user78470: I'm building what I thought was a simple Arduino Nano project... right up until it caught fire!
I am a long-time reader of stack exchange and I always find the answers to my questions somewhere on Google, but this seems to be a bit of a head scratcher.
The project is a 4 pin 7 segment LED screen with a timer that counts when Analog pin 0 receives a voltage signal of ~2.5-5v.
Testing the project worked as expected, but when I soldered everything together, I was getting static or white noise from the Analog pin with no voltage being supplied.
I figured I needed a Pull-Down resistor to keep the Analog pin grounded until it received a voltage signal to get rid of any interference.
I connected a 220ohm resistor DIRECTLY from GND and DIRECTLY to Analog Pin 0 and connected the voltage signal wire to Pin 0 as well.
When I actually tested the hardware while connected to the car battery, that's when it shorted out and caused a mini fire.
I was able to read the voltage with my multimeter before the chip burnt out, I was reading ~15.5v total. I'm guessing it's the car battery plus the input voltage on Pin 0.
I only do clean and precise soldering, so there were no unaccounted for connections.
I'm unsure if the issue was too many volts running through the Nano altogether or because I don't really understand how the Pull-Down resistor works and messed that up.
Please help me understand what the issue is and what I can do for a solution.
Thank you.


user14095: You violated the voltage input specification of A0 by a lot. What happened is what I would expect. The input protection diode on A0 conducted the battery voltage (- the protection diode drop) into the VCC of the Nano, this overvoltage fried just about all semiconductors and possibly several of the passive components on the board. It sounds like they do what they do when abused and they let the smoke out destroying the Nano and possible several other components. Hopefully this explains what happened. If you had connected the resistor between A0 and the battery it might have survived.

78470: <p>I'm building what I thought was a simple Arduino Nano project... right up until it caught fire!</p>
<p>I am a long-time reader of stack exchange and I always find the answers to my questions somewhere on Google, but this seems to be a bit of a head scratcher.</p>
<p>The project is a 4 pin 7 segment LED screen with a timer that counts when Analog pin 0 receives a voltage signal of ~2.5-5v.</p>
<p>Testing the project worked as expected, but when I soldered everything together, I was getting static or white noise from the Analog pin with no voltage being supplied.</p>
<p>I figured I needed a Pull-Down resistor to keep the Analog pin grounded until it received a voltage signal to get rid of any interference.</p>
<p>I connected a 220ohm resistor DIRECTLY from GND and DIRECTLY to Analog Pin 0 and connected the voltage signal wire to Pin 0 as well.</p>
<p>When I actually tested the hardware while connected to the car battery, that's when it shorted out and caused a mini fire.</p>
<p>I was able to read the voltage with my multimeter before the chip burnt out, I was reading ~15.5v total. I'm guessing it's the car battery plus the input voltage on Pin 0.</p>
<p>I only do clean and precise soldering, so there were no unaccounted for connections.</p>
<p>I'm unsure if the issue was too many volts running through the Nano altogether or because I don't really understand how the Pull-Down resistor works and messed that up.</p>
<p>Please help me understand what the issue is and what I can do for a solution.</p>
<p>Thank you.</p>
<p><a href="https://i.stack.imgur.com/AKWQl.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/AKWQl.png" alt="Schematic" /></a></p>
 14095: <p>You violated the voltage input specification of A0 by a lot. What happened is what I would expect. The input protection diode on A0 conducted the battery voltage (- the protection diode drop) into the VCC of the Nano, this overvoltage fried just about all semiconductors and possibly several of the passive components on the board. It sounds like they do what they do when abused and they let the smoke out destroying the Nano and possible several other components. Hopefully this explains what happened. If you had connected the resistor between A0 and the battery it might have survived.</p>
