Hi There! First off I want to apologize if this is not where it should be...

I have been in need of a display case for chocolates for a while now and the guy who built it for me, though a real nice guy with woodworking skills, didn't know how to do the electrical part. Neither do I. I'm a Chocolatier. I figured I should ask around for advice before I embark on this little adventure and blow myself up.

The Project:

It is a wood and plexiglass tabletop case 35"x26"x25" with sliding glass doors in the back. It needs to keep an internal temp between 65F-70F. Typical Ambient temp of places I will be would be 80F or lower so I'm looking for a 10-15 degree drop from Ambient.

I have been looking at low profile power supplies since I have a 4" high 20" deep 34" wide space to shove it in.

I have also been looking at The Peltier chip TEC1-12712 (12A/15.4v) maybe two in parallel. Not sure where to go from here.

So...anyone have any suggestions?

 

I think you got the cart before the horse and are trying to reinvent the wheel. I'm not sure wood is the best material for a refrigerated case and normally the cooling unit come with the display case and is engineered for that case but wait and see what the experts say.

 

Far from being an expert, although I like chocolate I agree with Ray. Wood will be a poor choice to refrigerate. Keep in mind, too, all the air you put into it cooled, must return to the atmosphere or to the pump in a cycle. Otherwise, if the case is sealed shut, your cooled air will stop flowing and will overheat your cooling device. Could you post a few pictures of the case so we can see what you see? Others may be giving advice also, so the pictures will definitely help. http://www.doityourself.com/forum/el...your-post.html

 

A Peltier could work. For best results you should incorporate a fan to circulate the chilled air. As it runs the cold side of the Peltier will probably accumulate moisture either liquid or frozen so you'll have to deal with that somehow. Powering it all is pretty easy with a DC power supply but you'll have to figure out the cooling part first then what you'll need to power it.

 

Ok. I guess I need to put a finer point to this. There ARE no tabletop display cases out there that fit what we needed so we needed to have one made.

This is what we wanted....




we ended up with something a tad bigger. It is an Eye catcher and draws the public at conventions. This is what we have...fans, condensation drains, no heat LED strips- good circulation of air flow.




It worked for the first day of the show then just stopped cooling. I was thinking the MacGyvered powersupply he used (from a XBox I think) is not enough. So I was going to remove and rebuild with the proper stuff.


The first pic is a case that a colleague from another forum had made up a while ago for the same reasons.

 

Here is one of it set up. It's not airtight- and the fans work great. It's just not cooling anymore.






oh by the way our website is being worked on but Facebook has a menu, prices and pics of product. ANYHOO...

 

more pics- don't know if they would be helpful or not but....








again...sorry if I'm overdoing it but I want everyone to know what we got.

I don't know the TEC numbers of the peltier chips since half of them were repurposed from an old wine chiller. Again, one of the reasons why I want to break it down and put in new components.

The Back shot (last pic) shows the space I have to work with-That black plate has a dual exhaust fan to suck out any power supply heat.

 

Howling Moon Chocolate


An Xbox supply isn't going to cut it.
Will this case be used around the clock or is this just for demo's on the road ?
Based on the current of the chips you are looking at..... 30A minimum power supply is a pretty good size and generates a lot of heat.

 

Computer power supplies do not have much 12 volt current. Like most have said, get a very high current 12 volt supply.

 

In post #5 you said you think the problem is the power supply. Have you tested your Peltiers with a different power source to make sure they work? If they do then you just need a appropriately sized power supply like others have mentioned. Depending on the space available and cost you might consider two power supplies. One for each cooler.

 

Thanks PJ!

It's just a display for conventions and shows so I don't see it being on more than 6-8 hours at a time. If we can get this beast working right we plan on making some smaller ones.

I don't think the power supply didn't quit- the fans are still running, but it stopped doing anything for the temperature.

Like I was saying before I was looking at how to use two TEC-12712 in parallel but as soon as I saw the amperage I knew I should ask for help somewhere.

I was looking at this thing: 12v/30A should work right?

Amazon.com: 12v 30a Dc Universal Regulated Switching Power Supply 360w for CCTV, Radio, Computer Project: Computers & Accessories



I have tested nothing as if yet. I opened the bottom- saw the rats nest and figured a gut and rebuild would be best since I have no clue what he used yet.

 

You could test each one separately using a car battery. In fact a car battery or better a couple of deep discharge marine batteries and a charger might be a short term emergency solution.

 

I liked the power supply you linked to but I'd use two of them. A power supply run near maximum output will not last long and run very hot.

 

So one power supply for each chip. Got it. Any suggestions for a single unit or am I pushing my luck?

Here are a few shots of the small space...



The twin fans- one blows in the other sucks out...






The LED light strip, front light and current PS plugged into heavy duty powerstrip...




That's about all other than this mess...which show nothing that I know of.

 

Alright...I ordered 2 of those power supplies as well as two AC plugs I can rewire. Don't I need some sort of regulator in the wiring somewhere? This is where it gets fuzzy...

