Personal Air Conditioner




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.

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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 (please replace the second 'i' with an 'e' to contact me.

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    14 Discussions


    3 years ago

    There actually IS a commercial version of this already available. Our house has the wrong kind of windows for AC units, so my parents bought two of them when I was much younger. They are massive plastic contraptions containing fans and an ice compartment that needs manual refilling. They look somewhat like space heaters. We found that in the high humidity we get in the summers here, while they did provide cool air, they made the humidity worse and was not worth the exchange, or the constant need to refill.

    9 replies
    R Jordan KreindlerNokota

    Reply 3 years ago


    Thanks for the information.

    This really works, so if you have the name of the commercial version that would be super. I would love to have a look at one. A commercial version need not be massive, as one even smaller than that in this Instructable should be possible. However, a massive version might be able to cool a small room rather than be a personal item. I look forward to seeing the massive one. Do you remember if the commercial version had drainage capability, as I do in this Instructable? As regards your observation, fortunately, we are not located in a high humidity area.

    Thank you so much for taking the time to write and for the information. It is really appreciated. I will look at our local dollar stores and also Walmart to see if I can locate the commercial version (these seem like appropriate locations to check), but if you can suggest other locations, I would certainly be pleased to check there as well. It would be super to find one. Please be kind enough to let me know if you can still locate any in your area.

    Thank you again, and the very best.

    NokotaR Jordan Kreindler

    Reply 3 years ago

    I have a suggestion for a modification to your design, actually. What if you used only half a carton for the top thing? the bottom half? perpendicular to the ice compartment? That way the air stream wouldn't have this optional detour to swirl around into and lose speed.

    R Jordan KreindlerNokota

    Reply 3 years ago

    Thank you again for your post. I am interested to see what you finally have built. Please be kind enough to post here, or provide a link if you have finished a personal air conditioner.

    As always, the very best.


    Reply 3 years ago

    Oh! If you did it like that, the bed of the resulting "L" shape could be used as the opening to add ice, rather than the tip of the side! You could put even more ice in it, or even make the fan portion on the half-carton detachable so you could put the entirety of the ice compartment in the freezer, resulting in one very large, long-lasting ice chunk...

    R Jordan KreindlerNokota

    Reply 3 years ago

    Thank you for all your comments. I seal the "wind tunnel" so that there is no air swirling around, except down to the lower carton. However, your idea is interesting, and I will be pleased to give some thought to it.

    If you decide to build what you suggest, please be kind enough to keep me informed. Either using the comment area here or, directly via my email address provided in this Instructable. Should you chose to contact me directly, rather than use the comment section here, my email address is provided in the last Step of this Instructable.

    Thanks again, and the very best.

    NokotaR Jordan Kreindler

    Reply 3 years ago

    Actually, having the attachment at a bit of an angle would help airflow, since it would flow more smoothly at a 70 or 50 degree angle rather than have the airflow take a 90 degree corner... Geeze, this is giving me so many ideas...

    NokotaR Jordan Kreindler

    Reply 3 years ago

    If I made it, it would be for a friend's computer, in Texas, which is always overheating. I would have him sit it next to it when he plays games! ^_^ My computer room is air conditioned, and the humidity would make it a not-good idea in New Hampshire anyway. Horrible humid summers, dry as desert winters. :P I might test it out in my computer room anyways to see if it has any effect.

    NokotaR Jordan Kreindler

    Reply 3 years ago

    I don't remember. It was more than ten years ago, sorry. I was a teenager.

    R Jordan KreindlerNokota

    Reply 3 years ago

    No problem.

    Clearly this has got you thinking (as a good Instructable should) about how you would go about extending this idea and possibly making it even better. If you have a chance to implement any of your ideas please let me know.Again, thank you for your comments and ideas. As always, the very best.


    3 years ago

    An idea would be to poke some small holes in your bottom milk carton and put the unit on a concave plate. (Drip pan). The water will work against your ice in the long run. Also putting the ice carton on top and air carton on bottom will allow you to take advantage of the natural down-flow of cold air/water/endothermic reactions. I made about 7 versions of a very similar project, so I can respect it. I had many people tell me it was worthless, and I would never cool anything with it. Well to that a say, killing a child's creativity and drive for science is a crime worse than murder, because it is murder without the dying part....( I didn't let it get to me, but between 10-15 years old, it can put a chip in your shoulder)

    Here are my material and revisions

    Version 1: 10 years old, begging for the parents to turn on the A/C.......Plywood box, inside a Tupperware container filled with ice, Fan that flowed downwards from the top of the box. (Worked when swamp effect was possible, but was more that push I needed to pursue the whole project and keep going)

    Version 2-3-4-5: 10 years old to 12 years old - Clear acrylic box with the bottom being a large CPUfan heatsink, ice on top, fan sucking air from heatsink. (This worked well, but it took adjusting the fan, redoing silicon sealant, and fatherly assistance to build/modify. Sometimes that is great, but it does teach you to use more exotic materials that adds build time, and scheduling to things)

    Version 6: High-Tech | 16 years old - So I revived the project and abandoned the ice for a thermal electric junction plate or TEC, metal water reservoir (on top/hotside), and a small heatsink fan on the bottom. So you put ice in the top metal pan (no holes) and the TEC moves the cool properties across the unit to the cold heatsink till the ice melts. Then it continues to do so after the water is at room temp (this is the improvement you get here), till the water was hot. The next stage was the water evaporating till it was gone. (if you didn't stop it at this point it would eventually fail). So across 3 states Ice, water, gas it worked and used all the previous failures/revisions to create a smooth cooling curve across the graph of it working. This took cooling about 10 sq feet to cooling about 100 sq feet, but traded off needing about 5 amps at 12v (fan and TEC) to do so.

    Version 7: ? not sure on age: added a basic stamp and later a 12v thermostat/solid state relay to prevent from running without anything in the top and possibly catching fire. If it got to 220F, it turned off the relay, and lit up a red LED warning you it is off.

    So my version of the idea took a few turns, but I outgrew it when I no longer had to beg my parents to turn on the AC because I moved into the basement. Funny how life solves it own problems and you never get it another thought. Hopefully this was worth reading......

    Anyway, negatives aside, if you had something like a can (tin/aluminium/steel) to contain the ice and drip into a pan across the air carton, the can gets cold, and prevents the hot air from attempting to steal your lower pressure cold area as to sweep it away. The Dripping adds it own cooling effect by reference to a swamp cooler. (This won't work in humid places like beaches, but will get the water away from the ice.)

    I say keep on the path your on, and keep the parts of the project renewable/recyclable common parts. Thank you for helping me think of one of my first inspirations for being an engineer and sharing your Instructable. I hope you will continue showing that things are worth pursuing, even if they are considered futile, because the pursuit always bears insiration and knowledge.

    1 reply

    Dear FlaredElectronics,

    Thank you for the message and comments. I found them interesting, and I am sure many of this Instructable's readers will as well. In particular, it was interesting to learn that you started building personal air conditioning units as a young child

    The very best.


    3 years ago

    Very cool!!.. As it says it is a "personal" cooling unit, not designed for a whole house..

    1 reply