I wanted to make a mini fridge to use while working in the workshop or in the office, but it could also fit nicely for a camper van!
- 2x electronic refrigeration modules
- AC to DC power supply (12v, 15amps)
- Cold white LED strip
- Wire terminals
- Shrink tubes
- Power plug AC
- Power plug 12v
- Momentary push button
- Aluminium channel holder
- Aluminium tape
- Self-adhesive rubber seal
- White sticker paper
- Acrylic glass
- Doorknobs (used as legs)
- Aluminium handlebar (on lid)
- Aluminium angles
- Spray paint + clear coat
Take care when dealing with electronics, especially mains power. Make sure you know what you are doing, or consult an expert. If the AC power plugs connects with the aluminium foil or anything else that conducts power, it may be lethal if touched.
Step 1: Planning the Electronics
It's always important to plan and test the electronics before actually making the build, so I made sure to hook everything up like in the schematic before starting to build the fridge. When I knew how to connect what, I could move on to make an appropriate design.
Step 2: Cutting the Styrofoam Pieces
As you can see from the sketches, I'm not having it stand upright as most of the other mini fridges I've seen, and this is because I want to try to avoid letting the cool air flow out every time I open it. With this design and the lid on top, most of the cool air will stay inside the fridge, and it won't take long to cool it down again.
The first thing I had to deal with was the styrofoam insulation that would make the whole inside of the fridge. The first shape I created was the one shown in the second picture, which would be the main room. It should be just big enough to fit 5 half litre bottles of soda.
I built a styro slicer mainly for this purpose, and I'll probably need it for later projects. It's an awesome tool, it cuts foam and styrofoam like butter, and it's easy to use. If you want to know how to build this tool, you can check out King of Random's video on how to make it here.
This particular styrofoam that I chose to use is very thick, so I had to split it in half, making sure to push it against an angle so the cut became straight.
Step 3: Gluing the Main Compartment
When I had all my pieces for the main compartment, I had to glue it together. I found this glue called Multibond that in addition to gluing also fills any small gaps, and it works on most materials. It had to dry for a couple of hours before I could deal with it further, so in the meantime I had time to cut and split some more styrofoam that I could use later.
Step 4: Cutting the MDF Bottom Piece
I also had time to make a bottom piece out of MDF. I began cutting a square that fit my measurements, and then I had to cut and drill some holes in it. Four holes in each corners for the legs, first of all. To figure out where to cut holes for the fans of the cooling modules, I had to line them up properly.
Step 5: Figuring Out the Positions
Just testing out the placement of the main components of the build before continuing.
Step 6: Fitting the Cooling Modules
When I had lined the fans up properly, I had to cut some holes in the styrofoam where they would enter the main compartment. This was easily done with a utility knife. I made sure to make extra space around them on the inside as well.
Step 7: Making Space for a Snack Shelf
Nice, the fit looks pretty good. I just had to make one more cut in this piece before gluing it on. This will make room for a snack shelf right above the cooling modules. I glued it on, making sure to get the Multibond into all the cracks to avoid air leakage later.
Step 8: Cutting Holes for the Fans
Now that I had the proper placement of the fans, I could finally mark them up on the MDF, and cut the center circles out. That's quickly fixed with a drill and a jigsaw. The warm air will now be able to escape through the holes on the bottom.
Step 9: Finishing Up the MDF
Here are the "legs" I used, which are actually just knobs for cupboards. I'm going to use a couple of aluminium parts that'll match, which I think will look really good in the end. I fastened all the legs, and now on to the lighting.
Step 10: Making the LED Channels
I wanted the fridge to light up whenever I opened the door, and therefore I need some lighting that's well incorporated in the design, so I chose to use these angled channel holders for LED-strips. I just used a tiny piece of styrofoam to cover the top, and I could cut them to the right size with a hacksaw. I chose to use regular cold white LED strips for this, and attached a couple of long wires to it.
