circuit design help: momentary switch activates/cancels electronic switch

Discussion in 'Electronic Design' started by matthewuw, Oct 12, 2005.

  1. matthewuw

    matthewuw Guest

    Here is the application:

    I have a momentary switch. When I press it, I want to switch something
    on (light bulb) and have it stay on even though momentary switch was
    released. maybe 500 mA draw.

    When I press it again, it turns the light bulb off. How do I do this?
    This is in a 12VDC circuit.

    Thanks!
    matthewuw, Oct 12, 2005
    #1
  2. matthewuw

    Ken Taylor Guest

    Do you particularly want to use that switch or would you be prepared to swap
    it for a push-on/push-off momentary action one?

    Ken

    "matthewuw" <> wrote in message
    news:...
    > Here is the application:
    >
    > I have a momentary switch. When I press it, I want to switch something
    > on (light bulb) and have it stay on even though momentary switch was
    > released. maybe 500 mA draw.
    >
    > When I press it again, it turns the light bulb off. How do I do this?
    > This is in a 12VDC circuit.
    >
    > Thanks!
    >
    Ken Taylor, Oct 12, 2005
    #2
  3. matthewuw

    ehsjr Guest

    Re: circuit design help: momentary switch activates/cancels electronicswitch

    matthewuw wrote:
    > Here is the application:
    >
    > I have a momentary switch. When I press it, I want to switch something
    > on (light bulb) and have it stay on even though momentary switch was
    > released. maybe 500 mA draw.
    >
    > When I press it again, it turns the light bulb off. How do I do this?
    > This is in a 12VDC circuit.
    >
    > Thanks!
    >


    There are a number of ways to do this. Do you want
    to learn, or are you just interested in having
    a circuit that will do it?

    Ed
    ehsjr, Oct 13, 2005
    #3
  4. matthewuw

    matthewuw Guest

    Will in the end, I need a circuit to do this. But I do want to learn.
    What I asked for is actually only part of the functionality, but I see
    it as a building block to start with and was hoping I might figure the
    rest out on my own.
    matthewuw, Oct 13, 2005
    #4
  5. matthewuw

    matthewuw Guest

    Well a push-on push-off switch isn't really momentary. It feels like a
    momentary switch, but doesn't function like one. I have to use a
    momentary switch, no option because or existing hardware.
    matthewuw, Oct 13, 2005
    #5
  6. matthewuw

    matthewuw Guest

    Well a push-on push-off switch isn't really momentary. It feels like a
    momentary switch, but doesn't function like one. I have to use a
    momentary switch, no option because of existing hardware.
    matthewuw, Oct 13, 2005
    #6
  7. "matthewuw" <> wrote:

    >Here is the application:
    >
    >I have a momentary switch. When I press it, I want to switch something
    >on (light bulb) and have it stay on even though momentary switch was
    >released. maybe 500 mA draw.
    >
    >When I press it again, it turns the light bulb off. How do I do this?
    >This is in a 12VDC circuit.
    >
    >Thanks!


    This should do it.
    http://www.terrypin.dial.pipex.com/Images/Momentary1.gif

    There are many circuits for a 'toggle' or flip-flop, but that's the
    simplest/cheapest I know of.

    --
    Terry Pinnell
    Hobbyist, West Sussex, UK
    Terry Pinnell, Oct 13, 2005
    #7
  8. matthewuw

    Fred Bloggs Guest

    Re: circuit design help: momentary switch activates/cancels electronicswitch

    Terry Pinnell wrote:
    > "matthewuw" <> wrote:
    >
    >
    >>Here is the application:
    >>
    >>I have a momentary switch. When I press it, I want to switch something
    >>on (light bulb) and have it stay on even though momentary switch was
    >>released. maybe 500 mA draw.
    >>
    >>When I press it again, it turns the light bulb off. How do I do this?
    >>This is in a 12VDC circuit.
    >>
    >>Thanks!

    >
    >
    > This should do it.
    > http://www.terrypin.dial.pipex.com/Images/Momentary1.gif
    >
    > There are many circuits for a 'toggle' or flip-flop, but that's the
    > simplest/cheapest I know of.
    >


    Did you simulate that?
    Fred Bloggs, Oct 13, 2005
    #8
  9. matthewuw

    Ken Moffett Guest

    "matthewuw" <> wrote in news:1129097288.402163.260420
    @o13g2000cwo.googlegroups.com:

    > Here is the application:
    >
    > I have a momentary switch. When I press it, I want to switch something
    > on (light bulb) and have it stay on even though momentary switch was
    > released. maybe 500 mA draw.
    >
    > When I press it again, it turns the light bulb off. How do I do this?
    > This is in a 12VDC circuit.
    >
    > Thanks!
    >



