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Topic: How many mA? (Read 738 times) previous topic - next topic

Drew Davis

Does anybody know how many mA the Arduino Mega's 5v pin can safely supply?


Thanks!!!

DVDdoug

That depends... How much current do you need?   

It's a linear regulator, so the power (and heat) depends on the volatage dropped across the regulator and the current through it.   If you are powering the board from 7V (with 2V dropped across the regulator) you can get more current than if you are powering the board from 12V (with 7V dropped across the regulator).

Itr also depends on what your Arduino is powering...   If you've got a bunch of LEDs connected to the Arduino's outputs, that means less "extra" current avaliable for your other circuitry.

CrossRoads

Up to 800mA thru the 5V regulator with a low voltage source, as DVDdoug says.
http://www.digikey.com/product-detail/en/LM1117MPX-5.0%2FNOPB/LM1117MPX-5.0%2FNOPBCT-ND/660149

http://www.dipmicro.com/store/DCA-07510
Above that voltage, you need to worry about overheating.
Out of that 800, the Mega 2560 uC uses some, the USB/Serial uses some, the 3.3V regulator uses some, whatever IO you are driving uses some ...
So probably on the order of 700mA if you have little to no IO using energy.

If powering from the USB port, the starting number is 500mA, limited by USB port and the onboard 500mA PTC resettable fuse.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Drew Davis


James C4S


It's a linear regulator, so the power (and heat) depends on the volatage dropped across the regulator and the current through it. 

This is, of course, only true when powered by Vin or the Barrel Jack.  If powered by USB, the limit is less than 500mA.  (The USB max minus some for whatever the board itself is drawing.)
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

dhenry

Quote
This is, of course, only true when powered by Vin or the Barrel Jack.


DVDdoug's statement is always true, as it is the law of physics.

James C4S


Quote
This is, of course, only true when powered by Vin or the Barrel Jack.

DVDdoug's statement is always true, as it is the law of physics.

Everything I said in my post is true as well.  The only not adding anything to this conversation is you.
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

dhenry

Quote
Everything I said in my post is true as well.


I beg to differ.

What DVDdoug said is unconditionally true. You conditioned it on how it is powered.

So it is not possible both of you can be true.

James C4S


Quote
Everything I said in my post is true as well.

I beg to differ.
What DVDdoug said is unconditionally true. You conditioned it on how it is powered.
So it is not possible both of you can be true.

In the context of the original question, they are both true.

Again, you are the only one not contributing to this thread.
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

dhenry

Quote
In the context of the original question, they are both true.


Under no scenarios can be both be true. It is pure logic.

What you described is a subset of scenarios covered by DVDdoug's statement. But you made the mistake of stating:

Quote
This is, of course, only true when...


The word "only" killed any chance of it being true, ever.

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