Accidentally swapped 5v and 12v on PCB, what did I fry?

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Hi, small accident happened and avr did catch little fire.

 

What I'm wondering did I fry anything else in the process for sure? All the other components should be rated above 12v, so did those survive if I don't see any visible damage? 

 

What I'm wondering also is that the tiny841 did not even get hot or show any signs of failure, while the atmega328pb now have burn marks and all pins close to the vcc(pin4) are in short circuit.

 

E: PCB itself does not show any visible damage either.

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Last Edited: Tue. Mar 7, 2017 - 02:13 PM
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YOU tell us what else could have fried!  How the hell are we to know without a schematic?  Whatever was connected to the 5V rail has most likely taken a hit for the worse depending on how long your boo boo was connected.

 

 

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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As Jim says, we have no idea what else was on your board, how they are connected together, or anything which would give us any basis for any opinion or advice!

 

JoniS wrote:
did those survive if I don't see any visible damage?

That would not be a safe assumption.

 

It is entirely possible that things have been destroyed or damaged even without showing any externally-visible signs.

It's also possible that there are signs - but you haven't recognised them.

 

 

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jgmdesign wrote:
YOU tell us what else could have fried!  How the hell are we to know without a schematic?

 

yeah, sorry i had a little "panic attack" earlier :P i added the complete schematic as attachement.(Kicad).

 

jgmdesign wrote:
Whatever was connected to the 5V rail has most likely taken a hit for the worse depending on how long your boo boo was connected.

 

I did instantly cut the power when i saw smoke, but yeah i guess the damage allready happened.(maybe 2-5s time window when the 12v was there instead of 5v).

 

i think these are the relevant parts ->

 

 

 

 

Then ofc if the AVR i/o pins did forward the voltage there is FTDI ic which might be dead too.(ftdi is powered from usb, while the avr's are not).

 

Attachment(s): 

This reply has been marked as the solution. 
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Quite frankly, if you really let the smoke out of a device, I would trash the board and make a new one.  Especially if it is to be sent to a customer.  No telling what was destroyed.

 

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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jgmdesign wrote:

Quite frankly, if you really let the smoke out of a device, I would trash the board and make a new one.  Especially if it is to be sent to a customer.  No telling what was destroyed.

 

Jim

I guess I trash the PCB then, it was only for me which is good thing, so I don't have to explain anyone why they are not getting it today.

Well I'm sure to double check power connector in the future to avoid this, I guess one could say this was learning exorcise of some sort.

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JoniS wrote:
Well I'm sure to double check power connector in the future to avoid this,...
JST connectors are popular for a polarized connection to a battery.

A battery can supply a lot of current such that the PCB epoxy will ignite causing fire and/or smoke (a hazard worse than popped IC encapsulation)

Same with PC power supplies; a former co-worker described the fire on his PC graphics card (a short between power and ground layers on the PCB)

If the power supply is current-limited enough then an AVR would have survived.

A PolyZen would of limited the 12V to about 6V at the megaAVR and greatly limited the current (case - correct polarization at the PCBA but the connector was mis-wired)

 


BatterySpace.com

BEC, Hitec, JST Connectors

http://www.batteryspace.com/bechitecjstconnectors.aspx

Mouser

Polyzen USB Protection - Littelfuse

http://www.mouser.com/new/littelfuse/tepolyzenusb/

...

PolyZen devices are polymer-enhanced Zener diodes that help provide coordinated protection against damage caused by overvoltage, overcurrent, and ESD transients in a single package.

...

The new device offers designers the simplicity of a high-power clamping diode while obviating the need for significant heat sinking.

...

PolyZen USB 2 application, polymer enhanced zener diode

...

 

"Dare to be naïve." - Buckminster Fuller

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gchapman wrote:
JST connectors are popular for a polarized connection to a battery.

 

 

The connector I'm using cannot be plugged in reversed either, if that is what you did mean.

 

After doing some research why this mistake happened I did come to conclusion that PCB designer had mirrored connector on schematic and forgot to do the same in PCB layout or document this stupid action so the one who assembly this PCB would know that he needs to mount the big molex on bottom side of the PCB, I can only look to mirror :)

 

Besides this newbie mistake, most of the PCB seems to work as expected, did not yet get to the 12v side since I did discover that there is ~3.3v voltage when no +12v is connected.....Guess that's topic of its own if I can't figure it myself.