Re: helpppppppppppppppppppppppp!for design timer

From: Robert C Monsen (rcsurname_at_comcast.net)
Date: 07/29/04

  • Next message: Rich Grise: "Re: Help: Non-working Speakers" 
    Date: Thu, 29 Jul 2004 01:32:14 GMT

    "petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message
    news:ixWNc.58025$qK.15794@amsnews02.chello.com...
    >
    > "yar" <st_yar@yahoo.com> schreef in bericht
    > news:9581531f.0407271655.69d5da17@posting.google.com...
    > > I asked a question before and received answers which, although
    > > helpful
    > > to some extent, did not provide me with what I need to know. So,
    I
    > > decided to rephrase the question.
    > >
    > >
    > > HI'
    > > I am yar intellegence then I decide send my problem to solve
    it
    > > for me .I want to make a timer circuit to control 4point with this
    > > following specification :
    > >
    > > 1- point one connect for an adjustable time with(variable
    > > resistance)then point one disconect aand point two is connect
    > >
    > > 2- point two connect for an adjustable time with(variable
    > > resistance)then point two disconect and point three is connect
    > >
    > > 3- point three connect for an adjustable time with(variable
    > > resistance)then point three disconect and point four is connect
    > >
    > > 4- point four connect for an adjustable time with(variable
    > > resistance)then point four disconect and point one is connect
    another
    > > time
    > >
    > > note: my problem is how can make the first circuit (555) triger
    the
    > > next circuit
    > > IF there is aanother useful IC's to catch my goal then why not
    > >
    > > note :I try this circuit but it isnot worked
    > >
    right(http://www.tarrypin.dail.pipex.com/images/555Timingchain-yar.gif
    )
    > > and I this component for each 555
    > >
    > > pin1----gnd
    > > pin2----10k resistance&in4148diode&connect to the next 555 pin 3
    > > pin3----connect to a coil relay
    > > pin4----connect to pin8
    > > pin5----connect to 0.01 uf ceramic capacitor(the capacitor in
    between
    > > pin 5 &gnd)
    > > pin6----connect to 1000 uf&25volt electrolytic(polar)(the negative
    leg
    > > is connected to gnd)&39k ohm connected in between pin6 & pin7
    > > pin7----connect to 1 M ohm variable resistance in between pin
    7&pin 8
    > > pin 8----connect to the vcc (the power supply is 12volt adapter)
    > >
    > >
    > > I want any help
    > >
    > >
    > > thank you YAR
    >
    >
    > Can't find your site and in a first impression the description of
    your
    > circuit does not look well. My firtst question is, what triggers the
    first
    > timer the first time? The moment the first timer has been triggered
    you can
    > always trigger the next one on the falling edge of its predecessor.
    The same
    > problem occurs when some disturbance resets the whole circuit. So
    you have
    > to provide a watchdog timer, a retriggerable monostable that
    preferably is
    > triggered by all four other timers. Once the triggering of this
    timer stops
    > due to lack of activity, it times out and the falling edge has to
    trigger
    > the first timer again. This watchdog timer has also to be triggered
    a first
    > time. This can be done by the power on reset. A more reliable
    approach is
    > using a slow astable. This can be reset by one or more of the four
    timers
    > all the time. When this resetting stops, the astable will produce u
    pulse
    > that can be used to trigger the first timer again.
    >
    > I should not use 555s for this circuit but CMOS timers like the
    4538.
    >
    > petrus bitbyter
    >

    I think a 555 is OK for this. Just trigger off of the falling edge of
    the prior retriggerable monostable, which is simple to do with a cap,
    resistor, and diode. Have a circle of these, with the timeout
    controllable by a pot.

    The first one can be started with a pushbutton to ground, which will
    override the trigger input.

    Another way would be to use an analog switch and a 4017 to switch in
    different resistors on a single 555.

    Regards,
     Bob Monsen

  • Next message: Rich Grise: "Re: Help: Non-working Speakers"

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