This week I am helping my school to organize a wearable electronics event for undergrads. Since none of us has done this before, the biggest question is to find out how to sew LEDs and other electronic components onto clothes. We ordered 2 spools of conductive threads, but shipping is a bit slow. While waiting for the order to arrive, I am thinking about alternative options to make wearable LEDs. Looking around my toolbox, I found some wire wrap wires. These are very thin, 30AWG wires typically used for wire wrapping. I was curious if it’s possible to use these thin wires for ‘sewing’ electronics onto fabric and clothes. After experimenting with it a bit, I found it is actually a feasible method. Check my end result first:
How does this compare to conductive thread?
No needle required, because the wire is stiff enough to go through fabric by itself.
Available in many stores and relatively cheap.
May break if stretched too much, again because the wire is stiff.
Can form small curls during sewing if not careful.
So how does this method work? Just follow my illustrated examples below:
First, get some 30AWG wire wrap wires,. These can be found in many stores (Sparkfun, Digikey, RadioShack etc). Use a wire stripper to strip the plastic exterior. You can also get 28AWG stringing wires (used for beading) available from craft stores. These wires are un-insulated, so you don’t even need to strip them.
Next, pick the fabric or textile you want to sew LEDs onto. I happen to have this awesome Make T-shirt. So let me use that!
Sketch your design with a chalk. I am going to have a string of LEDs connected in parallel along a heart shape. Here is my sketch. Not too bad.
Cut a piece of stripped wire, about 20 inch long. At one end, make a small knot and tighten it.
Hold the other end using your thumb and index finger, and push it through the fabric, just like how you would use a needle. Since the wire is quite stiff, it can penetrate fabric quite easily.
Follow your sketched pattern and move the wire forward, just like how you sew normally. When pulling the wire out, be careful not to form small curls. Use your finger to keep the wire as smooth as possible. Watch the video above for demonstration.
This is the outer layer of the heart shape.
On the inner side of the fabric, use an electric tape to fix the wire, and also to avoid shorting it with other wires.
One advantage of using the wire is that you can solder electronic components directly onto it. But if you want to avoid soldering, you can still use the wire to sew the component leads to the fabric (in the same way as conductive thread). In this image, the upper lead of the LED is sewed using the wire (without soldering), and the lower lead is soldered.
Now the inner layer is also finished. I didn’t draw a sketch for the inner layer, so it’s not perfectly parallel to the outer layer
Now I will solder LEDs onto the two wires. All LEDs are connected in parallel. The outer wire corresponds to positive lead, and inner wire negative.
A good way to keep everything organized is to first prepare all LEDs: bend their leads, and cut the negative leads short. This way, you won’t forget which lead is positive!
Try to keep an even spacing between LEDs, and fix them with a small amount of solder. After this is completed, connect the two wires to a battery to test if all LEDs are working.
Now use a wire cutter to cut all excessive leads. I actually like the spikes in the previous image. Looks more artistic :).
To provide programmable LED patterns, I use an Arduino Pro from Sparkfun. I sewed it onto the bottom of the shirt using normal threads.
I use Arduino Pin 11 to provide PWM control. Since there are 18 LEDs connected in parallel, driving them together requires a current that exceeds the limit of a single IO pin. So I use a BS170 MOSFET to switch the LEDs directly from power supply.
Here I am, wearing the Make T-Shirt customized with an LED heart! The LEDs are programmed with three modes: constant on, flashing, and fading. See the video above for demo. Enjoy!