help need in triggering interrupt............

Discussion in 'General Electronics Chat' started by sanddune, Dec 3, 2008.

  1. sanddune

    Thread Starter Member

    Dec 2, 2008
    10
    0
    Hi All,

    Need ideas in designing triggering circuit....

    basic idea:

    triggering int when the switch is closed........were the switch is connected to 240V AC, 60Hz supply......All I need is a pulse at the int pin when switched ON.

    Felt using transformer could increase the size of the board......Is there a way to reduce the size of the board using optocouplers or something else if so how?

    I found an AC switch detector .....follow link

    http://www.st.com/stonline/products/...592/stcc08.pdf

    will this useful for achieving the above idea?:confused:

    all i need is pulse to INT pin(PIC16F628A) when AC switch is closed .........

    Thanks to all in advance
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Yes you can use it.
     
  3. sanddune

    Thread Starter Member

    Dec 2, 2008
    10
    0
    Thanks for your time....

    Purpose of this project is to

    Detect A closed switch(eg: door bell switch at 240V 60Hz) will trigger my micro controller to send certain commands.


    Is it okay to use optocouplers. As mentioned in the link below

    http://www.datasheetcatalog.org/data.../486754_DS.pdf
    and
    http://www.datasheetcatalog.org/data...shay/83676.pdf


    Especially SFH620AA(Siemens).......

    Is this correct:
    I would be connecting my EXT INT pin of micro controller to the 3rd PIN of SFH620AA(Siemens), With the Pin 1 connected through 50 K resistor to the supply

    Will this provide a perfect isolation between high and low voltages?:confused:



     
  4. sanddune

    Thread Starter Member

    Dec 2, 2008
    10
    0
    will this be fine?.....
     
  5. nanovate

    Distinguished Member

    May 7, 2007
    665
    1
    Maybe, can you post a schematic?
     
  6. sanddune

    Thread Starter Member

    Dec 2, 2008
    10
    0
    i haven't yet finalized the triggering circuit and that's the reason i am here........

    All i need is a pulse to my INT pin stating that whether door bell is active or not.

    Basic idea:

    I would be connecting my microcontroller in series with the switch which uses the AC 240V supply. When a closed circuit is detected send commands.

    As i mentioned earlier, using rectifier is certainly an option.What i would be looking at is reducing my board size without an transformer and rectifier circuit .
     
  7. sanddune

    Thread Starter Member

    Dec 2, 2008
    10
    0
    I guess i will go with

    Connecting my EXT INT pin of micro controller to the 4th PIN(C) of SFH620A(Vishay), With the Pin 1 connected through 50 K resistor supply(240V). With the optocoupler connected in series with the switch.

    Is there anythings I need to take care?besides the current limiting resistor at the AC input stage.


     
  8. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Well, I don't think the doorbell switch closes the circuit of the 240VAC supply. Usually doorbells are supplied with step down transformers 240/24 VAC and its the 24 VAC which is connected to the switch for safety reasons. An easier solution from the IC is to use a relay to sense the switch and dive the appropriate signal to the PIC. However, be careful to include a de-bounce code in the PIC program (if needed) because relay conducts bounce for a few ms before they set down to a stable state when the relay is used.
     
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