how to convert the doorbell signal?

probably it's easy for you i have 2 arduino connected via nrf24l01 modules one of the arduino is meant to receive an input when the doorbell is playing. actually the doorbell is working with a 12v signal... how can i interface that with arduino so that a pin can become HIGH when the doorbell is ringing?

thank you

komarek: the doorbell is working with a 12v signal... how can i interface that with arduino

Drop the 12V to 5V with a voltage divider. (Scroll down to Level Shifters)

what if your doorbell works on 24vac? seem like it might be easier to just use a hall sensor beside the magnet for the bells rather than trying to convert 24vac to 5vdc?

My door bell runs from AC . I have placed two diodes back to back with two other diodes ( to keep the current balanced in series with the bell. This drops about 1.2 volts . Across these I have an led with a resistor ( 47 ohm). When the bell rings the led lights. I have the led in a tube with a photo resistor at the other end . This in turn connects to a digital Input with a pull up resistor ( you need to twiddle this value) when the bell rings the digital input is pulled low. You might need an interrupt on this pin to " read"'the door bell

indeed the doorbell works on 12vAC which complicates things

i dont know these Hall Sensors... is that cheap?

PaulHammy: My door bell runs from AC . I have placed two diodes back to back with two other diodes ( to keep the current balanced in series with the bell. This drops about 1.2 volts . Across these I have an led with a resistor ( 47 ohm). When the bell rings the led lights. I have the led in a tube with a photo resistor at the other end . This in turn connects to a digital Input with a pull up resistor ( you need to twiddle this value) when the bell rings the digital input is pulled low. You might need an interrupt on this pin to " read"'the door bell

that's insanely genius :)