This is my interactive cactus sculpture. It's called “Cactus” because of its shape and also because it's spiny with exposed power supplies of several hundred volts. You want to be very careful how you touch a cactus.
Cactus's behavior is based on an observation by Christiaan Hyugens (1629-1695) that oscillators will sometimes fall into sync due to an amazingly small amount of contact with each other.
There are two pairs of control knobs to interact with. Beware of the spines! Each pair of knobs controls the speed and sensitivity a very slow thyratron oscillator (tube type is 884). The oscillators are loosely connected and can influence each other's timing. One oscillator pulses a mechanical relay which makes a click and makes the indicator light flash. The other oscillator drives a dekatron tube. Dekatron tubes count input pulses (a 0-9 endless loop) by transferring the the glow of a neon electrode to an adjacent electrode at each oscillator pulse.
The control knobs on the cactus oscillators allow the person interacting with the cactus to search for combinations of settings that produce interesting rhythms and chaotic sequences of clicking and counting. These pattens are difficult to achieve and are not stable – they morph and disappear on their own.
Cactus and I had the privilege of being the first 300 seconds of fame presenters in the first public meeting at Pumping Station:One's new space.