Instructables

Mini Fridge

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Here are some pictures of a mini fridge i made from 1 peltier unit, 2 heat-sinks, 2 small fans, some corrugated plastic, sealant, a 10 by 5.5 inch piece of cardboard tube about 1/4th inch thick, a piece of glass, and super glue.
I also added another layer to the fridge to make dead space of air in between the inner wall and the new outer wall i would recommend adding insulation between the 2 layers. i also made the door double paned with glass and double sided foam tape. and finally i added a better fan for the peltier hot side heat sink and a fan for the cold side heat sink.
before it only got around 12 degrees of temperature drop now it gets around 25 to 30 degrees Fahrenheit temp drop.
BodenM2 years ago
Hey guys,
For anyone building this that has access to a 3D printer, I have made a body, door and window for this in SketchUp, files are here: http://www.mediafire.com/?m7qzk9ck7lu4d4m
BodenM BodenM2 years ago
Also, this doesn't have hinges, but you can buy door hinges and screw them on.
mr. clean (author)  BodenM2 years ago
I had been meaning to add normal hinges but theres no good way to attach them to the glass, have any ideas?
USE 3M VHB 2 sided tape they use this to replace screws in airplanes
I meant my SketchUp file, but for this, I would get just 1 door hinge, and use epoxy or superglue to stick it to the glass and cardboard. Make sure you wipe the excess of the glass, and get it right first time, 'cause epoxy won't come off glass easily.
mr. clean (author)  BodenM2 years ago
Hmm I'll try epoxy thanks!
AWeaver2 years ago
Has nobody tried mounting a CPU cooler onto the hot side of the peltier unit, such as this:
http://www.techeta.com/wp-content/uploads/2012/01/ARCTIC-Freezer-i30-CPU-processor-heatsink-Intel-Core-i3-i5-i7-image.jpg

That's a new model, but similar ones are easily available? Wouldn't that in fact, keep the hot side of the peltier from getting too hot to limit the cold side?
jannemesis2 years ago
I'm interested in buying your project. Can I? :) :) :)
mr. clean (author)  jannemesis2 years ago
sorry but its been dismantled for a long time now and I don't think I will rebuild it.
Hello,

I'm trying to build a solar power fridge for camping using peltier elements.
I see you cool the air in your fridge by convection. (heat sink+ Fan).
Isn't cooling by conduction a more efficient way? mounting an aluminium plate on the peltier to create bigger surface area. And place a can of beer (of course, what else...) on the plate.

Age

mr. clean (author)  age_instructables2 years ago
Yes it is definitely more efficient to use conduction to cool an item or heat an item.

The reason I went with convection is because it is how a full size fridge works and I wanted to do it in that fashion for fun.

But for efficiency I would absolutely use conduction involving a cold plate to set the beverage on.
mak242 years ago
how can i make my own Peltier unit
Jodex mak242 years ago
I'd say that it would be rather impossible to do at home.
mak24 Jodex2 years ago
here in india its really expensive to get it shippedc from the us or other countries....
at INR 3000 for a peltier unit ill rather buy a conventional second hand fridge 250 litres....
sheldonr2 years ago
I am building a fridge like this, I can't get a temp drop more than 20 degrees F. The lowest temperature I got was 55 degrees F (13 C) inside the fridge with ambient being 75 degrees F (24 C). 55 degrees isnt quite cold enough. The problem seems to be that the peltier isn't capable of colder temperatures (cold sink only reaches about 50*F, but it is bigger than it needs to be). Will adding another peltier to the same heat sink reduce temperature or just provide more cooling capacity? Or do I need a more powerful peltier. Its a standard 8.5A max 40x40 tec being powered by either one or two 12v 6A power supplies (another power supply in parallel doesn't seem to affect anything though, so one is probably adequate). What can I do to get at least a 25 degree or 30 degree F temp drop? Thanks.
mr. clean (author)  sheldonr2 years ago
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Thanks. I guess I'll need to work on the insulation and unfortunately maybe cover the see through glass door, but that might be what I need to do. Maybe cool the heat sink more too like you said.
mr. clean (author)  sheldonr2 years ago
yes that is what i would try first is add insulation, and also if your door is a single pane then it is not being a very good thermal barrier, try making it double paned like i did with mine. if all else fails find a better heatsink for the hot side.
well, after messing around with some more door insulation and stuff, I found my real problem. The peltier I was using was only drawing around 48-50 watts, which having no prior experience with peltiers, didn't bother me. When I tested two other peltiers I had bought with it, they drew 73-74 watts, which I guess is what they should draw? Anyways I guess I'll have to rip the whole thing apart now.
can i ask what is the specs of the peltier you used for this fridge? because we're planning to use peltier device for our project that should at least have a temp drop from about 2-8 degrees Celsius.. is it possible for the peltier to have that temp?

