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Help needed

Discussion in 'Electronic Basics' started by C Logan, Jul 28, 2004.

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  1. C Logan

    C Logan Guest

    I am simply a hack at electronics but I need a little help...

    I have two cats. One is fat because it eats the other one's food. I have
    create a special sensor using simple reed sensor switches, a 9 volt and a
    piezo buzzer. There is a magnet attached to the cats collar. It works
    quite well, when the cat approaches, the magnet triggers one of the reed
    switches to close setting off the buzzer.

    The problem is that the buzzer only buzzes for a micro - second as the
    magnet passes over the reed switch. I want a simple circuit or relay that
    stays on for say 5 seconds. When the reed switch closes, it sends 9 volts
    to the piezo...isn't there a simple relay or simple basic circuit that can
    hold a relay or switch closed for 5 seconds and then open again?
  2. Neil

    Neil Guest

    ANY 555 timer will do what you need. Google for 555 timers.
  3. Or adapt this:

    The 12V supply i sreplaced with your 9V. Change the 10uF cap to 4.7uF
    to get a 5 second period. Wire the 555 output to your buzzer.
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