Arduino Uno smells like burnt

Hello,
I've connected the long leg of LED to 5v and the short one to a high resistor ( by mistake ) that was about 10K Ohm. after just connecting it that, I smelt like burning and quickly (after just 1 second of connecting the circuit ) unplugged the power source ( that was a mobile charger that output 5V and 1A ).

So:

  1. Can the charger ( that was power source to arduino ) be damaged ? I'm afraid to connect it to the mobile to test it as I don't want my mobile to get any problem.

  2. Can the arduino be still working ?

  3. Is it safe to connect it to PC or it can damage the usb port or even the PC itself ?

I just checked the charger on a mobile phone and it's still working..
I also uploaded the on-board led blinking example and it worked..
So what's the reason for that smell in arduino ? ( I think it's coming from the ATMega 328 but not sure )

Huh, if you connected as you described, there shouldn't be any burning smell...

It was exactly connected as described. I thought that the mistake with the 10K Ohm resistor is too high for a led to illuminate.. I checked the board now but the Digital I/O aren't working except the pin 0
all pins from 1 to 13 are dead.. :frowning:

Edit: I re-uploaded the program and the pins are working fine.
The board smell is decreased a little but still smells bad.

Is something on the board getting hot? If so, what?

An LED will light up in series with a 10k resistor. say 2.5v forward voltage and 5v supply... you're dropping 2.5v through 10k, so 0.25mA. That will definitely be visible in a modern LED. Dim, but you'd see it.

Nothing on the board is getting hot ( I tested for just few minuites, does it need more time to test ? ).

The strange thing I just connected a led so if the resistor isn't a problem I can't see there is any reason for that.
Note: The led is burnt and I see black inside it.

Are you sure it's a 10k resistor, not some other value?

You have to really work at it to get an LED to have a visible black spot in it... (unless you're misidentifying the dark red die of a red LED as a burned spot)

Sure you don't jhave hte LED the wrong way around?

Yes , It was 10K Ohm ( to be specific it was 10K Ohm Potentiometer )
here is a picture of the burnt led

As I removed all the wires after smelling burn, I really don't know if I maybe wired something wrong, but as I used just 10K Ohm & LED, the only possible mistake can be the following ( assuming that positive of battery is 5v if arduino and the negative is GND ). I don't know if that was the mistake what damage can it cause.

A 10k pot is not the same as a 10k resistor.
A 10K potentiometer can have a resistance of anywhere from zero to 10k ohms between one end and the wiper. If you wired the LED through the wiper, you must have had the pot turned such that it was at or near zero ohms. That will allow a lot more current to flow than the LED can handle.

Pete

You wired it wrong; the resistor must be in series with the LED, not in parallel.

With your setup (second picture in reply #7), you basically short the pin of the Arduino.

el_supremo:
A 10k pot is not the same as a 10k resistor.
A 10K potentiometer can have a resistance of anywhere from zero to 10k ohms between one end and the wiper. If you wired the LED through the wiper, you must have had the pot turned such that it was at or near zero ohms. That will allow a lot more current to flow than the LED can handle.

Pete

The potentiometer was at its maximum value

sterretje:
You wired it wrong; the resistor must be in series with the LED, not in parallel.

With your setup (second picture in reply #7), you basically short the pin of the Arduino.

I know it must be series and I really don't know if I made it parallel or not, but as replies said that the high value of resistor isn't a problem so I should wired it wrong.. The pins of Arduino still working, but does it mean I have shortened its life ?

Finally, I could determine the source of the burn smell… It’s the voltage regulator behind the external power source, Should it be replaced if I use ONLY USB Power Source ? How can it be damaged and I was working with USB as a power source ?

Edit:
So, Here is the final results I could tell:

  1. I connected the 10K Ohm resistor parallel with RED LED ( The positive leg of led was connected to 5v pin and the negative leg to ground ) ( The arduino was taking the power from mobile charger )
  2. The mobile charger is working
  3. Both of the red led and the arduino uno made a burn smell.
  4. The arduino still working with USB Cable connected to 5v
  5. I still can upload sketches to the board
  6. The smell from arduino is exactly from the voltage regulator
  7. connecting the board to 9v battery makes it auto-reset itself
  8. from a long time ( before I connect the led parallel … etc ) the board was auto-resetting itself while connected to 9v battery, but it was doing that after sometime of working on the battery ( I thought it’s a weak battery but now, I don’t think so )

Now the questions are:

  1. Can I still use the board with USB Power while the regulator is burnt without making any damage to other components on the board ? I mean: Is there any role of the regulator if I give the board 5v from USB Cable ?
  2. What causes the regulator to burn if the board was taking power from 5v of USB not Battery ?

UP
I just have final results in the last reply with everything clear..

Does the regulator get hot when powered from USB? If not, you're fine to use it like that, just don't use it with external power.

If it does get hot, that means it's damaged badly enough that it's loading the arduino's power supply, and I would either replace the regulator, replace the board, or at least remove the offending part.

The wiring diagram you posted is wrong. No wonder you burned out the LED (and yes, that does indeed look like a burned spot to me too) - you had the LED connected directly between 5v and ground; the parallel resistor was doing nothing to limit the current (as far as the LED was concerned, it might as well not have been there). You need it in series (ie, 5v ---resistor---LED---Gnd ), not in parallel. I'm still surprised it damaged the regulator though...

When you determined that the regulator was what was getting hot, what was the Arduino doing? When you smelled burning, how was it powered?

It doesn't get hot when powered from USB but the smell is still there.
I connected the arduino to USB Charger ( 5v - 1A ) then I smelt the burning

Now, after it was working good, I connected the board to PC and I get this message "one of the USB devices attached to this computer has malfunctioned and Windows does not recognize it"

I would give up on that board. You basically have done damage beyond repair; it's probably the usb-to-serial chip on the ardurino (16U2). If you manage to replace it, you might find that something else is also damaged.

I changed the cable and the windows could recognize it again and I could upload sketches. I also replaced the battery and it works with both USB and battery. The burn smell is still on the board although it works.