Making a very basic pulse delay.

Discussion in 'General Electronics Chat' started by Hybz, Jul 16, 2010.

  1. Hybz

    Thread Starter New Member

    Jul 16, 2010
    3
    0
    Hi everyone.
    New to these forums, and read T&C + Rules, so hopefully I've put this thread in the right place.

    Just needed some assistance with making a very basic delay circuit.

    I have looked at a few basic 555/Schmitt trigger circuits but can't seem to find one for this exact application.

    I basically have a 12 volt supply which is going from low to high state (0v to 12v). I need to create a very basic circuit which delays this action by a short amount of time (between 0.5 and 2 seconds, although implementation of a variable resistor so that adjustments could be made would be ideal.

    Simply put, I need a small circuit which has an input of 0V, which then becomes 12V, and I need the output to be identical, however moving from 0V to 12V is slightly delayed.

    I thank you in advance for taking the time to read this :)
     
  2. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    Do you want to do a "soft start" type of application?

    Or, simply: When this line gets 12v, wait (x) amount of time, put 12v on this other line.

    A simple 555 circuit operating a relay, or even a FET or BJT, depending on the current you will need.

    A 555 monostable circuit that is operating off of the 12v line you are watching, so when the power is applied, the 555 starts counting the amount of time you have it set for; which is adjustable with a potentiometer. When the timer runs out, a relay is activated that connects the same 12v line to the output.
     
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  3. newbies_hobbyist

    Member

    Jun 4, 2010
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    It sounds like you are looking for the soft start. Maybe you can try integrator, just pick the right value of Cf (feedback cap). depending on your delay requirement.
     
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  4. Hybz

    Thread Starter New Member

    Jul 16, 2010
    3
    0
    I don't need a soft-start, just a delay which has the same slew-rate (or lack thereof) as the initial low-to-high process.

    To be honest, I'm not sure what the current will be.

    To put it into context it's for a friend's car's ignition system. We are trying to implement a remote-start system, but the current installation applies 12 volts to the "on" wire and "start" simultaneously. For some reason the car doesn't start when this is done, but when we manually delayed the connection of one wire to the 12v supply, it worked, so I just need something which will do this.
     
  5. gerty

    AAC Fanatic!

    Aug 30, 2007
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    NacIK and Hybz like this.
  6. Hybz

    Thread Starter New Member

    Jul 16, 2010
    3
    0
    Perfect, Gerty.

    Thanks a lot guys, I think this should do the trick! :)
     
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