How Do You Build a Mini Fridge

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Updated on April 18, 2022

I always love to drink chilled Coke. But when I go for a outing, no more any chance to get the chilled Coke.So I seriously wanted to have a portable mini refrigerator, so that I can carry, wherever I go.

I have gone through few videos on YouTube and Instructables to know how to make a Refrigerator. After some research, I made one for myself.The outcome is really awesome.

7 Steps to Build a Mini Fridge

Step 1: Materials

The enclosure:

-500x400x3mm White PVC sheet – £5.98 – Ebay UK (you can actually use a 400×400 sheet, but I would recommend getting a slightly bigger piece incase you make a mistake and so you can sand each piece)

-White Plastic 3 inch cupboard door handle – £1.29 – Ebay UK

-Small Brass hinges – FREE – found in garage

-Small magnetic sheet – £0.69 – Hobbycraft (any thin magnets will do, but I wouldnt recommend the neodymium ones or you probably wont be able to open the door!)

-Small amount of scrap steel – FREE – I found an old sheet of steel in my garage and cut off some 2cmx1cm strips, and let them soak in white spirit and alcohol to clean them. Anything steel works, you could even cut up an empty coke can if you need to. Make sure it is real steel though and not stainless, because it isn’t very magnetic and only contains about 2% iron. Real steel contains about 99% iron which is why it is so magnetic. Iron and nickel are also magnetic so they will work too, but may be harder to find and harder to cut.
-Soft touch 6mm knob – £0.55 – Maplin (optional, recommended if you have a potentiometer for better grip and professional finish. I didn’t buy one in the end)

The electronics:

-91.2W 40x40mm Peltier cooling unit – £3.37 – Ebay UK
-Akasa chipset cooling kit – £6.96 – Ebay UK (you can also get them for £10 in maplin. All you need is an active chipset heatsink and a small flat passive chipset heatsink. MY heatsinks were actually recycled and the fan was bought for £2.50 on ebay)
-Sub-miniature lever microswitch – £1.29 – Maplin (optional, for door light. Make sure it is a 3 pin one of a push to break one. This was recycled from an old project)

-5mm 12V white LED – £1.29 – Maplin (optional, for door light. You can also use a lower voltage LED if you have a resistor. I actually got mine on ebay for the same price.)

-Miniature Potentiometer 10K – £0.80 – Maplin (optional, but  recommended to control temperature. Any large value potentiometer will do really, it just needs to be able to increase/decrease resistance for the peltier unit. I didn’t buy one in the end.)

-Single hole 2.1mm DV power jack – £1.69 – Maplin (or any other DC power jack to match your power supply)

-12V DC power supply – This is not included in the parts/price list since I used a recycled computer power supply. You can use anything as long as it is over about 5V and under 12V. The peltier unit uses 7.6A of power, so remember wattage of peltier unit ÷ power supply voltage = Peltier cell amperage. If it is anything lower than 7.6A (which is probably is) Then the peltier unit won’t be running as cool as possible, and this is ok, since we are making a fridge, not a freezer, but make sure it isn’t too low. I will show you how to convert an old computer power supply (or new one, it probably works out cheaper)

-Wire – This also isn’t on the price list because it is too cheap to measure and all good electronics hobbyists should have plenty of it
-Small amount of double sided tape and thermal compound, or thermal tape – not included on the price list since the amount you will use is unmeasurably small. You just need a teeny squirt of compound and a few strips of tape.

Tools:

-Hacksaw, coping saw, or wood saw (or if you have one, a jigsaw or band saw)
-Drill (preferably a pillar drill, but a handheld drill will work just as well)
-Files (kind of optional but not if you want smooth edges. Alternatively you can use sandpaper)
-Hot glue gun (to stick it together, you could use a drill and screws or araldite/epoxy)
-Ruler, measuring tape, or large vernier caliper to measure the plastic
-Soldering iron
-Solder
-Screwdriver

Step 2: The Power Supply

 The first thing you need to do is make the power supply. If you are reading this, I am assuming you have a computer power supply to convert. Locate and remove the screws on the metal enclosure (sometimes hidden under stickers which will void the warranty). Cut the wire to the mains plug, fan, and switch. Unscrew the ground wire. Now, unscrew the circuit board from the case and remove it. Locate the 20/24 pin motherboard connector.
Cut the connector off, and all of the wires from the power supply that go to the motherboard connector except the green wire (if there isn’t one or multiple green wires, its the one 4 along from the top left if the clip is on top) and any of the black (ground) wires. Keep those two wires over to one side to avoid cutting them off. Locate the sata/molex power connector, and cut the first connector closest to the power supply off.
Then cut off the red, orange, and ONE of the two black wire, or just red and black if its molex only. Now, cut off any other connectors such as the 4-pin 12v motherboard connector or any other connectors the board may have. You should be left with two wires for mains in, two wires for a fan, a green and a black wire to simulate a motherboard being attached, and a yellow and black wire which is your >100W 12v output.
Now, you will need to either mount it back in its old box, or buy a plastic one. (make sure you connect the ground if you mount it in its old box or any metal enclosure). Mount the power connector, switch (optional) and fan on the case. Solder the fan onto the fan wires. If you bought a new fan, cut off the connector, cut off the yellow/white/blue wire and solder the red and black wires to the corresponding red and black wires on the board.
Next, solder the power connector and switch (if you have one). Make sure it is connected the right way round or you could blow up the power supply. Cut the green and black wires a bit shorter so they can touch each other but not much more, strip them, solder them together, and coat in insulating tape. Now, strip the remaining yellow and black wires, strip them, and add in an extra length of wire so it is as long as required for your setup.
Now, take the 2.1mm dc plug, unscrew it, and solder on the wires. Note which one is positive and negative for when you solder the socket on the fridge itself. Now close the enclosure, plug it in, and test it with a multimeter. If you don’t have a multimeter, turn it on, and if it doesn’t blow up, it probably works! I also made a cover out of polymorph (a great material that you can put in hot water and mould it, then when it cools down it hardens into a strong plastic) for the power connector since I wired a mains plug straight into it, which is why it looks like there is melted glue all over the back.

