fried uno with 12volts but did the shields survive?

Development Tools IDE 1.x
1

Ok stupid newbie mistake and I fried arduino uno r3 with 12 volts.

The setup was:
arduino uno r3
w5100 ethernet shield
funduino Sensor Shield I/O Expansion Board RS485

what I was suppose to do was connect two inputs from non standard modbus device to funduino shields RS485 interface A and B sockets but the rookie mistake which I made was that I also connected funduinos GND and VCC and in my case the VCC was 12 volts...

I removed all shields and started troubleshooting the board. Loop-back test fails.
Solid ON and L-Leds, TX and RX leds not showing any blinks when trying to communicate with the board even it's recognized as arduino uno r3 on windows and linux computers.

Board and shields has no any physical evidence of over voltage, no blown up components what so ever and ethnet shields leds blink when sending data over network

My conclusion is that atleast mega16u2 is toasted since the tx and rx leds are not blinking.

I already ordered new board so it's a lesson learned hard way but did the shields survive overvoltage or do they usually fry too or just let the overvoltage flow trough them? If I connect the shields to new board is there possibility to fry it too?

2

ok I did some research and the io shields VCC and GND goes to shields IC and to the arduinos +5 volt and gnd rails so the over voltage has gone trhough whole board :sob:

But I checked with voltmeters the boards 3.3v and 5v outputs which where both ok and shields ic. Hopefully arduinos atmega chip only fried and rest is ok but I will see that when the new board comes later this week.

3

Why not get a new chip with bootloader to checkout the main MCU? Assuming yours has the 28-pin socket.
See Farnell/Element 14 stock number 1848694 £3.35 plus tax, probably cheaper elsewhere, but these are genuine. Cheaper than a whole new UNO and you can also use it on it's own when you get a bit more ambitious. Useful to have some spares anyhow.
If the 16 chip has gone then you are stuffed