ITP has a tradition, which goes back I don’t know how far, that early on in the Intro to Physical Computing class each student builds his first production assignment, called the Stupid Pet Trick. I guess the name comes from David Letterman; probably it’s calculated to ramp down the intimidation factor associated with building something for the first time.
My first thought (which I still think is cool) was to cut a sphere into orange-slice shapes, hinged on one end so they would open and close. I envisioned a walking bug, which would snap into a sphere when a photo-resistor detected someone too close.
I then decided it would be too hard as a first project, and inverted the ‘bug’ in my mind into a kind of flower. The flower would have a few LEDs in it and look very pretty, but if anyone tried to sniff it it would snap shut on their nose.
Then, however, I did the week 4 labs, and was quite charmed when I got the piezo buzzer to play Ride of the Valkyries, with some green and red LEDs flashing in accompaniment. Then in a flash I also remembered that my wife’s birthday was two days after the Pet Trick was due.
Eliza is British, and I have a great mental image of her singing Rule Britannia at the top of her lungs after an argument with our former housemate who decided the Union Jacks we’d brought back from the royal wedding were imperialist and shouldn’t be hung in front of our house. Also, she has a thing for pirates. So I thought I’d create a little something to celebrate her adventurous nature and give her a lift when she was homesick – diorama with an animated ship sailing the sea, playing Rule Britannia as it went.
When I am deep in concentration I get lost to the world and become frightening single-minded. So my documentation is not as thorough as I’d wish….
First we have the electronics, which were already well in place after the Ride of the Valkyries bit. I just had to reprogram the Ardiuno sketch to produce a new song, and add a pair of servos to move the waves and ship.
Then I got to work on the box. This meant I got to play with the coolest toy ever invented by man: the laser cutter.
The laser cutter is so cool there should be a little lightning bolt that comes out of your head when you say it. Just design something in Illustrator and the machine will cut it out perfectly. Check it out:
And the cut box in pieces:
The box turned out to be a bit of a problem because I made it too small. It took a lot of extra work to stuff all the components in there. It’s 9″x 6″ by 4″.
Here is something that was left on the workbench where I spent most of Friday, Saturday and Sunday:
A fairly typical thing to see sitting around at ITP.
I glued the box together, and while it was setting I began what became by far the hardest part of the project: building the mechanism.
Way, way harder than I expected. (Though in hindsight I should have expected it.) But the great thing about the laser cutter is that it really changes the way you think about a project. Instead of thinking about what components might be available and where to get them, you can just make the components you need.
I realized quite early that it would be much better to affix all the parts to an independent base board that could be removed from the box completely. I added a grid to help me match up to the plan I’d made in Illustrator, because I’d already realized by this time that space was going to be a premium. Time on the laser cutter is also at a premium, so I made many more bits than I needed, using different sizes to ensure a fit.
But in the end the wooden servo arms didn’t work, so I had to make them out of leftover acrylic from the ocean waves:
Here’s how my workbench looked sometime in the middle of this:
And here is the work in progress:
As I said, the biggest challenge at this point was to get all that electronic junk to fit in that little area behind the waves. In fact, I was unable to do it in time to show the project on Monday’s class. I spent most of Wednesday on this final task.
And here is where my documentation fails me. That Wednesday, Eliza’s birthday, we were due to meet at 7:15 after she got out of work. At 7:00 I was soldering the switch. I don’t think it occurred to me once to take a picture.
But here’s the finished article:
There are definitely some things I would change in the next version. Instead of the swing-arm attached the servos I’d use a rack-and-pinion system for the waves. I’d build the box with a front and back section, so all the electronic bits could be in the back out of sight. And I don’t think the LEDs really work: the red ones are much darker than the blue, and it doesn’t really fit the mood. I’d maybe use white ones and just leave them on while the music plays. And I would reprogram it so the servos aren’t so jerky; I’d really like the motion to be more smooth and wavelike.
But overall, I’m happy with it.
(More Stupid Pet Tricks can by found in the Stupid Pet Cemetery).