dc power on-off with single pole momentary switch

Discussion in 'Electronic Design' started by John Bachman, Feb 13, 2008.

  1. John Bachman

    John Bachman Guest

    The subject tells the goal. Here is the rest of the story. There is
    no micro available. It is preferred to use a dual comparator such as
    393 as one of those is already part of the design and having two of
    one device is preferable to one of these and one of those.

    I have tried and failed. Others care to give it a crack?

    John
    John Bachman, Feb 13, 2008
    #1
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  2. John Bachman

    Jim Thompson Guest

    On Wed, 13 Feb 2008 13:15:11 -0500, John Bachman
    <> wrote:

    >The subject tells the goal. Here is the rest of the story. There is
    >no micro available. It is preferred to use a dual comparator such as
    >393 as one of those is already part of the design and having two of
    >one device is preferable to one of these and one of those.
    >
    >I have tried and failed. Others care to give it a crack?
    >
    >John


    Input Voltage?

    How much "stand-by" power can be drawn by the switching circuitry?

    Load Current?

    ...Jim Thompson
    --
    | James E.Thompson, P.E. | mens |
    | Analog Innovations, Inc. | et |
    | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
    | Phoenix, Arizona Voice:(480)460-2350 | |
    | E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
    | http://www.analog-innovations.com | 1962 |

    America: Land of the Free, Because of the Brave
    Jim Thompson, Feb 13, 2008
    #2
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  3. On a sunny day (Wed, 13 Feb 2008 13:15:11 -0500) it happened John Bachman
    <> wrote in
    <>:

    >The subject tells the goal. Here is the rest of the story. There is
    >no micro available. It is preferred to use a dual comparator such as
    >393 as one of those is already part of the design and having two of
    >one device is preferable to one of these and one of those.
    >
    >I have tried and failed. Others care to give it a crack?
    >
    >John


    Use a 74HC74 flipflop, it has reset for correct power up too.
    Screw the comparator.
    Jan Panteltje, Feb 13, 2008
    #3
  4. John Bachman

    John Bachman Guest

    On Wed, 13 Feb 2008 11:27:02 -0700, Jim Thompson
    <> wrote:

    >On Wed, 13 Feb 2008 13:15:11 -0500, John Bachman
    ><> wrote:
    >
    >>The subject tells the goal. Here is the rest of the story. There is
    >>no micro available. It is preferred to use a dual comparator such as
    >>393 as one of those is already part of the design and having two of
    >>one device is preferable to one of these and one of those.
    >>
    >>I have tried and failed. Others care to give it a crack?
    >>
    >>John

    >
    >Input Voltage?
    >
    >How much "stand-by" power can be drawn by the switching circuitry?
    >
    >Load Current?
    >

    9 volt battery supply. Load is 12 ma. I figure a pass transistor
    operated by the switch and/or circuitry will be fine.

    Ideally the switching circuitry is on the load side of the pass
    transistor, hence no quiescent draw. That may not be possible. If it
    must draw quiescent current then I will have to assess the feasibility
    of it. Two switches is not the end of the world, just not as elegant.

    John
    John Bachman, Feb 13, 2008
    #4
  5. John Bachman

    John Bachman Guest

    On Wed, 13 Feb 2008 18:42:44 GMT, Jan Panteltje
    <> wrote:

    >On a sunny day (Wed, 13 Feb 2008 13:15:11 -0500) it happened John Bachman
    ><> wrote in
    ><>:
    >
    >>The subject tells the goal. Here is the rest of the story. There is
    >>no micro available. It is preferred to use a dual comparator such as
    >>393 as one of those is already part of the design and having two of
    >>one device is preferable to one of these and one of those.
    >>
    >>I have tried and failed. Others care to give it a crack?
    >>
    >>John

    >
    >Use a 74HC74 flipflop, it has reset for correct power up too.
    >Screw the comparator.


    Yeah, I know. Sigh.

