$5 Mini USB Fridge!




About: I've had many different jobs in my life, but I've discovered my passion: Mental Health Counseling. However, that doesn't keep me from still being a technogeek!

Now that we're seeing those 12 volt camper coolers turning up at garage sales and thrift stores (I found one for $2.50), here's a neat little idea for turning it into a customizable mini-fridge powered by a USB port!

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Step 1: Taking Out the Peltier/Heatsink Unit

You'll basically just need a phillips head screwdriver and thin socket or needlenose pliers to take apart the heatsink and fans, which will allow you to remove the unit from the cooler. Now, you might ask why you'd want to do this and not just use the cooler. The answer is because most of the time when you find one of these the case will be cracked and the cord is missing, but that's not a problem...

Step 2: The Peltier Unit and Clean Up

Sandwiched in between the heatsinks, you'll find the Peltier unit, which loks about the same size and thickness as a computer CPU. In between the top and bottom layer, you'll see the special substrates that have the unique properties that make the Peltier unit cool on one side while heating the other when an electrical current is applied. There will, in some cases, be spray foam insulation in between the two heatsinks, which is very easily broken away with just your fingers. You can safely remove the peltier unit from the other heatsink, as it will be held only by thermal compound. Once you've cleaned up the top and bottom heatsinks, place the peltier back in between the two heatsinks and retighten the bolts. If you have any thermal paste left over from putting together your own PC, you can optionally clean the old paste away and reapply new paste to each heatsink just as you would on a CPU heatsink/fan assembly before attaching it to a CPU.

Step 3: Attch a USB Cable

Peltier units are designed to operate at a voltage between 3-12 volts, and the 5 volts from your USB port work just fine. Although the amperage could ideally be higher, the 500 mw output is acceptable. Cut away the end of an old USB cable (or pick up a cheapy) and strip back a couple of inches of the plastic covering. Inside you will find 4 wires, usually within a braided or thin aluminum shield. The wire colors will be white, green, red, and black. Trim back the white and green wires, strip off a small bit of the black and red wires, and solder them to the red and black wires of the peltier unit. Wrap with electrical tape or use heatshrink tubing. If you need information on correct soldering procedure or the use of heatshrink tubing, there are many excellent Instructables that will gve you all the information you need, simply do a search!

Optionally, you can attach a 1K limiting resister in between the red and black wires, although you are quite safe at the voltage and mA to not really need one.

Now, plug in your USB cable to a USB port on your PC, and within about 30 seconds you will be able to feel one heatsink become very cool while the other becomes warm. Note which heatsink becomes cool, as that's what we'll want to encase inside the mini fridge.

Step 4: Building the Fridge!

I used foamboard because of its ease in cutting with an xacto knife and its insular properties, and basically built a box around the heatsink using a hot glue gun to attach the sides and top, and then ran a line of hot glue along the seams to ensure an airtight compartment. The bottom piece is cut into two halves, with a square section cut out in the center to make room for the peltier unit. I then glued the two halves to the underside of the cooling heatsink, then glued the left, back, and right sides of the fridge, and finally the top. See the diagram below:

Step 5: Final Assembly and Extra Touches

I used white plastic tape to hinge the door, although you could certainly use small hinges from a hardware store and simply glue them into place with the door fit into the front for proper opening and closing. I glued small lengths of foamboard inside the fridge assembly and then glued cut pieces of a flexible refridgerator magnet on both the inside of the door and the foamboard lengths to make a magnetic "catch" to hold the door closed. I also threw in a battery powered White LED and used a leaf switch to turn the light on when the door was open. I ran the wiring of the leaf switch along the inside and through a small hole in the back to attach to the AA battery holder glued to the outside back of the fridge, then used white plastic tape along the wire run, attaching it to the interior side.

For the handle I used a cheap hardware store drawer pull.

As you can see by the door, I wanted this to look like a store "cooler" that you see for drinks, so I cut a window and hot glued a section of plexiglass in the window.

Step 6: The Final Result

As you can see by the pictures, this cooler will hold a large bottled water, or a tall 20 oz plastic soda bottle, although my drink of choice is a Starbucks Vanilla Frappucino! The cooler will keep drinks at about 45-50 degrees and works best when your drink is already cold for obvious reasons. Optionally, you could use a 1 amp 7.5 volt DC adapter, which will lower the temperature significantly without making the lower heatsink too hot for placement on regular surfaces. In this instance, I would strongly recommend that you add the 1K limiting resistor in order to keep the DC adapter from becoming hot.

Step 7: Tricking It Out!

Now, add graphics from your favorite game or website and make your mini-fridge a one of a kind creation. I printed out on a sheet of inkjet transparency film to create the see through graphics you see here. Have fun, and watch the video for the nice ending... ;)

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    456 Discussions


    10 years ago on Step 5

    If I were making this fridge, I would put the heatsinks at the top...cold air falls, hot air rises. I would think it would be more effective.

