One touch

Discussion in 'The Projects Forum' started by skynet_2010, Mar 18, 2011.

  1. skynet_2010

    Thread Starter New Member

    Mar 18, 2011
    2
    0
    Hi dear members, Im new to this and i can use your help, i know very little about designing a circuit. I am looking for a simple circuit diagram for some gadgets to put in my car (12v) which would give a constant output of 12V (or the same input that powers the circuit) by pressing a button (contacting 2 wires for a second) then i need to cut off the output of 12V by pressing the same button (contacting the same 2 wires) just like you pressing the A/C button on newer vehicles where u simply press the button once and the A/C is activated and u press the same button to deactivate A/C. my car has a old system switch which u press the button it goes in and lock to keep the contact of the 2 wires and u press it again release the lock and the button comes out. i need to upgrade this to one touch. Please any one can draw a simple diagram with all the components? i would greatly appreciate this.
     
  2. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    This is one I collected in my archive and kept for years. Not built or tested myself but I'm quite sure it will work.

    Note: You would need a 6V DPDT relay instead of a 12V one. I have also added the voltage rating of the capacitors.

    In case your 6V relay is not 28Ω, then yoy can use the formula in the drawing to calculate the new values.

    [​IMG]
     
    Last edited: Mar 18, 2011
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  3. skynet_2010

    Thread Starter New Member

    Mar 18, 2011
    2
    0
    hi, thank you so much for your reply, forgive me for troubling you, im abit confused. according to the diagram, it seems that the relay occupies 3 wires, shouldn't that be just 2 to power the relay and another 2 wires from the relay for the gadget to power on as the contacted 2 wires? as i said forgive me, it looks abit confusing, if you would be so kind to give me a small explanation
     
  4. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    You would need a 2PDT relay for this to work.

    One pole is used to implement the internal On/Off function, leaving you the spare pole to do the actual switching on/Off of the supply to the gadget.

    I have again updated the drawing to indicate this.
     
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  5. Wendy

    Moderator

    Mar 24, 2008
    20,765
    2,536
    Depending on how adventitious you are this takes fewer parts and would also be smaller...

    [​IMG]

    555 Bistable Multivibrator

    Modify the design like so...

    [​IMG]

    and you're good to go.

    Parts List
    555 I.C.
    R1,R2 10KΩ ¼W resistor
    R3 100KΩ ¼W resistor
    R4 1KΩ ¼W resistor
    Q1 2N2222A or equivalent
    CR1 1N4001 or equivalent
    Toggle Momentary contact switch
    C1 1µF capacitor
    C2 100µF 35VDC electrolytic cap
    C3 0.1µF capacitor
     
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  6. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,681
    900
    Wouldn't a latching, push button switch do the same? Here is part of a Digikey search, check out CKN9392 and CKN9395 (http://dkc3.digikey.com/PDF/US2011/P2310.pdf ). You could also just get an OEM switch from a newer car...not necessarily from the dealer, but from a junk yard -- auto recycling center.

    John
     
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