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time activated relay.

Discussion in 'The Projects Forum' started by agapis, Feb 4, 2009.

  1. agapis

    Thread Starter New Member

    Feb 2, 2009
    1
    0
    hi:

    i have to design a undercarriage for a model hand launched glider for a competition.

    the undercarriage must deploy AFTER 2 seconds, and the glider must remain airborn for at least 5.

    heres the problem: it CANT use radio control.

    so obviously a timer is the way to go.

    i have the mechanical system designed, it just needs a timed actuator to pull the pin. once the pin is released the (torsion) spring loaded frame will deploy.

    so i need a timed servo/rotary dc motor to activate after 2 seconds.

    HOW CAN I DO THIS?

    i have one real life 555 circuit built, and a simulated one in MULTISIM, but the output off the relay is showing decay on oscilloscope. it should be showing a square wave of a specified pulse witdth. it ISNT.

    does anyone know ANYTHING about this kind of thing who can help me? i have spent many hours on google, and all the circuits seem to fail when simulated.

    what i need a is a 5v-12v DC "monostable one-shot" circuit, that starts timing after i press a button, and either keeps the relay open for short/long enough to move my motor OR sends a correctly modified pulse (1.5ms) to my servo.

    any ideas?
     
  2. Wendy

    Moderator

    Mar 24, 2008
    21,838
    3,047
    A simple 555 monostable will do the timing, but you need to figure out the mechanics from an electrical signal, also how you want to start the timing circuit.
     
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