Step 11: Fastening the LEDs
The cables needed a path to the outside, and the soldering iron did the job. Before attaching the LED channels, I added this aluminium tape to the corners. This will cover the whole inside eventually. I pushed the wire through the hole, glued the channels to the corners, and then the tiny styrofoam piece at the top. Finally, not forgetting to push as much multibond I could into the hole to prevent air leakage, again.
Step 12: Aluminium Tape
This is the difference with and without aluminium tape. The reason I'm using it is both because it looks a lot better and because it is heat reflecting. I'll cover the whole inside with this tape eventually.
Step 13: Making Paths for the Cables
Here I'm just making some paths for the cables so it will sit flush against the MDF when I'll glue this whole compartment to the bottom. I'm also checking what the lights looked like (don't worry, I made sure to check if they actually worked before gluing it in place). As this main compartment is done, I can glue it to the MDF with the Multibond.
Step 14: Clean Up and Attaching the Cooling Modules
The electronic refrigeration modules had 4 red and 4 black cables each that made a bit of a mess, so I cleaned that up using shrink tubes. I added a terminal at each of ends of the groups of 4. They looked a lot better with after the clean up.
At the opposite end of the terminals, I added another cable that'll extend to the thermostat. At this point, I could fit the modules in place and screw them to the MDF. There was a tiny gap at the bottom, and to make sure all the warm air flows through to the bottom, I added some tape and hot glue around them. I hot glued the foam around the front to the styrofoam as well.
Step 15: Hooking Up the Thermostat
Time to hook the modules to the thermostat, and you can see clearly how to do that in the schematic above. I hooked up both the modules, and a separate cable that'll go to the power supply. As you can see I'm splitting that wire in two, so the power supply can power both the thermostat and the modules. All of them are connected to a common ground. The placement of the thermostat is just temporary, by the way. I moved it later.
Step 16: The Power Supply
This is the cable that will be the main power source for the fridge, and it will go to a power inlet of the same type that's used in computers and computer screens. I stripped the wire, and added this wire terminal that's easy to connect to the power supply. The supply I'm using is a 12V 15amps AC to DC power supply. You can find that above in the supply list.
Step 17: Finishing Up the Electronics
Here I've hooked up everything to the power supply. I ended up adding a momentary push button to the LED strips later, which you can see in the schematic. There's also one loose cable there, which will go to another power inlet that'll take 12v. I also made sure to place the sensor of the thermostat inside the main compartment close to the bottom before continuing
Step 18: Completing the Snack Shelf
Let's move on to the snack shelf. I just made sure to get the right measurements, and then the same process went here, with the styro slicer and multibond. To give it some support I added two tiny pillars to keep it in place. Now that the whole styrofoam shape is finished, I could cover the entire inside with the aluminium tape.
Step 19: Acrylic Glass Exterior
The whole thing will be covered with 5mm acrylic glass, and I used this scoring knife to make nice and straight cuts. When I thought the cuts were deep enough, I could line it up against the edge of the workbench, and give it a hard push with a plank to make it break. It worked every time. It didn't take long before I had the four pieces that would make the exterior.
Step 20: Designing a Logo
I want our channel name on the front, so I downloaded the font I wanted, typed in our YouTube channel name and made some small changes in Photoshop before printing it out. I should have printed one regular and one mirrored version, and you'll see why in a second. I cut all the letters out mirrored in white sticker paper.
Step 21: Taping on the Letters
The reason I made them mirrored is because now I can stick them to the inside of the acrylic pieces, and this way the outside surface is plain glass that'll look shiny and be easy to clean.
This is where I should have had a mirrored printed version, because it would be easier to line up the letters when taping them on. I managed to tape them on correctly anyway, so it wasn't a big issue. As a final touch, I'm adding some wave shapes to give it more detail.
Step 22: Drilling Air Holes
On the back I need to include some air holes to let the air through. I made a grid, and drilled holes at every cross. I thought this would suffice, but later I figured I had to include holes on the left and right sides too to keep it cool enough. If I had known, I'd do it at this point.
Step 23: Painting the Acrylic
I clear coated it first, and when it was dry I had to paint over the stickers with white acrylic paint because they were a bit transparent. After that I used red spray paint for automobiles, and finally a thick layer of clear coat.
