accidentally connected 12v (AC) to analog input

hi guys,

new with arduino.

created voltage divider so 12V is like 3V and wanted to test it

it is connected to A0

but.. I have a lamp on my table (220V => 12V) and decided to use its wires to give 12v input into voltage divider = was expecting 3V

but.. it was not DC but AC 12Volts

arduino connected to macbook (working on battery)

ALL RESET - macbook goes black, arduino too..

restarted macbook - works!

but arduino just power led and led13 is on

trying to upload code and:

avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00

is it dead? did I somehow destroy atmel or whole arduino?

should I try to replace atmel chip or is there any easer way? reset button is not doing anything :confused:

thanks for help!

Friend you generated a current in AC to the arduino LINK REMOVED which could generate the damage of the card

220 volts does not equal 12 volts unless changed by a properly designed circuit or transformer.

AC does not give off DC unless rectified in some manner.

If you measured 12 volts on a 220 volt lamp chances are your multimeter was set wrongly or you mis-read it.

It would be safer to kiss the whole board goodbye and get another as simply replacing the chips will still not guarantee and success with such a basic but catastrophic error.

He's probably talking about a 12V AC halogen desk lamp.

But yeah,

  1. you can't put AC onto an Arduino pin without much more care and understanding than you have.

  2. with no load, those 12VAC transformers for the halogen lights may well put out considerably more than 12V....

  3. Can you post a diagram of your resistor dividers, and what you connected to the Arduino? I suspect that what you did was something other than what you think you did. With appropriate resistors, I would expect that this wouldn't have such dramatic results, quite honestly. Either the resistors were far too small, or you connected them wrong, or something like that.

My suspicion is that 12+ VAC was applied between arduino ground and an I/O pin with very little series resistance. Naturally that flowed back through the protection diodes (trashing the '328p in the process), getting onto the power rails (where it would damage the rest of the sensitive parts on the board) and from there to the USB rails, at which point the mac saw that something was terribly wrong and powered down.

Your arduino is trashed, throw it away and buy a new one, and learn more about electronics before involving AC power with the replacement. Say thanks to the gods of technology that your laptop still works (macbooks typically gun the whole system when you do something heinous like that to the USB port, and usually survive. When you do something bad enough that it triggers that, though, the arduino is almost invariably toast).

thanks DrAzzy, you got it right..

lamp is 220V but there is 12V bulb - so there are 2 wires with 12Volts (not 220) and I used that 12V (with voltage divider so no problem with value), just it was AC 12V, not DC 12V..

I have bought a new chip atmel328p - if I change it, will it works? or whole arduino board is destroyed?

update:

after half day of "fun", I have made a LPT parallel programmer, and was successful flashing a new atmel chip under linux (hint: copy avrdude command into terminal when logged as root to be able to access /dev/parport0)

arduino works like a new :slight_smile: