I'm designing a project in which I'm using an Arduino Uno R3. As the power supply, I'd like to use the 5V pin with 6VDC applied to it. Does anyone know what the max voltage is applied to this pin?
5V, who would have guessed.
Is this documented anywhere?
The reason I ask is because it's pretty tough to have a power supply that is exactly 5VDC connected to the 5V pin. There should be some +/- tolerance for this pin's voltage.
All the chips and components on your device have a maximum allowed voltage
on their power supply pins, documented in their data sheets.
Often the complete system also has specifications regarding the power supply.
I doubt that, I think the reason you ask is that you want to connect a 6V supply to a 5V input.
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According to the ATmega datasheet, the "absolute maximum" is 6V. There are other chips on the board and I assume they are rated similarly. You are unlikely to fry the board but it is a slight risk and depending on what's connected it may not function as expected.
You can use Vin and you'll get close-enough to 5V out of the voltage regulator for the board to work. You MIGHT even get 5V out of the regulator with 6V applied. But I assume you are using batteries so as they drain more voltage will be lost across the regulator. (You might also have slightly more than 6V when the batteries are fresh.)
I work on some 5V boards at work. Some have a built-in regulator so I apply around 7V. Sometimes I forget and apply 7V to 5V circuitry. I've NEVER fried a board with 7V but with 12V the RAM chip fries EVERY TIME, and sometimes the CPU and other chips also die.
If you do this say good bye to your hardware.
On an UNO, if you do this and the UNO is connected to your laptop, say good bye to the laptop.
I've had a circuit that was running perfect while connected to PC (USB), nut not from 12V external power. The onboard regulater was defective so all components got 7.1V ! Nothing burned - not even the SDcardreader. Replaced regulator.. all OK. This is mind.. 6V wont burn your arduino
And you will back this up how ?
Thanks, but I'd rather trust the engineers who designed the chips and respect whatever they specified as a maximum voltage.
I believe the max voltage by specification is 5.5 Volts. 6 Volts will work but will also reduce the life of the device.
The tolerance is typically +-5%. I don't find it tough to find 5V supplies. A couple $ or less each for old cell phone chargers at the local thrift store (check before use - most are fine).
Put a 1N4003 diode in series between the 6V supply and 5V pin, cathode (end with band) toward 5V pin, that will drop 0.6 ~ 0.7V to 5.3 ~ 5.4V.
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Better explain that.
I can't think of any reason why you want to do this.
Leo..
Yes. But I wonder if the 6 volt supply is rekulated. If it is not there's one more reason not to use it.
~6 volts would be enough for a low dropout linear regulator if it's only the Arduino that needs 5. It wouldn't take much of one nor waste that much.
a7
Processor data sheet. Your very best source of advice on Arduino electrical questions.
I thought about it and you're right. I changed my plans... Now I'm going to feed the barrel jack input with 9VDC.
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