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Author Topic: Arduino MEGA 2560 R3 possible broken pin?  (Read 439 times)
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Well, I'll keep it short and simple: My almost brand new Arduino MEGA 2560 R3 board has a broken digital pin (I think), it always sends 2.2V out even if the BareMinimum sketch is uploaded. What, if anything, can be done about this? It's the digital pin 5. When it's pulled HIGH or LOW, it still always outputs 2.2V. So... What gives?
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Can you please post the exact sketch you are running when you are measuring digital pin 5? In code tags. The BareMinimum sketch would not influence pin 5.
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Code:
void setup() {
  pinMode(2,OUTPUT);
  pinMode(3,OUTPUT);
  pinMode(4,OUTPUT);
  pinMode(5,OUTPUT);
  pinMode(6,OUTPUT);
  pinMode(7,OUTPUT);
  pinMode(8,OUTPUT);
  pinMode(9,OUTPUT);
  pinMode(10,OUTPUT);
  pinMode(11,OUTPUT);
  pinMode(12,OUTPUT);
  pinMode(13,OUTPUT);
}

void loop() {
  digitalWrite(2,HIGH);
  digitalWrite(3,HIGH);
  digitalWrite(4,HIGH);
  digitalWrite(5,HIGH);
  digitalWrite(6,HIGH);
  digitalWrite(7,HIGH);
  digitalWrite(8,HIGH);
  digitalWrite(9,HIGH);
  digitalWrite(10,HIGH);
  digitalWrite(11,HIGH);
  digitalWrite(12,HIGH);
  digitalWrite(13,HIGH);
}

Then, I go to every pin and test them with my multimeter. I've found that both 5 AND 9 give me low voltages (2.2V for 5, 1.1V for 9). And everything else is ~4.77V, except 8, which is 3.89V. Is that normal?
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They should be nowhere near that low. Using your sketch all my pins read about 4.9V.

How are you powering it? Is anything else connected?
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It's plugged in the computer in a 3.0 USB port, I think. Nothing's connected to the arduino, and my multimeter isn't faulty, as I just tested it with my bench power supply.
I don't ever remember doing anything that would mess the pins up, but I do have the receipt from Radio Shack. bought it two weeks ago. I'll probably end up replacing it with another. Unless you think it's not faulty!  smiley-wink
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It's plugged in the computer in a 3.0 USB port, I think. Nothing's connected to the arduino, and my multimeter isn't faulty, as I just tested it with my bench power supply.
I don't ever remember doing anything that would mess the pins up, but I do have the receipt from Radio Shack. bought it two weeks ago. I'll probably end up replacing it with another. Unless you think it's not faulty!  smiley-wink

Well it's not normal that is for sure. I would see if RS might exchange it, but if you ever wired anything to those pins one could make the case that you did so in error somehow and caused the damage, whether you remember the event or not. Drawing too much current from an output pin is a frequent cause for output pin damage.

Lefty
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I don't ever remember doing anything that would mess the pins up, but I do have the receipt from Radio Shack. bought it two weeks ago. I'll probably end up replacing it with another.

What have you been doing with it? Connecting motors? LEDs? If so, in what way? It's possible you damaged it without realizing it. I mention this because it's no good getting it replaced if you do the same thing to the next one.
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I haven't been directly powering motors with it, I do use some L293DNE's with it to power some small 5V motors, just to test the chip. I also used some mosfets to make an H-Bridge once, but it was protected with Schlottky diodes. But yes, I do agree with you that I need to be MUCH more careful in the future. And you do think that it's been damaged by me?
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I haven't been directly powering motors with it, I do use some L293DNE's with it to power some small 5V motors, just to test the chip. I also used some mosfets to make an H-Bridge once, but it was protected with Schlottky diodes. But yes, I do agree with you that I need to be MUCH more careful in the future. And you do think that it's been damaged by me?

Well it's not to somehow cast blame on you just to be cruel, and of course there is no way for any of us to know for certain if you were the cause or not. But lets just say it's very rare and very unlikely that the damage was cause by anything other then whatever you were attempting to do with the board at one time or another. But don't feel alone it happens to the best of us. I once accidental wired -12vdc to a analog input pin on a 644p chip mounted on a solderless bread board set-up, a $10 chip at the time. And kind of like your case it just took out 4 pins, the rest of the chip continued to work fine.


Lefty
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Ah, don't worry, I wasn't being defensive or anything smiley Just making sure. And yeah, I'll remember this whole ordeal and I doubt I'll do it again!
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