Was playing around with a servo motor and a blink LED on my Arduino Nano board. I was powering it through the VIN pin when I accidentally connected the 9V battery the wrong way... something bad happened. It smells burned now, and nothing happens if I connect the 9V battery the right way to the board...
If I however connect the Arduino Nano board to the PC via the USB port it seems to work as before.
Can someone explain to me what happened, and if it is possible to fix it? Is it the VIN pin that is "broken" or the GND pin? Or is it the capacitors (2 psc of 100 uF, 25V)?
Here is a nano schematic which may help identify the damaged component.
I imagine the 5v regulator is possibly damaged as a result of the error. That powering the nano through the USB works (where the voltage regulator is bypassed) works indicates that there is a voltage regulator problem.
Can't tell from the picture. You may have taken out the 5V regulator on the bottom of the board.
You can try replacing it if 5V is no longer output when 9V is applied.
As far as the capacitors go, you probably don't need to test the capacitance value - what you want to know is are they shorted. Try holding the board very close to your nose and see if you can localize (either side of the board) where the burned smell is coming from. Use a magnifying glass and look for any obvious signs of over heating. The regulator is probably a good guess though.
Now about an hour later it still smell the burned smell from the breadboard just below where the voltage regulator was, and the actual voltage regulator on the board.
I can not smell anything from the capacitors and they look fine even under a magnifying glass. That said I thought I smelled something from the capacitors just after the incident, however it might have come from the regulator (they are only 2 cm apart). What is the likelihood of all of them being fried / shorted.
The most likely thing is the regulator pulled all the power and protected the rest, but that is just a guess. Only testing will reveal the truth. Start by replacing the regulator and apply power (with the right polarity) through a 100 ohm resistor for example to limit current. Check the output of the regulator - you should see 5v, but the 100 ohm resistor will prevent it from smoking something else if something else is shorted (or if you have a current limiting power supply, set it for 100ma or something like that).
You can test caps to see if they are still working by shorting the cap to discharge it, connecting your DMM on ohms and probing the cap leads. The meter will briefly show low ohms and then climb to infinity (or there abouts) if it is good. The higher the value the longer they should take to charge. Open or short will be easy to see. Observe polarity on polarity sensitive caps.
Christian_83:
Now about an hour later it still smell the burned smell from the breadboard just below where the voltage regulator was, and the actual voltage regulator on the board.
I can not smell anything from the capacitors and they look fine even under a magnifying glass. That said I thought I smelled something from the capacitors just after the incident, however it might have come from the regulator (they are only 2 cm apart). What is the likelihood of all of them being fried / shorted.
You said it still works fine on USB? Your electrolytics are likely fine then since they are both on the 5V.
The US78M05 datasheet has a schematic on page 2. It doesn't look like putting -9V betwen INPUT and COMMON should result in anything coming out on OUTPUT.
