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AC to DC adapter...12 amps?

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#1 Jon Rista

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Posted 06 August 2014 - 11:02 AM

Hi guys,

 

I have a quick question. I've built myself a DSLR cold box. This puppy actually uses two peltiers, one attached to either side of the box, for maximum cooling in the event I need it. I think normally (spring/fall) I'll only need one peltier to be running, but I want to be able to switch the other on for more rapid cooldown and better cooling during the heart of summer. It is actually still a project in progress, as I am also working on an Arduino-powered PWM-driven regulator that will use thermistor input to regulate the power to the peltiers. I'm waiting on a couple mosfet and inductor & capacitor parts to build an LC filter to feed clean consistent power to the peltiers.

 

The kicker is the power. Both of these peltiers are 12v (7-15.4v range) 5.8 amp. At maximum power, they draw 11.6 amps. I've been looking around, and for the most part it seems most AC to DC converters are 5 amp. I found one that was 10 amp. Is it even possible to find an AC/DC converter capable of supplying 12 amps of power? Once initial cooling is done, the Arduino setup should throttle the power, so during sustained operation I shouldn't need that much...but I don't want to have to wait an hour or so for the temperature to settle at it's minimum level so I can get started on imaging. It would be great if I could find a single adapter capable of supplying the power I need, so I don't have to use two adapters just to power the cold box.

 

 



#2 BarryBrown

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Posted 06 August 2014 - 11:21 AM

An inexpensive computer power supply should be able to provide that much current. A 400W power supply can deliver over 20 amps of 12V power if you bundle all the wires together.

 

http://www.instructa...-Powe/?ALLSTEPS



#3 aorion314

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Posted 06 August 2014 - 11:46 AM

 aorion314 here, this may be an ignorant comment ????? 12 amps of power isn't that a major overkill in the amps dept., most everything i read here in CN quotes max power usage in the 0.5 to maybe 2 amps max. My concern is are you going to blow out your electronics? Hell my vacumn cleaner uses 12 amps and will actually dim the light in 1 room in my home. ??? does a peltier cooler draw that energy to lower the temp.Perhaps you misplaced a decimal when doing your calcualtions for power needs.


Edited by aorion314, 06 August 2014 - 11:48 AM.


#4 SMigol

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Posted 06 August 2014 - 12:20 PM

Peltier devices will pull that much at 100% power, especially the ones used to cool CPUs and DSLRs.  The ones I use on my system will pull 6 A at 12V.

 

I picked up a 20 A power supply from Radio Shack about a year ago.  Now that they're going out of business, you might be able to find one on clearance.  Look at the reviews on Ham radio sites for power supplies that provide noise-free power.  Pyramid is a common brand of bench power supplies.  Note that bench supplies don't like to be exposed to dew.  Might consider a LED power supply since those can handle full weather exposure. 

 

At home, I leave the power supply on overnight and the internal heat keeps dew at bay.  So far, it's working fine.



#5 Midnight Dan

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Posted 06 August 2014 - 01:52 PM

Hi Jon:

 

Just want to point out that the peltiers are cooling the air in the box, not the camera directly.  As such, there will be very little heat load on the peltiers initially, even when warm.  A single peltier will cool the air in the box very quickly. 

 

The time involved has to do with the camera and sensor slowly giving off their heat to the cooled air.  The outside of the camera will cool down reasonably fast, but there is little air circulation occurring inside the camera so it will take a while for the camera parts to conduct the heat to the outside where the peltiers are cooling the air.  This will happen slowly, and if the one peltier can keep up with the heat load (which I think it probably will), then 2 of them will not make it happen much more quickly.

 

Personally, I'd go with one device.  A 5 amp unit should be plenty.  But ... don't forget to add the current needed for other parts of the system like the fans.

 

-Dan



#6 amicus sidera

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Posted 06 August 2014 - 05:02 PM

You need a power supply for that much current, not an adapter! Here's one that will cruise at 12 amps:

 

http://www.mfjenterp...ctid=MFJ-4035MV

 

Not too expensive for its abilities; no RF hash, either. Hope this helps.

 

P.s. Be absolutely sure to fuse your setup properly, as that supply can easily produce enough current to melt wires and start a fire.


Edited by amicus sidera, 06 August 2014 - 05:10 PM.


#7 plav1959

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Posted 06 August 2014 - 05:18 PM

http://www.amazon.co...y/dp/B0002JTD20

 

 

Light weight and low cost. Never had any problems with any of mine.


Edited by plav1959, 06 August 2014 - 05:25 PM.


#8 ccs_hello

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Posted 06 August 2014 - 07:59 PM

I'd suggest getting two 12V 6A "sealed" power adapters (72W each.)

Each should be good enough for your one-unit peltier (60W.)

Each of these power bricks looks like a laptop power supply and I have seen them selling at less than $10 shipped.

 

BTW, I do not recommend "open frame" power supply such as Desktop PC's power supply in the outside (hazardous energy inside!)

 

Clear Skies!

 

ccs_hello 



#9 Jon Rista

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Posted 07 August 2014 - 06:28 PM

Hey guys, thanks for all the feedback. I appreciate it. I think your all right, I probably need a power supply to run both peltiers at once. I'm going to stick with just one for now, see how things go. Temperatures have dropped a bit recently, we no longer have 75°F or higher nights, temps are down into the 50s at night now, and one peltier should do. The heatsinks I ordered for the hot plates turned out NOT to be what I thought they were, so I gotta figure out a solution for that. Doesnt look like I'll have any clear nights until the 16th at this point, though, so I have time.






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