 

The power supply has a voltage regulator built in. You might want to see if you can mount the power supplies outside of the unit like under the table to get them better cooling and to keep that heat away from the chilled portion of the case. Heat kills power supplies -- the better you can keep them vented the longer they will last. The polystyrene foam might be keeping the power supply too hot. If you really want to keep them inside the case, add some louvers or ducts to the exhaust fans to make sure you have constant air flow directly over the power supplies.

 

Thanks IB! Yeah I was planning on taking all the styrofoam out of there and putting something on the floor of the case itself. Keeping in mind this needs to be "mobile". That's a laugh- I can't move it myself as is. I'm trying to keep weight and danglers to a minimum. I'm hoping vents and fans will be enough- I don't think I'm going to be running it at Max though.

Thanks for all the advice and guidance so far! When I get the bits here in hand so I can look at them I'll be asking for help about wiring. I was asking about the regulator because I was afraid that if I just wired it and plugged it in- it would toast something (like me). Yeah the PS can put out 30amps but am I going to NEED all 30...maybe I was asking about the wrong thing- not a regulator but maybe some sort of rheostat (wow...digging back to Highschool for these terms)

Things going through my mind about this (feel free to warn me if I'm gunna kill myself now )

Going to try running it with ONE chip first to see how cool it brings it down- then will two work better at a lower draw.

Will the fans (computer case cans) be able to be wired to the same PS or will it burn them out...


Well enough for today- I got to start making truffles for V-Day. Thanks again for all the Help!

 

Try to split your load evenly on the two power supplies. You mentioned one module on each supply which is good. Then place several fans on each supply.

The power supplies are regulated to 12vdc at 30amps. Since they are switching supplies they draw very little power and create very little heat with no load. As the load increases on them.... they work harder and the heat they generate increases.

 

Ouch. I just contacted a TE company that specializes in making cooler units to see how much it would cost just to buy off the shelf... The Rep was real Helpful and nice but...

Suggested Cooling unit- $250
http://www.inbthermoelectric.com/inb...b340-24-AA.pdf

Power supply (24VDC) and temperature controller- $480

So a total of $730





When I started this project 3 years back I got an off the Shelf price of $600...
At least now I got a ballpark of what I need...

So. Back to the DYI!

 

I agree you have done the right thing getting two supplies so your not running the supplies near maximum current. Your supplies may have an adjustment for the voltage output so maybe you can get some cooling adjustment that way.

Plywood is very heavy. Fiber glassed foam would be best but you need experience to build it that way.

 

Yeah- like I said it's a prototype. If I get the bones right then the sky's the limit. My Wife kicks butt with fiberglassing...If I get a core system going and have different shells... That would open the doors to Steampunk, Ren Fair and Gothic venues. Man I am glad I found you guys. You are a great think tank! Well...that is if I can get this thing working without killing myself.

I just had a chance to pull part of the coolers apart- the one by the top shelf had 4 small chips strung in series, one of which looked to be cracked when he tightened the anchor points.

The two bottom cooling units are actual full units he pulled from the wine chiller so I'm going to wait till the PS get here to see what THEY can do.

I still need to get some type of temperature controller but damn $200+ better come with a happy ending.

 

Would something like this work for the temp controller?

Temperature Controller Thermistor 110V F from Cole-Parmer

 

I think I found a better Temp controller...

http://www.amazon.com/Elitech-All-Pu...Z9B58JMHBBHR0Z


Got the power supplies in today and wired them up.

From the Plug to the wall I have:
Green: Ground
White: Negative
Black: Positive

The DC Block I took:
Red: Positive
Black: Negative

each pair I separated and heat shrunk them. One will be for fans- the other for the coolers.



Waiting on the Multimeter I ordered to show up so I can test the voltage before I hook it up to anything.

Now if I got the controller I linked to above...I would wire the PS to it...and then the Chiller unit to the Controller right?

 

Ehhhhhh.... yes that controller will work but it's not ideal. It's 16amps and runs on 12vdc. That means you can't use it to control the AC to the power supplies since when you turn off the power supplies you no longer have 12v.

If you wanted to switch the 12v on the output of the power supplies you would need one for each power supply or a relay to control power from each supply to its own chip and fans.

I think I'd opt for a mechanical thermostat with a two pole switch.

 

I also agree it would be best to have your thermostat or controller switching the AC power. That way you will only need to switch an amp or two. Just make sure your thermostat or controller can handle the 120 VAC and a few amps or more of current.

 

So having it through the Ac is better... so THIS one?

http://www.amazon.com/Docooler-Tempe...ref=pd_cp_hi_0

How would I wire that? Wall plug-Controller-Power supply?



This one lists 110-120V
http://www.amazon.com/110~120V-Digit...ure+Controller

 

Looks like that first one should work and it has a lot of good reviews. My guess is you wire a normal 120 VAC plug to it and it has a relay that drives the load. Can't be sure until you see the users manual.

