Hi,
Thanks for your fast reply but it doesn't realy help. I'm sorry I'm not clear. My english may be bad. I've draw some schems in paint to explain myself.
This one is doable, but the mechanism of the electromagnet is hard to access.
This one is what I hope I can do. But I don't know how to supply power to my arduino without triggering the logic level detection of the push button.
From my point of view, the second option is just impossible. I post my problem here to see if there was a way i didn't think of. I thought of using a battery but opening the button system every week is not easy. I would prefer the first option.
So If someone find a way to make the arduino "invisible" please let me know.
Thanks for your help, and sorry again for the poor english.