timed circuits

Discussion in 'The Projects Forum' started by mrbob, May 31, 2007.

  1. mrbob

    Thread Starter New Member

    May 31, 2007
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    Hey

    Iam new to the fourm and electronics in general so bare with me if i dont pick up quickly or understand anything.

    With that said I am looking for laymens help with an idea I had:

    I have a electronic/hydraulic hood system on my car, To put the hood down you open the front push and hold a button in for 20 or so seconds till the hoods in its bin and tucked away same for it to come up hold it in for 20 or so seconds and then clip it in when its done.

    I was thinking the other night if it would be possible to make a timed relay circuit that would open apon me pushing the button and it stay open (even if the down/up button is pushed) for 25 seconds (extra few seconds for insurance) and then close, making it a 1 touch push button operation rather than having to hold the button till the hood is down.

    I dont have much electronic knowledge so if you have the answer/circuit diagram could you explain as simply as possable please all help will be greatly appreciated. :)
     
  2. mozikluv

    AAC Fanatic!

    Jan 22, 2004
    1,437
    1
    they way i understand your description you power up the system by pushing the on button for 20 seconds until it has fully done its mechanical function.

    now you want to extend the time element of opening/closing with just a push of a button (without pushing the button continually for 20 seconds)

    with that in mind a 555 timer configured as an astable and a relay to do the continous power feed to the system for about 25 secs. with this set up you can use the normally open push button of the present system to trigger the 555 timer and use the relay to sub the push button function.

    i can't draw up the schem for the moment.

    moz
     
  3. mrbob

    Thread Starter New Member

    May 31, 2007
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    Yes thats exactly what Iam looking for however it may be worth noting the button that needs pushed is a push button (only you need to hold it) but it has 2 points one for up one for down.

    Does this mean I will need 2 circuts\relays for the 2 functions or is it possible it can be done in 1, Iam not to botherd if it needs 2 its just good to know
     
  4. mozikluv

    AAC Fanatic!

    Jan 22, 2004
    1,437
    1
    you can use the 556 timer. its a dual. you can still use your push button having a dual function. also you have to use a transistor to make sure that the relay will be turned on. the 555 timer is capable of sinking/source current to a max of 200ma which is more than enough to turn on a 12v relay with a coil resistance of 80 ohms.

    moz
     
  5. mrbob

    Thread Starter New Member

    May 31, 2007
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    good news all i need now is part list and diagram as i said before i don't know much about electronics
    thanks again
    bob :)
     
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