Poinsetta Greenhouse Device

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

Background:
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
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.

Design Decision
 Spring arm vs. Chain Drive Initially we had a decision between using a spring arm and a chain drive to open and close the covering system. The advantage to using the chain drive was that there would be no danger of having the spring fail, or having a "mousetrap" scenario. However, using the chain drive presented problems including; increased ares of danger (pinching and rolling points), increased mechanical complexity (harder to replicate), and higher cost of components. Therefore, we chose to implement the spring arm design. The spring arm can be ordered from any truck tarp company amking it easy to procure. Also, the assembly of the components is straight forward and will be easily reproducible.Lastly, the spring arm is less likely to cause injury. 