    John
    John Bachman, Feb 13, 2008
    #5
  6. John Bachman <> wrote:

    > On Wed, 13 Feb 2008 11:27:02 -0700, Jim Thompson
    > <> wrote:
    >
    > >On Wed, 13 Feb 2008 13:15:11 -0500, John Bachman
    > ><> wrote:
    > >
    > >>The subject tells the goal. Here is the rest of the story. There is
    > >>no micro available. It is preferred to use a dual comparator such as
    > >>393 as one of those is already part of the design and having two of
    > >>one device is preferable to one of these and one of those.
    > >>
    > >>I have tried and failed. Others care to give it a crack?
    > >>
    > >>John

    > >
    > >Input Voltage?
    > >
    > >How much "stand-by" power can be drawn by the switching circuitry?
    > >
    > >Load Current?
    > >

    > 9 volt battery supply. Load is 12 ma. I figure a pass transistor
    > operated by the switch and/or circuitry will be fine.
    >
    > Ideally the switching circuitry is on the load side of the pass
    > transistor, hence no quiescent draw. That may not be possible. If it
    > must draw quiescent current then I will have to assess the feasibility
    > of it. Two switches is not the end of the world, just not as elegant.


    Is there any reason why you can't use a straightforward single pole
    toggle switch? It is cheap, ergonomic to operate, draws no quiescent
    current when open, gives negligible volt-drop when closed - and is
    self-indicating.

    If they had only just been invented, they would be regarded as one of
    the biggest steps forward in technology of the past 30 years.


    --
    ~ Adrian Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk
    Adrian Tuddenham, Feb 13, 2008
    #6
  7. John Bachman

    linnix Guest

    > > >>The subject tells the goal. Here is the rest of the story. There is
    > > >>no micro available.


    Why not? Bad design!

    > It is preferred to use a dual comparator such as


    >
    > Is there any reason why you can't use a straightforward single pole
    > toggle switch?


    Yes, it can't turn itself off.

    > It is cheap, ergonomic to operate, draws no quiescent
    > current when open, gives negligible volt-drop when closed - and is
    > self-indicating.
    >
    > If they had only just been invented, they would be regarded as one of
    > the biggest steps forward in technology of the past 30 years.


    Except for wasting batteries. Auto off is the second biggest step
    forward ...
    linnix, Feb 13, 2008
    #7
  8. John Bachman wrote:
    >
    > The subject tells the goal. Here is the rest of the story. There is
    > no micro available. It is preferred to use a dual comparator such as
    > 393 as one of those is already part of the design and having two of
    > one device is preferable to one of these and one of those.
    >
    > I have tried and failed. Others care to give it a crack?
    >
    > John


    Go down to your local hardware store. They have lamp switches that push
    on, push off. All done mechanically.

    --
    Paul Hovnanian
    -----------------------------------------------------------------------
    Procrastinators: The leaders for tomorrow.
    Paul Hovnanian P.E., Feb 13, 2008
    #8
  9. linnix <-for.us> wrote:


    > > Is there any reason why you can't use a straightforward single pole
    > > toggle switch?

    >
    > Yes, it can't turn itself off.
    >
    > > It is cheap, ergonomic to operate, draws no quiescent
    > > current when open, gives negligible volt-drop when closed - and is
    > > self-indicating.
    > >
    > > If they had only just been invented, they would be regarded as one of
    > > the biggest steps forward in technology of the past 30 years.

    >
    > Except for wasting batteries. Auto off is the second biggest step
    > forward ...


    Unless the item is a camera which switches itself off just in time to
    miss as the shot you have been waiting for !


    --
    ~ Adrian Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk
    Adrian Tuddenham, Feb 13, 2008
    #9
  10. John Bachman

    linnix Guest

    On Feb 13, 1:47 pm, "Paul Hovnanian P.E." <> wrote:
    > John Bachman wrote:
    >
    > > The subject tells the goal. Here is the rest of the story. There is
    > > no micro available. It is preferred to use a dual comparator such as
    > > 393 as one of those is already part of the design and having two of
    > > one device is preferable to one of these and one of those.

