Knit Stretch Sensor (2010)
This stretch sensor is knit from a stainless steel and polyester yarn blend. It is roughly 10 cm long and about 1cm in diameter. The values of the sensor range from roughly 4000 Ohm when relaxed, to 200 Ohm when fully stretched.
>> Knit Stretch Sensor blog post
>> Instructable
>> Flickr photo set
>> Download Instruction PDF
Here is an example of a basic circuit sewn with conductive thread that uses the knit stretch sensor to turn an LED light on and make it shine brighter, the more it is stretched.
The Yarn
The conductive yarn that this sensor is made from is a stainless steel and polyester blend called Nm10/3 which is distributed by Plug and Wear (www.plugandwear.com).
The stainless steel strands in the yarn are short and not continuous, so that stretching the yarn causes a decrease in electrical resistance, as the individual conductive fibers make better contact.
While even a single strand of this yarn demonstrates stretch-sensitive properties, knitting the yarn into a narrow tube on a spool knitter makes the sensor stretchy and more robust. The knit structure also accumulates more yarn and thus more resistance in less length, giving you greater range.
Even without knitting the yarn into a structure you can use it as a stretch sensor by simply pulling it taught or relaxing it. But a single strand of yarn wears out more quickly and can tear more easily.
Find out more about conductive yarns >> http://www.kobakant.at/DIY/?p=1978
Spool Knitters and Circular Knitting Machines
pool knitters or wire knitters are tiny hand-crank circular knitting machines that have 4 needles and resemble knitting dolls. After threading the spool knitter you simply turn the handle and the machine produces a knit tube. Circular knitting machines are larger versions and come in various sizes. While industrial versions exist, you can also find cheap plastic versions that range in price from 20-250 US$. They differ in diameter, number of needles and spacing of needles.
Find out more about spool knitters and circular knitting machines >> http://www.kobakant.at/DIY/?p=1144
Download editable sensor kit instructions >> http://plusea.at/downloads/kits.svg
