Most of the people that play around with flexible circuits using conductive thread start with embroider techniques to connect the electronic components. This is a good way to do it, but extremely time consuming and, if you do not do a clean job, it might get messy and the chance that you create a short circuit is pretty big.
Here we will learn how a sewing machine can be adapted to use conductive thread.
Step 1: Sewing Machine
I found this adapted sewing machine in a residency I am doing at Sliperiet, in Umeå, Sweden. They have a place called SoftLab where you can explore soft circuits among other things. We all should thank Emma Ewadotter for her work on having this machine up and running ;-)
Here, they used a sewing machine model Pfaff expression 3.5 but you can perform this modification in any sewing machine.
Step 2: Changing the Bobine
The problem of using conductive thread directly on a sewing machine is that most of the time the thread is thick and unravel quite easily. This can cause a tension on the thread that might break your machine.
You can try to adjust the tension to begin with. However, the safer is to change the original bobine for one that could accept thicker threads.
For this model they used the one in the picture (Viking product number: 920 211-096). You can find it in this link: http://www.amazon.com/Husqvarna-Viking-Specialty-Bobbin-920211096/dp/B0046MVXOA
I advise you to talk with your local sewing machine shop and discuss with them the best alternative for your model. When you buy a bobine it comes with instruction on how to change it. I will not go into that.
Step 3: Examples of Sewing With Conductive Thread and Tips
Here you find an image of the how the sewing looks. As you can see it looks clean and pretty.
Bare in mind that you should only use conductive thread on the lower bobine and do not use the automatic cuter.
I hope this helps.