tnx.:)
mr. clean (author)  angeline_12102 years ago
The specs for my TEC are as follows:
Vmax: 15.4 volts
Imax: 11A
40x 40 x 3.3 mm
Max differential: 68'C
Resistance: 1.16 ohm
# of couples: 127

With enough insulation the TEC could easily reach 2 - 8 degrees C drop. My TEC mini fridge reaches about 7 degrees C when room temp is about 22'C Which is about 15'C drop.
Hope this helps, feel free to ask any more questions.
ymasamune2 years ago
hi, can i redesign the fridge you made by using a peltier pad with 5V , 1A power supply ie USB power ? Do you think its a good idea to get the temperature drop as yours?
mr. clean (author)  ymasamune2 years ago
I wouldn't risk powering a peltier off a USB plug as most motherboards cant handle that much amperage that a peltier draws. Also powering a peltier with a lower voltage means that it will need to consume even more power so the fridge wont get as cold as if u ran it off 12 volts.
one more question, is the temperature drop you mentioned in celcius or fahrenheit? and is the temperature drop you mentioned corresponds to that of the ambient air in the container, or the cold side of the peltier pad? I have used 12V 60 W peltier pad, but only got 4 degree C drop of ambient air temperature in a well-insulated container.
mr. clean (author)  ymasamune2 years ago
the temp drop i recorded was in Fahrenheit. and i was measuring the ambient air inside of the container not the peltier pad.
bingo1122 years ago
You know, this reminds me of an elevator in Portal. lol
znine3 years ago
how much you've got temp difference ? since i'm still trying to reach 12 degrees of room temp (30 degrees)
mr. clean (author)  znine3 years ago
mine gets around 28 degrees of temp drop to obtain more you need to add a thick layer of insulation depending on what wattage your peltier is. if its low wattage the insulation needs to be quite thick so the peltier wont have to work as hard to cool the fridge down and its the opposite for one thats high wattage. also what helps is to add a heat sink on the cold side too so theres more cold suraface area. feel free to ask any more questions you may have.
znine mr. clean2 years ago
well, after several testing (that make 8 of 10 peltier broken), i reach 20 C degrees from room temperature (30 C degrees). I use normal styrofoam that i buy from local shop. (picture attached) and it powered by old computer Power supply in behind (that i've already jumper it). Want to buy another "crazy fan" of dell parts to circulate the inner of the styrofoam box but still waiting next month payment (my wallet almost empty for this project >.<). In the last picture (the one who display the temperature) is the result of direct measurement of peltier surface. i can't go more lower than that since the surface was beginning to moisture and create several water (and make the sensor broken >.<) it sure can goes down. but, how long it can go to minus is still in question. thanks for your instructables and bablin5 for motivating me to built this project ^^
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mr. clean (author)  znine2 years ago
Do you have a heat sink on the side of the peltier that gets hot? if not then the peltier will definitely break.
znine mr. clean2 years ago
sorry, i forgot to include the schematic. i use head sink in both side and having that "crazy fan" to flew away the heat so the peltier can't even got hot.
for the peltier, dunno why but i've bought 10 of it, and only 2 that can work normally. (the rest only work for 10 minutes and became extremely hot after that)
perhaps you can suggest me where to buy good peltier ?

ps: i forgot to include the detail of the fan. so, for those who seek the fan, i'll include the specs.

