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Re: Need 555 Time Monostable Help......

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  • mariss92705
    Hi, Yeah, I forgot to mention that; always have a power supply bypass (10uF to 100uF) capacitor at your circuit. Circuits will not run properly without them.
    Message 1 of 8 , Aug 27, 2002
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      Hi,

      Yeah, I forgot to mention that; always have a power supply bypass
      (10uF to 100uF) capacitor at your circuit. Circuits will not run
      properly without them.

      Regards to the 4000 series one-shot. I have used a 4013 D-Flop.
      Connect a resistor R from Q to RESET and a capacitor C from RESET to
      ground. Clock the flop with your switch. Q will go high, charge the
      RC connected to RESET, which will reset Q back to "0" after 1 time
      constant (T = RC).

      I also use 40106 hex schmidt inverters. Connect a capacitor C from
      the output of INV1 to the input of INV2. Connect a resistor R from
      the input of INV2 to + supply. Again, INV2 output pulse width is
      equal to RC. Low-pass filter (R from SW to INV1 input, C from INV1
      input to ground), the switch input to de-bounce it, 10 milliseconds
      will do.

      Mariss

      --- In Electronics_101@y..., "zuggetsr" <zugget@a...> wrote:
      > Thanks, for the info. I put a 10 uF across the supply and ground
      of
      > my 556 and it took care of the problem. I have included the RC
      node
      > as you mentioned below to turn the one shot circuit into a
      repeatable
      > circuit, otherwise you have to ground the cap for it to fire
      again.
      >
      > So using 4000 series technology, what would your circuit look
      like?
      > Remember I need a clean pulse from a NO switch to advance my
      digital
      > LED counter. My circuit using 555's work regardless of how long
      (10
      > secs) or short (< 1 sec) the NO switch is held closed.
      >
      >
      > --- In Electronics_101@y..., "mariss92705" <mariss92705@y...> wrote:
      > > Curtis,
      > >
      > > You are absolutely right. The circuit will not function again
      until
      > > the cap charge leaks away. What is needed here is a 10K pull-up
      > from
      > > the switch and cap node to + supply. Possibly a diode connected
      > anode
      > > from the other end of said cap with cathode to +supply as well.
      The
      > > RC node would be forced to twice the power supply voltage when
      the
      > > switch is released. That could be a problem, the diode would
      clamp
      > > it.
      > >
      > > I'm not much of a 555 guru because I never use them. I prefer to
      > use
      > > 4000 series CMOS gates and D-flops for all my oscillator and
      > > monostable needs. It takes less parts, is more flexible and
      > consumes
      > > much less current.
      > >
      > > Mariss
      > >
      > > --- In Electronics_101@y..., Curtis Sakima
      > <electronichobbyist@y...>
      > > wrote:
      > > > Hmmm ... it loads correctly on my web browser now.
      > > > You must've found the problem ....
      > > >
      > > > Anyways ... hey mariss, doesn't the 555 timer circuit
      > > > need a pullup resistor from the pushbutton up to Vcc
      > > > ... plus a diode from pin 2 of the 555 to Vcc??
      > > >
      > > > I mean to discharge the input differentiator cap when
      > > > the pushbutton is released. So that the diff can
      > > > "reset to fight another day"?
      > > >
      > > > Curtis
      > > >
      > > >
      > > > --- mariss92705 <mariss92705@y...> wrote:
      > > > Here's what should fix it.
      > > >
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