim the conductive thread. You may wish to apply a dab of white glue to the ends of the thread to prevent fraying. If the thread frays, it can cause a short.
Try the garment on and push the two snaps together to watch it light up.