The Conductive Thread: PROTOTYPE

Thanks to REACTIVEfashion on Instructables for their ideas on how to do this...

Below is my first experiment with sewing with conductive thread, building a simple circuit in a fabric and making a switch from conductive Velcro.

Conductive thread is available from a number of suppliers and the spool I used was from Sparkfun Electronics and is a two-ply thread.

To use conductive thread in a sewing machine, I suggest putting the thread in the bobbin. If conductive thread is used in the needle thread, the tension of the stitch tends to loop and it becomes messy on either face of the fabric. Wind the bobbin as you would any other on your machine. If the conductive thread comes on a cone larger than your machine is capable of holding, just firmly hold it on a flat surface, at the base of the cone, and wind the bobbin as normal.

Next, I stitched, with conductive thread, two parallel lines: one, which was the ground and the other positive. I left about an about inch in between the two lines. I also marked the fabric, with a pen, closest to the positive side to remind me which line was positive. At the end of the positive line I stitched the male piece of some Velcro (aka the hook side).

After I sewed these two lines, I was careful to leave long thread tails to attach components or to securing to other lines that might be needed to complete the circuit.

Since the bobbin thread typically faces the back side of the fabric when sewing a straight stitch, I had to be conscious that the right side of the fabric would be the reverse of any regular sewing project. So, I went ahead and marked the front and the back of this prototype too.

Crimp the leads on the LEDs for attaching to fabric with thread. For LEDs that have long leads, it’s easy to crimp the leads around a needle nose pliers. All you have to do is bend the leads so that they are at 90-degree angles from the LED, and then, simply crimp the leads into little beads on either side. If you are using surface mount LEDs, SMD, you will have to solder small metal crimp rings to the anode and cathode sides of the LEDs. Here is the before and after.

Also, VERY IMPORTANT, mark the leads that are positive with a permanent marker or nail polish because when the leads are bent into beads, you wont’ be able to tell which side is the anode or the cathode.

A note about LEDs: If you are going to use different colors, make sure you use the proper resistors because some LEDs will eat up the juice of your circuit. You can always use the LED resistor calculator website if you are unsure. http://www.ledcalc.com/

Next, I attached the LEDs by hand sewing them to the positive and negative lines of the circuit. When tacking by hand, I first took a small stitch over the machine-sewn line, and then crossed over it again, to make sure that the initial hand stitch was making contact with the sewn lines.

Then, I securely attached the LEDs. In the photo below, I am attaching the LEDs to the positive side first. Quadruple tight tacks allowed the contacts to remain secure. Then, I sewed individual lines from the ground line to the other side of the LEDs.

The form, I created with this simple prototype, is a tube, which, required the Velcro switch to be on the front and the back. So as you can see (pls look below) the hook part of the switch is on the front and loop side of the Velcro is on the back.