Arduino Uno on 3.3 volts instead of 5?

Can I use a 3.3 voltage regulator to power a board with a ATmega328 Arduino Optiboot (Uno) and expect it to work just as well as with a 5 volt voltage regulator?

thanks in advance, f

fabienLyrique: Can I use a 3.3 voltage regulator to power a board with a ATmega328 Arduino Optiboot (Uno) and expect it to work just as well as with a 5 volt voltage regulator?

thanks in advance, f

Atmel rates their 328p chip operating voltage range depending on the clock speed you are running the chip at. For 16Mhz clocking that the standard Uno board uses, 3.3vdc is too low to meet their recommendations. That aside many people have run a 328p @ 16Mhz and @ 3.3vdc for Vcc voltage and reported no problem. So it depends on if you wish to follow the manufactures recommended operating conditions or not. Running a 8Mhz at 3.3vdc Vcc voltage is within recommended specifications.

Lefty

oh, I forgot. If this is doable, I can use a 3.3 voltage regulator straight from a 9 volt battery (with the regulating caps on each pin to ground)? Like this one; http://www.sparkfun.com/products/526

or do I still need to go from 9 volts to a 5volt regulator THEN to the 3.3 one? Sorry. NoooobbBB here... :-(

huh. Thanks Lefty. I guess the best way is to just try it and see if I works! Thanks again. But if so, can I still go from 9 volts to the 3.3 voltage regulator?

fabienLyrique: oh, I forgot. If this is doable, I can use a 3.3 voltage regulator straight from a 9 volt battery (with the regulating caps on each pin to ground)? Like this one; http://www.sparkfun.com/products/526

or do I still need to go from 9 volts to a 5volt regulator THEN to the 3.3 one? Sorry. NoooobbBB here... :-(

It would work in theory but it is very poor choice from a efficency point of view (wasting battery power) and could even cause overheating shutdown of the 3.3v regulator depending how much current your project consumes. Those small 9vdc batteries are a very poor choice for powering a arduino project, they are very expensive for the very small amount of total energy they supply. Why don't you consider using 3 series AA battery cells, either alkaline or rechargable? They would last a lot longer and you would then be within recommended voltage for running at 20Mhz and rechargable AA cells are the most cost effective route to take over the long term.

Lefty

wow. never thought of that! And considering I am using it with a bluesmirf and efficiency with power is important, this is even better. I have already gone through 2 9v batteries just in testing....

or even better, I could use AAA's which are even smaller!

fabienLyrique: wow. never thought of that! And considering I am using it with a bluesmirf and efficiency with power is important, this is even better. I have already gone through 2 9v batteries just in testing....

Good, I'm glad you understand that. So many newcomers see the pretty pictures of using a cute 9vdc battery plugged into an arduino external power connector using those simple cable/connector supplied free from many sellers and think that's cool I understand that perfectly, just like a smoke alarm uses. ;) The truth is that is probably the worst possible way to power a arduino board and is a real rip off in battery consumption cost.

So if you use non-rechargable alkaline AA cells, use 3 series connected (for a 4.5v nominal voltage). If you use rechargable Nihm or Nicad AA cells use 4 series connected (for 4.8v nominal voltage) as their voltage is a little lower then the alkiline types.

Lefty

fabienLyrique: or even better, I could use AAA's which are even smaller!

But with lower current capacity and lower total battery run life (mah rating). AA cells are the best from a cost Vs run time point of view. If size and battery current capacity is critical to a specific arduino portable application then Lipo cells offer the best energy density Vs size and weight point of view.

Lefty

Oh, ok. then AAA's are not good for my project. It seems AA's are the way to go! Wish they told me that in school. I would have saved a lot of money on 9v batteries....

fabienLyrique: Oh, ok. then AAA's are not good for my project. It seems AA's are the way to go! Wish they told me that in school. I would have saved a lot of money on 9v batteries....

Here is what you should look for:

3 cell for using alkaline AA batteries: http://parts.digikey.com/1/parts/5290-holder-batt-3-aa-cells-sldr-lugs-bc3aal.html

4 cell for using recharagable AA batteries: http://www.amazon.com/4-AA-Cell-Battery-Holder/dp/B000LFVFT4