10 Tips for Conductive Thread
I prefer to work with stainless steel conductive thread. It’s thin, strong, and smooth.
It’s thicker than normal sewing thread, but thin enough to be sewn by hand in medium-eye needles or in the bobbin of a sewing machine that can handle ‘heavy’ thread. Because it is strong and smooth, its ideal for any wearable/e-textile project. 2-ply has fairly low resistivity, 16 ohms per foot so you can use it to drive LEDs and other electronic components that use under ~50mA.
3 ply thread has a resistance of 10 ohms per foot for components that use under ~100mA. It is thicker than standard cotton/poly thread and can be used for hand sewing or in industrial sewing machines.
Because it is made of stainless steel fibers, it will not oxidize like silver does: your projects will not ‘stop working’ because of oxidation after a few months and its safe to wash. However, this thread is a little ‘stiff’, it feels a little like ‘waxed thread’ and is not ideal for making iPhone-compatible gloves (use conductive yarn for that instead).
Tools & supplies
You’ll need some conductive thread, scissors, needles, fabric or a garment, a battery pack, and the following:
- Multimeter
- Sharp scissors
- Embroidery hoop
- Fabric or garment
- Alligator clips
- Snaps and other metal fasteners
- Circuit board components
- Low viscosity, quick-setting adhesive such as clear nail polish or Starbond
Prep thread and fabric
Cut a length of thread roughly the length of one arm. Much longer and the thread will start to be unwieldy and twisted.
Thread a medium size needle with the conductive thread. You may need to moisten the thread end to help it stay pointy for threading.
Place your fabric in an embroidery hoop. Beginners will find this helps a TON when learning. For more information on using an embroidery hoop correctly, check out my Cross Stitch tutorial. More advanced folks may wish to stitch directly to a stiff garment.
Stitching around circuit boards
Get an idea of where your circuit will go. You may wish to mark traces with tailor’s chalk or a water-soluable embroidery marker, or just freehand it! Get your circuit board onto your taut fabric and pick up your threaded needle.
Bring the needle through the fabric from back to front, right next to the circuit board.
Pull the needle all the way through and continue pulling the thread tail until only 6 inches remains at the back of the fabric.
Leave this tail dangling for now– we’ll tie it in a knot later.
Bring your needle from front to back through the hole in the circuit board. Pull the needle and slack thread all the way through until the thread snugly hugs the conductive pad ad the edge of the board.
Repeat with a few more stitches to make a secure mechanical and electrical connection.
End with both ends at the back of the fabric and get ready to tie a knot.
Tying knots
Before cutting anything, tie the threads in a tight square knot at the back of the fabric.
Seal this knot by applying a drop of clear nail polish or CA glue.
When dry, trim the tail end of the thread very closely to the sealed knot. Now you can continue stitching with the long tail to connect up different parts of your circuit!
Connecting components
The thread must travel between components to connect them, while avoiding other paths of conductive thread in the circuit. The thread acts like uninsulated wire or traces on a circuit board, but this circuit board is made out of fabric!
The most straightforward connection is a running stitch. You can also learn many more hand embroidery stitches that can have decorative or functional appeal in your project.
As you stitch along, pause periodically to whip-stitch a chainable pixel’s ground pad (-).
Turning 180 degrees
Now that all the pixels are anchored by one pad, clean up any stray threads on the back.
Tie a knot with a sewing needle! Insert the needle under a previous stitch.
Pull the thread almost all the way through, leaving a small loop. Put your needle through this loop and pull the thread through, creating a tight knot.
Don’t forget to seal the knot with Fray Check or clear nail polish before trimming the tail closely.
Preventing short circuits
Keep your stitches small and snug throughout your circuit. An embroidery hoop comes in handy to keep the fabric flat.
Keep power and ground lines far apart from each other. A short between power and ground will prevent your project from working and may even cause your battery to heat up.
Use a multimeter’s continuity tester to check your circuit for shorts. The meter will beep any time the two probes are electrically connected.
Put one probe on power and one probe on ground. There should be no beep!
Check your circuit for shorts after finishing each path in your circuit. This way if you do discover a problem, you will know the likely location of the stray thread/short circuit.
Machine sewing
You can use our 2 ply conductive thread in the bobbin of a sewing machine. Thread the machine’s needle with plain thread.
Use a water-dissolvable marker to plan out your circuit traces.
You may need to adjust the tension on your machine. Experiment on a scrap piece of fabric and examine the balance between the conductive and regular thread. Adjust the tension and experiment again until you are satisfied.
Machine stitch your circuit.
Leave long tails of conductive thread at the ends of your stitching lines in case you need to pick them up with a hand sewing needle and connect to other components.
Spritz away the markings with water. Be sure to let the fabric completely dry before powering up your circuit.