    >
    > > I have tried and failed. Others care to give it a crack?

    >
    > > John

    >
    > Go down to your local hardware store. They have lamp switches that push
    > on, push off. All done mechanically.


    But many customers just push on and leave on battery devices. On
    second thought, I am going to randomly disable the auto-off feature.
    I am starting a batteries on-line business.

    >
    > --
    > Paul Hovnanian
    > -----------------------------------------------------------------------
    > Procrastinators: The leaders for tomorrow.
    linnix, Feb 13, 2008
    #10
  11. John Bachman

    linnix Guest

    On Feb 13, 1:48 pm, (Adrian
    Tuddenham) wrote:
    > linnix <-for.us> wrote:
    > > > Is there any reason why you can't use a straightforward single pole
    > > > toggle switch?

    >
    > > Yes, it can't turn itself off.

    >
    > > > It is cheap, ergonomic to operate, draws no quiescent
    > > > current when open, gives negligible volt-drop when closed - and is
    > > > self-indicating.

    >
    > > > If they had only just been invented, they would be regarded as one of
    > > > the biggest steps forward in technology of the past 30 years.

    >
    > > Except for wasting batteries. Auto off is the second biggest step
    > > forward ...

    >
    > Unless the item is a camera which switches itself off just in time to
    > miss as the shot you have been waiting for !


    But the camera button (trigger) should be auto-on as well.

    >
    > --
    > ~ Adrian Tuddenham ~
    > (Remove the ".invalid"s and add ".co.uk" to reply)www.poppyrecords.co.uk
    linnix, Feb 13, 2008
    #11
  12. John Bachman

    Tam Guest

    "Paul Hovnanian P.E." <> wrote in message
    news:...
    > John Bachman wrote:
    >>
    >> The subject tells the goal. Here is the rest of the story. There is
    >> no micro available. It is preferred to use a dual comparator such as
    >> 393 as one of those is already part of the design and having two of
    >> one device is preferable to one of these and one of those.
    >>
    >> I have tried and failed. Others care to give it a crack?
    >>
    >> John

    >
    > Go down to your local hardware store. They have lamp switches that push
    > on, push off. All done mechanically.
    >
    > --
    > Paul Hovnanian
    > -----------------------------------------------------------------------
    > Procrastinators: The leaders for tomorrow.


    And if you need to switch more current than the lamp switch can handle, use
    it to operate a power relay. BTW, if you go the 7474 route, be sure to
    debounce the switch.

    Tam
    Tam, Feb 13, 2008
    #12
  13. John Bachman

    Arie Guest

    "John Bachman" <> wrote in message
    news:...
    > The subject tells the goal. Here is the rest of the story. There is
    > no micro available. It is preferred to use a dual comparator such as
    > 393 as one of those is already part of the design and having two of
    > one device is preferable to one of these and one of those.
    >
    > I have tried and failed. Others care to give it a crack?
    >
    > John



    Something like this?


    +
    | ====
    100k GND- 10n -------o o------ 1uF -- GND +
    | | | |
    | | |\ 1M 10k
    |-- 100k ----------|-\ | |
    | | }--------------------------------->
    |-- 100k ----------|+/ |
    | | |/ |
    | | |
    | ----- 100k ---
    100k
    |
    GND

    The comparator is self-latching, after power-on output is high (for minimum
    current drawn).
    Alternative: connect the 10n to +, then it starts with output low.

    Pressing the switch less than 1 sec switches the state.
    Repeating the switch presses fast does not switch state (slow debounce).