    13 replies

    Reply 10 years ago on Introduction

    you should add the heatsink on the side and stick a fan on it


    Reply 10 years ago on Introduction

    keep in mind the current drain

    5V is fine for powering a fan (well duh you can get USB powered fans comercially). I am not sure how much current a USB port can handle.

    Too be safe I would buy a cheap USB Hub with its own power supply and power the "fridge" off of that. It may or may not be as reliable but since it is powered off the hubs power supply you won't fry the power on your computers usb. I have two notebooks that have fried power on their usb ports (data connectivity still works but you need external power on the device, such as a hub).

    For temp control couldn't you build a switch with some resistors to regular the current going into the module? Also, for a desktop hack perhaps you could wire the module directly to the power supply on the computer by routing the cable through an expansion slot. Of coarse with that you might get two effects. Firstly you might end up with a freezer rather than a fridge, and two the heatsink will could get extreamly hot. In that case you would def need some additional cooling.

    Thanks for this instructable it has given me some ideas. Such as building a custom case (perhaps using styrofoam as an insulator) and a brand new module. Such as this one http://store.qkits.com/moreinfo.cfm/QK66


    Reply 2 years ago

    Here is the updated link for the peltier module:



    Reply 10 years ago on Introduction

    please say you haven't bought that module yet? if you've got the time to build your own custom case (I know i haven't) buy a peltier from virtual village.com! ive got a 400watt one on its way that only cost 12 pounds! i'm guessing that if you want to make your own custom case your either a keen gamer or just want external power from the psu? if you just want external power from your psu you could adapt a spare pci slot on the case to be a dc power outlet? btw the max current that can be drawn from a usb is 100ma without request (there's no way to request 500ma other than through hardware, so don't even go there.


    Reply 9 years ago on Step 5

    with a unit like that do you think i could make an actaul minifridge, like 2 by 3 size, hooked up to a socket of course, and any cheap but affective insulations i can use, was thinking foam baord on the outside with a wood frame and more foam board with insulation inbetween that.


    Reply 10 years ago on Introduction

    thanks for the link/info, no I havn't bought any of the parts yet, I just tought this project up as soon as I found this instructable, currently I have a limited budget and upgrading my harddrive is a bigger priority sorta a keen gamer, but mosty just like building electronics wanna get my advanced amateur radio licence so I can tinker with transmitters *evil grin*


    Reply 10 years ago on Introduction

    what i would do is make another fridge on the other side of the heatsink which wouldn't really be a fridge but a toaster(kinda) that way hot air goes up cold air goes down.


    Reply 9 years ago on Step 5

     but there is a fixed temperature differential with a peltier unit... if you capture the heat of the other side then it will heat up as will the cool side so that wont work... unfourtunatly, cool idea tho


    Reply 9 years ago on Step 5

     im making a project for geometry like this... im making a usb mini fridge out of a great rhombicuboctahedron 3d solid and since i feared it wasnt going to be cold enough i was going to do exactly that!


    3 years ago

    Another thing I thought I might add is, you can help the cooling heatsink by polishing it to an almost mirrored finish, it should transfer the cold way better then. I'm not sure on that, but it makes sense to me.

    Heres my logic, If you take a mirror finish polished aluminum, brass, or copper heatsink and put it in the freezer you won't find that it has frost on it after 24 hours. But, put the same kind of heatsink that has been scuffed up slightly in the freezer for the same amount of time and 9 times out of 10 where the scuff marks are you will find frost, maybe even a thick layer of frost.

    Just kind of thinking out loud, but hopefully it helps.

    BTW Chocolate from a Hershey's candybar works pretty good to polish aluminum that isn't too pitted..

    1 reply

    Reply 3 years ago

    Just to interject quickly before someone takes this advice: The effect is actually the other way around. Highly polished surfaces reflect heat more effectively, and thus don't work quite as well for heat transfer. I doubt in this case it would make much difference, but it would be less effective for it to be shiny.


    3 years ago

    ok not sure if anyone has thought of this, but if you have a peltier that runs on 5-12 volts you could always use two seperate USB cords and attach them both to a single peltier... This would more than likely allow you to use just one Usb at 5 volts, or use both Usb's at around 10 volts. I would imagine doing it this way would almost double your cooling effect inside, but I can guarantee you that a larger heatsink with a fan would also be needed on the heat side. On the outside to get rid of the heat more efficiently it might also be a good idea to try and incorporate some sort of a heatpipe, kind of like inside a laptop for the CPU cooler... these are just a couple of thoughts that might help if someone wanted to actually figure out how to make a way more efficient version. BTW I loved the way this information was put together, I don't think I could have done it any better myself. Keep up the creativity!


    3 years ago

    It would be better if you added batteries to make it portable