Press and hold switch to power a relay.

Discussion in 'The Projects Forum' started by SelfSilent, Apr 28, 2010.

  1. SelfSilent

    Thread Starter Member

    Jan 23, 2005
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    0
    Hi guys,
    I'm the first to admit that anything except a few resistors and leds and I'm stuck. So instead of wasting my time desperately attempting to luckily cobble together something that will work I decided the best option by far was to trade.

    You have the knowledge, I have money. So if you want to make a quick £10 (or whatever the conversion is to your money) and have a PayPal account, here's your chance.

    In my car (12v, negative earth) I have a boot opening switch (momentary) that opens the boot by triggering a solenoid. All well and good but they situated it right next to the power windows. The number of times I have just brushed it whilst opening the window is getting beyond a joke and quite embarrassing at traffic lights.

    What I would like to do is to have to hold the switch down for 2 or 3 seconds before it passes the voltage to the existing relay that feeds the boot solenoid. If the switch is pressed and released then the timer is reset (obviously don't want accidental presses building up).

    The existing switch has power in to power an LED, an earth, the switch and an output that goes off to a relay.

    I did look for delay circuits but they seem to delay the amount of time the power is on. As easy as possible would be great as no doubt it'll get thrown together on a vero board using bits from Maplin.

    Thanks.
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Hmmm. This is going to be easy, not that I need the money though.
    By the time I rig up a circuit, I think Sgt will beat me to it, still I will work on it and when it is time to post, if any one has answered then it's OK.
     
  3. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Is the switch SPST or SPDT?
    By the way, if you want to make an add on, then you better give ur connection details, that way it will be much easier to design.
     
    Last edited: Apr 28, 2010
  4. retched

    AAC Fanatic!

    Dec 5, 2009
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    A delay-on-make circuit is what you want. When you press the button to complete the circuit, the delay starts, after the 3 seconds or so, the signal passes to the solenoid.
     
  5. kingdano

    Member

    Apr 14, 2010
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  6. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    yeah !!! that would make a whole lot easier
     
  7. VoodooMojo

    Active Member

    Nov 28, 2009
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  8. retched

    AAC Fanatic!

    Dec 5, 2009
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    Wow, I am a repeating Petey. I dont even remember that thread. Jeesh.

    Time to make a doctors appointment.

    VoodooMojo, know a good Alzheimer Doctor in B-more?
     
  9. VoodooMojo

    Active Member

    Nov 28, 2009
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    yeah but I forgot where.*


    [​IMG]
    [​IMG]



    *predictable response
     
  10. t06afre

    AAC Fanatic!

    May 11, 2009
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    I would have used a small PIC MCU for this. But I leave the scene to the 555 gurus ;)
     
  11. SelfSilent

    Thread Starter Member

    Jan 23, 2005
    18
    0
    Thanks for all the replies,

    The switch I have is a single push to make switch. It has a 12v in, earth out and the switched out. Inside the PCB it has a resistor and an LED and the push to make switch. (see attachment).

    I like the look of the one on this page, seems simple enough.
    http://www.electronics-project-design.com/timedelaycircuit.html

    [​IMG]

    I assume it would be as easy as connecting the 12v in to the Vin on the circuit, the earth to the earth and the connection after the switch to the input (just before resistor R1). Then connect the wire that was attached to the switch to the output wire of the circuit.

    2 questions. On that diagram, the discharge pin (7) goes nowhere, is that right or should it be attached to something?
    And... t=0.69RC, errr, uh huh.
    Can anyone tell me the ratings for the 2 resistors and the capacitor for a delay of anything between 2 and 3 seconds.

    Electronics just isn't my thing and think it's best I stick with being an engineer and a mechanic. Cheers all.
     
  12. SelfSilent

    Thread Starter Member

    Jan 23, 2005
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    0
    OK, eventually found a site that told me the units for the t=0.69RC formula.
    T is in microseconds
    R is in Ohms
    C is in microfarads

    I'm looking for between 2 and 3 million microseconds so using formula reversal I should be able to suss something out.
     
  13. chaka

    New Member

    Jan 14, 2011
    1
    0

    Hi SelfSilent.

    Did you resolve your problem? how?
     
  14. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
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    A low-tech solution is to put a mechanical guard over the switch so it's less likely to be pressed accidentally. As an example, we have a button on our RV refrigerator that's easy to bump and turn it off. I just glued an annulus of some plastic pipe around it so you have to put your finger down inside to access the switch.
     
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