Arduino working at 3.3volts

WARNING! DO NOT TRY THIS!!! (for fear of being vilified like me if you do)
As a lot of the devices I use with arduino are 3.3v logic, I was having to use level shifter I.C's. I found an article on another forum that showed how to convert an UNO to 3.3v by just changing the onboard regulator and adding a diode. I tried this and it works perfectly.
Having had such success, I wondered if I could do the same to a MEGA 2560 r3 but was informed that the processor required a minimum of 4.5 volts. Nonetheless, I thought I would give it a try. I carefully set my power supply to 5volts and fed this to the 5v pin on the board. I ran a fairly complex sketch and lowered the input voltage.
At 3.3volts it was working and continued right down to 2.8volts when it stopped. I then increased the voltage, and it re-started at 2.89volts.
I have since run about a dozen different sketches at 3.3v and all worked flawlessly. Now I will mount a 3.3v regulator and diode on a small sub board and add a switch to select either 3.3v or 5v.
If you try this, be sure to set your power supply to 5volts maximum BEFORE you connect it to the 5v pin as excessive voltage here will destroy the processor and cause other damage.

have since run about a dozen different sketches at 3.3v and all worked flawlessly.

It matters not what you have done the point is that operation at these voltages at 16MHz is outside the processors specification. As detailed in the data sheet.

The "I tried it and it works" argument is very naive and is why there is such a lot of bad electronic designs floating about on the internet. You might find that it stops working at higher temperatures, or at aging of a few months, or in fact anything. If you stick to the spec you still have a job getting a decent design, go outside it and it is impossible.

Well nothing ventured, nothing gained eh! I would agree that trying to run it at a higher voltage would be fraught with risk, but as its running at lower power, there is very little chance of of it causing a problem.
So many times, when someone makes something or tries something that is not "textbook", out come the kerbside and armchair critics who are so ready to pour scorn on inventiveness.
When I worked as a development engineer on several secret government projects, many times "designs" did not work as expected, but trial and error prevailed to success!
Take Sir FranK Whittle for instance, Where would we be if he had just accepted the ministries dismissive attitude? sure Ohain was working on the same thing, but at least he was getting state support!
Anyway, Arduino is designed for experimentation and hacking, and I for one will continue along my own happy path 8)

Them's fightin' words around these parts, stranger :stuck_out_tongue_closed_eyes:

Oh no offence meant, each to his own I guess :grin:

So many times, when someone makes something or tries something that is not "textbook", out come the kerbside and armchair critics who are so ready to pour scorn on inventiveness.

And so many times people come up with what they think is a brilliant idea only to find out it is rubbish. But they play the victim "I am misunderstood card" or say it is trial and error.
I am not an armchair critic I am an engineer with many years experience. Ignoring what is in the data sheet is not inventiveness it is folly of the highest order.

Take Sir FranK Whittle for instance, Where would we be if he had just accepted the ministries dismissive attitude?

If Frank Whittle was ignoring the limits on the basic forces that his materials would accept he would have failed.
I am telling you that what you have done is a failure and the fact that you have "got one working" and therefore think it is fine only goes to prove how little you know.

When I worked as a development engineer on several secret government projects, many times "designs" did not work as expected, but trial and error prevailed to success!

When I worked as a development engineer on several secret government projects, no one used trial and error. Everything was designed correctly. Then in the light of testing improvements were made. This is not trial and error which implies a haphazard unthinking approach. If secret government research proceeds in the way you describe then it is an utter shambles, quite honestly I don't believe you.
The very first thing you do is to follow the data sheet, then you try and improve on that.

and I for one will continue along my own happy path

You are free to do so but don't come here spouting rubbish and expect not to get shot down in flames. This is a forum for beginners who want to learn and offering such advice as ignoring the data sheet is harmful to their development.

