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[Reply #30 on:]

6 AAA cells are considerably smaller... and Lefty is right.. use the on-board Band Gap Reference.

Bob

[Reply #31 on:]

But will a 12 v battery work? Since its within the input voltage range, can I hook it up to the voltage in pin of the arduino?

[Reply #32 on:]

But will a 12 v battery work?

Just hook up your 4 aa batteries and you will have known by now if it works - no point of wasting your time on all the non-sense.

Just do it.

[Reply #33 on:]

You can always rig up a dc-dc converter to bypass the v.reg, but why even bother? It's
10X easier to just use 6 cells. GOSH! "it's wasting battery power". Gee, it's only 70%
efficient [100%*5V/7.2V] instead of 80-90% efficient, so what, maybe the world will
end tomorrow too.

Maybe it needs to be small.

[Reply #34 on:]

But will a 12 v battery work? Since its within the input voltage range, can I hook it up to the voltage in pin of the arduino?

It's kind of on the limit, but yes.

The main problem is you're throwing away over half the battery power as heat (that might be a problem to you but it makes the engineers on this forum cringe...)

[Reply #35 on:]

I'm building game show buttons. It has 16 LEDs, and one small speaker. The lights only go on when someone pushes a button.

3xAAA plus a DC booster...

http://www.ebay.com/sch/i.html?_nkw=5v+dc+boost+-usb

Also ...an Arduino Uno is a big waste of power if you have a regulated supply. Use something like this for the final gadget:

http://evilmadscience.com/productsmenu/tinykitlist/180

No voltage regulator and no USB-to-serial circuitry - the batteries will last a lot longer and the difference in price means you get the DC booster for free.

They even have a battery box option, but I'd still use the DC booster just to make sure everything runs at 5V.

[Reply #36 on:]

http://evilmadscience.com/productsmenu/tinykitlist/180

Note: That page shows a Diavolino with a 3xAA battery pack. A Diavolino will run off 3xAA batteries because there's no voltage regulator circuitry, protection diodes or anything else on the board to get in the way (unlike an Arduino Uno which has all of those).

With A Diavolino you only need 5V if whatever you're connecting up to it needs 5V.