switch/relay circuit that ignores short pulses

Discussion in 'The Projects Forum' started by septimus, Oct 3, 2012.

  1. septimus

    Thread Starter New Member

    Oct 3, 2012
    Complete novice here --

    I need to make a TTL switch/relay DC circuit (no real load) that does the following:

    -Ignores short 'turn on' pulses, or a series of short pulses
    -Time delay on in response to a steady 'turn on' signal (DC on, I guess)
    - Immediate off when the steady signal is removed

    The device involved is a rotating turret. If the turret is clicked into and held at a particular position, a downstream switch should be turned 'ON' with a short delay. If the turret is spun (clicking through several positions), the switch should stay off until the turret reaches a desired position and is held there.

    Voltages involved are TTL 5V or so, but could be higher if needed.

    Any advice will be greatly appreciated
  2. crutschow


    Mar 14, 2008
    You could use a series resistor with a capacitor to ground to delay the operation of the circuit and ignore pulses. To get it to turn off immediately you could add a diode across the resistor (cathode towards signal source) to rapidly discharge the cap.
  3. ScottWang


    Aug 23, 2012
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
    Here's an attempt to put suggestions down on paper. Comparator used for schmitt trigger & comp. Load is still an unknown to me.