Anyone know any good latching IC's?

Discussion in 'The Projects Forum' started by magnet18, Jan 26, 2012.

  1. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    By that I mean, I need an IC that, when an input goes high (set), will make an output high until a different input goes high (the reset)
    or, if the set and reset were the same pin, i suppose that would work also
    anyone know anything that will work?
    The 555 version is being more of a pain than it's worth in troubleshooting and components, I'm just looking for simplicity and reliability right now
     
  2. MrChips

    Moderator

    Oct 2, 2009
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    Yeah, it's called a flip-flop.
     
  3. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    AAAND nows when I feel like an idiot
    a 4013 will work, wont it?
     
  4. MrChips

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    You can also make a flip-flop from a pair of NAND or NOR gates or even two inverters or two transistors.
     
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  5. crutschow

    Expert

    Mar 14, 2008
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    A definition nit--;)

    Typically a bistable circuit made from a couple of gates or transistors that immediately responds to a set or reset signal is called a latch. Flip-flop usually refers to a bistable circuit that changes state (as determined by the state of a separate D or JK input) in response to a clock input (although flip-flops often have set and reset inputs that allow them to act as latches).
     
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  6. MrChips

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    Point taken. Let's call it a bistable.
     
  7. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    Yes. Disable Clock and Data. You can connect them to Gnd.

    Note that when using the 4013 both Outputs can be set if you apply for whatever reason a HIGH to SET and RESET.

    If that is a problem you can couple the SET / RESET commands via a capacitor to their corresponding inputs. Don't forget the pulldown resistor and a diode in parallel with it.
     
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  8. ErnieM

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    Apr 24, 2011
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  9. MrChips

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    No offense. What crutschow was saying is that he (crustchow) was going to nit-pic about definition. The terms used are bistable (two-state device) and astable (oscillator) - (not to be confused with a monostable and a horse stable). An R-S flip-flop is a bistable device. A flip-flop is usually a clocked bistable but does not have to be clocked. A D-latch is a different beast - a clocked transparent D-register. Still confused?
     
    Last edited: Jan 27, 2012
  10. MrChips

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    Here is a bistable using two inverters:

    [​IMG]
     
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  11. crutschow

    Expert

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    You can do that with a flip-flop by triggering the clock input. If you connect the inverted (not) output of the FF to the D input of a D FF, or connect the JK inputs to a logic high on a JK FF, their outputs will toggle between states for each clock pulse input.
     
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  12. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    Alright, thanks for the advice guys :)
    Hopefully I'll get a simple schematic up tomorrow for approval to make sure I know what I'm doing :)
     
  13. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    Will this work?
    will it work if I have a diode right at the output of the 4017 that feeds the reset?
    [EDIT]
    See the second attachment
     
    Last edited: Jan 28, 2012
  14. magnet18

    Thread Starter Senior Member

    Dec 22, 2010
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    the only reason I could see for that not working is if holding the clock at gnd while triggering set and reset is unacceptable
    Will it work?
     
  15. crutschow

    Expert

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    The set and reset inputs are independent of the clock state, so keeping the clock at ground is fine.
     
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  16. Wendy

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    Mar 24, 2008
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    They also make them for BCD counters. The chips are called latch and hold.
     
  17. sheldons

    Active Member

    Oct 26, 2011
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    [​IMG]

    heres one i built earlier.....calibrated wires are optional extras
     
    Last edited: Jan 30, 2012
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