Mini Fridge

So this guy at work got a neat little mini fridge for a can of coke. I thought to myself "I can make one better than that". And so my home made mini fridge was born. It has 3 peltier coolers enclosed is a 4 inch diameter pvc T joint. It's powered (underpowered by about 120 watts) by a 55 watt 5 volt power supply. The power supply was only $6.00 and I couldn't find one more powerful that fit my specifications and was relatively cheap. It cooled the inside down to 68 F when it was 96 F outside. I took it inside and it cooled down to 46 F. Unfortunately I didn't think to make an Instructable until afterwards. I haven't actually made an instructable yet but I think I've got a good one brewing. In the mean time, here are some picture.

Comments

[Xixfas]

*overkill* lol

[nsmf]

i have a question, i basically have very little knowledge in electronics. Will it be a problem to have a power supply lower/higher Amps than my peltier? what if I have 2 or more peltier and power it up straight to the power supply will it equaly have the same voltage, or i have to do extra wiring for multiple peltier?

[CaptPikel]

Overpowering any device can be fatal to the device and power suplies life. It's always recommended to stay within operating parameters. If you need more out of peltier junctions, I would suggest to use more of them or use ones that are rated for higher power. I found the most drastic increase in effectiveness was by making the insulation better. This old thing I made was 3 coolers off of one power supply connected in parallel.

[mr. clean]

actually ive found that using a computer power supply is the best because the computer supply wont force in more current than the peltier can handle, i use a 430 watt supply with a 168 watt peltier and it works perfectly

[CaptPikel]

Have you measured the actual voltage and amps going through the peltier? And are you using one of the 12v rails. I've never tried it with a pc power supply so I'm curious what it would actually draw power wise.

[mr. clean]

yes ive measured the amperage and it is only pulling about 8 amps at 12 volts, and i am only using one 12v rails out of 2.
the TEC specs are Vmax 15.4v Imax 11A resistance 1.16 ohm.
Do u have any ideas on how get the TEC to use full amperage, because if i am correct then the TEC should use 14 amps at 12 volts.

[CaptPikel]

The limitation is most likely the power supply. Peltier coolers have no limitation in what voltage or amperage you can push to them. Too much power and they will fry of course. It may be a 430 watt power supply but thats for all voltage rails combined. Check the label and it should say the max amperage for the 12v rail. I have a 450watt and the 12 volt rail is rated for 16 amps. Under load it only puts out around 11 though. As with most components, pushing them to their max power levels usually will decrease the life span. I don't like buying stuff that burned out so I usually under power everything. So 12 volts at 8 amps has a lot of head room but I'm honestly not sure about the performance difference. You should measure the temp for the current power level and see if there is a big difference if you can get it to the 15 volts at 11 amps.

[mr. clean]

yes I think you may be right as one 12 volt rail offers 14 amps and the other offers about 16 amps. so it is most likely the supply that is limiting the amperage. Do you think it may be possible to link the two 12 volt rails in parallel for more power delivery or would i risk frying the power supply?

[CaptPikel]

I don't really know too much about pc power supplies. It could very well fry it. I know I've used wall wart power supplies at varying voltages and amperage in parallel and they didn't fry. But pc power supplies are pretty refined in their output so changing that may have a bad reaction. You may want to ask that in the instructables forum and maybe someone there has tried. A quick google search and it looks like people say it's possible and works but take that at your own risk.

[reddog92396]

Alright... I just have a few questions, How many peltiers would you recommend for a 2 liter soda bottle holder? How is it in a not so well ventilated space? How long do you keep it on, how many hours (or none) straight? Thanks

[CaptPikel]

Two liter bottle, Two or 3 peltier coolers would do fine as long as you have the proper insulation for the container. Mine would have worked a lot better if I used something that actually insulated (PVC sucks at that). More coolers will cool quicker but not necessarily get it colder. So how many depends on how quickly you want to cool really. Ventilation is a big part for the hot and cold sides. The hot side for it's obvious reasons. It doesn't have to be well ventilated honestly, but the better cooling for the hot side, the colder the cold side gets. So less ventilation will obviously just be a warmer result. Ventilation for the cold side is also a big deal. At the time, the cold side of my coolers were flat metal plates. This worked...but slow. I added heatsinks later and it cooled much quicker. Heatsinks help the flow of heat by increasing your surface area. So adding heatsinks to the cold side effectively helps pull heat out of the air inside the cooler at a much faster pace. I kept the unit on solid over 24 hrs testing it, never had an issue. I never actually ended up using it because it looked questionable. I dismantled it in an attempt to make a more safe for work look, but it still was not something I'd want to take in to my work place so the project has been scrapped.

