Poinsetta Greenhouse Device

Euphorbia pulcherrima, or the poinsettia is a popular flower often associated with Christmas. The University of Idaho's Plant and Soil Science club annually grows poinsettias to sell as a fundraiser around the holidays. These poinsettias are located in the Sixth Street Greenhouse complex on the University of Idaho campus.

Problem Definition
Our main goal is to design a covering system that autonomously encloses the poinsettias with black cloth to block out all nighttime artificial light.

Background:
Poinsettias are very sensitive to changes in their photoperiod. This means that they require a specific period of darkness every day to flower properly, 14 hours is preferable. In nature this isn't a problem because any light up to that of a full moon won't affect its photoperiod. The Sixth Street Greenhouse, however, has streetlamps as well as internal lighting that invades the room where the poinsettias are stored. For this reason, the students involved in the Plant/Soils Science Club have had to manually cover and uncover the poinsettias every day.

Design Goals and Deliverables
1. The system must have minimal human interaction.
 * The system must have at minimum a push button control to retract and extend the cover.
 * Ideally, the system would be integrated into the greenhouse's control program, Argus, and would run on a timer.

2. Plants have to be covered in a manner that shields them from a specified number of lumens (less than that of a full moon) from dusk until dawn.
 * The sides, ends, and undersides of the benches must be covered during the night to minimize light exposure.
 * Blackcloth, or some similar material must be used in order to insure there is no light penetrating through the covering.

3. Ventilation and watering cannot be hindered by the apparatus.
 * Watering is as important as covering the plants at night and the apparatus we make cannot make it more difficult to handle and water the plants.
 * Fungus and disease is a concern for the enclosed area, so the cover has to provide adequate ventilation during the day to prevent growth of any undesirables.

4. The budget is restricted to $3,000 and the system needs to be designed accordingly.
 * We are tasked with designing and constructing a device that is not only robust, but also affordable and able to be replicated.

5. The system needs to have minimal impact on daytime light (cannot shade the plants from natural light during the day).
 * Our system cannot interfere with the normal daylight, the light the plant receives during the day is as important as the lack of light at night.

Bench
The benches are what were existing in the greenhouse prior to us starting the project. We decided to design a modular system that covers each bench individually (5 benches in each greenhouse room). The bench layout requires the tops of the benches to be able to roll from side to side. This accessibility feature is the driving motivation to build a modular system.

Hoops
We had several options when it came to cover design. We researched many different current designs for systems similar to ours. The biggest advantage to having a semicircular hoop design is that the ends of the benches can be covered with the top and sides simultaneously. At this point in the design stage we are trying to figure out how and were to stage the black cloth roll.

Motor
We have many options when it comes to motors. One design question that needs to be answered is if the motor needs to be able to turn both directions. One of the most important aspects of the motor for our situation is the torque. For our system it won't matter if it takes the cover several minutes to retract/close. There fore we are looking at geared ac motors with high torque to speed ratios. (Also, having ac motors will enable us to implement a design that requires bi-directional control)