My first soft circuit - ambitious

For my first soft circuit, I decided to make a coaster that would light a series of LEDs when a drink is placed upon it.  Sounds simple, right?  Well, it wasn’t.  My biggest obstacle was my horrendously poor sewing ability.

My breadboard circuit was easy enough:

That’s a momentary switch to turn on the LEDs, just as the coaster’s soft switch would be.

Then I made the freeform circuit, which was really just connecting the four LEDs in parallel and hookin ‘em up to power:

(thanks to Seungran Woo for modeling)

Finally, it took time to make the soft switch.  I used a piece of foam rubber in square shape with the center cut out, two patches of conductive fabric , and glued them together:

 It actually worked well, but I did make a mistake by not leaving a tab of fabric to sew my circuit to.

Then I sewed the battery compartment, and that was my biggest point of failure.  I used a small square of conductive fabric as the anode, and sewed a series of stitches to the underside of the coaster.

I had to sew a patch of fabric to the canvas of the coaster to act as one side of the switch, and then I sewed the the conductive fabric to the coaster to form a pocket, which was then connected to the other side of the switch:

This battery compartment ended up just shorting itself out due to my poor sewing ability.  Frayed ends on the inside of the pocket contacted the conductive fabric, shorting the battery continuously.  So, when I sewed one LED to test it out, I found it would not work:

It took me a while to figure out what was happening, so that’s as far as I got.  What did I learn?  Well, sewing is really hard. Keeping conductive threads from touching each other in a two layer circuit is difficult.  You should always have a plan for contact areas to sew to on soft switches.  And battery compartments for coin cell batteries are very hard to make snug.

I was very disappointed in myself, but I guess it was just my first attempt, so I’m hoping to get better.  But it was a very frustrating initial experience.