The Slinky Metronome is now fully operational. I gave a presentation and demonstration of it in Mechanisms on Thursday. The Slinky Metronome is a Sociable Object. It keeps a steady beat, based upon the period of the Slinky spring, and broadcasts that beat out via 802.15.4 radio to the entire ITP floor. Electronic musical instruments, dynamic artworks and kinetic sculptures can all pick up the broadcast beat and synchronize with each other for an orchestrated performance. The Slinky Metronome is human-operated, so the beat it broadcasts is rooted in tangible physical interactions. Now that it’s working, the next step is to collaborate and share sample code with a few instrument and kinetic projects. This is a project I’m looking forward to exploring more in the fall.
Slinky Metronome Proof-of-Concept
The initial proof-of-concept for the Slinky Metronome, a Sociable Object for my thesis, is complete and it works. It uses a Slinky spring toy as a pendulum. An accelerometer at the base of the Slinky tracks the (primarily) sinusoidal movement as the bottom of the spring rises and falls. An Arduino microcontroller processes the Z axis from the accelerometer to figure out when the pendulum phase shifts from negative to positive, signaling a beat. The current code then takes this information and sends out those beats with measure codes over a XBee 802.15.4 radio.
The idea is that different musical and art projects in the same space can use this metronome wirelessly to coordinate their sounds, motions and lights with each other. The result should create a diverse orchestrated work where the whole is greater than the parts.
The current proof-of-concept leaves the electronics off-board, with only the accelerometer on the bottom of the Slinky. The next prototype version will use a printed circuit board, bigger Slinky and place all of the electronics radio and battery in a lightweight case that rides along at the base of the spring. Here’s a schematic for the new system:
Metronome Schematic
And a movie showing the metronome sending to a simple Processing program that wirelessly claps along in time:
Click to play movie
Kate, Jenny, Rebecca, Kati and I were invited to speak this morning to a roomful of high school girls in a panel discussion of Art and Technology for the Trendsetters Network. We gave an overview of our projects and process in the 40-minute session. They got to hear a bit about Botanicalls, the Meatrix, Portable Phone Booth, Popularity Dialer, WildLight, Social Genius, a Sopranos game, Go-go Gloves and Collective Collage. About half of the girls in the room were interested in engineering as a career. Every single one had a cell phone that could take pictures. The future should be cool.
Click to Play Movie
Lesley and I created a lever set (with 100% reused materials) to experiment with and demonstrate first, second and third-class levers. Our working model was made from masonite arms, wooden dowels for pivots and linkage points, some gears for spacers and a couple metal parts as simple counterweights.
To calculate the forces involved we use the formula Torque = Force × Distance to fulcrum × sin ϑ. Since sin ϑ is 1 at 90 °, this reduces to Torque = Force x Distance. According to my calculations, our experimental system produces a 55% reduction in force, with a proportional increase in travel distance, as demonstrated in the video.
Click to Enlarge
I built several motors from the handy Make Magazine HowToons instructions from Issue #1. They’re easy to build and fun to watch. All that was required was some magnet wire from Radio Shack and a few permanent magnets. Todd Holoubeck was kind enough to lend me a few of the powerful magnets that he collects.
Here’s the two motors in action:
Click to Play Movie
Click to Play Movie
The prototype push charger is now complete. Starting where I left off on the disassembled remote-control car, I added a diode bridge between the wires coming from the gearhead motor and the battery compartment. The diode bridge ensures that the battery always receives the same polarity of current. Even if the push charger is being pulled backwards, voltage will always flow in the same direction.
Diode bridge:
Completed push charger, with diode bridge covered by insulating shrink-wrap:
Pushing sticks made from reused bamboo, attached to the push charger:
Leif, the local beast of burden, charges my batteries:
I started the power generation monorail project by trying out a quick LEGO prototype. First I created a conveyor system using their instructions:
It worked:
Continue reading ‘Monorail: Lego Prototyping’
For the kinetic energy project, I’m prototyping a human powered battery charging system. ITP has very long hallways, so I’d like to take harness the traffic up and down the halls to power projects. The end product is envisioned as a monorail tramway type of system. A handle dangles from the overhead tramway, and tugging that handle will pull the tram down the hall, charging a battery as it goes.
The initial prototype won’t be suspended. To quickly mock it up, I’m taking apart a remote control car, purchased at Goodwill, and turning it into a push-charger. The first job is to get access to the geared motor, figure out the wiring and hook it up to a multimeter to check the voltage and amperage generated.
Here’s the car:
And here’s the main body with the decorative casing removed:
The innards with all the radio electronics won’t be needed, so those are removed:
Continue reading ‘Car Charger Testing’