Step 24: Preparing the Fridge for Gluing
While the paint dried, I could prepare the fridge for gluing. I removed the aluminium tape on the top square to further prevent the cold from escaping. Also adding more tape to the outside for insulation. On the front part I added 4 magnets that'll push the lid down, and covered it all with white tape.
Step 25: Final Drilling in the Acrylic
Now I got the plug in the mail, I could mark it and make a hole for it. The small hole on the left will be a power socket where I can connect a 12V power supply, and a car battery for example is perfect for this inlet. The other one, which I'll use more, is the AC input. Also making a hole for the thermostat display, as I'm moving it, like I said before.
Step 26: Gluing the Acrylic
All I have to do now is attach the front and side pieces, and let it dry. I'll make the back piece detachable so I can access the electronics. Overnight I tested four different types of glue, and after pulling them apart, only one was standing, so that's the one I'll use. It's a glue meant for plastics like acrylic.
Step 27: Completing and Attaching the Back Piece
I fixed up a couple of angles with a spacer and nut, and glued those with strong metal epoxy, making sure not to get any on the screw. In the meantime, I could cut some aluminium angles with a hacksaw, and glue them to the acrylic front with plastic glue.
When the metal epoxy had dried I could remove the screws, and glue the angles to the inside of the box. With a piece of large paper I could mark the holes, and drill them in the acrylic back piece. It fit, and I could add the corner angles here too, making sure to not get any glue on the sides.
Step 28: Connecting the Wires and Power Plugs
I added another type of terminals to the wire on the AC input. These will be easy to connect to the power inlet, and they're fixed firmly in place with a crimping tool. Now I could just insert both my power inlets and hook them up with their wires.
The thermostat is supported by spacers, and I made sure that I was able to see the display from the other side when gluing it on with hot glue.
Step 29: Hinges for the Lid
The lid will be kept in place by some hinges, and I just have to make space for them at the top of the back. To remove mass I used my Dremel, and finished off the shape with a file. When I had the right fit I could glue it on with the plastic glue.
Step 30: Creating the Lid
The lid will consist of two pieces of acrylic attached together with double sided tape. I quickly cut two pieces and drilled holes for the hinges on one of them.
I wanted the logo on the lid as well, but this time I used our Silhouette Cameo 3 to cut it out instead of the scalpel. As shown already you don't need this tool, but it makes cleaner cuts. I attached the letters on the bottom layer of acrylic, so it sits inside the air seal between them.
Finally I added the double sided tape and the top acrylic piece, drilled the holes through, and the lid is finished!
Step 31: Sealing It Tight
To seal the lid tight enough I used self adhesive rubber seal meant for sealing doors and windows. Then I added magnets on top of the other ones, that I could cover with glue before putting on the lid. The lid was fastened to the hinges with screws, spacers and nuts. I made sure to remove the rubber seal undetneath the screws to be able to push it shut, and then I glued on an aluminium door handle.
Step 32: The Momentary Push Button
The only thing left for me to to was to hook up the momentary push button that I'd got in the mail, and you can see how and where it's hooked up in the schematic above. The most important thing is that it's normally closed. Its function is to make the lights turn on only when the lid is opened, and turn them off when it's shut. This means I'm actually finished, and I can finally enjoy peeling the plastic off!
Step 33: Final Thoughts
So I have been using the fridge for a while now, and it reaches temperatures around 6 celsius degrees in about 30 minutes without anything in it. When there's something that needs to be cooled, it takes a little longer, and the other way round; when you put something cold in it, it cools down faster.
The thermostat saves some energy, but I wouldn't consider this particularily energy efficient, but I imagine it is something that will be useful on a desk, on LAN-parties, or in a camper van. If you really pay attention to the insulation, I think its possible to get it to a decent energy efficiency, and I could probably have done more to really optimize it.
Overall I think it's a nice and useful mini fridge, and I'll probably use it when working long hours in the workshop or in the office, for example, but I probably won't leave it on permanently. Thanks for reading, hope it was worth your time!