Step 3: Cutting the PVC

The next thing you will need to do is to cut the PVC to make the enclosure. You can make your own or use my template. You will probably have to change some things, like the size of the hole to fit your peltier cell or heatsink, power jack, potentiometer knob at the back, magnetic door plates, microswitch, or the size of the LED. Cut out all the pieces of PVC and file/sand them but don’t put anything together yet because you need to put in the electronics. Here is the template I used. I have also included a .svg of the template so you can edit it and resize it so it is full scale. I can also give you a .AI file if you message me. I was considering paying £33 to have some guy cut me some acrylic professionally, but in the end I decided it was not worth the money so I bought the PVC instead.

Step 4: The Peltier Unit

first thing I would recommend doing is to attach your power supply to the peltier unit, and make sure it works right, and note which side is cold and which side is hot. Also note which end is positive and which is negative, because most peltier units don’t have a polarity. Don’t leave it on for too long. Now, you can start attaching your heatsinks. first, take your active (fan cooled) heatsink and attach it with thermal tape or double sided tape and thermal paste to the hot side of the peltier unit. cut the connector off the end of the fan using side cutters or scissors if you don’t have any.
you can cut the yellow wire all the way back, as you don’t need it. Strip the yellow and black wire, and solder them in parallel to the peltier unit, making sure that red (positive) matches with the positive of the peltier, and black matched with black. If you have a potentiometer, mount in on the back panel now. solder the positive wires to the variable output, and solder a wire, preferably red, to either end of the potentiometer. Solder a wire to the negative (black) wires from the peltier unit and heatsink fan. Mount the power jack in the back panel now.
solder the black wire to the negative and the red wire to the positive. If you attach the power supply now, the peltier unit should cool down/warm up and the fan should come on, and fan should go quieter and louder and peltier unit should get warmer and cooler when you adjust the potentiometer. If it works fine, move on. If not, check back on your electronics and compare it to the circuit diagrams. If it works, attach the flat passive heatsink with thermal tape to the cold side of the peltier unit.
Hot  glue the peltier unit into the 10x10cm square with the hole cut out, making sure you only glue the cold part (if you glue the hot part, the glue will probably remelt and it will fall apart). Try and get it so the heatsink is lying flush with the top part of the plastic. Carefully glue the bottom part to the back panel, 4cm up. Measure it each side and make sure it fits perfecty, or the inside of your fridge will be at an angle.

Step 5: Paint the Acrylic Sheets

First, peel up the protective cover from the acrylic.I have transparent acrylic sheets in my stock, but I wanted to make it white.So I spray painted the sheets to make white except the front door and compartments.

This step is optional as the choice of the color is depends on you. If you want to make similar to mine, you can buy the white acrylic sheets.

Safety Warning :

Prefer to paint the sheets outside or in a well ventilated space.Never forget to wear the nose mask.

Step 6: Making Holes for Air Flow

To dissipate the heat from the hot side heat sink of the cooler unit have two 12V fans. As the entire unit will be kept inside the enclosure, we have to make provision for air flow.

Marked the fans size on the two side walls.The outline is square shape,use a drafter compass to make a inscribed circle.Then make holes at all around.

Note :First I tried to make the holes by using my drill with a 8mm bit, but its really difficult and time taking to make bigger holes in acrylic. So I used my Dremel work station to make the holes inside the circle.

Step 7: Glue the Cooler Unit

Take the slotted sheet and glue the Cooler plastic radiator.

Apply sufficient glue all around to make perfect sealing.This is really important, otherwise the hot air ingress through the side joints.

Step 8: Mounting the Separator

Keep any of the side wall on the table as shown in the picture.

Then place the cooling unit, measure its entire length. Mark a line for separation between hot and cold side.

Apply hot glue along the line and place the separator sheet.

To hold the sheet perpendicular,take support of a solid rectangular object.I used a 12V lead acid battery.

Step 7: Fitting the Door and Adding Finishing Touches

Your fridge is almost complete now, and you have probably tested it already. Take the remaining 10x15cm piece with two holes in, and attach your door handle with the screws from the back. Make sure it is more than 1cm from the right or it will collide with the door latch. Take the magnetic part for the door latch and glue these in place in the door.
glue the hinge to the door on the left side, and then to the left side of the fridge. Make sure it can open and close freely. Your fridge is now complete. You can now add the knob to the back of the potentiometer, adjust the temperature, add any stickers, plug it in and set it up next to your computer, and fill it up with your favorite drink. Enjoy!
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