This was a 6 week project created for the Spring 2012 Things That Think course at the University of Colorado at Boulder.
Our project is an autonomous Sunflower. As in nature, the highest priority for our flower is sunlight, necessary for photosynthesis. Our Arduino controlled sunflower is constructed using 3D printing and laser cutting technologies. Primarily, our flower finds and follows the brightest source of light. This flower is different than your typical sunflower, because when a person comes close enough, the flower moves its petals to acknowledge their presence. We were able to utilize Shape Memory Alloy (SMA), in the form of a nickel/titanium alloy (Nitinol), to facilitate the opening and closing of the flower's petals. Our goal was to combine technology with a green initiative to create a truly interactive plant.
Here's a link to a short video of the sunflower in action!
Step 1: Prototyping
Prototyping is a very important step in any project. Since our main goal of this project was to have the sunflower find and follow a light source, our first prototype was a simple single axis light finding machine. This prototype consists of a seesaw like apparatus with a photoresistor on each end of the see saw. We use a stepper motor to angle the seesaw towards the brightest source of light. This is a simple mechanism where the goal is to get the two photoresistors to have the same value. The motor will pull the seesaw from the end where the photoresistor has the higher value (more light), and stop when the sensor values are within an allowable range of each other. In order to make sure the motors did not continue to pull past the limit of the seesaw mechanism, we used small momentary switches that we'll call "limit switches". We programmed the Arduino so that the motors would not turn in a given direction if the limit had been reached.
We used a simple motor driver circuit with an SN754410 H-Bridge to run the motor in this prototype. The motor was powered by a 6-volt lantern battery.
Here's a video of the prototype in action: