Gordon Robertson
Project Goals
​This was an open-ended project for my DIY Design course. I decided I wanted to:
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Design a cooler for my desk-side table that keeps drinks cool
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Make the cooler appealing enough that I would want to purchase it
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Create a flyer for the cooler
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Be able to make the cooler
Moodboards
To start off, I wanted to map out my room, what I wanted to store, where I wanted to store it, and the major problem with a moodboard
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Then I used a moodboard to explore the general theme I wanted and other similar products
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Design and Assembly
The Cooler is made up of inch thick styrofoam walls that are cut to shape and glued together. The interior has 3D printer separators to keep the can/bottles from rolling around. It is cooled by a Peltier device that used thin aluminum walls on the side to the temperature uniform. The device is controlled by an Arduino board attached to a temperature sensor in the cooler. The three sub-assemblies and their purpose are as follows:
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Door Assembly - Function as the door.
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Peltier Assembly - House and spread the heating and cooling of the Peltier device, and attach the Peltier device to a heatsink.
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Air Assembly - Run air through the heatsink and keep the heatsink safe from being touched.
Cooler Design
Color - I was really going for an iceberg look of blue mixed with some white. So I opted to only paint the outside of the cooler and white for the add-ons.
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Visible Wiring - Since I was already ordering clear acrylic for the door and coaster, I decided to use it to cover the wiring and make my cooler look that much cooler.
Appearance Decisions
Design Decisions
Walls - To keep heat out of the cooler, I opted for inch thick styrofoam walls. Styrofoam is cheap, easy to shape, and a very good insulator.
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Internal Capacity - Since I knew how thick my walls were, I measured the size of bottles and cans and tried to maximize the amount of each I could fit.
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Sizing - Based on the above constraints and the size of my table, I figured out the optimal size for my cooler. Unfortunately, I could not find a pre-made Styrofoam cooler of that size so I had to design one from scratch.
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Securing Arms - These have slots for one-wrap velcro and secure to the table, preventing me from accidentally pushing against the door and breaking everything.
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Arduino Control System - To control the Peltier device, I wanted a simple solution. I found a guide for an Arduino thermostat that toggles an LED on/off based on a temperature sensor and decided to adapt that. Fortunately, an Arduino Nano can output up to 5V, so it could power the Peltier device.
Filled Cooler
Coaster and Button
Coaster - The coaster is a nice quality of life addition. I looked at first inserting it into the door but that took up too much space or would be awkward to remove, so I decided to put it under the cooler where I could easily pull it out.
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Button - The button serves as an easy way to turn the cooler on and off without unplugging it. I originally intended to use a traditional switch but that motion proves to be awkward and annoying
Mounted USB Power Bank - I wanted this device to be able to run even if I unplugged it. The power bank is located on the left side as that is the side that is closest to my computer so I could charge it easily.
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Wire Management - Because I wanted this to have a high level of polish, I decided that the wiring should be built into the design. To accomplish this, I cut channels in key parts of the design to map where the wires would go.
Mounted Power Bank
Door Design
Design Decisions
Sliding Motion - I tested multiple hand-motions for opening the door. Pulling forward, pulling around a hinge, and lifting all felt awkward. Sliding was the best one. I chose to have it slide to the left, between the table and my desk, so I wouldn't accidentally walk into it.
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Acrylic Backing Plate - The plate has a nub on the top that prevents it from sliding all the way out.
The Handle Without the Grip
Color Decision - When choosing which shade of blue I wanted to use, I used the door as a model because it has painted styrofoam, unpainted styrofoam, acrylic, and white 3D printed parts. If it looked good, it was likely that the rest of the cooler would as well.
Custom Grip - The handle itself is designed in such a way that I could mold clay around it to create a grip customized to my hand. I could then use this clay shape in a mold to create the actual plastic grip.
Peltier Assembly
Thermal Analysis
I did some back of the envelope estimation of the heat loss of the cooler to roughly find a suitable Peltier device and heatsink.
I estimated the room temperature to be 79F and the cooler temperature to be 43F.