    I've tried this and it works. Simple and cheap. Sub in a 12vdc supply and a
    12v relay.

    http://beradio.com/news/radio_pushonpushoff_switch_2/
    Ken Moffett, Oct 13, 2005
    #9
  10. matthewuw

    Fred Bloggs Guest

    Re: circuit design help: momentary switch activates/cancels electronicswitch

    > Here is the application:
    >
    > I have a momentary switch. When I press it, I want to switch something
    > on (light bulb) and have it stay on even though momentary switch was
    > released. maybe 500 mA draw.
    >
    > When I press it again, it turns the light bulb off. How do I do this?
    > This is in a 12VDC circuit.


    You can use a miniature SCR bistable:
    View in a fixed-width font such as Courier.
    Fred Bloggs, Oct 13, 2005
    #10
  11. matthewuw

    Fred Bloggs Guest

    Re: circuit design help: momentary switch activates/cancels electronicswitch

    Should be:
    View in a fixed-width font such as Courier.
    Fred Bloggs, Oct 13, 2005
    #11
  12. Fred Bloggs <> wrote:

    >Did you simulate that?


    No, but maybe I'll have a crack at it when I get some time. Meanwhile,
    I've put together this scan from my original source: "Elektor 302
    Circuits", ~1985
    http://www.terrypin.dial.pipex.com/Images/MomentaryScan1.jpg
    which explains its working.

    And I'm pretty sure I breadboarded it successfully a decade or two
    ago.

    --
    Terry Pinnell
    Hobbyist, West Sussex, UK
    Terry Pinnell, Oct 13, 2005
    #12
  13. matthewuw

    Jim Thompson Guest

    On 11 Oct 2005 23:08:08 -0700, "matthewuw" <> wrote:

    >Here is the application:
    >
    >I have a momentary switch. When I press it, I want to switch something
    >on (light bulb) and have it stay on even though momentary switch was
    >released. maybe 500 mA draw.
    >
    >When I press it again, it turns the light bulb off. How do I do this?
    >This is in a 12VDC circuit.
    >
    >Thanks!


    See "TogggleFlopAncient.pdf" on the S.E.D/Schematics page of my
    website.

    ...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 |

    I love to cook with wine. Sometimes I even put it in the food.
    Jim Thompson, Oct 13, 2005
    #13
  14. matthewuw

    Fred Bloggs Guest

    Re: circuit design help: momentary switch activates/cancels electronicswitch

    > Here is the application:
    >
    > I have a momentary switch. When I press it, I want to switch something
    > on (light bulb) and have it stay on even though momentary switch was
    > released. maybe 500 mA draw.
    >
    > When I press it again, it turns the light bulb off. How do I do this?
    > This is in a 12VDC circuit.


    Here is a less parts intensive version of the same thing, consumes about
    50uA in the off state:
    View in a fixed-width font such as Courier.
    Fred Bloggs, Oct 14, 2005
    #14
  15. matthewuw

    Fred Bloggs Guest

    Re: circuit design help: momentary switch activates/cancels electronicswitch

    Terry Pinnell wrote:
    > Fred Bloggs <> wrote:
    >
    >
    >>Did you simulate that?

    >
    >
    > No, but maybe I'll have a crack at it when I get some time. Meanwhile,
    > I've put together this scan from my original source: "Elektor 302
    > Circuits", ~1985
    > http://www.terrypin.dial.pipex.com/Images/MomentaryScan1.jpg
    > which explains its working.
    >
    > And I'm pretty sure I breadboarded it successfully a decade or two
    > ago.
    >


    Thanks- I think I recall that article now, clever.
    Fred Bloggs, Oct 14, 2005
    #15
  16. matthewuw

    Fred Bloggs Guest

    Re: circuit design help: momentary switch activates/cancels electronicswitch

    Jim Thompson wrote:
    > On 11 Oct 2005 23:08:08 -0700, "matthewuw" <> wrote:
    >
    >
    >>Here is the application:
    >>
    >>I have a momentary switch. When I press it, I want to switch something
    >>on (light bulb) and have it stay on even though momentary switch was
    >>released. maybe 500 mA draw.
    >>
    >>When I press it again, it turns the light bulb off. How do I do this?
    >>This is in a 12VDC circuit.
    >>
    >>Thanks!

