AC voltage --> PC

[sonaiko]

I have this door bell at home. Im trying to connect the bell to my PC such that when sm1 rings I can have like smthng on my PC to tell me that some1 is ringing the bell.

Im using the parallel port to do that, so i need the input to be either 5v or 0v.
the voltage between the bell terminals in its idle state is 12v RMS (AC voltage) [how is this possible?] and it is 4v RMS when some1 rings. [Guys i dont understand isnt it supposed to be the opposite? higher voltage when sm1 rings?]

So i want to do manipulation to these voltages such that they become 5v and 0v DC. My questions here:

1- is the 12v and 4v RMS has any DC value? how can i measure that value?
2- Im thinking of using a Low Pass Filter to get rid of the AC and have DC value, then use a regulator. But what if the RMS value has no DC?
3- Is there a regulator or smthng, that can have 12v RMS AC value and give an output of 5v DC? and if input was 4v RMS the output is 0v?

Guys u get the idea of my design, help me here plz.

 

[Nigel Goodwin]

I have this door bell at home. Im trying to connect the bell to my PC such that when sm1 rings I can have like smthng on my PC to tell me that some1 is ringing the bell.

Im using the parallel port to do that, so i need the input to be either 5v or 0v.
the voltage between the bell terminals in its idle state is 12v RMS (AC voltage) [how is this possible?] and it is 4v RMS when some1 rings. [Guys i dont understand isnt it supposed to be the opposite? higher voltage when sm1 rings?]

So i want to do manipulation to these voltages such that they become 5v and 0v DC. My questions here:

1- is the 12v and 4v RMS has any DC value? how can i measure that value?
2- Im thinking of using a Low Pass Filter to get rid of the AC and have DC value, then use a regulator. But what if the RMS value has no DC?
3- Is there a regulator or smthng, that can have 12v RMS AC value and give an output of 5v DC? and if input was 4v RMS the output is 0v?

You need a rectifier to convert the AC to DC, and a smoothing capacitor to remove the mains hum.

However, your values don't make much sense?, I suspect you're not measuring them in the correct place.

 

[sonaiko]

ya i know they dont make sense. Thats why im wondering! but i have checked them alot!!

u know, the bell isnt a normal bell, it consists of circles of wires just like an inductor! weird huh? and it buzzes not a normal bell sound.

cant u help me with the type of rectifier i need to get the value i want?