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Beverage Cooler with Arduino

 Post subject: Beverage Cooler with Arduino
PostPosted: Thu Dec 12, 2013 11:04 am 
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Hello,

For one of my classes next semester I am going to propose this idea.

I want to take the standard 12oz can of soda from room temp(75F/23.88C) to chilled temp of (45F/7.2C) relatively quickly

I would like to use a Computer Power supply since they are a cheaper alternative. How can I power the TEC from a computer PSU? From what I read or know right now is that a computer PSU is a constant voltage source whereas the TEC is a constant current.

How does that work?



Overview:
I am looking to buy two TEC's to run @12 volts
Cool from room temp to 45F(chilled) within 2 min
Closed Looped Zalman LQ310 heatsink has a QMAX of 300

The computer parts I will source used to keep prices low.

Arduino to control the circuit and what not...


Any Advices on TEC selection? I want to run the TEC at full blast at 12v to cool as fast as possible so I dont think I need a PWM right?

I am looking at 12711-6M31-30CZ

I want to keep this project ~$400


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 Post subject: Re: Beverage Cooler with Arduino
PostPosted: Thu Jan 02, 2014 3:51 pm 
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Alright, well the first problem you have is figuring out how you plan on getting a good contact with the can, without having a large surface area to allow for good thermal conduction the idea won't work. Second TEC's are semiconductors and at different temperatures they draw a slightly different current, but since you've identified which TEC you want and that you want to run it at 12v we can figure out approximately how much current it will draw.

If you look on the manufacturers website you'll find a PDF: http://www.customthermoelectric.com/tecs/pdf/12711-6M31-30CZ_spec_sht.pdf with a chart showing the voltage and current. So for the purpose of these numbers we'll just pick an arbitrary delta. We're going to say that the Delta T is 40C, and the operating voltage is 12V. So according to the chart that gives us around 23A of current that the TEC will draw. So given P = IV, each TEC will draw around 276W. At the same Delta T that gives us around 88w Qmax for each TEC according to the other chart. So 88w Qmax * 2 is 176 Qmax. What this means is that you'll be able to move a maximum of 176W of energy while maintaining a 40C Delta. This means that if you can hold the hot side at a constant 25C the cold side would sit at a constant -15C. However this means you'll require a very large power supply because assuming the TECs are wired in parallel then the current is 46A. At this you'd have to use many different cables from the 12V line to be able to provide this current without burning up the wires. I wouldn't want to draw more than around 7A from a regular PSU wire. So given this value you'd need 7 or 8 different wires providing 12v in parallel to spread the 46A load safely.

If you are really serious about this project, A you'll need to study a lot more about TEC cooling. Also I would recommend a dedicated external 12V PSU that you can wire up heavier gauge wire to it. In this case you'd probably need around a 600W dedicated PSU. Until you are a bit more comfortable with the exacts of how you would plan on completing such a project I wouldn't bother attempting it. At best working with TECs is fairly complicated because of design complexities and the requirement for having the ability to provide power at usually quite high currents.

I would suggest before going any further that you would want to look at this guide: http://www.scribd.com/doc/16803737/Melc ... c-Handbook, it gives some more detail about TECs, how they work, and some design information. Anyways, if you do decide to go ahead with this project good luck and feel free to ask more questions.


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 Post subject: Re: Beverage Cooler with Arduino
PostPosted: Thu Jan 02, 2014 4:50 pm 
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Joined: Thu Dec 12, 2013 10:29 am
Posts: 4
Thank for the reply.

I will take a look at that link. yea I have already phasing out the idea of using a computer PSU :)


Recently my boss asked me for something that he could pay me for and would work for this class so I might focus on that instead. In any event ill let you know if I have any more questions. This site is a great Resource.


Danny


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 Post subject: Re: Beverage Cooler with Arduino
PostPosted: Fri Jan 10, 2014 1:56 am 
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Ok so I decided to try this Peltier project out.

Current Part List

Going to use this pelt because its available the one in the OP isnt.

2x 12711-6M31-26CW
2x 12v 30a Dc Universal Regulated Switching Power Supply 360w
2x Thermaltake WATER2.0 Pro 
Copper Hot Plate Either 3/8ths or 1/4 inch thick
Aluminum Stock
Aurduino Uno
Many Temp Sensors (Soda can, Aluminum and hot side of pelts)


For the 12711-6M31-26CW, looking at the data sheet

Running it at 12 Volts 19.5-18 Amps (10-40 Delta)
Which Means it will produce (P=IV) 234-216 Watts of Heat
while having a Qmax around 70-175 watts, so with two we should be able to move 140- 350 watts of energy

For the HeatSink, I looked up reviews for it and found that an Corsair H70 can keep a delta of an overclocked i7920 chip requiring ~266watts of power at 18.6C , further looking at the Corsair H70 vs Thermaltake 2.0 Pro in reviews shows that the Thermaltake is better. Meaning I should be able to have a delta about ~20 or better at 18 amps (216 watts)

http://www.hardocp.com/article/2011/03/ ... s6pDPRDv1F


The Interface between the Cold side and the can will be of Machine Aluminum to give as much surface area to the can.

The hot side will have a Copper Hot plate of either 1/4 to 3/8th " thickness.


The Heatsinks Retaining clips will provide the necessary preload (150-300 inch lbs) needed onto the pelts which I will drill and tap holes into the aluminum.


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 Post subject: Re: Beverage Cooler with Arduino
PostPosted: Tue Jan 14, 2014 9:48 am 
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Keep it up, I'll try and help as any time I can (I can't promise I'll be able to respond quickly, as I'm doing senior courses in university).


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 Post subject: Re: Beverage Cooler with Arduino
PostPosted: Sun Jan 19, 2014 4:22 am 
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Image


I ordered my peltiers and actually went with these ones 19911-5M31-28CZ Peltiers @12 volts much better than the ones I listed. Produce a much more manageable amount of heat. http://www.customthermoelectric.com/tec ... ec_sht.pdf

I am running into a little issue with the hot side.

http://www.frostytech.com/articleview.c ... cleID=2697

The waterblock on my heatsinks are 30x30mm my peltier is 62x62mm

So I need a hot plate or heat spreader.

I just purchased an half inch thick piece of copper with the purpose of milling it down.

I need to find the optimal thickness.

I found this for cold plates

Image
http://www.overclockers.com/cold-plate- ... thickness/

but I am confused as to what I should use? I read that cold plates are used as like a shock absober to slow down how fast it can cool..ect so for hot plates I do not want it to be too thick then.

But I need to make sure I can pull heat effectively from the outside area of the peltier that my water block cannot cover.

What do you think?


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 Post subject: Re: Beverage Cooler with Arduino
PostPosted: Mon Jan 20, 2014 10:53 am 
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I'm going to suggest since you are going with air cooling the hotplate should be fairly thin, 1/4" is probably the thinnest that I could suggest, aluminum and copper aren't particularly strong and you don't want either the coldplate or hotplate bending. The trick is both the coldplate and hotplate will add to lost energy and reduce your delta a little. So always build that in to your expectations. Also try and make sure that anything directly contacting a TEC has been lapped or is pretty darn close to flat, TECs surfaces are made of ceramic and they don't tolerate surface variation very well so lapping is a good idea.


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