Steve redesigned the interactive component of the Movable Party machine. This time, Steve made the the Max interface function like a sequencer. The rider can use the hub motor sensor (RPM) to advance through a sequence of preset patterns while varying the BPM and and pitch. Enjoy.
In this workshop, Josef Taylor, structural engineer of Buro Happold, LLC, took us through the steps of using a hub motor on a bicycle to generate power, while explaining the laws of physics related to electricity. We compared the resultant voltage generated while using various levels of resistance in the circuit.
Movable Party 1.0 // Workshop 2: Sensors, Arduino, & Interactive Media
#MovableParty Workshop 2 was about the design of an interactive system. We placed sensors of various types on the handlebars of one of the bikes with a hub motor. Our workshop leader Steven Kemper mapped the pressure sensor data through Max MSP to demonstrate different effects (parameters of low-pass filter) on a song. The Hall Effect sensor was used to set the tempo of the audio playback. Jack Moreau is our DJ on the handlebars for this round! This workshop took place at Occidental College’s Brown LearnLab. Participants included students from Occidental College and members of The Bike Oven.
We’ve just received many of the parts for the generator, and will test them out this week! Suddenly all of the planning and fund-raising and cogitating is going to be attached to a couple of bikes with power cables coming out of them. This is a big step, so I suppose it’s time to update everybody on how this thing is going to work.
We bought our motors from ebikes.ca in Vancouver BC. There are more local options, but these come highly recommended, and there is a wealth of information and support at their website. The motors are “brushless DC motors,” which is a bit of a misnomer, as the motor itself runs on (or outputs) three phase AC. In a motor application, that AC comes from a motor controller which converts 12V DC into a variable frequency, variable voltage power signal according to the desired speed and power. Since we’re using the motors backward, taking power out instead of putting it in, we’ll need to make sense of that 3 phase AC.
The motors come in three different windings, from 6 turns to 8 turns. This is equivalent to using gears of different sizes on your bike; if you supply a given voltage, the 6 turn motor turns faster than the 8 turn motor, but with less torque. What this means to us is that the 8 turn motor will supply our target of 14V at a lower speed, meaning that we can use the low gears we’ll need for hauling cargo. However, it might be too much, and we’ll have to use super low gears to keep our voltage low. We ordered a 7 and an 8 turn motor, and we’ll figure out which one we need once we have the bike in the trainer and a load attached.
A rectifier takes the alternating output of a motor and converts both the positive and negative peaks into positive current, effectively flipping all the troughs into peaks. It works by feeding the alternating current through an arrangement of diodes (which only allow current in one direction, like a check-valve). Ours are packaged in neat little boxes with spade terminals and a must be mounted on a heat sink; the diodes don’t put out a lot of heat, but it’s enough to damage them if they can’t dissipate it.
We’re using the element from a ceramic space heater as a load. This is basically a big resistor; current has to pass through a series of special ceramic blocks that are poor electrical conductors. These heat up, normally to heat the air blown through them. This element is unfortunately a bit too strong, with a resistance of 180 ohms, but since there two elements, we can connect them in parallel, cutting that resistance down to 90 ohms. If I’d been able to find a traditional coil element, we could clamp on anywhere along the coil to adjust the resistance.
For a more visible effect, we picked up three 100Watt light bulbs. These have a resistance of 144ohms apiece, but connected in parallel we’ll get 48 ohms, which is a pretty reasonable load to power.
One of the toys we received is the Watt’s Up meter. This little guy connects in line with our power, allowing us to see just how much power, in volts, amps, and watts (just so you don’t have to compute the product). This means we can finally get a good idea of what a person puts out on our system! This is really exciting.
Alright, see you at the workshop!
How many times have you gone to a charge station at an airport only to find that all the plugs are being used? Have many conversations not mediated by a cell phone or other mobile computing devices have you witnessed in public spaces lately? It’s true that people don’t engage with one another in an embodied, face-to-face anymore. But sometimes people come into physical proximity when they need something – electricity. They crowd around charge stations or sit awkwardly in spaces around electrical outlets in order to gain access to electricity.
A group of students – Judy Toretti, Jacob Brancasi, Maria Lamadrid, and Cory Bloor – at Art Center College of Design recognized this social pattern and took it to heart in their design of an interactive media system for a homeless youth organization called Jovenes in east LA. Working with the youth participants, the student designers came up with Conversation Space, an interactive cellphone charging booth that requires at least two individuals to step on a foot pedal in order to activate electrical current. The design calls for a coordinated effort on the part of the users. To achieve the common goal of charging cell phones (and other handheld devices critical to the lifeline of homeless youth), users must engage in a face-to-face social interaction. It could be as much as a conversation, as little as a nod, an eye contact, or a chin-up.
