Introduction

We created an interactive art piece that functions as a fountain while making a statement about sustainable agriculture. Our fountain consists of three terraces growing edible plants watered by three pumps, which take water out of a lower basin. An IR distance sensor will track the distance between a person and the fountain and increase the flow of water the closer the person comes.

Although water will fall through the soil and back into the basin, if people stay too close for too long, the basin will dry up and the soil will become over-saturated with water. This outcome is evocative of natural disasters such as the drought in California, which is being exacerbated by the wastefulness of the agriculture industry. But if people step back and let the system return to its natural state, water will leak through the soil and refill the basin, allowing them to begin watering again, perhaps this time responsibly.

Our fountain is a “one-in-one-out” system; the input is distance between a person and the fountain , and the output is a flow of water. Since the water does not affect the IR distance sensor’s tracking, the system strictly converts physical position into flow of water.

Video

Technical Notes

We decided to use a minimal, tiered design constructed from transparent acrylic plexiglass as the form for our fountain. The structure was first sketched in 3D using Rhinoceros, then tweaked with final modifications, and then modeled to the exact dimensions needed. To ensure our sensors and hardware would fit snugly, calipers were used to obtain precise dimensions of all these parts. The thickness of the chosen piece of acrylic was also taken into account so that snug, secure joints could be designed. This ensured structural stability in the final piece. Once the design was finalized with all the proper dimensions, the parts were unrolled into a 2D vector image for laser cutting.

Trial and error was used to obtain the proper power settings for the laser cutter on our acrylic plexiglass, and once the proper settings of 10% speed, 100% power, and a frequency of 5000hz were determined, the pieces for our model were cut. 

The fountain’s structure was assembled using hot glue as an adhesive both for its usefulness as a sealant as well as its strength and ease of use. Finally the plants, hardware, and circuitry were added, completing the design. 

In order to achieve control of the motor speed in the pumps from the output from an IR distance sensor, a couple components had to be used. The IR distance sensor only outputs approximately 0-3v, so first we needed to amplify this voltage to 0-5v using a simple non-inverting op-amp circuit. This circuit multiplies the output from the IR sensor by 1.84, which we found through experimentation was the amplification needed to change the 0-3v output into the usable 0-5v control voltage for a PWM timer module. The timer module is used to create a 5v PWM signal of varying duty cycles (low duty cycle for 0v control voltage and higher as the control voltage approaches 5v). An LED is attached to the output of this module in order to be able to easily observe when this section of the circuit is working and the PWM duty cycle is changing with regards to the distance from the IR sensor. This PWM signal is used to drive a motor driver, which will take that 5v PWM signal and amplify it to an 11.1 v signal, then use that to drive the motors. Thus the motor appears slow when the bursts of power are shorter and less frequent and appears fast when the bursts of power are longer and more frequent (definition of PWM motor control).

In order to power the circuit off grid, two 3.7 Li-On batteries with attached step-up regulators provide the 6v and -6v needed to drive the op-amp and provide power to the IR sensor. For powering the motors, an 11.1 v Li-On battery is used. All of these batteries are connected through switches to make it easy for anyone to run our device.

Photos

Circuit Diagram

Fountain and Circuit

Fountain

Circuit

Switches