    >
    >
    > See "TogggleFlopAncient.pdf" on the S.E.D/Schematics page of my
    > website.
    >
    > ...Jim Thompson


    A little before my time, but those were the days...toggle on release.
    Fred Bloggs, Oct 14, 2005
    #16
  17. matthewuw

    Ken Moffett Guest

    Ken Moffett <> wrote in
    news:Xns96EE4ED95F5AEqwerty@24.94.170.94:

    > "matthewuw" <> wrote in news:1129097288.402163.260420
    > @o13g2000cwo.googlegroups.com:
    >
    >> Here is the application:
    >>
    >> I have a momentary switch. When I press it, I want to switch
    >> something on (light bulb) and have it stay on even though momentary
    >> switch was released. maybe 500 mA draw.
    >>
    >> When I press it again, it turns the light bulb off. How do I do
    >> this? This is in a 12VDC circuit.
    >>
    >> Thanks!
    >>

    >
    >
    > I've tried this and it works. Simple and cheap. Sub in a 12vdc supply
    > and a 12v relay.
    >
    > http://beradio.com/news/radio_pushonpushoff_switch_2/
    >
    >


    I looked back at the circuit again and noted something they had left out.
    The relay in their circuit was a 12vdc for the 24v supply. So for a 12v
    supply you would choose a 5vdc or 6vdc DPDT relay. The resistance of R1,
    R2, and relay's coil would all be approximately equal.
    Ken Moffett, Oct 14, 2005
    #17
  18. matthewuw

    matthewuw Guest

    Okay, thanks for all the replies. Sorry to change things up on
    you...but like I said early on, this is a learning experience for me.
    It has occured to me that I don't want to worry about contact bounce
    and that in reality, this will fit my application much better if there
    are 2 momentary switches. pressing one of them turns the system on and
    pressing the other turns the system off. i can probably adapt this
    setup somehow from some of the provided circuits, so I will look into
    it. this might actually simplify the circuit too i would think.
    THANKS!
    matthewuw, Oct 14, 2005
    #18
  19. "matthewuw" <> wrote:

    >Okay, thanks for all the replies. Sorry to change things up on
    >you...but like I said early on, this is a learning experience for me.
    >It has occured to me that I don't want to worry about contact bounce
    >and that in reality, this will fit my application much better if there
    >are 2 momentary switches. pressing one of them turns the system on and
    >pressing the other turns the system off. i can probably adapt this
    >setup somehow from some of the provided circuits, so I will look into
    >it. this might actually simplify the circuit too i would think.
    >THANKS!


    How much simpler can you get than the circuits posted? Have you tried
    any of them yet?

    Hey, how about an even simpler approach: a single toggle switch? No
    buttons, no electronics. AC or DC power supply in at one side, and out
    of the other to whatever you want to control. Its explanation is as
    follows: when you switch it one way, the circuit is powered on. When
    you switch it the other way, the circuit is powered off again. Very
    reliable, parts easily obtained. What's more, it has another advantage
    over a button-based approach: the status of the circuit is always
    visibly obvious (providing the two switch positions have been marked
    accordingly, e.g. 'On' and 'Off' or whatever.) This advantage over
    buttons applies even if the load has failed somehow (lamp filament
    burned out, motor stalled, etc).

    --
    Terry Pinnell
    Hobbyist, West Sussex, UK
    Terry Pinnell, Oct 14, 2005
    #19
  20. matthewuw

    Fred Bloggs Guest

    Re: circuit design help: momentary switch activates/cancels electronicswitch

    > Okay, thanks for all the replies. Sorry to change things up on
    > you...but like I said early on, this is a learning experience for me.
    > It has occured to me that I don't want to worry about contact bounce
    > and that in reality, this will fit my application much better if there
    > are 2 momentary switches. pressing one of them turns the system on and
    > pressing the other turns the system off. i can probably adapt this
    > setup somehow from some of the provided circuits, so I will look into
    > it. this might actually simplify the circuit too i would think.


    View in a fixed-width font such as Courier.

    ..
    ..
    .. 12VDC>---+-------+-----+-------+
    .. | | | |
    .. | | | 12VDC |
    .. | | --RELAY---
    .. | | |\ COM|
    .. | - |/ |
    .. | ^ |\ |
    .. | 1N4001 |/ NO |
    .. | | ----------
    .. | | | |
    .. o +-----+ +-----+
    .. -| SWon | | |
    .. o | | |
    .. | | | |
    .. +----[2.2K]---|-------+ |
    .. | | |
    .. [2.2K] | |
    .. | | LAMP
    .. | ||- |
    .. +-------+--||< IRF510 |
    .. | | ||- |
    .. o === | |
    .. -| SWoff 0.1U | |
    .. o | | |
    .. | | | |
    .. +-------+-----+-------------+
    .. ---
    .. ///
    ..
    ..
    ..
    Fred Bloggs, Oct 14, 2005
    #20

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