Circuitry or Relay Suggestions for a 1 or 2 Second Contact Closure?

Discussion in 'General Electronics Chat' started by MrZener, Feb 14, 2015.

  1. MrZener

    Thread Starter New Member

    Apr 4, 2014
    Hi everyone.

    I wanted to see if anyone has suggestions for circuitry or a device that I could connect to a N.O. momentary pushbutton to provide a 1 - 2 second latched contact closure whenever the pushbutton is pressed. Essentially, I need something like a latching relay, except that I want the latching to occur for only a second or two.

    I'm not sure if there exist any pushbuttons with some type of integrated latching, or relays with an adjustable latching duration, but I'm guessing that some sort of external circuitry will be my only option. Ideally I'd like to keep it simple and small, as I'm working with a relatively small enclosure and have about 2 cubic inches of available space. Also, I'm working with 5 VDC inside the enclosure, so I'd like to be able to power any circuitry with the existing 5 VDC. This isn't anything that needs to be heavy duty, as I'd just be using the latched contact closure to trigger a dry GPI input on an external device.

  2. Reloadron

    Well-Known Member

    Jan 15, 2015
    Sounds like what you are after is a "One Shot" which can be done using a 555 timer as well as several other ways. A Google of 555 One Shot should bring up a dozen or more hits.

  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
    Can it be done with a signal that goes low when the push button is pushed, stays low for ~2s after the button is released?
    How fast does the low-to-high transition need to be at the end of the delay period?

    Here is about the simplest circuit I can think of:

    The switch closes at 1sec, and is released at 1.5sec.

    Last edited: Feb 14, 2015
  4. #12


    Nov 30, 2010
    I suppose the mirror image of that is a 2N7000 but too many questions remain. Pulse is high? Pulse is Low? Pulse counts from the contact moment? Pulse times from the release moment? How fast does it have to be? Is contact bounce important?

    Half a dozen of us could have done this 2 hours ago, but too many parameters are missing.