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Does this button exist?

Discussion in 'General Electronics Discussion' started by vlowe, Jan 4, 2012.

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  1. vlowe

    vlowe

    9
    0
    Dec 15, 2011
    I require a button that is Push-to-Make momentarily (a quick switch on)

    for the duration that the button is held it is the same as it not been pressed

    Then on release there is a Release-to-Make (a quick switch on again)

    Does it exist and does it have a name?

    Thanks
     
  2. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
    I have no idea to be honest with you, but places like digikey.com have online chat with live reps. If I ever had a question like that I always just open up the chat and ask.
     
  3. Harald Kapp

    Harald Kapp Moderator Moderator

    11,662
    2,697
    Nov 17, 2011
    I doubt...

    ... that this type of pushbutton exists as a catalog part.
    If you have the space, you could build one from a standard microswitch and an actuator (aka bushbutton) that moves sideways over the switch, closing it on its way forth and back.
    [​IMG]

    An electronic solution would use a non-retriggerable monoflop. You could couple this monoflop to a standard pushbutton via a capacitor, thus only a change in state (push/release) of the pushbutton will trigger the monoflop and deliver a defined pulse.

    Regards,
    Harald
     

    Attached Files:

  4. KMoffett

    KMoffett

    723
    75
    Jan 21, 2009
    What are you switching? How much...voltage?...current? How long does the ON-time need to be at push and release? What is the minimum push to release time?

    Ken
     
  5. vlowe

    vlowe

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    0
    Dec 15, 2011
    yes that diagram looks like it will do the job.

    can you buy such things or do you have to make them?
     
    Last edited: Jan 10, 2012
  6. vlowe

    vlowe

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    0
    Dec 15, 2011
    It is a button to initiate a Push-To-Talk call in a wired headset (so needs to be small). I am not sure about the voltage and current im afraid. The ON-time is just a brief touch (I can just tap the bare wires together).

    Im not sure about the minimum push to release time, is this configuratble?
     
  7. Harald Kapp

    Harald Kapp Moderator Moderator

    11,662
    2,697
    Nov 17, 2011
    I think you'd have to build this.

    For your application, why not use a simple standard bushbutton?
    Push once (and release) -> talk
    Push second time (and release) -> stop talking

    Harald
     
  8. vlowe

    vlowe

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    0
    Dec 15, 2011
    thats what we do at the moment, but people dont like it.

    they want it to be like a walkie talkie / radio where you press to talk - release to listen
     
  9. Harald Kapp

    Harald Kapp Moderator Moderator

    11,662
    2,697
    Nov 17, 2011
    O.K., so it has to be small, very small.
    Building it from standard components (microswitch etc) should be too bulky.What ressources do you have? Does it have to be off the shelf components, or could you build a custom switch?

    In a custom setup you could build a contraption like the on I sketched from some bronce contacts and a plastic actuator.

    If it has to be off the shelf components, it could be constructed from the smallest microswitch you can find plus an actuator made from e.g. plastic. But at least the mechanical construction would be a custom setup, too.

    I haven't been able to find a pushbutton which has this function integrated. Some old Tube-TVs used to have a similar function as part of their mains switch. The contact would energize the de-magnetizing coil whenever the TV was turned on. Even if you could locate such a switch, it will be too bulky for your application.

    Another way to go would be an electronic solution. You'd need a monoflop (e.g. NE555 based) that is triggered by the contact opening and closing, this being the tricky part because the monoflop needs to be triggered by the rising edge and the falling edge of the input (button closing and opening). You might need an addiional transistor and a pair of diodes to generate two edges of the same type from the button action.
    The output of the monoflop could short circuit the two wires using a transistor.
    Downside of this setup is that you need some kind of power supply to energize the monoflop circuit.

    Regards,
    Harald
     
    Last edited: Jan 10, 2012
  10. vlowe

    vlowe

    9
    0
    Dec 15, 2011
    nice one Harald, its beyond me to built myself.

    I think i have enough info now to pass to the guys who manufacture our current headset and see if they can build this button
     
  11. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    One challenge as I can see it is how to ensure that the actual "transmitting" stays in sync with the button operation.
    It only takes one false pulse, noise spike, or glitch to make the circuit operate in the opposite way of the intended.
     
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