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Topic: Why not a voltage selector on the Arduino board? (Read 1 time) previous topic - next topic


Yep. But as far as the original topic of this thread is concerned:

My home brew boards all have jumpers to select Vdd = 5V or 3.3V. I've been running 328's
at 3.3V and 16 Mhz fine for year now, but all the guys say wait till next year, ya never know.
[just do it, it'll work fine - famous last words, I hope].


My home brew boards all have jumpers to select Vdd = 5V or 3.3V. I've been running 328's
at 3.3V and 16 Mhz fine for year now

That's your choice, but anecdotal tales of running parts outside their spec proves nothing. Going around telling people it's OK to do so isn't doing anybody a service.

No, I don't answer questions sent in private messages (but I do accept thank-you notes...)


are there any possible difficulties or disadvantages to this?

Cost; board space; reliability; etc.


Why Not a 3V3 option? Indeed.
The cost might be in the high $.50 or so.. burdened. Change that 150mA regulator out for a 500mA one and add a 3 pin jumper for Vcc selection. But This Thread really poses a good question, Why Not a 3V3 Option?. From the inception of the Arduino project in 2005 - 6? to now there's been a major paradigm shift in all digital electronics due to "The Need for Speed". Cmos is now king for many reasons and along with it some issues, one being the gate capacitor. Lowering the supply voltage does two things, one is to lower the overall circuit impedance which raises the drive level available to charge the gate region the second is a result of the first. In lowering the voltage the necessary silicon active area becomes smaller and thus capacitance's both of design and stray, etc. become proportionally smaller allowing speed to go up again until the original factors become an issue again. The new 3V3 is 1V5 - 8. So for a 'New' Arduino I should think that provisions to serve both voltages is well in order. If the spirit of a really basic and reasonably indestructible "Trainer" that is well within the budget of nearly anyone who can use the Internet is to be preserved. The Secondary thought that the "Trainer" is surprisingly sophisticated only adds to it's appeal. Some will grow beyond the "Trainer" and for those there are other devices but the form is so well ingrained in the public eye that if anyone wants to sell a "trainer" it had better be "Arduino Compatible" which is a third argument for a dual voltage board as All of the newer devices are 3V3 Max and many now are lower still.

--> WA7EMS <--
"The solution of every problem is another problem." -Johann Wolfgang von Goethe
I do answer technical questions PM'd to me with whatever is in my clipboard


Why Not a 3V3 option? Indeed.

Well the new Due board solved that, it's 3.3v only, slap on a 5 volt shield and it might ruin your day.  ;)

The original Arduino board used a simple 3 pin jumper chip to select USB or external DC power for the board. But I guess that must have resulted in too many questions for problems for begineers so we now have the auto-voltage selector circuit which to me is a waste of board space that could have been used for some more useful function.


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