This project shows you how to make a light-up bracelet using tiny LED bulbs, conductive thread, and a coin battery. Some basic sewing skills or experience will be helpful while you sew your circuit into the fabric, as keeping your sewn circuit tidy will prevent any short circuits.
Make sure you store your bracelet somewhere safely out of reach of small children and pets, as the coin batteries are harmful if swallowed.
This is a great project to help grade 7 science students visualize batteries as a source of electricity, brainstorm other applications for lightweight batteries, discuss or explore the environmental impacts of battery production and disposal, as well brainstorm or look up alternate ways to power LEDs. It can also be a fun way to introduce the differences between series vs parallel circuits, as the LEDs are all sewn in parallel in this design.
Make sure you store your bracelet somewhere safely out of reach of small children and pets, as the coin batteries are harmful if swallowed.
This is a great project to help grade 7 science students visualize batteries as a source of electricity, brainstorm other applications for lightweight batteries, discuss or explore the environmental impacts of battery production and disposal, as well brainstorm or look up alternate ways to power LEDs. It can also be a fun way to introduce the differences between series vs parallel circuits, as the LEDs are all sewn in parallel in this design.
Tools & Materials
Material List
- one 3V coin battery (CR2016 or similar)
- five 3m LED bulbs (any colour)
- 3' stainless steel conductive thread
- ~ 2 1/2" x 8" sturdy scrap fabric (eg, denim or canvas)
- 3' regular sewing thread
- two small buttons
- 1' light string or embroidery thread
Tool list
- measuring tape or ruler
- black felt pen
- needle nose pliers
- large sewing needle
- scissors
- pencil
- hot glue gun
Optional
Procedure
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Splay the LED wires apart, and use the felt pen to colour the LONG wire of each LED black.
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Before you go to step 4, examine the diagram for this step. This is what the INSIDE of your bracelet will look like before you fold it in half. The LEDs are lined up on the bottom half of the fabric with the black (long) wires pointing DOWN. The coin battery will be sandwiched between the two circles on the right when you fold the fabric in half. The black stitches represent the stainless conductive thread: one thread connecting the positive side of the battery to all the black LED wires, the other conductive thread connecting the negative side of the battery to all the short (uncoloured) LED wires. Refer back to this diagram as you position your LEDs and sew your conductive thread lines.
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Sew the POSITIVE side of your circuit: use one 1 1/2' piece of conductive thread. Start by securing the thread with a knot, then sewing a few long stitches into the bottom “+” circle, then stitch a line towards the lower black LED wires. When your stitches reach the LEDs, stitch the BLACK wire of each LED onto the fabric as shown, using three tight stitches wrapped around each wire. Tie a knot in the conductive thread and cut the tail end short.
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Optional step: if you are concerned about short circuits in the section of sewing between the battery and the LEDs, you can run a line of hot glue along these stitch lines to insulate them electrically. Make sure not to get glue on the stitches in the CIRCLES, as this will prevent the thread from connecting to the battery.
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Fold your bracelet in half lengthwise, flipping the bottom up to meet the top edge so you can see your LED bulbs poking through the fabric. Place a coin battery between the two circles to test your circuit. Does it light up? If yes, move on to the next step. If no, try flipping it around, or refer to the troubleshooting steps at the end of this project.
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Use plain thread to sew a tight “U” shape around the battery, as in the diagram. Stitch closely to the battery so it fits snugly, but so that you can still push it out of the pocket to turn it off. (Also, because LEDs only work when the electricity flows in one direction, you can flip the battery BACKWARDS in the pocket when you’re not wearing it to store it in the off position).
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Sew the second button on (see the picture in step 14). The distance between the two buttons should be the diameter of your wrist; use your measuring tape to confirm this measurement.
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Make sure that you start with a fresh battery (you can check the voltage with your multimeter).
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Keep in mind that when you sew with conductive thread, you are making a circuit. Your LEDs must be sewn in “parallel”, like a ladder: side rails made of thread, and the LEDs forming the rungs in between. If any part of the left rail of your ladder touches the right rail, you will get a short circuit, and the LEDs won’t light up properly. One way to prevent a short circuit if you’ve sewn one side too close to another is to coat the inside conductive stitches with dots of hot glue before folding the bracelet in half.
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Do only some of your LEDs light up? You may have sewn them in backwards. Start again, making sure you colour each LED’s long wire black so you can keep track of them. Sew all of the black wires together with one piece of conductive thread, and all of the plain wires together with a separate piece of conductive thread.
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Does your battery fall out? Put another “U” of regular thread stitching around it to hold it in more tightly, make a flap to hold it in place, or use a coin battery holder made for sewing projects.
Prepare your LEDs for sewing:
Layout the bracelet circuit:
Sew the stainless conductive thread circuit:
Plain thread stitching: (Use the diagram in step 11 as you work through to step 15))
Make the closure mechanism:
TROUBLESHOOTING IDEAS
Extension Challenges
- Use a different closure mechanism of your choice to secure the bracelet on your wrist.
- Use the circuit-sewing skills you learned in this project to add LEDs to a toque, jacket, headband, or whatever wearable item you choose.
- Add LEDs to a patterned T-shirt to add detail and highlights (eg, light-up eyes, headlights, wherever on the design might need a light).
- Search "etextiles" on the internet for more ideas!