    Arie de Muynck
    Arie, Feb 13, 2008
    #13
  14. John Bachman

    John Bachman Guest

    On Wed, 13 Feb 2008 20:31:17 +0000, lid
    (Adrian Tuddenham) wrote:

    >John Bachman <> wrote:
    >
    >> On Wed, 13 Feb 2008 11:27:02 -0700, Jim Thompson
    >> <> wrote:
    >>
    >> >On Wed, 13 Feb 2008 13:15:11 -0500, John Bachman
    >> ><> wrote:
    >> >
    >> >>The subject tells the goal. Here is the rest of the story. There is
    >> >>no micro available. It is preferred to use a dual comparator such as
    >> >>393 as one of those is already part of the design and having two of
    >> >>one device is preferable to one of these and one of those.
    >> >>
    >> >>I have tried and failed. Others care to give it a crack?
    >> >>
    >> >>John
    >> >
    >> >Input Voltage?
    >> >
    >> >How much "stand-by" power can be drawn by the switching circuitry?
    >> >
    >> >Load Current?
    >> >

    >> 9 volt battery supply. Load is 12 ma. I figure a pass transistor
    >> operated by the switch and/or circuitry will be fine.
    >>
    >> Ideally the switching circuitry is on the load side of the pass
    >> transistor, hence no quiescent draw. That may not be possible. If it
    >> must draw quiescent current then I will have to assess the feasibility
    >> of it. Two switches is not the end of the world, just not as elegant.

    >
    >Is there any reason why you can't use a straightforward single pole
    >toggle switch? It is cheap, ergonomic to operate, draws no quiescent
    >current when open, gives negligible volt-drop when closed - and is
    >self-indicating.
    >
    >If they had only just been invented, they would be regarded as one of
    >the biggest steps forward in technology of the past 30 years.


    Cost is the only objection. A tactile momentary costs .16. A toggle
    is a buck or more. When the total product part cost is $12 then $.84+
    is lot.

    Two momentaries cost $.32 and will do the job, but Oh, that is ugly.

    John
    John Bachman, Feb 13, 2008
    #14
  15. John Bachman <> wrote:

    > On Wed, 13 Feb 2008 20:31:17 +0000, lid
    > (Adrian Tuddenham) wrote:
    >
    > >John Bachman <> wrote:
    > >
    > >> On Wed, 13 Feb 2008 11:27:02 -0700, Jim Thompson
    > >> <> wrote:
    > >>
    > >> >On Wed, 13 Feb 2008 13:15:11 -0500, John Bachman
    > >> ><> wrote:
    > >> >
    > >> >>The subject tells the goal. Here is the rest of the story. There is
    > >> >>no micro available. It is preferred to use a dual comparator such as
    > >> >>393 as one of those is already part of the design and having two of
    > >> >>one device is preferable to one of these and one of those.
    > >> >>
    > >> >>I have tried and failed. Others care to give it a crack?
    > >> >>
    > >> >>John
    > >> >
    > >> >Input Voltage?
    > >> >
    > >> >How much "stand-by" power can be drawn by the switching circuitry?
    > >> >
    > >> >Load Current?
    > >> >
    > >> 9 volt battery supply. Load is 12 ma. I figure a pass transistor
    > >> operated by the switch and/or circuitry will be fine.
    > >>
    > >> Ideally the switching circuitry is on the load side of the pass
    > >> transistor, hence no quiescent draw. That may not be possible. If it
    > >> must draw quiescent current then I will have to assess the feasibility
    > >> of it. Two switches is not the end of the world, just not as elegant.

    > >
    > >Is there any reason why you can't use a straightforward single pole
    > >toggle switch? It is cheap, ergonomic to operate, draws no quiescent
    > >current when open, gives negligible volt-drop when closed - and is
    > >self-indicating.
    > >
    > >If they had only just been invented, they would be regarded as one of
    > >the biggest steps forward in technology of the past 30 years.

    >
    > Cost is the only objection. A tactile momentary costs .16. A toggle
    > is a buck or more. When the total product part cost is $12 then $.84+
    > is lot.
    >
    > Two momentaries cost $.32 and will do the job, but Oh, that is ugly.


    I'd be willing to pay the extra for a decent switch, but I suppose it
    depends on which sector of the market the product is aimed at.