Dc 12v 2.50 A
Model 0912DE
Dell P/N T5994
Delta Electronic inc.
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ASCAS3 years ago
Thats very nice! I made a lager version of this, I added a 300w peltier and a 5 inche cooling fan. It worked very well in our last camping trip. I suggest to add a high power amperage adjuster. Good job!!
mr. clean (author)  ASCAS3 years ago
thanks! yours sounds awesome too, i would love to see some pictures!
nsmf3 years ago
i really wanna make this for my dorm, but i really dont know the electronics part. Can anyone help me?

Would be nice if someone can draw the parts and where the wire goes. I am in the mid of ordering n finding the parts but, once the peltier and the other parts came, i dont know how to put it together. Please help, i am a real beginner.
mr. clean (author)  nsmf3 years ago
The wiring is very simple assuming you understand the basics of positive polarity and negative polarity, my fridge didn't require any fancy wiring as long as you aren't planning on using LED's anyway to wire this you only need to bundle all the positive wires, commonly colored red, to the positive feed on your power supply, and then bundle all the negative wires, commonly colored black, to the negative of your power supply. that's pretty much all there is to wiring it. then for your Peltier your must attach a heat-sink to the hot side of the unit, the best way to find out what side is hot is to momentarily connect it to a power source and feel what side gets hot, it should only take a few seconds. i recommend using thermal paste as this will greatly increase efficiency, then if you are using a fan just attach it to your heat-sink in a way that air will flow through the heat sink plus you should check out the other mini fridge projects on Instructables, they may provide a more in depth explanation. I am sorry that i'm not a great teacher I hope I have helped somewhat, feel fee to ask if you have any more questions.
nsmf mr. clean3 years ago
Thank you very much, your explanation are very much understandable for me. No im not planning of having LEDs for now. I have few more questions.

1. Can i bundle the peltier and the fan wires (same polarity) ?
2. Can a lower power source power up 15V peltier, will it still work?
3. Can I use the 12V computer power supply?or I have to consider more than just the voltage?

I most probably buy peltier from this site http://www.bkbelectronics.com/peltier%20cooler.html
but there's 12VDC peltier but differ in amps. The higher the amps, colder it can gets?

sorry for my english.
mr. clean (author)  nsmf3 years ago
A1 yes it is perfectly fine to bundle the fan and peltier wires together with the same polarity, ive done the same with mine and haven't had a single problem.

A2 A lower power source can be used, 15V means that it is the limit of the peltier, so no more than 15V will be fine. however with a lower voltage the peltier wont cool down as fast.

A3 When choosing a power supply you need to keep the rating of your peltier in mind. lets say that i have a 14V 168 watt peltier, that means my power supply cannot supply more than 14V and the supply needs to be rated at 168 watts or more, if the watt rating is less then you risk overheating the supply. Most computer power supplys wont provide more than 12.5V so yours should be rated around 12V and the wattage it is capable of needs to be more than what the peltier draws.

Also if you choose a peltier with a higher amp rating It wont get colder it will just reach its lowest temperature faster. i viewed the peltier you have in mind they would both be fine to use, the higher watt one will cool your fridge faster.

As always feel free to ask any more questions.
Here's a simple wiring diagram.
Peltier wiring diagram.jpg
so does it work like an actual fridge?
mr. clean (author)  ducktape.mac3 years ago
if by that u mean it gets cold enough to keep food fresh then yes but you cant get more than a soda and a candy bar in it.
good enough. does it freeze the candy bar?
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