Senior Capstone Design Project at the University of Colorado Boulder
August 2015 - May 2016
My senior design team right after winning the People's Choice Award at the Spring 2016
Senior Design Expo.
Back row, from left to right: Systems Engineer Andriy Wybaczynsky,
Test Engineer Alex Enright, Financial Manager Sawyer Bluhm, Advisor/Director Stefan Berkower,
CAD Engineer Zachary Ott. Front row, from left to right: Communications Director Victoria
Danner, Project Manager Catherine Villa, Test Engineer Hannah Hall, Manufacturing Engineer Ashley
Zimmerer, Systems Engineer Alex Karpilow.
All undergraduate Mechanical Engineering students complete a
Project prior to graduating. Teams of five or more ME students work for two semesters on an
industry sponsored project for the sponsoring client.
Interactive Model Greenhouse Senior Design Project
My team of eight other ME students and I worked on a project for Surna, a local Boulder
start-up that makes agricultural technology. Surna needed a model of their 'hybrid' greenhouse,
a large-scale smart greenhouse that combined the best aspects of indoor and outdoor
agriculture. They wanted to take a interactive model of the product to tradeshows around the
country to demonstrate its functionality to potential customers. My team worked closely with
Surna to determine which aspects of their greenhouse to model.
As the Manufacturing Engineer for my team, I was responsible for reviewing our designs for
manufacturability, scheduling shop time, and ensuring that our manufacturing schedule stayed
on track. I also took responsibility for the complete design of the model's electro-mechanical
blackout curtain system.
We designed the model in two halves so it could be opened for people to get a closer look at
the different systems. My team and I built a cardboard model of our initial design so we
could visualize where all the systems would go. We presented this model to Surna to get
I built a simple prototype of the curtain system as a proof-of-concept. I thought that
the curtain could be held up by a series of 'curtain rods' to prevent it from sagging
in the middle. These rods would slide along a closed track as the curtain opened and
My blackout curtain system was composed of two identical curtains each opened and closed
by its own stepper motor. This diagram shows my concept of the different parts making up
the electro-mechanical curtain. Each motor would rotate a shaft fitted with drive pulleys.
A loop of cable would wrap around the drive pulleys and corresponding free-spinning pulleys
on the opposite side of the model. The loop would be fixed to the leading 'curtain rod',
pulling the curtain open or closed depending on the direction of the motor.
In my final design for the blackout curtain, I used a ball chain and chain sprockets
like those used on a roller curtain to pull the curtain. Rather than a closed track, the
'curtain rods' hang from rails by small metal loops, to eliminate the risk of binding if
the curtain slid at an angle.
The curtain was mounted in the hallways adjacent to the floor of the greenhouse, to
minimize shadows cast by the hardware.
I designed a customized ball chain sprocket for the curtain system. A set screw
secured each sprocket to the rotating shafts. The ball shaped depressions fit
the ball chain perfectly, so the risk of the chain slipping or getting stuck is
minimal. The final parts were 3D printed and are easy to replace, should the
metal chain wear down the plastic over time.
I designed special plates to secure the stepper motors to the floors of the hallway.
The motor bolts to the plate, and the plate bolts to the floor.
This is part of the drawing I used to manufacture the motor mounting plates.
I made one plate for each motor. I manufactured them at the same time, stacking
the aluminum plate and using a CNC mill to cut them out.
I used a motor driver board with each of the stepper motors. I tested
each motor on a breadboard with simple code.
I uploaded the test code to control the motors to an Arduino-like board.
Once the motors behaved as intended, I hooked them up to the custom board
we used in the model.
I integrated the curtain system with the rest of the greenhouse to test
the functionality of the code. This also allowed me to determine how many
steps each motor should take so they would stop when the leading edges of
curtains contacted the walls.
The model worked beautifully. When the 'sun' reaches a certain position,
representing how many hours of light the greenhouse receives, the control
system closes the curtain. Users can also operate all systems independently,
including the curtain. The model greenhouse won the People's Choice award for
excellence in design at our Senior Design Expo. Surna was impressed with the
quality and interactivity of the model, and planned to begin showing it at
tradeshows soon after.
The model curtain works exactly as designed.
Created by Ashley Zimmerer