Using conductive fabric and thread to sew circuits

Posted on August 14, 2010 in Hardware, Teaching

This last week I spent some time learning how to sew (barely) so that I can use some conductive thread and fabric to create a soft circuit and embed it into a pillow. I wanted to show how one could use the parts available in our New Media Lab to implement a simple LED circuit using fabric and thread instead of metal and wires.


The conductive thread and fabric

We acquired the thread and fabric from SparkFun.com, here’s some links if you’re interested in purchasing some yourself:

Threadhttp://www.sparkfun.com/commerce/product_info.php?products_id=8549
Fabric: http://www.sparkfun.com/commerce/product_info.php?products_id=10055

Both the thread and the fabric are made of silver-plated nylon and conduct electricity very well! In my testing I was able to barely brush the stranded metal lead from my battery holder onto a couple of tiny frayed threads on a piece of conductive fabric and see the LED light up immediately. Very cool.

The circuit

The circuit is ridiculously simple, and truthfully isn’t probably the best. In general when you hook up a power source to an LED you should use a current-limiting resistor to help ensure that the LED won’t die unexpectedly. But I live on the wild side, so let’s be dangerous. In theory the conductive thread and fabric have their own resistance, and should help a little bit. However they are rated at < 1 ohm / sq inch, which means that in practice it probably isn’t helping much. But thats ok! The pillow is only to demonstrate what it is like to use and play with soft circuit technology, and if someone wants to take this project further they will have plenty of cool stuff to learn!

The next step and further reading

This is a very, very basic project meant only to demonstrate how cool working with fabric and thread instead of wires and traditional components is. Even though we do have a LilyPad Arduino (and lots of awesome accessories) meant to be sewn into clothing for this exact purpose, I didn’t want to waste them on this project. Instead, here’s a list of ideas and thoughts if you want to play with soft circuits yourself!

  • Don’t make a switch the way I tried; it doesn’t work very well! Instead try out the technique of using conductive foam as a switch or think of something else and give it a shot
  • Do a Google search soft circuit and check out whats out there. There’s lots of great info on the web already.

When you find something or think of something you want to try, let me know! The New Media Lab has two 12″x13″ pieces of conductive fabric and one spool of conductive thread (both are linked to above, if you want more specs). Its all available for use now, so if you want to create some fancy clothing or modify an existing item let me know and I can set you up with some cool stuff!