What the heck is a "soft circuit"?

I don't know how I got dragged into this. A coordinator from ChickTech was looking for volunteers to help create a soft-circuit electronic project for 100 high-school age girls with a budget of about five dollars a piece? It didn't seem possible. Oh, and could it be programmable? Definitely not possible.

I didn't know anything about soft circuits other than they used conductive thread. The microcontroller project I did for our family reunion ended up being more than $10/ea, and I didn't think I could have got it down much, but then again I've been working on the scale of a dozen. When you look at pricing out components, there is an amazing price drop when you start talking quantities of a hundred. I figured I would at least do some research to see what others have done.
Fortunately, MIT's High-Low Tech Group has blazed a pretty bright trail for both microcontrollers and soft circuits. They have created a way to program an Attiny like an Arduino, using an Arduino. Brilliant! No special chip programmer or hard to set up tool chain. They also created a small board for soft circuits set up to blink different patterns depending on which pin to attach the LED to. Genius! And of course the put together some excellent tutorials and examples. Awesome.

While the MIT board alone cost more than our budget, they have posted all their design files and firmware under a Creative Commons license.  This allowed me to whip up a similar board, have it created locally as a donation (thanks OSH Park!), and modify their firmware to do what we wanted, which was a night-light behavior with a photo cell. When I priced out the components, it was not only under budget, there was plenty of margin for the craft supplies!

In any project, here are a combination of limiting factors that usually involve price, time, and features. Given the time and price limits, I'm amazed how this project has turned out. We were able to not only add some cool functionally at very little cost, but also increase the battery life significantly. Hopefully, some of the girls will be interested in learning programming so they can change the firmware. This would be the perfect hook to get them involved with the library's Teen Makers!

Here are the "notes" I created for the event to help the girls learn a bit about the circuitry:

I'm fascinated by the concept of soft circuits and being freed from the hard cold world of PCBs and enclosures. I was also excited that we were able to build on all MITs hard work and then share it in the same manner. Being able to reduce the cost will also enable others to get it in to the hands of more Makers. Hopefully I can find some time to continue work along these lines, or else that someone else can take it even farther in true open source fashion.

Stay tuned for a report from the event. I can't wait to see what creative ideas the girls come up with! That will be the true reward for all this work.