I'm using an Arduino UNO to monitor some of the digital I/O pins. I'm also using the Ethernet shield and I can access my program and view the digital I/O pins status via the Web Server code posted on this site.
All is working very well, but it seems when I supply more than 5V to the digital I/O pins the board locks up and stops responding. Is this something that has been noted before, if so what is the max voltage that the board can handle?
When in doubt, RTM:
Each of the 14 digital pins on the Uno ... operate at 5 volts
I understand it says they operate on 0V - 5V. I'm just wondering if others have noticed problems when say higher voltage is sent to the digital I/O pins.
eSietsema:
I understand it says they operate on 0V - 5V. I'm just wondering if others have noticed problems when say higher voltage is sent to the digital I/O pins.
Why would you even expect it work at all, when it clearly says it works at 5V?
eSietsema:
I understand it says they operate on 0V - 5V. I'm just wondering if others have noticed problems when say higher voltage is sent to the digital I/O pins.
Problems are usually the pin stops working all together and if your really unlucky/stupid the entire chip with it.
Learn about voltage dividers or buffer chips before you damage the Arduino.
[u]Diode/resistor protection circuit[/u].
If the voltage is not tightly-controlled/limited (such as an automotive application) you can combine both concepts by adding the protection diodes to the Arduino input following the voltage divider.
The Max Rating of the pins, when running on 5V is 5.5V, or in other words... Maximim input voltage for an I/O pin is Vcc + 0.5V. This is what the fine manual will tell you.
I understand it says they operate on 0V - 5V. I'm just wondering if others have noticed problems when say higher voltage is sent to the digital I/O pins
Simply put, this is a STUPID question, considering that you said this:
I understand it says they operate on 0V - 5V
raschemmel:
Simply put, this is a STUPID question,
Gotta give you +1 for that. 
An old topic, but I thought that a comment may help, especially as some of the replies verge upon aggressive.
This is not a stupid question, but asked by a novice without knowledge or understanding.
It should be understood that projects like Arduino attract people with little or no underlying knowledge. monkey see, monkey do and you have a flashing LED or whatever - no skill or background needed (no offense intended to anyone!).
Those of us with a background in electronics will ALWAYS pull the manufacturers datasheet. They are the word! If it says max 5V that is what the manufacturer means! Not 5.1, but 5! Exceed this at your peril! It may not fail right away, but it will fail and not always as you expect!
If some dip-stick on a forum tells you data that is contrary to the manufacturers data, treat them with the respect that they deserve.
So to all budding electronics engineers out there. Pull the datasheet and READ it! write notes on it, understand it! I will admit that upon first encounter they appear baffling, they are not! After all, the manufacturer wants you to understand their products so that you will use them and be successful with them.
It may be worth noting that electronic components can not be made 100% successfully. So they are tested to see that they fall within spec. So some will have more headroom for abuse than others, but they will all perform within spec. A good example is microprocessors. Manufacturers to not manufacture a range of speeds. Only top speed devices are created, Lets say 3Ghz clock. If it works perfectly at 3Ghz, it's labeled up as such and sold at a premium price! But if it only works without failure at 2.8Ghz, then that what it's sold as, and so on. And yes, one can over-clock, but this almost always involves extra cooling to bring the device into spec (heat is the enemy of electronics).
I hope this is useful to novices.
The takeaway from this is RTFM and believe it!
Lets say 3Ghz clock. If it works perfectly at 3Ghz, it's labeled up as such and sold at a premium price!
That assumes that you can test a 3Ghz microprocessor completely, which you can't. Assume you can put in one configuration per micro second, it will take well over a century to test fully all the states that microprocessor can fall into.
That sort of thinking used to apply to resistors but these days manufacturer is much more precise and you very regularly get a lot of 1% resistors in a batch of 5% ones.
Technically there is no limit to what voltage you put on a pin from outside but with a with qualifications. The microprocessor pin has "diodes" on the inputs which limit the voltage until they are destroyed, maybe 10mA but all are not the same. If you want to put 24 VDC fine but use at least a 20K in series (no problem with open connections), if not by-by micro. Two other common approach is a voltage divider, I use them then put a series resistor to the pin to protect the micro in case the ground resistor lifts, happens a lot on breadboards. Another approach is to use a zener diode about 4.1 volts to ground limiting the voltage to the pin but it typically has a series resistor to limit the current. One of the worse environments you will encounter is the automotive arena. In the automotive world 12V is not 12 volt the system voltage can range from about Plus or minus from 0 to 24 volts before transients Normal operating voltage is about 13.8 because the battery is being charged. Before you get upset note the huge amount of electronic parts that are automotive rated. I would suggest anybody that does not have experience in the automotive electronics read a few automotive electronics design manuals. Here is a short section from Automotive Quality Standards 101. This is just a start of what happens. Most of the parts are specified to much tougher standards then military components. For a component to be automotive qualified, manufacturers have to meet specific industry standards throughout the manufacturing and testing process. Three key standards are IATF 16949, AEC-Q100 and AEC-Q200:
IATF 16949. The global automotive industry standard for quality management systems. The automotive industry generally expects parts to be manufactured, assembled and tested in IATF 16949-qualified facilities.
AEC-Q100 & AEC-Q200. During the qualification phase before the release of the device, each component must survive a battery of industry-standard tests:
AEC-Q100 defines the standard tests for active components such as switches and power amplifiers (PAs).
AEC-Q200 covers similar tests for passive devices such as RF filters used in Wi-Fi and cellular communications.
Some of these tests are unique to the automotive industry and aren't conducted at all on parts intended for commercial use. Examples are the test for early life failure rate (ELFR), which subjects multiple samples of 800 components to temperatures of at least 125°C, and the power temperature cycling (PTC) test, which repeatedly cycles between extremely high (125°C) and extremely low (‑40°C or even lower) temperatures.
Other tests are conducted under harsher conditions -- such as higher temperatures -- than when testing commercial parts, or using larger lot sizes to provide greater statistical confidence in the reliability of production components.
Also, because cars last much longer than other electronic devices, manufacturers typically must ensure a supply of each automotive component will be available for 10 years. All of this and more will become apparent when looking at automotive rated components.
https://www.qorvo.com/design-hub/blog/automotive-quality-standards-101-what-qualification-really-gets-you. This response is to help you get started in solving your problem, not solve it for you.
Good Luck & Have Fun!
Gil
"An old topic, but I thought that a comment may help, especially as some of the replies verge upon aggressive"
That's just the way it is with some members, at least for then last ~9 years I've been observing. Nothing new, probably won't change with them. Just be helpful to the new members.
This is not a stupid question
I understand it says they operate on 0V - 5V. I'm just wondering if others have noticed problems when say higher voltage is sent to the digital I/O pins
So then you are implying that "0-5V" is just too ambiguous or somehow not clear ?
How does that work ?
That's like saying "I understand the speed limit is 65 MPH. I was just wondering if others have noticed
problems whey say they go faster ?"
[That's like saying "I understand the speed limit is 65 MPH. I was just wondering if others have noticed
problems whey say they go faster ?"]
Fair question, no problem. Response: 'Yeah, no biggie, I just start seeing red and blue flashing lights.....'
I recommend decaf and more dietary fiber.