AC voltage --> PC

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.

sonaiko said:

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?

Click to expand...

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.

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?