You are of course entitled to have a contrary view, and I fully take your point about mis-information, except that it is not quite that when all I've done is to try something and shown the results of the tests I made, no-one is obliged to follow the example, but the fact that the results differ from the published data goes to show that the manufacturer has set a minimum value which they can guarantee to work and in my case I have succeeded in my own intended purpose.
As for not believing me, well again that's your choice, But, I know what went on and what I witnessed so I need not bother to prove it to anyone.
I notice that you have made no comment regarding Arduino being for experimenters and hackers as stated by one of the original designers in his own publications.
You certainly have a very appropriate forum name, as have I :smiley:
P.S Regarding SIR Frank Whittle, in a program some years ago about the development of his engine, one of his engineers was quoted as saying that due to the limited funds and lack of materials, they used what they could get hold of and basically hoped for the best, he certainly had failures but learned a lot from them.

Congratulations, you get the privilege of supporting all the noobs with their out-of-spec projects from now on.
OK with you?

I notice that you have made no comment regarding Arduino being for experimenters and hackers as stated by one of the original designers in his own publications.

You seem to not understand a lot of things and here the definition of hackers and experimenters appear to have escaped you. You can do both without producing unreproducible designs. You sound like a child experimenting with a chemistry set and think it is a perfectly viable experiment to mix every chemical in the set together. An experiment only has value if there is a result you expect.

But, I know what went on and what I witnessed so I need not bother to prove it to anyone.

I suspect you were working for a government contractor rather than directly for the government. If what you are saying is true then the standard of scientific work has vastly declined over the last couple of decades and I would be ashamed to associate myself with such low standards. You however think low standards are fine. Hence your attitude about this "momentous discovery" of yours. Along with the rigor (not) of your verification techniques.

but the fact that the results differ from the published data goes to show that the manufacturer has set a minimum value which they can guarantee to work and in my case I have succeeded in my own intended purpose.

Look to your self, is this the best you can do? Do better. Try and learn a bit about electronics before spouting rubbish.

I not “supporting” anyone, I simply said that I (me personally) did not like having to add the level shifters and, having followed an arduino forum advice run by a very well respected supplier of arduino’s and shields etc, I had had great success with their mod to the Uno to run at 3.3v. Having then consulted them, and being advised by them that it would “do no harm” I tried it for myself with the Mega 2560. The results of which are what I published and actually got a thank you from them for letting them know.
If they had indicated that there could be the possibility of causing damage, I would not have proceeded any further.
As to all intents and purposes the only likely result in trying it is that it may not work in every case, that is up to any individual to decide whether to try it or not. I also did say to be careful in powering via the 5 v socket as over voltage would almost certainly damage the board.
I’m not implying carte blanche a carefree attitude to working, but the results of others experiments can be of use and possibly solve a particular problem or open up a new direction in the working of some project.
It does seem though that some of the original premise for the concept of Arduino is being forgotten.
P.S Maybe you would be happier if I just added “DONT TRY THIS” to my original post?

Massimo Banzi co- founder of Arduino, says "classic engineering relies on a strict process for getting from A to B; the Arduino way delights in the possibility of getting lost on the way and finding C instead"
" This is the tinkering process that we are so fond of- playing with the medium in an open-ended way and finding the unexpected"
His hero is James Dyson, who made 5127 prototypes of his vacuum cleaner before he was satisfied that he'd gotten it right.
He also states that he likes "circuit benders" because of their ability to create the wildest devices by tinkering away with technology without necessarily understanding what they are doing on the theoretical side.
He goes on to say a lot more in a similar vein about his approach to tinkering and designing.
So please Mr grumpy Mike, calm down, try and relax and be less vitriolic in your responses and maybe life will be sweet :smiley:

Massimo Banzi co- founder of Arduino, says "classic engineering relies on a strict process for getting from A to B; the Arduino way delights in the possibility of getting lost on the way and finding C instead"

I am sure that Massimo ( who I have met twice ) would not endorse running components outside their rated values. But let's ask him should we. PM sent.

Judging by the datasheet you can safely operate the Atmega2560 at 16 MHz down to 4.5V, but down to 2.7V at 8 MHz.

You may well have some code working at higher frequencies at 3.3V but some parts may not be guaranteed (eg. full-speed SPI for example).

These specs would also take into account manufacturing variances in the chips, so whilst one chip may work OK, another one with slightly different chemical composition (or trace thicknesses etc.) may not work.*

  • if operated out of spec.

