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Amp question


barmer

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I am installing a cold cathode computer light for a moonlight. I could use a big bulky pc power supply I have lying around or a 12V adapter I have. The problem is the adapter is rated at 1200 mAmps. A typical computer supply is rated at 12 Amps for 12V. I believe with a power supply that whatever is hooked up to it only draws what amps are needed, because it is a switching supply.? With the adapter I believe I am stuck with 1200mAmps. Is this the fact? Is 1200 mAmps enough or too much for these? They are dual 12" cathodes that have an inverter that converts the 12v's to around 640V. I know that other people have just hooked up an adapter and gotten by just fine, but I have been through a house fire once and don't want to go through that again. Besides I don't want to have to by new lights again. On the wall adapter one wire has a white line running down it's length and the other is totally black. Which is + and which is - ? Just checked the and the light package says"5 mAmp draw". So does this mean it will only use 5 of the 1200 mA on the wall adapter, with the 1200mAmps rating telling me that I can use items that DRAW up to 1200? Teach me wise ones.Thanks all:)

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neanderthalman

The 1200mA rating of the power supply is the maximum current output of the power supply. The power supply is a voltage source, the current output will depend on the device you are powering. It will provide only enough current that the device requires.

 

The only problem I see is that a great many 12V power supplies are not regulated. If you are only drawing a tiny fraction of the maximum current output of the power supply, then the voltage of the power supply may increase. This could damage your lighting.

 

The computer power supply is regulated, and does not suffer from this problem. It seems like overkill, however.

 

Try to find a 12V wallwart that's only got something like a 200mA max current. You'll be fine with that.

 

The black vs. black w/ white stripe is supposed to be a standard, but it rarely is. Try it one way, and if it doesn't work, flip it around. If you're concerned about damaging the light by doing this, test it on a 12V fan. Once it's spinning in the right direction, you know your polarity. You can also get a cheap crappy multimeter for a few bucks at a DIY store. I wouldn't trust my life to one of them, but it will tell you the polarity of the wires.

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The 1200mA rating of the power supply is the maximum current output of the power supply. The power supply is a voltage source, the current output will depend on the device you are powering. It will provide only enough current that the device requires.

 

The only problem I see is that a great many 12V power supplies are not regulated. If you are only drawing a tiny fraction of the maximum current output of the power supply, then the voltage of the power supply may increase. This could damage your lighting.

 

The computer power supply is regulated, and does not suffer from this problem. It seems like overkill, however.

 

Try to find a 12V wallwart that's only got something like a 200mA max current. You'll be fine with that.

 

The black vs. black w/ white stripe is supposed to be a standard, but it rarely is. Try it one way, and if it doesn't work, flip it around. If you're concerned about damaging the light by doing this, test it on a 12V fan. Once it's spinning in the right direction, you know your polarity. You can also get a cheap crappy multimeter for a few bucks at a DIY store. I wouldn't trust my life to one of them, but it will tell you the polarity of the wires.

Thanks

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The 1200mA rating of the power supply is the maximum current output of the power supply. The power supply is a voltage source, the current output will depend on the device you are powering. It will provide only enough current that the device requires.

 

The only problem I see is that a great many 12V power supplies are not regulated. If you are only drawing a tiny fraction of the maximum current output of the power supply, then the voltage of the power supply may increase. This could damage your lighting.

 

Try to find a 12V wallwart that's only got something like a 200mA max current. You'll be fine with that.

Just checked out a basic electronics sight and had various people give me AC/DC converter 101. All said that as long as the amps don't exceed the max listed your o.k. even if it is only 5mAmps on a 1200mAmps converter. Hope this helps some one else out. :D

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neanderthalman

Just letting you know what I've learned from experience. You'll probably be fine, but you reduce your chances of catastrophe if you use an appropriately sized power supply. Most applications with "basic electronics" aren't dealing with sensitive electronics, including LEDs, microcontrollers, and possibly your CC driver circuitry.

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