Sending an impulse with pauses

Discussion in 'General Electronics Chat' started by orwikcons, May 7, 2008.

  1. orwikcons

    Thread Starter Member

    May 2, 2008

    Depending on impendance that comes in the circuit (R1<R2<R3<R4), on B will go short impulses +12V (0.25 - 1 seconds) in a periods of 3 seconds, responding to R1, up to 14 seconds, responding to R4.

    I am trying to improvise the windwasher work, where I can define the pause lenght, by these four values. So the pauses should be proportional to impendances. Lenght of impulse don't need to be precise value, but to be under one wiper period (cycle), so it can be proportional to resistors too.
  2. Papabravo


    Feb 24, 2006
    Is there a question in there?
  3. SgtWookie


    Jul 17, 2007
    Sounds like you want to vary the time between wipes of a windshield wiper.

    In order for this to work properly, you'll first need a way to detect when the wiper is at the end of it's travel.
  4. Wendy


    Mar 24, 2008
    The classic way to do this is a variable timer, where the wiper goes the same speed but pauses between wipes in variable increments. Is this what you're trying to do?
  5. orwikcons

    Thread Starter Member

    May 2, 2008
    Sorry, my English is not so good, so I couldn't explain what I had wanted.

    The factory circuit gives an impulse to the wiper-motor, every 6 seconds. That impulse is enough to move wipers from the start, then automatic circuit in the motor drives wipers to the end of there way, and back them to start (because the length of impulse is not so important, it only has to move wipers from the start, but masn't be longer than one cycle, because then two cycles would happen). So, I want to make the circuit which will give such impulses, but pause between wipes will be defined with those four impendances (the switch is from other car). For example the circuit which will give an impulse, and then wait a few seconds, and depending on selected resistor, the lenghts of pause and impulse will be multiplied with proportional coefficient.
    Last edited: May 7, 2008
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    Many years ago, I put together a kit that allowed a variable time between strokes of the wiper blades. The active part was a unijunction transistor that pulled in a relay briefly when it went into conduction. The control was a pot configured as a variable resistor that controlled the rate of charge onto a capacitor.

    If you look up "unijunction relaxation oscillator", you can find how the control worked.