# Mini Fridge!



## Obinice (Sep 7, 2004)

Good evening, this may take a little explaining so please bear with me 

*Compartment Thickness -* 1mm
*Compartment Volume -* 1701" squared
*Compartment Measurements - * 10.5" tall, 18" wide, 9" deep

*Heatsink Material -* Aluminium Alloy
*Heatsink Measurements -* 11.5" tall, 18" wide, _(base is 5mm thick, fins are 2.5cm tall, 7mm gap between fins, fins run horizontally)_

*Peltier Model Number -* TEC1-12706
*Peltier Specs PDF -* http://www.hebeiltd.com.cn/peltier.datasheet/TEC1-12706.pdf
*Peltier Measurements -* 40 x 40 x 3.8mm

We've all seen mini-fridges. Unless you go for the more expensive ones, they usually consist of a few bits and bobs inside like a little heatsink and an 80mm fan. You can fit two cans into them, and are in short, rubbish.

I've decided to have a go at building my own (I'm one for crazy projects ). Not because I think I can make a better one than one I can get from a store, but to prove that I can build one that works well myself.

I have 10 Peltier Units as detailed above (_they came in a pack of 10 from the magical land of Ebay)_, and they will be my source of refrigeration. However many I end up using will be cooled via the large heatsink as detailed above, which will then be cooled by fans.

The compartment can hold roughly 18 bottles of beer _(what else!) (bottles roughly 9" tall, & 2.5" deep)_.

*Now here are my questions.....*


How many of these peltier units do I need to use in order to adequately chill the compartment's contents?
What am I looking at in terms of a PSU to power that amount of peltiers?
What would be the best fan cooling arrangement for the heatsink (assuming the peltiers are spread out as evenly as possible)? For example, should I use two 220mm fans, or perhaps 4-6 120mm fans?

I've been thinking about this myself, looking around for ideas, but at the end of the day I need somebody elses opinion, and so of course the first place I think of is Techguy 

I'll bet some of you will be able to think of a better way of doing this than my idea, or perhaps something silly that I've overlooked. Please, throw that in too. Although since I have the peltiers & heatsink already, no matter what the eventual outcome, I'll be using those in some capacity.

Thanks in advance for any thoughts or advice!


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## Elvandil (Aug 1, 2003)

Very interesting! I have some of those junctions myself and have been considering a similar project. Reversing polarity, of course, makes a heater, so you may want to consider that in your design in case you want to keep something warm.

Are the fans for cooling the backs of the Peltiers or to circulate the cooled air?

The power requirements are really pretty modest for those junctions, but you have to keep in mind that though they will work with low inputs, the more you add, the more cooling you'll get. So the total amount of heat actually moved will be the equivalent of the input energy less the losses. You probably already know all this, but the better the insulation, the less power required. Generally, the commercial ones seem to only guarantee a few degrees above freezing for a minimum. That is due to size and insulation restrictions and has nothing to do with the Peltier's capacity.

Forgive me. I'm beginning to think out loud.


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## Obinice (Sep 7, 2004)

The fans are to draw the hot air away from the heatsink that's cooling the peltiers, at the rear of the fridge. I've found that ambient cooling just won't cut it.

Hmm good point about polarity, I'll keep it in mind for when I'm deciding how to wire it up. Why have just a cooler when you can have both


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## Elvandil (Aug 1, 2003)

Yes, I agree that passive air-flow will just not do much cooling.

Do you know what the lowest temp is that you can get on the surface of the Peltier? Are they to be in direct contact with the interior?


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## Obinice (Sep 7, 2004)

Unfortunately I don't have a non-contact thermometer (or for that matter, a thermometer), so I can't take any readings 

They will be in direct contact with the rear of the metal compartment from the outside, as opposed to the actual interior of the compartment (I think that's what you meant anyway?).


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## hewee (Oct 26, 2001)

Get a laser/infrared thermometer to find out what the temp.

I got this one and it works great.
Non-Contact Handheld Infrared Thermometer
I paid more at http://www.x-tremegeek.com/ or http://www.cyberguys.com/ because there warehouse is down the street but you can get anything they sell from the smaller store out front or ask and they will it from the warehouse.

http://www.google.com/products?hl=e...a=X&oi=product_result_group&resnum=1&ct=title
Got a new range that will be installed later in the week that has a "TrueTemp System", Electronic Controls, Temperature Display and it will display I guess the true temp. So I will test it also with my infrared thermometer gun.


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## JohnWill (Oct 19, 2002)

I bought a non-contact thermometer from Harbor Freight for $10, price was right and it works pretty well.


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## Obinice (Sep 7, 2004)

I found one that looks decent enough on Ebay for £12.99 ($17.87), I think I'll go with that one. Any other thoughts on the topics I mentioned? 

Also a bit off topic but wow, that exchange rate has _really_ changed since I last checked.


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## hewee (Oct 26, 2001)

They got them also with a probe that are good for cooking.
I seem at some cooking site and it was the non-contact thermometer type but the probe would fold down. 
Now that is cool because your reading would not be the same inside of something that your getting from the outside.


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## kiwiguy (Aug 17, 2003)

You have to factor in how often it will be opened (and the cold air falls out if vertical).

I have seen a single Peltier take a can of coke to freezing in a cheap mini fridge, because to door was not opened.

Had one in my office once, but the fan noise and power consumption (60 watts 24/7) worked out at $90+ per year....(NZ price) when a "real" fridge out in the kitchen area was actually a lot less and needed to be going anyway.

With that number of Peltiers, you will need a thermostat, which will lower running costs and save freezing the beer.


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## JohnWill (Oct 19, 2002)

Of course, there are many mini-fridge products already built that will probably be as cheap or cheaper.


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## hewee (Oct 26, 2001)

Large Hot+Cold Mini Fridge Deluxe $69.95
Fridge dimensions: 16"H x 10"W x 12.6"D

Medium Hot+Cold Mini Fridge Deluxe $49.95
Fridge dimensions: 10.75"H x 7.25"W x 9.75"D

Now for that price why make something. It may cost even less but that was first place I looked and still look what you get.

Then if your without power you turn it on it's back and put ice in it.

This one looks cool.
ThinkGeek :: Deluxe Mini Fridge -Warmer w/ Digital Thermostat
Additional Images and Customer Action Shots


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## Obinice (Sep 7, 2004)

kiwiguy, interesting I hadn't given much thought to a themostat. I had decided it would open from the top though, to keep the cool air in.

Like I said in my original post "_Not because I think I can make a better one than one I can get from a store, but to prove that I can build one that works well myself_". You're right that I could just go get one (and thanks for the links. I looked, they are pretty sweet), but that's not why I want to do this 

When I get a nice day (not raining) I'll set up and get the compartment built. :up:


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