Introduction: Personal Air Conditioner

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In an earlier Instructable, RCLifeOn presented a “DIY Mini Air Conditioner”. This was a project I built. However after construction, I found I needed greater cooling capacity, and the small milk carton cap output of the earlier Instructable was not adequate for my needs. Although, the single milk carton air conditioner was not quite sufficient for my requirements, the concept was outstanding.

I wanted to be able to easily add additional ice. However, the original Instructable required that ice be added through the milk carton cap, which was, to me, a bit restrictive, as I found it necessary to periodically recharge the air conditioner with ice. Thus, easy access to, and easy water removal from, the ice compartment were added to my design goals. Since the air conditioner used water in the form of melting ice and its fan ran on mains electricity, an additional goal was to minimize or eliminate the chance that water might get to the fan.

So, I extended RCLifeOn's original concept, and developed this improved version. As it turned out, the timing could not have been better, as one of our home air conditioner's was having problems, and we did not know how long it would take to repair.

This personal air conditioner will allow me to continue working at my desk while staying cool, regardless of any home air conditioning problems, and it will never need a compressor replacement :->). What more could anyone ask from an air conditioner.

Step 1: Required Items

The required items are:

- A fan (these come in a variety of sizes). For example, they can easily be found in 20mm to 80mm sizes, and are available in larger and smaller ones as well. You need to measure the size of your milk container. Mine allowed me to install an 80mm fan for this project. Other containers for milk may be larger or smaller, but 80mm seems to be a fairly common size.

- A wall adapter. I used an 80mm x 10 mm fan requiring 5v DC, so I used a “wall wart”/wall adapter providing 5v DC output.

- A female plug adapter 2.1mm x 5.5mm to connect the fan wires to.

- A glue gun and glue

- Two milk containers. I used ones from almond milk

- An X-acto blade, or scalpel, and scissors. Anything that will allow you to cut through the cardboard milk cartons are made of.

That’s it, and as you see only a small number of items are required. The likelihood is high that you already have most of these items in your workroom and refrigerator. Although you may have to obtain an 80mm fan. All items, except the milk cartons are readily available on eBay, Banggood, etc. Obviously, milk cartons, if you do not already have them, are available at your local grocery store or Walmart.

Step 2: How It Works

The idea is simple. Two milk cartons are stacked on one another and a pass through opening, i.e., two openings are cut in the top carton, to allow the air from a fan mounted on the top carton to pass through to the lower container The second carton has an opening to allow the air from the fan to pass over ice cubes before it is output, and thus the output is cool air.

Unlike a typical fan, the air is not just moved around but cooled. To quote from the original Instructable by RCLifeOn “An air conditioner works by pulling hot air inside a container, cool it down and then push the cold air out. This is the main difference from an ordinary fan that simply moves air, instead of cooling it down.”

This Instructable uses the same basic principle as the original one, but allows for a larger cooled air output, and has a larger opening to add ice to the air conditioner. As can be seen from the attached pictures, the top container could be reduced in length to be only slightly longer than the cooling fan's air output "tunnel". However, leaving this carton full-size aids stability, and so the length of the top container was not shortened.

The attached illustration should help clarify how it works.

Step 3: Cutting the Top Milk Carton

I used a X-Acto blade (a box cutter should also work) and scissors in combination to make the cuts in the cartons. The fan should be placed against the top of the top carton to use as a template and the top cut to match the fan (this opening will later be where the fan is glued). The bottom of that same carton needs to also be cut to provide a through opening for the output of the fan. However, before cutting the top container, measure the length of the milk container from top to bottom, this length is important. This second cut should be as long as the length of the milk container, as the cardboard cut will run the full length of the opening in the top carton to insure the 'wind tunnel' is well sealed and does not 'leak' into the top container. That is, I "sealed" the upper "wind tunnel" to insure that none of the air from the fan went anywhere but to the lower container. After the two cuts were made I used wide, clear plastic tape to insure the “tunnel” did not leak into the remainder of the top carton. The cuts do not have to be exact, only functional.

Step 4: Cutting the Bottom Milk Carton

The milk cartons have two approximately 30 degree angles where one of the tilted sides contains the milk container cap. Before cutting be sure the cap on this side is facing down, i.e., is on the side facing the desk, workbench, or table on which you will be making the cut. Now cutout as much of the slanted side opposite the cap as possible. This will become the output opening for the air conditioner, and thus this cut need not be exactly measured but it should be quite wide.

The bottom milk carton mates with the top one, and so the bottom cutout from the top container will mate with a similar cutout in the bottom one. You can easily use a ruler to take these measurements. As with earlier cuts, these need not be exact but only functional. You can use the glue gun to seal any potential air "leaks".

