Your help needed (for noob): Trippy A/C project for rat cage

[Ken B.]

Hey guys,

I wanna get some pet rats, but where I live it can get hot some days. I am thinking I can build a room (within the cage) for them that has a mini TEC-based (Peltier junction) air conditioner blowing cool air into that room. I can get the required parts for super cheap on Ebay, so I thought it would be worth checking out.

Now this isn't a very efficient way to cool a rat home, I know. But I just want them to be safe when it gets past the 80's, because they can suffer heat stroke/exhaustion when it gets too hot unless there is a way for them to cool down. Turning on a small A/C setup would allow me to go somewhere for a little while if I need too and wasn't able to monitor them.

So my question basically centers around PSU requirements for either a 70 watt/10amp or 123Watt/8amp (or thereabouts) Peltier element. I have a spare Enhance uATX PSU laying around that is brand new. The specs are as follows:

DC Output
+3.3V/17A
+5V/21A
+12V/13A
-12V/0.8A
+5Vsb/2A

+3.3V & +5V combined load = 130W
+3.3V & +5V & +12V combined load 190W
TOTAL OUTPUT MAX LOAD 200W

If I use the 12V off the molex connections to power the TEC, then am I reading correctly that I only have about 60-70W of available power to juice a TEC, using this PSU?

If so...are there options that I could implement to use the 123W TEC using this same power supply (like combining connections or something to get the full 200W)?

[mantralord]

The PSU has 156W available on the 12v, which should be enough to power the peltiers. I would personally use a PSU with a larger 12v amperage to avoid any crossload issues but give it a try anyway.

Rats don't like breezes, but a small amount of airflow will help cool them down a bit. If you manage to get this implemented somehow, keep the airflow over the cage to a minimum. Instead, help them cool off by putting some ice in their water bottle, and feeding them some frozen fruits/veggies. I've even given my rat an ice cube to lick on and she likes it.

[Ken B.]

Hi mantralord,

Hey, thanks for responding!

Ok, so how did you calculate that I had 156W available?

I was thinking if the 3.3v and 5v lines combined were 130W, then I only had 60-70 more watts available on something else, which I would suppose to be the 12v lines. But then again, I really don't know much about electric, or PSU's really.

By the way, I was considering deflecting and dissipating the cool air flow from the cool side of the TEC into the rat room so that the breeze issue wouldn't be an issue.

[Denbob99]

Volts x Amps = Watts. Think back to Physics Ken! Think!

[Ken B.]

Hi Denbob99,

I don't understand. If volts x amps = watts, how come some power supplies list the combined output of 3.3v/17A and 5v/12A as 70watts output, when it's supposed to be 116.1W?

Obviously, I don't know jack about PSUs or electricity. Any help is appreciated.

Thanks!

P.S. Maybe someone can list a site that talks about how power supplies work?

[Dapper Dan]

dude you are my hero ... sersly ac for pet rats omg genious

[UglyChild]

By the time you spend all the time and money building one of them AC coolers. You can go to HomeDepot, K-Mart, or Wallmart and get a nice very simple room AC unit, for about the same or less amount.

If you still want to build one. Then get your self a +250watt Peltier. That will get things cool.

[Mdogs444]

But for rats?!

[emceepecks]

But for rats?!

:clap:

[Kil4Thril]

Rats ROCK! Great pets. I picked up a room A/C unit brand new at Sears for $60. It helps 2-fold. I have 4 computers and my rats in my office. Keeps all of them (and me) cool enough. I only need to run it at 25% to make it actually too cold. The only thing I worry about is total power consumption on the breaker. a Single 15 amp circuit is a bit light for what I have running, but it's fine so far.

[Section8]

Walmart has an air conditioner for like $100 that has to be cheaper than what your planning on doing. It will cool like a 12Ft X 12Ft room no problem.

http://www.walmart.com/catalog/product.do?product_id=4456963

http://i.walmart.com/i/p/00/68/80/57/34/0068805734444_500X500.jpg

[Moto7451]

Hi Denbob99,

I don't understand. If volts x amps = watts, how come some power supplies list the combined output of 3.3v/17A and 5v/12A as 70watts output, when it's supposed to be 116.1W?

Obviously, I don't know jack about PSUs or electricity. Any help is appreciated.

Thanks!

P.S. Maybe someone can list a site that talks about how power supplies work?


Thats because the two rails are actually from one power rail that maxes out at 70 watts.