Issue 155 June 2003
Good Vibrations

BAGS AND BEYOND

Let’s face it, the number of Circuit Cellar readers who design airbag systems for a living isn’t large. For the rest of us, the real interest in the ’33794 likely lies with “thinking outside the car” applications. Motorola mentions liquid-level and spill detection (e.g., a stove that automatically shuts off when the pot boils over).

I explored that concept a bit by putting a water glass on top of two electrodes. One was connected to the chip, and the other was connected to ground. Sure enough, putting even a tiny amount of water (less than a teaspoon) in the glass caused a noticeable change—approximately 10% of the full-scale difference between Ref A and Ref B capacitors.

Better yet, I noticed that touching the water with my finger also produced a solid 10% step (see Photo 3). Just brainstorming brings to mind a possible solution to the certainly worthy problem of childproofing pools and hot tubs. Other interesting application ideas include harsh environment no-key keypads that are hermetic without moving parts; or perhaps even a let-your-finger-do-the-walking mouseless pad.

I think creative designers are going to have a lot of fun with this chip. Hey, maybe it can even find its way into a modern-day incarnation of the theremin. Queen of Outer Space II anyone?