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12v DC converter question

post #1 of 9
Thread Starter 
If I am trying to wire 2 Scythe GT1500s and one pump requiring 3a of 12v power together, and I wanted to supply this power directly from a wall socket, what kind of DC converter should I use? I've felt those things get really hot when using them for the wrong appliance, and just want to understand the restrictions.
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post #2 of 9
    That's a lot of power for a wall-wart.  As far as understanding the restrictions: You'll need a switching style (instead of transformer style) power supply.  Most all power supplies have their ratings listed on a sticker.  You need one that supplies 12v with more power (in Amps) than you need.
    First of all, I don't know why you don't just connect the devices to your PC's excellent 12v output rail.  Anyway, the best source of high-power 12v power supplies are LCD monitors.  Many of them (and most all of the LED backlit ones) use an external tabletop AC/DC converter that is 12v and can do several amps.  Tabletop converter means that it sits on the table and has a cord coming out of both sides, one for the wall and one for the device.  Laptops almost always use these; but they're usually 18–20v instead of 12v.

    I hope that helps! thumb.gif  Don't forget to check voltage and polarity with a voltmeter before connecting your device!
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post #3 of 9
How about a cheep computer power supply?

Rosewill SL-300TFX 300W TFX12V Power Supply - OEM $25.

Or do you have something just laying around?
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post #4 of 9
Thread Starter 
This isn't for a PC. It's for an air conditioner. A bilge pump mounted in an ice chest pumps ice water through a heater core, air is taken in through a vent in the top of the cooler, and pulled through the heater core, also mounted in the top of the cooler.

I understand I could use one of the extra PSUs I have laying around, but I'd prefer this be more portable.
Quote:
Originally Posted by Techie007 View Post

Anyway, the best source of high-power 12v power supplies are LCD monitors.  Many of them (and most all of the LED backlit ones) use an external tabletop AC/DC converter that is 12v and can do several amps.  Tabletop converter means that it sits on the table and has a cord coming out of both sides, one for the wall and one for the device.  Laptops almost always use these; but they're usually 18–20v instead of 12v.

I like this idea. Could I use an inline car-type fuse to protect both the circuit and the supply? My 27" 2560x1440 LED has one of these but it puts out 24v. Any way to safely convert that to 12v?
Edited by jadawgis732 - 6/6/13 at 12:35pm
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post #5 of 9
    Yes, it can be converted to 12v with some difficulty (you would have to build a buck converter); however, I recommend simply looking for a different LCD monitor power supply.  All the ones I've come across output 12v (and I sometimes cut the cords off and connect them to one of the 12v outputs on their computer's power supply, thus powering the LCD monitor directly from the computer).  So the 24v one that you have would have to be an exception!
    If you have any thrift-stores near you, you could look for old LCD monitors with external power supplies there.  Some thrift-stores even have a collection (heap?) of wallwarts and tabletop power supplies that you could look through.  Wait—I just got an idea...I just did a search for "LCD monitor power supply" on eBay, and there are over 5,000 listings.  Many have the specs listed adequately, so you should be able to find a 12v one that does enough power there.
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post #6 of 9
36watt is pushing it for a wall wart, but they make them...

http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2151208_-1


High-power 12v PSUs aren't hard to come by, look around long enough and you'll find one. You could also get one of those home cigeratte-adapter things for powering car things in your house. The higher voltage won't hurt anything.
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post #7 of 9
Thread Starter 
Okay, I checked my stock. I have one 19v and one 31v laptop power supply. If higher voltage won't hurt anything, can I use the 19v one? If not, eBay will not be an issue. I can use a spare desktop PSU in the mean time and order a 12v one online.
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post #8 of 9
    19v is 158% the rated voltage (assuming that the rated voltage is 12v).  I wouldn't push my luck with it.  If it is a DC brush motor, it will run a lot faster and won't last as long (it may even burn up), and if it is a brushless DC motor, that much of an overvoltage will probably burn it up in a few minutes.  I would go with the computer PSU for now.
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post #9 of 9
Thread Starter 
Thanks for the help guys. Picked up this guy on Amazon for less than $10, and it works perfectly!
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