Introduction

Yellow bird is a water-based interaction with a bird and Chinese lantern-inspired flower. Our project started with the question of how to get interaction into the air. We wanted to take advantage of the light weight of low tech materials and design a more ephemeral interaction. While taking our inspiration from things seen in the air, we also sought to appeal to elements found there, such as a bird soaring or a mobile twirling above. We hoped to use low-tech materials to manipulate aspects of the natural environment typically beyond reach, by simulating some of its properties. Yellow bird uses low tech materials to explore interaction with a bird and using water to manipulate plant growth.
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The Design

We directly used successful techniques adopted by others in our designs. In order to simulate plant growth and decay we created a double layer cage design using the technique of Jason Bruges's design for the Aerial Dynamics installation: creating a cage structure in white for the decayed state and puffed up red structure for the living state. Bruges's design uses a motor to spin the entire structure, but we wanted a low tech interaction and a more naturalistic mechanism. We used flexinol, a well-known substitute for motors and a material which returns to a pre-defined shape once voltage is applied. This method has been used by Jie Qi to simulate plant response in some of her projects. We also turned to some of Jie Qi's pop-up book designs to keep the pod self-contained, and so designed an ATTiny85 into the pod to control the pod's activation state in lieu of a Arduino microcontroller. This would allow our design to depart from computer control and to be run off a battery. The Makey-Makey inspired our design's use of alternative conductive materials to activate interaction. We incorporated water as a switch for our circuit: a person would pour water eliciting our system's response and a chirp from the bird. Our design uses a metaphorical birdbath as the most intuitive way of getting a bird to come down from the air and eliciting a response from it. Water ties the pod and bird response together as a basic material which would impact the responses of both plants and animals.

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Technical goals for our project included realization of low-tech techniques using flexinol to simulate naturalistic movement and miniaturization of circuit design as well as integrating water and gravitational pull into our interaction. Flexinol is a nickel-titanium alloy which can contract and move to a preset state when current is applied to it. Flexinol has been successfully used to contract against gravitational pull by Jie Qi in her animated vines design. We hoped to use flexinol to contract to preset curled state, and to then be counteracted by gravitational pull in its resting state. For miniaturization we selected the ATTiny85 20 mHz to replace an Arduino microcontroller. The ATTiny is well suited to low-overhead programming such as turning a circuit on or off and provides 5 pins for input and output. This functionality is all we needed to provide current to the flexinol and turn an LED on. Yet, these on/off states needed interactivity and we selected a material typically unseen in electronics: water, as a fun and underexplored way to manipulate a circuit.

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Challenges

Gravity turned out to be a more formidable challenge to flexinol than we anticipated. We used 0.05" diameter flexinol because it is less sensitive to timing of applied current than higher diameters. Because .05" flexinol has a pull force of .49 lbs. we looked for ways for the flexinol to take advantage of weak points along the pod structure and chose to use tissue rather other more structured papers. We were able to get the flexinol to work using a hinging mechanism so that the flexinol was attached at the base of a flower petal and the tip, and providing a hinge with a preset curl in the petal. We preset the flexinol's shape over an open flame, curling it into a spring. The spring form would help us to get the most linear pull out of the flexinol. Yet, when we finally constructed the full flower pod, our enclosure of the one petal with three others--painting a thin coat of Elmer's glue to the seams--overcame the flexinol's pulling force. We think this is because the glue structure was too much for the flexinol. We iterated again on several pod structures: accordian-style walls, origami folds to provide 'paper memory', thin-metal thread guides to the tissue to simulate a paper fold, doubling flexinol length per petal, etc. Ultimately, we abandoned the pod separating out the petals into a flower-like structure.

The ATTiny85, while a promising ATTinyBattery.jpgmicrocontroller alternative, proved volatile to program. Those experienced with the device confess that it is difficult to debug with no serial support, and often the successful admit their success remains a bit of a mystery to them. Ways to overcome some of the ATTiny's challenges include activating a verbose output in the Arduino IDE in order to identify communication between the computer and microcontroller when uploading a sketch. The printout will tell whether the correct device signature is sent and received, whether there is unsynchronized timing between devices, and whether or not you have robust connections to your desired device. The latter is extremely important for ATTiny programming. Success stories often wedge the connecting wires next to the pin in a single hole of the breadboard. The ATTiny requires you to turn your Arduino microcontroller into an in service programmer for the ATTiny. A20mHz devices are not robustly supported by the ATTiny hardware library, and it is better to stay in the 1-8 mHz range. 1 mHz is the default for programming the ATTiny, otherwise you will need to burn the bootloader when uploading the sketch. This disconnect in timing will impact the ability to program the ATTiny. For example, when we successfully uploaded the blink sketch to the ATTiny, there was no blinking. We chose not to rely on the ATTiny for our purpose because we did not fully uncover how to successfully program the device and get predictable results.

We were able to successfully incorporate water into our design, especially after raiding the kitchen. Plain water proved not to be conductive enough for our purposes, but we had great success with adding soy sauce, salt, and lemon juice to the mix. These additives enabled us to send an electrical signal through standing water, but the methods were not robust enough to allow us to use pouring water as a switch. Because the current through the pouring water was too low to complete the circuit, we needed a way to detect small shifts in the system. To solve this problem, we followed the design of the Makey-Makey by adding a voltage divider and used the moving average filter library for the sampled values provided through a tutorial. Rather than relying on the completion of the circuit to trigger our system, the voltage divider detects a change in voltage at the end of our twig to trigger our system. Voltage to V-out drops once water provides a conduit between the twig and the bowl (which is also part of our system). Because this measure alone proves too sensitive to minor atmospheric changes, we ran a moving average filter over the value so that the system is only triggered once the resistance has changed for a prolonged period of time.

IMG_20140323_183600.jpgConstruction & Future Work

Yellow Bird's construction offered many opportunities and challenges on its own. Most of our effort was concentrated on constructing the pod flower so that the circuitry did not touch. The four petal design afforded a natural hub for power, but also required careful construction to prevent shorts. We experimented with routing major inputs and outputs along the edges of the petals in a series, but required power made this approach impossible. Instead each petal is implemented in parallel, as is the LED. Insulation materials were included to prevent wires from touching each other at the hub, and power was run through the top of the pod flower while ground is run through the bottom.

Future work on Yellow Bird would include a review of literature on oribots, also known as origami robots. These creatures use flexinol and paper folds in order to amplify the slight movement of flexinol and to optimize its pull load. A future design would secure either an ATTiny 1 mHz or 8 mHz. These models are friendlier to the ATTiny library in Arduino.

GitHub:
https://github.com/sana-malik/Watering-Hole

Resources:
Thank you Noah & the Whale for 5 Years Time appearing in our video
Makey-Makey with an Arduino: http://blog.arduino.cc/2013/03/23/how-to-make-makey-makey/
Tutorials for ATTiny and using Flexinol: http://highlowtech.org
Play Melody on Arduino: http://www.arduino.cc/en/Tutorial/PlayMelody