The Concept
At last, I have an idea for a Technology: Art and Sound by Design final project. I’ve been struggling to think of anything interesting to do. As a musician, I’m dissatisfied with the beeps and boops that we can make with little chips; as a technologist, I’m more interested in building robotics that aren’t very artistic. But this morning, something clicked: I’d like to make a dancing water display.
I’ve been enchanted with dancing water fountains ever since I visited Disneyworld about twelve years ago. They have an amazing display with “snakes” of water frolicking from pot to pot and even leaping across the sidewalk over the heads of the guests. I’ve also watched the choreographed fountains at Atlanta’s Centennial Park, and recently I ran across the overview of a tutorial project called the Geyserbot at Bruce Shapiro’s The Art of Motion Control.
What
I’m thinking of a small display most akin to the Geyserbot–probably even a bit smaller (’cause it looks like it’s standing in a wading pool). I’d like it to be relatively easy to move around in order to display, and self-contained in a case to hide all the guts from the viewer. If it were ever formally exhibited, I might include a placard with a photo and description of the internal mechanism.
Complexity could be added in stages. First, get a basic mechanism running, with say eight jets (= 8 bits of control). Even if it did nothing more than the Geyserbot demo video–sequence the water jet to move back and forth down the line of nozzles, or shoot off alternating nozzles–I think it’d still be pretty interesting. Advanced versions could have more jets (maybe switch to the 40-pin version of the LogoChip with more I/O ports) and more choreography. If the valves could be actuated rapidly enough, it might even be possible to shoot simple pictures into the air–a heart shaped out of rising water droplets, for example.
I think I’d start with eight jets in a row pointing straight up, but it wouldn’t be hard to move them into a circle, tilt them inward so the jets met in the center, etc. With more jets, you could have sixteen in a circle with half pointing up and half pointing in. Lots of possibilities!
I haven’t decided whether I’d like it to be synchronized to music a la the Wizards of Winter Christmas display (which is a real display using a very high-end light sequencer, BTW), or silent except for the sounds of water splashing. Sequencing to music is obviously more difficult–and I don’t know whether it would really add anything. I rather like quiet sounds of water.
How
Since a pump takes longer to start up and shut off than a valve takes to open and close (I assume), I envision having one pump overall, and an electrically-operated valve for each jet. I don’t want the water to spray particularly high into the air–I’m more interested in having fat streams of water than thin sprays–so I think I’d need relatively low water pressure. It may be difficult finding a pump as slow/small as what I need (a small fraction of a cfm, by my estimations), so I might have to inflate some kind of bladder and use a pressure switch to turn the pump on and off on demand. And I’d be very interested if anyone has suggestions on where to get a pump and affordable valves–add a comment to this post if you have ideas!
Control is easy–start with eight jets and wire them to a single output register on the LogoChip. Build MOSFET drivers with back-EMF diodes for the valves, and I’m good to go. Eventually it’d be nice to have a sequencer program like Tom McGuire showed us on his drum machines, but I’d probably start out programming the jets by hand.
I’d like to build it into a case, and I haven’t thought much about what would be most appealing. I know I’d like to have the nozzles barely protruding from a pool of water, both from an aesthetic standpoint (hide the technology and focus on the art) and from a practical one (I think the pool will help dissipate splashing as all the water falls back down).
I’m not sure about the enclosure, though–what kind of material would be appropriate. I don’t want anything high-tech or flashy like aluminum to distract attention from the water show. The weathered metals we saw yesterday in the art workshop were gorgeous, but I don’t know whether they’re right for this project (and whether I could make them happen in time). I’m most comfortable working with wood, and a cherry enclosure (my old favorite) might not be too bad.
Comments welcome!
Don’t let the limited number of outputs hinder you. You can always use a decoder from the outputs and branch it out even more. There are commercially available ones: 3inputs-8outputs, 4in-8out (Binary combinations).
Muaz–if I used a few lines from the port register and demuxed them to branch out, I’d need a bank of latches to hold the on/off state of each branched line, right? And not an octal latch (which captures all inputs simultaneously), but a whole bank of separate latches with the demuxed signal connected to the individual enables?
I’m not afraid of TTL, but it seems to me like a lot less work to jump up to the 40-pin PIC version of the LogoChip. What do you think?