    --
    ~ Adrian Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk
    Adrian Tuddenham, Feb 14, 2008
    #15
  16. On a sunny day (Wed, 13 Feb 2008 23:13:22 +0100) it happened "Arie"
    <> wrote in <47b36c49$0$85784$4all.nl>:

    >Something like this?
    >
    >
    > +
    > | ====
    > 100k GND- 10n -------o o------ 1uF -- GND +
    > | | | |
    > | | |\ 1M 10k
    > |-- 100k ----------|-\ | |
    > | | }--------------------------------->
    > |-- 100k ----------|+/ |
    > | | |/ |
    > | | |
    > | ----- 100k ---
    > 100k
    > |
    > GND
    >
    >The comparator is self-latching, after power-on output is high (for minimum
    >current drawn).
    >Alternative: connect the 10n to +, then it starts with output low.
    >
    >Pressing the switch less than 1 sec switches the state.
    >Repeating the switch presses fast does not switch state (slow debounce).
    >
    >Arie de Muynck


    I must say I am impressed, a nice solution.
    As to the issue what is 'nest', this uses 10 components, 2 of which are capacitors.

    Placing, board size, vias....

    I did say 74HC74, but even that requires some debounce, as others have pointed out,
    so at least 2 more components.

    The OP says he has no micro.
    But how a about a simple 8 pin PIC?
    Use the internal osc, internal pullup at an input pin, trigger interrupt,
    flip output, hang some milliseconds in interrupt routine as debounce.....

    It is all there, with *1* component, say a PIC 12F629, only 67 cent in volume.
    http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=1001&mid=10&lang=en&pageId=74

    And, it also has a build in comparator that perhaps can replace some part
    of the rest of the circuit.....


    I would definitely go that way, have been using that PIC to replace simple circuits
    no several times.
    That way you need to have only 1 part in store.
    Jan Panteltje, Feb 14, 2008
    #16
  17. John Bachman

    Tam Guest

    "Jan Panteltje" <> wrote in message
    news:fp19s3$fur$...
    > On a sunny day (Wed, 13 Feb 2008 23:13:22 +0100) it happened "Arie"
    > <> wrote in <47b36c49$0$85784$4all.nl>:
    >
    >>Something like this?
    >>
    >>
    >> +
    >> | ====
    >> 100k GND- 10n -------o o------ 1uF -- GND +
    >> | | | |
    >> | | |\ 1M 10k
    >> |-- 100k ----------|-\ | |
    >> | | }--------------------------------->
    >> |-- 100k ----------|+/ |
    >> | | |/ |
    >> | | |
    >> | ----- 100k ---
    >> 100k
    >> |
    >> GND
    >>
    >>The comparator is self-latching, after power-on output is high (for
    >>minimum
    >>current drawn).
    >>Alternative: connect the 10n to +, then it starts with output low.
    >>
    >>Pressing the switch less than 1 sec switches the state.
    >>Repeating the switch presses fast does not switch state (slow debounce).
    >>
    >>Arie de Muynck

    >
    > I must say I am impressed, a nice solution.
    > As to the issue what is 'nest', this uses 10 components, 2 of which are
    > capacitors.
    >
    > Placing, board size, vias....
    >
    > I did say 74HC74, but even that requires some debounce, as others have
    > pointed out,
    > so at least 2 more components.
    >


    Actually, that is not that bad, because you use the other half of the HC74
    package to debounce. However, to do it right you need a SPDT switch: no
    capacitors needed.

    Tam

    > The OP says he has no micro.
    > But how a about a simple 8 pin PIC?
    > Use the internal osc, internal pullup at an input pin, trigger interrupt,
    > flip output, hang some milliseconds in interrupt routine as debounce.....
    >
    > It is all there, with *1* component, say a PIC 12F629, only 67 cent in
    > volume.
    > http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=1001&mid=10&lang=en&pageId=74
    >
    > And, it also has a build in comparator that perhaps can replace some part
    > of the rest of the circuit.....
    >
    >
    > I would definitely go that way, have been using that PIC to replace simple
    > circuits
    > no several times.
    > That way you need to have only 1 part in store.
    >
    >
    >
    >
    >
    Tam, Feb 14, 2008
    #17
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