Poinsetta Greenhouse Device

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Team Name Poinsettia Paradox
Duration Fall 2015 - Spring 2016
Faculty Advisers
  • Shawn Trimble
  • Daniel Flick
  • Andrew Brackebusch
  • Tyler Hutten
  • Jackson Stipe

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.


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[edit]

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[edit]

Design Spec Matrix

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 Ideas and Concepts[edit]

Design Decision[edit]

  • 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.

  • Current Design[edit]

    Design Components
    Image Summary
    2015 PGD Assembly1.PNG

    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.

    2015 PGD Motor Under Table.PNG

    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. We manufactured our own hoops using electrical conduit and a jig we constructed out of particle board. The advantage to making our own is the fact that the hoops can be made cheaply and effectively by whover trys to replicate our design.

    2015 PGD Blackout Cloth.png

    The cover is a blackout cloth made specifically to block light from reaching plants. The cloth we are currently using in our prototype is an old cloth that the client has given us.

    2015 PGD Garage Door Motor.JPG
    Garage Door Motor

    For the sake of reproducibility we chose to use a garage door motor for the electric driver of the system. We chose a ½ hp craftsman garage door motor. The intent is that if and when the plant and soil science club want to make another unit the parts are easy to find, order, and set up. The other incentive to using the garage door motor is that it already is set up to run both directions for opening and closing.

    2015 PGD Spring Arm.png
    Spring Arm

    Spring Arm- The spring arm is an arm with a torsional spring around the base. The spring arm provides the torque necessary to pull the tarp over the hoops when the flowers are covered. These spring arms can be purchased from companies that make tarp covers for dump trucks and modified for our use.

    2015 PGD North Side Assembly.JPG
    Accordion Ends

    One problem that arose from using a hemispherical covering system was how to close the ends. The current design will implement an “accordion end” which somewhat resembles a folding fan. When the tarp is closed, the ends will fan out (with cloth in between each rib) to cover the ends. When the tars is open the ends will be folded up at the edge of the table.

    2015 PGD Hoop Mount.JPG
    Table Mounts

    The table mounts connect the hoops to the table. The hoops fit into the square tubing and can easily slide in and out. Generic mounting plates are welded to the bottom of the square tubing and carriage bolts with wing nuts secure the mounts to the table.

    2015 PGD Roller Bearing.JPG

    The roll will be used to store the black cloth during the daytime (cover is open). Since the benches are 21 feet long we needed a material that was strong enough to hold the black cloth but not deflect across the span of the bench. We found 6061 schedule 40 aluminum pipe to be sufficient for the roll. The roll ends (which fit in the bearings and will also hold the sprocket hub) are machined out of 6061 aluminum as well.

    Team Members[edit]

    Picture Bio Discipline
    2015 PGD Daniel.jpg
    Daniel Flick:
         I am a senior in ag. engineering at the U of I. Having grown up on a family owned ranch/farm
    in Gooding, Idaho I have been involved in agriculture my entire life. I have a passion for
    agriculture and energy efficiency and aspire to be involved in ag machinery design or irrigation
    system design. I am a part of the Industrial assessment center at U of I and plan to implement the
    things I have learned there to wherever my career in engineering takes me. My goal as an ag engineer
    is to make agriculturalist's jobs easier and more efficient through the advancement of technology.
    Some of my hobbies include; hunting, fishing, playing guitar, water skiing, and downhill skiing. 
    2015 PGD Andrew.png
    Andrew Brackebusch:
        I’m a Senior Mechanical Engineer at the University of Idaho. I am from Wallace
    Idaho where I enjoy everything the outdoors has to offer. My interests include machine 
    component design and thermal systems. I have completed an internship with Hecla Mining
    Company and have been a Wildland Fire Fighter for the past three summers. 
    2015 PGD Tyler.jpg
    Tyler Hutten:
        All set to obtain my Bachelor of Science degree in Mechanical Engineering this spring,
    I hope to someday pursue my dream career of working in the sustainable and renewable energy
    industry to make the world a greener place to live. I enjoy the time I spends in the Sound
    of Idaho Vandal Marching Band, and I attend as many School of Music events as I can. My
    personal hobbies include music, swimming, bicycling, cooking, and CAD drafting followed
    up by 3D printing. 
    2015 PGD Jackson.jpg
    Jackson Stipe:
        I live in Ontario Oregon and am a senior at the University of Idaho. My plan is to 
    graduate with a degree in Agricultural Engineering and I plan to get a job involved in
    the design of irrigation systems for increased crop production. My hobbies include spending
    time in the great outdoors and winter sports.


    Glossary of terms[edit]

    Design Documents[edit]


    External Links[edit]