Step 5: The Fan

As can be seen in the attached photos fans come in a variety of sizes. Here we will be using an 80mm fan. The size fan you use will depend on the size of milk cartons you are using for this project. The fan I used had wires connected to a plastic female connector. I cut these wire and connected them to a female plug adapter, 2.1mm x 5.5mm. Before connecting the wires to the female adapter be sure you double check the polarity. Fortunately, it is marked on the outside of the connector, as can be seen in the photograph. The '+' connection should go to the center of the adapter and to the red wire of the fan.

I used the glue gun to firmly connect the fan to the top milk container. After attachment of the fan to the top milk container, I went around the fan with the glue gun to insure that no air from the fan could escape from its designed path.

Step 6: Abrading the Surfaces to Be Glued

Both the top and bottom cartons, as is to be expected of milk containers, are waxed. This is super for the ice compartment, but not good where the two cartons are to be joined. The surfaces where they will be glued together should first be abraded (i.e., some of the wax removed) before joining, to allow a secure attachment. This is probably best done with an X-acto blade, box cutter, scapel, or knife. The attached pictures show the surfaces after they have been abraded, but before gluing.

Step 7: Joining the Two Cartons

As can be seen in the attached photograph, the two cartons are joined at opposite ends. This is to allow unobstructed access for the air conditioner's output, and to also provide access to the bottom cap which allows easy drainage should water accumulate, if the ice does not vaporize completely when the air conditioner is run. It also allows for easy ingress to the bottom container to add ice as needed.

The design here allows the bottom container to be filled halfway full of ice without blocking the output area, and avoids any possibility of getting water on the fan. After abrading as required, I joined the cartons with the glue from a hot glue gun. The top container holding the fan is relatively far from the melting ice, so the goal of minimizing or eliminating the possibility of water getting to the fan was met by this arrangement.

Step 8: Using the Final Assembly

I connected the female adapter plug to a 5v wall adapter and added ice to the lower compartment (lower milk container). Upon plugging it in I obtained cold air out. That is, a working air conditioner. After you use the air conditioner and the ice melts, it is possible you will have a small quantity of water in the lower compartment. Fortunately, the cap of the lower milk container can be unscrewed to allow this water to drain. Please remember this is a personal air conditioner. It will not cool a whole room. However, if after building it you decide you would like more output, just use a fan with a huskier motor. The fan I used only requires 0.3 Amps so a fan requiring more current would likely provide more air output, and there are many of these readily available.

The attached pictures show that with the air conditioner working, the temperature at the intake is 74 degrees Fahrenheit, but at the output of the air conditioner it is 64 degrees Fahrenheit. This is a significant drop of 10 degrees Fahrenheit. These pictures were taken in one of the cooler locations in our home, perhaps with higher ambient temperatures, the difference would be even greater?

One of the photographs above shows how ice cubes are used, and the size of the opening where ice cubes can be added.

Step 9: Afterward

Congratulations, if you followed the steps above you now have your own personal portable air conditioner. Since the fan is 5v, this air conditioner could be run from a USB computer port or USB wall adapter.

If the 5v fan used here is changed to 12v, this air conditional should work in a car. Which might be great if your vehicle does not have air conditioning, or you have air but it is temporarily not working. That is, in an emergency, this concept could be used to build a personal automobile air conditioner.

In a follow-on project, I added a speed control offering a three speed option for this air conditioner, using an Arduino UNO. You may just want to add the speed control yourself as its relatively easy to do using the buttons on an LCD shield.

This clearly is a commercial product waiting to be manufactured. In a manufactured product the milk containers would be replaced with hard plastic containers, and the top box would be shortened to match the size of the “wind tunnel” needed for the fan, while still maintaining stability. If purpose made, the fan would be “beefed-up”, while still allowing the whole assembly to be smaller and still lightweight. With a “beefed-up” fan the cool air output would be even greater than it is here, which is already substantial. If you would like to manufacture this product, or know of a manufacturer that already has a commercial version, please contact me. I would just be interested in knowing, as I am not seeking any monetary gain. If this does become a manufactured product, this would be the reverse of how things often happen, i.e., we usually see how we can approach a commercial product with our own inexpensive clone. Fortunately, this Instructable already allows an effective and successful product to be constructed, and at a very low cost.

If you found this Instructable of value, and particularly if you have any suggestions for improvement or to increase my knowledge in this area, I would be pleased to hear from you. You can contact me at transiintbox@gmail.com. (please replace the second 'i' with an 'e' to contact me.