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Re: need help to build a card for driving 17 relays

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  • multiuseguy
    Using three 74374 IC s and three ULN2803a IC s you can drive 24 relays utlilizing the control pins to select the 74374 chips via software. I m not sure about
    Message 1 of 4 , Jan 9, 2004
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      Using three 74374 IC's and three ULN2803a IC's you can drive 24
      relays utlilizing the control pins to select the 74374 chips via
      software. I'm not sure about the sensors.


      --- In home_electronics@yahoogroups.com, "SADI Kheir-Eddine"
      <mindoverflow@y...> wrote:
      > hi,
      >
      > well, i need to build an electronic card to drive 17 relays by pc
      and return
      > two values read from 2 sensors.
      >
      > could any body help me please?
    • xxxtoytech
      Look in the Files section of this group for a PDF document parallel.pdf along with PDF data sheets for most of the components required. This describes a
      Message 2 of 4 , Jan 9, 2004
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        Look in the "Files" section of this group for a PDF
        document "parallel.pdf" along with PDF data sheets for most of the
        components required. This describes a simple interface for sending
        and receiving data via the parallel port. It doesn't cost too much
        and takes about an afternoon to build. You'll notice that not all 8
        bits of the control signal are used. You can use the unused bits to
        control additional IC's (look at the schematic to see how each IC is
        addressed). Depending upon your relays you may be able to drive them
        directly from the circuit given. The only caution is that you'll have
        to read the values from the sensors a bit at a time so if the values
        are rapidly changing it might present a minor problem. It also
        depends upon the resolution of the sensor (binary, 4-bit, 8-bit etc.)
        The programming is also described; you can used most popular
        programming languages including Java to access the parallel port. You
        can also use an old PC that has been discarded for experimentation.

        Regards
        xxxtoytech
        --- In home_electronics@yahoogroups.com, "SADI Kheir-Eddine"
        <mindoverflow@y...> wrote:
        > hi,
        >
        > well, i need to build an electronic card to drive 17 relays by pc
        and return
        > two values read from 2 sensors.
        >
        > could any body help me please?
      • SADI Kheir-Eddine
        hi, well, the real application of that project isn t to drive 17 relays but to drive 17 electromagnets to simulate a punched card, the photocell is used to
        Message 3 of 4 , Jan 10, 2004
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          hi,

          well, the real application of that project isn't to drive 17 relays
          but to drive 17 electromagnets to simulate a punched card, the
          photocell is used to determine if the reader is reading the card or
          not. I think that the electromagnet can't function for a long time
          without taking a pause then i am planing to use a triger so that when
          the photocell's signal is moving from high to low, the electromagnets
          will be turned off and when it's moving from low to high, the
          electromagnets gets activated. what do you think about it? about the
          current sensor i think it's no more needed cuz we'll know if the
          reader is on or off by adding a timeout to the photocell, when it's
          reached the reader is considered as of until it sends that signal.
          then the pc will send 3 bytes containing wich electromagnets to
          activate and the board will send 1bit (in 1 byte) wich is sent when
          the photocell changes it's state and is used to synchronize between
          the pc and the reader. I'll write the software part.

          What do you think about all that? am i missing some thing?
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