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McGuire AFB, NJ
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Hi All,
I modified an old ATX 250W power supply to provide 5V and 12V for little projects. When I plugged my arduino into the 12V line, it worked fine, but the IC next to the power jack (I'm assuming the power filter) got real hot, real quick so I unplugged it. So my question...

Is it safe to plug a 12V power supply around 10Amps into the arduino? Or will this destroy (or significantly shorten the life span) of the arduino?

Thanks
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Copenhagen / Denmark
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The IC next to the powerjack is the voltage regulator. It will trans´form the inputvoltage to 5V regulated.

It needs a voltage from 7 - 12 volts. The igher the voltage the more energi is converted to heat inside the regulator, and the warmer it will get.

You should be OK with a 12 V supply, read here: http://www.arduino.cc/en/Main/ArduinoBoardDiecimila

But depending on what you have connected to the Arduino board that is also powered from it you might need a heatsink on the regulator.

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Brisbane, Australia
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You can just use the 5v directly.
Dont put it through the power plug. Put it straight in to the 5V pin.
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Greenwood, Indiana
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http://www.fairchildsemi.com/products/discrete/packaging/dpak_to252.html

If it's that IC it's the voltage regulator which takes 7-12 volts and outputs +5. If the arduino was working and that got hot the switching supply may not be regulating which would place too much voltage on all of the power supply parts in the arduino.

http://web2.murraystate.edu/andy.batts/ps/POWERSUPPLY.HTM

This shows a resistive load on the +5V of the PC power supply to keep it happy. It even states that those supplies can be damaged without a load.

I highly suggest installing that resistor and also getting a multimeter.  Then get an automotive 12V bulb and put it across the +12V supply and read the voltage with a meter. If it's 12+-2V it should be ok.
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If it was designed by man it can be repaired by man.

McGuire AFB, NJ
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It is that IC.

There is a 10ohm 10W ceramic resistor on one of the 5V lines, I mostly followed the guide on the link you posted, along with this one.
http://www.instructables.com/id/Convert-an-ATX-Power-Supply-Into-a-Regular-DC-Powe/?ALLSTEPS

I haven't read the meter under load, but w/o a load the meter says 12V +/- less than 0.5
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