Hi Nick, Oh dear, I'm afraid you will now incur the wrath of grumpy mike for daring to mention the sacrilegeous words "if operated out of spec" I mean, how dare we think outside the box?

Seriously though, In fairness to mike, maybe I should not have referred his comments as being from an armchair engineer,
And I get that he hates giving mixed messages to inexperienced Noobs, but I really didn't think that this forum was only for noobs.
Sometimes in life we need to take a bold step to progress, and I was not advocating a general total ignoring of basic rules and practices. Many times enlightened intuition has speeded up the development of projects that "get stuck" at some point, and after all, it is my own fault if some experiment fails, and for which I would post the results with a warning that I tried it and it failed,
and Mike, take this as light heartedly as it is meant, as for fear of being "shot down in flames" at my age i'm pretty fireproof! Sorry if I offended you. :slight_smile:

Would you try and overclock a Mega328 to 25MHz? It will probably work but will you feel happy about doing it?

Running at 3.3V is a similar thing … just because the voltage is in a ‘legal’ range doesn’t make it any safer than overclocking to 25MHz.

We could come up with a thousand different analogies, I.e, would I stick my fingers into the mains socket to see if the power is on? obviously not! So just sticking with what I actually did, I now have something that works for ME and anyone else who may choose to try it and see if it is of use to them. As pointed out by more experienced arduino users that myself, this particular test had negligible to zero chance or doing any damage, and that is the basis of why I proceeded with it.

As stated on another forum:-

HOW TO START AN ARGUMENT ON A FORUM…
1.) state an opinion.
2.) WAIT!

I think the time has come to end any further discussion on this subject from myself, I wish you all enjoyment with your own projects :slight_smile:

HOW TO START AN ARGUMENT ON A FORUM.....
1.) state an opinion.
2.) WAIT!

No

HOW TO START AN ARGUMENT ON A FORUM.....
1.) state an wrong opinion.
2.) WAIT!

You still don't seem to get it. The "works for me" argument just does not cut it in electronics.

recklessrog:
So many times, when someone makes something or tries something that is not "textbook", out come the kerbside and armchair critics who are so ready to pour scorn on inventiveness.

What's "inventive" about lowering the voltage? The datasheet clearly says the chip will run at lower voltages (it's on the very first page).

The engineers at Atmel will have done far more testing than half an hour running half a dozen sketches on a single chip. If they publish a graph with the words "Safe Operating Area" on it, it's for a reason. It's not because they're being party-poopers, it's because they had things fail.

recklessrog:
Take Sir FranK Whittle for instance, Where would we be if he had just accepted the ministries dismissive attitude?

The counter example to that is the De Havilland Comet

Tell us, would you fly on an aircraft that "seems to work"? One that had survived a few test flights but where nobody ever really calculated the stresses on the wings?

Wrong opinion? as quoted from the oxford dictionary :- opinion,a view or judgement formed about something, not necessarily based on fact or knowledge. So therefore it is subjective and you cannot have a "wrong" (or right) opinion. As the old saying goes; A person convinced against their will, is a person or the same "opinion" still.

This is getting nowhere folks, hardly matters to me because as I have repeatedly stated, by trying it and finding that it works in my application, my opinion is solely based on the simple fact that mine is working as required by me. If you have a different "opinion" that's fine too.

recklessrog:
This is getting nowhere folks

By that you mean "I'm not winning..."

recklessrog:
as I have repeatedly stated, by trying it and finding that it works in my application, my opinion is solely based on the simple fact that mine is working as required by me. If you have a different "opinion" that's fine too.

Driving your car around in first gear at 7000RPM will get you to your destination but it's not good for engine life. Would you buy a car from somebody who did that? Of course not.

Your chip is outside the zone where it's designed to work. You might find it's "working" today, but stops working on hot days, crashes every few weeks, who knows?

It's not a "discovery". It doesn't make you a maverick. It's just bad engineering. Expect people to call you on it.

And ... comparing yourself to Frank Whittle? LOL!