 

The way I was thinking this would play out was each power supply would be hooked up to a single TE unit and a few fans. The AC plug of each power supply would go into the surge protector strip (which also has the plug for the led lights). The On/Of button is linked to the power strip.

It's either all on...or all off.

If I get the controller and wire it to the AC line I would still need 2 of them- one for each Power supply...or am I stringing the power supplies together somehow?

 

Alrighty then. Mad Valentines day rush is over and I got all my parts. Going to crack the bottom off and do a rough wiring...take some readings and see where that gets me. Going to see what a single chiller unit/psp/controller does first. Might not NEED two.

Wish me luck and thank for the Help!

 

Kidding...

Ok. I have the AC to DC PSU (wired in pic already), the TCU (as suggested I got the AC unit), and the DC Chilling unit.

Here is the wiring they give with the TCU:



How am I to wire this thing with the AC based TCU when the TCU will be controlling the AC power to the power supply and not the DC chiller unit? If I wire it like this won't that be a short?

Suggestions? Advice?

Thanks again.

 

I think all you need to do is plug your power supply that powers your cooler chip into the load (outlet).

 

Confused by that...

wall socket------>PSU for case---->(converts to DC)---->Cooling unit

The AC TCU would have to go between the 120VAC cable from the wall to the PSU to control a AC adjustments. But the wiring diagram looks like I would short it out to power the TCU AND use the TCU to control the PSU.

Wall socket------>TCU----->PSU input---->(Dc conversion)----->Cooling Unit

I must be missing something simple. I'm thinking I should have gotten the DC TCU.

 

The far left labeled power (black and white) is your power cord that plugs into the wall socket. The load is switched with a relay in the TSU and drives an AC outlet you have wired. So the TSU switches that load on or off according to the set temp. So when you plug your PSU into the load outlet it will switch the AC on or off to the PSU.

 

But that's where the confusion is. There IS no other plug or Ac outlet. The output was to be direct DC right to the chiller unit.

I have watched all the vids on Youtube. What they are doing is making this (The TCU) into something that has a floating outlet that they then plug an AC heater and/or an AC Chiller into it. The TCU turns off/on the power flow to one or the other outlet depending on the setting.

Not what I was shooting for.

What I needed was the plug from the wall to go into the AC PSU...convert to DC...connected to the DC Chiller unit and fans.

I then wanted to add a TCU in there. I was looking at a DC based unit so I could drop it right in line with the chiller on the PSU output side.

PJ suggested an AC unit so that it would adjust the power to the PSU...I figured I'd give it a swing...I just don't see how to wire it.

Times ticking so I went and ordered a DC version but if PJ is out there...if you can talk me through it I'll give your idea a shot.

 

It is much better to switch the AC to your power supply since the current of the AC would be much lower than switching the DC current. If you insist on switching the DC current, make sure the unit can handle that 30 amps of current.

 

I'll give it another try- if it's a better idea I'm all for it. It just looked like it would short out is all. I'll wire it up and see what happens.

 

Hi All! I'm back...

Just for slaps and tickles I went with the DC Temp Controler and two TEC1-12726 Peltiers.

It just didn't understand how to wire the AC controller like you guys were saying. I would have had to wire one power supply to the other to make it work and even THAT makes my head hurt. Anyhoo...

I wired everything all nice and neat- tested with the meter and got great juice to all points. I wired the TEC chips right to the PSP and they work (hot side hot/ Cold side cold) I then rewired in the Dc Controller. Still worked...

I closed it up and let it run for a few hours. There was no Temp Change in the case. I'm going to try to let it run all day tomorrow to see if I get ANYTHING.

I'm guessing adding more TEC chips might be in order... *sigh*

 

I was just looking back at your pictures...... how do you connect the module to the coldplate. I see fans to remove the heat from the one side but I don't see the cold side.

 

It's just about mirrored on the inside- There is a Heat sink thermal puttied to the cold side of the chip and a fan blowing on the heat sink. I'll try to get a pic.

Ironic thing here is I was just on Ebay and now they sell full kits for under $40. Damn prototyping is a costly game. Though I got the Chocolate Boards hopping if I can get this working. Hell if someone would have been able to sell these (smaller) cases for under $500 I would have bought a few. Anyway- I'll be back with a pic.

 

Here is one with the cold side Heatsink poking through...




Here is one of the fan that WAS blowing into the heatsink- I just reversed it so it will be blowing OUT into the case just for slaps and tickles...




Here is a inside shot of the TOP plate- no chiller attached yet...fan is dangeling below it.


When the remaining chips come in I'll have the fan blowing INTO the case...I never noticed he had them reversed before...




Thanks for still being there and willing to talk me off the ledge PJ. I need to get SOMETHING working so I can get back to selling shows-

Once I get the MONSTER going...then I got two more smaller units to build.

(Archer Voice) Yaaaay (/Archer Voice)