My first e-textile: A hoodie with LED lights

I had heard about various ways to make e-textiles but I had a lot of questions before I could actually make some myself. This is why I enrolled in an e-textile course at the Ommel festival in June. I decided to make a cool hoodie with LED lights for my son. It took some time to finish the project but now it is ready just as the winter is approaching.

The sewable e-textile components have been designed to withstand machine washing after you remove the batteries. However, if you are making something (like a Halloween costume) that doesn’t need to be washed, you can use even regular LEDs if you wind the LED legs into loops that can be sewed onto the fabric. However, the normal LEDs usually need a separate series resistor so that they won’t fry up as the regular 3 V coin cell battery voltage is too high for them.

The only thing you need to do before washing the e-textile garment is to remove the coin cell battery.

How to make an e-textile circuit

As I think that the regular wiring diagrams are too hard to interpret by a sewist that is not an engineer, I made an easier diagram with pictures of the different parts. This is the simplest circuit using one textile LED and a toggle switch that can be used to turn the circuit on and off:

The parts can be connected with an electric wire that in e-textile purposes is usually conductive thread or a conductive ribbon. There is also conductive fabric that can be used.

The textile LEDs are connected so that the “+”-end is connected to the “+”-end of the battery. As the toggle switch just opens and closes the circuit, it doesn’t matter which way it is sewn on.

Otherwise, you only need to remember that electricity chooses the easiest route. A shortcircuit means that you have a straight connection from the “+” side of the battery to the “-” side. If you do that, no current flows to the rest of the circuit and the current increases rapidly. The battery heats up as all the electric energy is released at once emptying the battery. With e-textiles, the voltages and the currents are still pretty low and the sewable thread holds enough resistance so that there should be no danger. You should still know that in a regular circuit a shortcircuit can lead to fire and or burns caused by the overheated battery.

When using multiple LEDs there are two different options. You can connect the LEDs in parallel or in series.

A series circuit

In series circuit you will connect the LEDs to each other like beads on a string. The “-” end of the first LED is connected to the “+” end of the next one and so on. Here is an example with two LEDs:

In a series circuit, the same current flows through all the components. You can add several LEDs in this circuit but the more LEDs you add, the dimmer light you will get. This also means that if one LED gets damaged, all the LEDs go off. This is a phenomenon that is familiar from many Christmas lights. The more LEDs you add in series, the dimmer they all are.

You can also use the series circuit idea to add another coin cell battery holder which means that you will double (if your cell batteries are identical) your voltage.

A parallel circuit

Another way to connect the LEDs is to make a parallel circuit. This, in my opinion, is the smarter way, since one damaged LED doesn’t break the circuit. Here is an example of a parallel circuit with two LEDs.

In an ideal world, the same voltage goes over each LED in a parallel circuit and all the LEDs should shine as brightly. In practice, the resistance of the wiring (like conductive thread) means that there are differences in brightness depending on how long the wiring is for each LED. Just like with the series circuit, you can add more LEDs this way.

Connecting batteries in parallel doesn’t affect the voltage. However, the parallel batteries are still used in many applications as the parallel connection increases battery life and stability of the voltage.

Making the hoodie

I chose to use the Ottobre design 4/2018 34. Fresh Breeze hoodie as a base for my project. I used black sweatshirting and added fun stripey ribbings to the cuffs and the hem. I left out most of the topstitching and finished the hood edge by folding the edge to the wrong side and double stitching with my cover stitch machine rather than using the band.

The way I designed the e-textile parts meant that I could finish sewing the hoodie first and then add the components to the finished garment. Yes, I could have hidden the wiring and covered the LEDs but I wanted to emphasize the e-textile idea by having it fully visible.

For my project, I used 5 green Electro Fashion LEDs, a coin-cell holder, a slide-switch and conductive thread.

I first hid the coin cell battery holder and the toggle switch to the left side pocket. I sewed them on with ordinary polyester sewing thread and then connected them together with conductive thread. To make a connection to each of the components I sewed three to four stitches around the connection holes.

I decided to put two LEDs in parallel at each of the front raglan seams and one at the top of the hood. First, I sewed the LEDs on at first with black sewing thread. Then I started wiring them together with the conductive thread. I did this entirely by hand. I left the conductive thread visible on purpose by making large running stitches with it.

My design doesn’t completely eliminate the change of accidental short circuits. However, they are usually very momentarily as the wearer quickly realised the lights going off. When the garment is folded up and stored, the switch is always in the “off”-position.

In the picture above I have connected most of the LEDs together. I am only missing one connection between the two LEDs at the right-hand side and the connection to the battery-switch part in the pocket.

The finished e-textile hoodie

It was hard to get proper pictures of the finished hoodie with the lights on! In real life, the LED lights are much brighter than they appear in the images.

The effect is even more eye-catching indoors. Here you can also see the difference that the resistance of the conductive sewing thread makes to the brightness of the LEDs:

Here the e-textile components show a bit better:

The switch is easily accessible through the pocket and you can turn the lights on and off by feel alone.

From the back the hoodie is very simple:

And one last jump picture, just because!

In Finland, the e-textile parts can be purchased via Kouluelektroniikka. In UK there is, for instance, this shop called Heart Educational. You can also buy various e-textile components through Amazon.com and Amazon.co.uk (an affiliate link).

I am sure that this won’t be my last e-textile project. In fact, my daughter is already asking me to make something for her, too!

Thank you for reading and do subscribe to follow me on my sewing adventures! Happy sewing!

Katja