The design of Movable Party is meant to accomplish something similar. Like the foot pedal charging booth, our system attempts to transform people’s interactions by redirecting the flow of electricity. We don’t mean this in a strictly physical sense [don’t ask me explain the physics behind the flow of electrons, ask Joe.] What I’m referring to is a design that yields particular desirable social sequences. This design challenges power consumption, a behavioral norm in most public and urban spaces in this country, and shifts our normative relationship to electrical power from consumptive to generative.
Our efforts aim at creating opportunities to generate, instead of compulsively consuming, power. Pedaling is an exciting, eco-friendly, and embodied practice. At an advocacy event like Ciclavia, collective cycling can instantiate the power of human-scale transportation. Moreoever, pedaling comes with a direct consequence of powering a musical performance within our system. This is a participatory event that involves lots of agents including the cyclists on the generator, DJs who will be spinning records, and bystanders and passersby who may be dancing to the music. The embedded sensors and Arduino microcontrollers will interface the system to fine-tune the interactivity among all the participants.
Through a system that re-routes the flow of energy, we hope to articulate the generative impact of pedaling, a goal that involves the translation of the significance of electricity from the physical into the social and symbolic domain. We want people to congregate in a public space. We want them to realize that the outcome of the event – a musical performance – is contingent upon a collaborative process of generating power.
We can’t take electricity for granted. Electricity is not just a physical resource; it is also a kind of social resource that can be harnessed to bring people together. Electricity can be used to power communication that happens in mediated platforms. But we know that already. We hope on at the Ciclavia event on April 21, we will start to see how electrical power plays a critical role in igniting positive and communal social interactions.
* * *
Incidentally, at the airport before my flight took off from LAX, I went looking for an electrical outlet to charge my laptop.
I shared an electrical outlet in the airport terminal with a lady who struck up a friendly conversation with me. “Is that plug available?”
I said, “of course!”
She and I exchanged stories about the overwhelming presence of mediated communication in our society today. She told me that she just saw a mother and her young son of eight or nine years of age dining somewhere. The mother was on the phone the entire time. The son was left to entertain himself.
“Isn’t that ridiculous that we are so dependent on these devices? What did people use to do before cell phones? I guess they talked to people around them,” she remarked.
I said, “It’s funny that we’re talking about this. I’m working on a project that involves the building of a bike generator to power a music event.” I told her the rest of the project.
A few minutes later, with my laptop charged at 84 percent, I disengaged from the electrical outlet and packed up my gear.
Before I scurried off to board my flight, she smiled and said, “good luck with your project!”
Thank you, lady, whoever you are, for your kind reinforcement of the meaning of our project.
My first human power project, the Seattle Bicycle Music Festival in 2010, was an amazing success. This, in large part, is why I want I’m so excited to put on another show! We built our own generator, inspired by Rock The Bike‘s Biker Bar (which has since been discontinued for reasons I will discuss later). Like the Biker Bar, our generator used a single generator coupled to the bikes by a long tire driven shaft. Like the Biker Bar, our generator folded in half to become an 8 foot long trailer. Unlike the Biker Bar, however, our shaft folded too, allowing us to squeeze five bikes onto the contraption, instead of three! A 90amp VW Bus alternator, with it’s own voltage regulation circuitry built in, converted those pedaler’s work to clean 12V, variable current DC. The volunteer cyclists were able to power all the acts, including quite a loud rock band who brought along three tube amplifiers! We had our share problems though, and I learned a great deal.
The bikes should be on display
One of the best parts of the bike powered concert is that the folks powering the concert are right next to the band, facing the audience. They’re on display. The audience knows that this is part of they act, and it’s their turn next! With a system like this, the volunteers are close enough to have a conversation with each-other. This, I think, kept people coming back to the bikes more than anything else.
for all it’s simplicity, The common-shaft approach has a major downfall in the form of mechanical losses; the tires contacting the shaft, the support bearings, the flexible shaft couplers, all of these are big energy sinks, which is why Rock the Bike has stopped building their Biker Bar system, and why Movable Parts is using a different system.
We made the mistake of taking our shaft bearings from the cheapest skateboards we could find ($25 apiece). Within an hour of use, the loose ball bearings inside had burned up all their lubrication and had moved on to burning up the polyurethane wheels:
The wheels rapidly conformed to the shape of the shaft and stopped spinning, polishing the shaft nicely and sprinkling shredded polyurethane all over the generator floor:
The above photographer was sent on a mission to a nearby skateshop (which kindly opened an hour early) for 20 high quality skateboard wheels and bearings (which cost about as much as five complete $25 skateboards), and the show went on.
Home