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I have a quick question. I read the sparkfun tutorial on building a regulated 5V power supply. However, the recommended input voltage for the Mega2560 is between 7V and 12V. Am I missing something? Thanks in advance.
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Am I missing something?
You are missing the question?

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the recommended input voltage for the Mega2560 is between 7V and 12V
Yes it is to minimise the heating that takes place. You can put in a higher voltage but the regulator gets too hot.
Read this:-
http://www.thebox.myzen.co.uk/Tutorial/Power.html
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Sorry, perhaps I should rephrase. Why would sparkfun create a tutorial on creating a 5V powersupply for the Arduino, when the Arduino is supposed to run on 7V-12V?
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I don't think you connected the grounds, Dave.
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Because the AVR runs off 5V?
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I think I understand. The Arduino has a built in regulator that brings the voltage down to the 5v needed to operate. That means you can power it externally by a wallwart or battery pack, but the voltage should not be higher than 12v, else you would burn up the built regulator on the board. Sorry for the noob questions, I have only been programming and using a microcontroller for 2 days.
« Last Edit: March 29, 2011, 02:59:12 pm by polykarbon » Logged

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I'm fairly new to all of this, so anyone feel free to correct me if I'm wrong, but...
You have two basic options to power the board, the first is to give it a regulated 5V, which would come in either from the barrel plug, usb, or directly to the +5V pin on the board.  The second option is to supply unregulated voltage of between 7-12V to the Vin pin, which the on-board regulator will limit to 5V.  Voltage lower than 7V might not be enough for the regulator to produce a steady 5V and greater than 12V can cause the regulator to overheat.  The end result of this is, if you want to use batteries, then you should have 7-12V and hook them up to Vin.
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The barrel jack is on the input side of the regulator so it needs 7V+ (in fact it connects to Vin via a reverse-protection diode) - the board auto-switches between USB and regulator as needed.
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