Based on these calculations, I determined specs for the Peltier device and heatsink.
Peltier Device
ΔT = 40℃
Q = 10W
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Chosen Model - Custom Thermoelectric 07111-5P31-10CL
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Size - 30 x 30 x 3.9 mm
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Voltage - 4V
Current - 4A
Heatsink
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Q = 10W heat + 16W electric
R <= 0.75
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Chosen Model - PushPIN ATS heat sink
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Size - 45 x 45 x 25 mm
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Requires airflow
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Note: This heatsink is a bit too small to fully do the job but since it was cheap and water/soda doesn't spoil, I felt it was acceptable.
Thermal Design Decisions
Aluminum Wall In the Case - The aluminum walls were used because they are light, cheap, and conduct heat very easily. This lets the cooler maintain a more uniform temperature through conduction since a filled cooler will not have much space for convection. The thin walls let me bend it into shape by hand with the help of a jig.
Aluminum Heat-Spreader - The half-inch aluminum plates serve the spread the heat to the heatsink and the wall in the case. Because aluminum is easily machineable and lightweight, I can easily cut them from stock material and drill all the needed holes.
Air Assembly
Design Decisions
Purpose of the Cover - Because the heatsink could get relatively hot, around 110F, I wanted to add a cover so I don't bump into it and get a minor burn. I also needed to house a fan that blows air through he heatsink.
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Shape of the Cover - I wanted a more natural cover with slits for air intake. This part is the one I am the least happy with because I think it looks rather bulky.
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Airflow Direction - I wanted the hot air to flow to the left of the cooler because that area is an unused corner in my room. I didn't want it going up or down and heating my table or blowing where I walk
Internal View
Engineering Drawings
Bill of Materials and Cost
Off-the-Shelf Supplies
Raw Materials
General Supplies
Cost Breakdown
Assembly Guidelines
Acrylic - Cut Acrylic to size with a laser cutter.
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Aluminum - Machine and drill the aluminum parts
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PLA - Use FFF 3D printing to print the PLA parts, add supports as needed, and sand the final product for a nice finish
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Styrofoam - Use a knife to cut the Styrofoam to shape. Use a Dremel to form pockets in the Styrofoam. Fill any gaps with caulk to insulate.
Possible Flaws and Mitigation Strategies
Unfamiliarity with Peltier devices - While I know how they work in theory, I have never had hands-on experience with a Peltier device, this could present a problem.
To mitigate this, I made sure the Peltier device could work with Arduino and could over-perform if needed.
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Unfamiliarity with working with Styrofoam - I do not have much experience working with styrofoam and might have made some erroneous assumptions when I designed the Styrofoam parts.
To mitigate this, I order the caulk and found a Styrofoam vendor that sold extra. Additionally, all precision parts held in the Styrofoam, like the Arduino, is embedded in a PLA structure that I simply have to glue to the Styrofoam. The wire routing does not have to be particularly precise for the cooler to functions. Assuming the styrofoam does not buckle, which is unlikely given how thick the weight-bearing elements are, the styrofoam should be able to support everything.
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Rusty with Arduino - While I have programmed an Arduino, it has been a while and so that could cause complications as I use the Nano as the control system.
To mitigate this, I found a guide for making a basic on/off control system with an Arduino and the RHTO3 temperature sensor.
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Insufficient Cooling - The thermal analysis I performed for the cooler made numerous large assumptions and used a simplified view of the cooler. Additionally, the heatsink chosen does not meet the specifications for the cooler.
To mitigate this, I designed the cooler to store water/soda, which is still potable at room temperature, it just isn't as refreshing.
Time Estimate
Based on the complexity of the parts, the needed 3D printing time, the likelihood of failures, and not having built one of these before, I estimated the following build-time for a single prototype.
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Optimistic - 5 days
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Conservative - 2 weeks
Final Thoughts
This project was a lot of fun, even when it started to consume my life.
Taking lessons I've learned from multiple courses and applying them with a high level of polish is really rewarding.
One day, I hope to build this because it would be really cool, especially if I use a good heatsink.