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I have a 12V battery and I am running a few circuits along with my arduino uno threw it.  I am using every I/O pin and I am powering the arduino through a 9V 2A regulator.  I have two heat sinks on it and it still gets pretty hot to the touch.  I am using the arduino to run a home security system so I will need it on all the time...24/7 365.  Can the regulator possibly overheat and burn up my system or just my arduino?  I'm not sure what everything on the specs sheet means but it says this:
Junction to Ambient 65C/W
Junction to Case       5C/W
Maximum Operating Temp  125 Degrees C
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Yes. There was a post today where the user actually vaporized one of the regulator pins.
Use an external regulator (such as LM317) and bring the input voltage down to 7.5V.
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Yes, you can burn things out.

Whatever you're doing, it doesn't sound like a good design for a dependable system that has to run 24/7.

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I am using something like the LM317.  Its a three pin 9V regulator.  I think its a LM7809CT.  I'm not 100% sure though.  I have it hooked up through the input jack.  My arduino originally came with a 9V battery pack to power the arduino so could someone explain to me why that would work but the voltage regulator could possibly burn up the arduino???
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I am using something like the LM317.  Its a three pin 9V regulator.  I think its a LM7809CT.  I'm not 100% sure though.  I have it hooked up through the input jack.  My arduino originally came with a 9V battery pack to power the arduino so could someone explain to me why that would work but the voltage regulator could possibly burn up the arduino???

In theory, it ought to be OK.
But statements like "I am using something like the LM317.  Its a three pin 9V regulator.  I think its a LM7809CT.  I'm not 100% sure though" don't make me want to leap up and shout, "Yes, Do It!" 
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An LM78XXCT (and most other linear regulators -- check your datasheet) has thermal overload protection. Not that that is something you should rely on; it's still very easy to vaporize them if you overload them quickly.

Your LM7809 regulating 12V down to 9V at (e.g.) 1A will burn off (12 - 9) * 1 = 3W of heat. That's just how linear regulators work. 3W might not seem like much but it is.

Switching regulator modules based on the LM2596 can be purchased on eBay for under $2 each. They are much more efficient (~90% or more) than linear regulators and should be used for projects that are driving more than ~500ma consistently or when you're on a battery.
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So should I order the LM2596?  Just to make sure.  I have 4 cameras, a DVR and about 5 sensors, also a key pad (that takes up seven of my pins) and I will eventually hook up some burglar alarms when I have this thing fully constructed plus an LCD screen.  Every one of the pins on my uno will be in use.  How much current would that be pulling?  And if I order this voltage regulator what voltage would you suggest I keep it on?  Is 9V too high?  I will have to go out and buy a new arduino because I must have burnt something up.  It is acting funny and I didn't change any of my code or hardware other than hooking that regulator to it.  Thanks for all your help.
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you're better off supplying it 5v with a switching regulator.

http://www.ebay.com.au/itm/DC-DC-Adjustable-Buck-Step-Down-Converter-LM2596-Voltage-Regulator-Input-4-35V-/151006957150?pt=AU_B_I_Electrical_Test_Equipment&hash=item2328b74e5e
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Yes. There was a post today where the user actually vaporized one of the regulator pins.
Use an external regulator (such as LM317) and bring the input voltage down to 7.5V.

While yes, any arduino clone, anything over 9v will usually fry the regulator, the official one supports 12v just fine, the cheap ones (cloned with cheap parts) don't they get so hot and let the current through that in turn gives 9v+ to the poor microprocessor.

however.

Can my Arduino burn up if my voltage regulator overheats?

depends what the voltage regulator it is..... that should answer the question properly, i can't imagine a lm317 doing anything but reducing the current if there's a short or overload.



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I have 4 cameras, a DVR and about 5 sensors, also a key pad

...but you can't afford a proper 5V regulated power supply, you're relying on the Arduino's tiny onboard regulator?

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Affording it isn't the problem it is the lack of knowledge.  Although I guess making mistakes along the way is a great for learning what to do and what not to do.  Can anyone tell me how much current my board eats up?
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if you have a multimeter, you can use that to measure the current...
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