[reddog92396]

Also I almost forgot to ask where you got your power supply? Thanks again

[CaptPikel]

I bought it from allelectronics.com
http://www.allelectronics.com/make-a-store/item/PS-575/5-VDC-11A-SWITCHING-POWER-SUPPLY/1.html

But as I looked this up I saw another good looking power supply if you plan to run multiple peltier coolers:
http://www.allelectronics.com/make-a-store/item/PS-1265/12-VDC-5.4-AMP-POWER-SUPPLY/1.html

Most peltier coolers run from about 5 to 15 volts. But just make sure to check the specs on them before so you you don't burn them up.

[reddog92396]

Thank you so much, I can't wait to start this project, Happy Thanksgiving by the way (unless you're not from the US).

[reddog92396]

Thanks so much, sorry I didn't see that you replied right away. Wow 24 hours sounds great! though....it looked.....questionable haha thanks for the info though.

[reddog92396]

The only reason I ask about the ventilation question is because when one side of the peltier gets cold, one side gets hot, so basically how well did your heatsinks or fans do for the hot side? Once again thank you very much

[The1PublicEnemy]

where do you get a peltier thermoelectric module?

[www.bkbelectronics.com]

http://www.bkbelectronics.com/peltier%20cooler.html

[edfel01]

Please make an instructables there's nothing on how to make a mini fridge like this and it's looks like the best I've seen by far

[rackne]

to improve WMD look&feel I suggest red LED display counting down time to reach desired temperature. It may also beep every second ;)

[oakironworker]

That was funny my friend

[dagenius]

yah, but when you are just passing through customs, and they see a pipe device counting down, you are not going to last very long...

[covey12]

with a hear pounding in the back ground like 24 lol

[fredrikher]

realy good project;)

[CaptPikel]

So I guess I should give a little bit more information on it. The build time for the whole project was 3 days after I got parts. It took that long because of the foam drying and I only worked on it for about an hour a day. The fans and power supply are from allelectronics.com (great site) and the peltier coolers were $5 each from woot.com. The time it took to cool down the inside to 46 degrees was about 45 minutes. One thing to note is that, yes, I used expanding foam to secure the coolers, but most of the cooler is uninsulated. I imagine with some insulation it would be more efficient but this was kind of a spur of the moment project. Quality was not the goal in this project really. Just kind of a "can I do that?" thing. And no, it was not suppoes to look like a "questionable" device to begin with. Just kind of ended up that way.

[H3xx]

You could use an Igloo cooler lunchbox. It might look like a bigger bomb, but would be more efficient and have a handy carrying handle.

[Galforg]

Haha, looks like a time machine.

[ben_k]

Great project. I'm tempted to make one, stick a fan and a vent in it, and stick it in my computer case. An idea for an improvement would be to use an old ATX computer powersupply. Even the cheapest easily have over 20 amps on the 5 volt rail. This would make it slightly bulkier, but you could easily get sub freezing temps, and have a mini freezer if you wanted.

[dagenius]

Yeah, but I would not want to risk putting 20 amps through one of these units. A 20 amp peltier unit could cost a fortune.

[ben_k]

Congrats, you made it onto Engadget!

http://www.engadget.com/2009/08/27/diy-mini-fridge-is-just-big-enough-for-a-can-of-soda-just-odd-e/

[CaptPikel]

Yeah. Someone pointed that out today at my work. They told me not to bring in the mini fridge :), might be a bad idea. I guess I should have made it an instructable instead of just a weak slideshow. Oh well, there are plenty of projects left to do out there. Like a plasma gun.

[dagenius]

you could disassemble it, and then make an instructable...

[Whales]

What nice comments revolve around in that weird community....

[shortwave]

seriously I would consider this project for a water cooling system for my PC figure out a way to seal the pelter's to the PVC pipe and or get a 4 way pipe that size seal the pipes with caps and out fit the insides with a coil of copper and fill it with antifreeze and a small pump to circulate the fluid to each pelter heat sink THEN foam the pipe without blocking the pelter's heat output. know what look forward for me to add to this i got a good idea and i need 4 pelter's

[dmastachief]

i bet if you got within sight of an airport with that you'd have bullet in your head before they would even try to stop you

[conrad2468]

ITS NOT A PIPE BOMB ITS NOT A PIPE BOMB!!!!! ha ha ha!!!

[dmastachief]

to late BLAM!! and now your brains are on the ground

[AndyGadget]

That is so way beyond ugly that it's GORGEOUS! Really not something to be seen carrying in public for all sorts of reasons. (How about adding a big red digital temperature readout?)

[CaptPikel]

It was initially meant to be used at work but as I finished I could only describe the design as "Questionable". Not one to bring in to work really. The temp readout was going to be the IR thermometer you can see in the background of one of the pics but I didn't want to destroy my only one.

[codongolev]

you could possibly make a second enclosure out of metal or something... then put it around the pvc and add insulation.