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Thread: Some help with this design?...Please!

  1. #1
    Newbie mrspangle's Avatar
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    Some help with this design?...Please!

    Hi,

    This is what i'm trying to achieve, with no experience of electronics! I have to learn somewhere

    Device 1

    One 12v input.
    One 12v Output - this will be connected to the input of device 2:

    Device 2

    One 12v input.
    One 12v output.

    Hre comes the tricky part.

    When I press a button on device 1, 12v will be presented at the output (to device 2's input). Device 2 would then present 12v @ the output.
    However! If the 12v on device 1 is cut/lost/ whatever I still want device 2's output to be active. Only by pressing a button on device 2 can the 12v be shorted.

    As I mentioned I have no experience on electronics, and want to learn badly (I have many plans).

    Any guidence would be much appeciated!!

    Thanks

    john

  2. #2
    Super Moderator. If my typing sucks it's probably because I'm driving.... turbocad6's Avatar
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    this can be done real easy with a relay... the relay coil gets energized by device 1,(which is only a momentary switch).. the output from the relay(device 2 as you call it) can then also be connected to the coil of the relay itself with a diode, this will keep it energized as long as there is 12v present... the reason for the diode is so that no load is seen by the switch for the few milliseconds it takes for the relay to energize

    the way to turn it off is either remove the 12v, or interupt it with another momentary switch that is nc...

    if you need a diagram I can draw one up...

    this is a simple crude but effective way to do what your saying...

  3. #3
    Newbie mrspangle's Avatar
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    turbocad6 -

    Thanks for your prompt reply!

    Okay I sort of get what you mean, but probably would understand better if you could draw a quick diagram

    thanks

    John

  4. #4
    Super Moderator. If my typing sucks it's probably because I'm driving.... turbocad6's Avatar
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    sure, sorry for just scribbling, but you should get the point...

    the diode backfeeds the relay coil & holds it till power is interupted on the input...

    simple & effective.... I used to do magnet cut-off switches this way, pass a magnet over a sensor to activate... stays powered through the whole ign cycle, but when powered down reverts to cut-off again until magnet is swiped again...

    I've done a bunch of these
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