Powering an Arduino

If I'm using a 9V battery to power an Arduino Uno, can I still use the +5V pin instead of the Vin pin?

NO!

The Vin pin is BEFORE the 5v regulator. The +5V pin is AFTER the 5v regulator. Putting 9v on the 5v pin would likely fry your Arduino.

If I'm using a 9V battery to power an Arduino Uno

I hope you have deep pockets.

I think you've misread the question. If you power the Arduino form 9V (via the jack or Vin) then the 5V pin is available to serve 5V to other components.

I think that was what was meant? Basically you can provide a well-regulated 5V to the 5V pin, OR provide 7+ V to the Vin or jack. In either case the 5V pin is at 5V and can provide some power to other parts of the system.

I hope you have deep pockets.

The next one-line out of context question will be, "Why does Arduino stop working after a few minutes?"

You guys misunderstood my question, only MarkT got it. I'm powering the Arduino through the power jack, I just want to know is the 5V pin available at 5V for use while powering 9V through the power jack.

I'm powering the Arduino through the power jack,

If you're powering the Arduino from a 9V battery through the power jack, my earlier comment still stands. (I think James C4S's comment stands too)

he he , how to create a lot of confusion, just ask ]:)

No offence :)

So how to not spoil my Arduino?

Is connecting a 9V battery to the power jack ok then?

Is connecting a 9V battery to the power jack ok then?

Yes, but 9V batteries are terrible devices for use with the Arduino. They have a very low amp hour rating, so they can not supply much current, for very long. For the price per amp hour, they are the highest cost batteries generally used.

4 AA batteries in a holder are a much better choice.

So using 4~6x AA batteries would be OK, right?

But why do others say that using a 9V will fry my Arduino?

But why do others say that using a 9V will fry my Arduino?

Nobody said that. We were making the point that 9Vs are very lousy choices for most projects because of their low current capacity. After using one your next question was sure to be "why doesn't this work for very long?"

ohh, i'd thought that it had fried the Arduino till it's stopped working. What a misunderstanding.

low5545: But why do others say that using a 9V will fry my Arduino?

Your original question said: "If I'm using a 9V battery to power an Arduino Uno, can I still use the +5V pin instead of the Vin pin?"

The natural interpretation was that you wanted to use the +5V pin for your 9V battery input. That would be bad for the processor.

O, my fault, sorry