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12 v relay

Discussion in 'Electronic Basics' started by redls1bird, Oct 6, 2005.

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  1. redls1bird

    redls1bird Guest

    is there a widely available 12 v time delay relay? what i need is
    relay that will run between 30 seconds to 1 min, (or anywhere i
    between) to run a low amperage circuit (a few leds). anyone got an
  2. I remember old dokatimers did this things although they switched mains
    powered bulbs. Never heard about others ever since. Think you can easily
    build one yourself using a 555 timer.

    petrus bitbyter
  3. ehsjr

    ehsjr Guest

    Here's a simple circuit:

    +12 ---+----------------------+-----+
    | | |k
    +--o o--+ [RLY] [D1] 1N400x
    S1\ | | |
    [10R] +-----+
    | |
    | /c
    +--------+---[3.3K]---| Tip120
    | | + \e
    [POT]20K [C1]4700uF |
    | | |
    Gnd ---+--------+-------------+

    The pot can be used to set the time delay. When you close S1,
    the relay will energize. When you open S1, the relay will
    remain energized until the capacitor discharges to approximately
    20% of Vcc (about 2.4 volts in the circuit shown). With the
    values shown, the delay time range should be from 0 to over
    1 minute. The exact range will depend on the transistor gain
    and the relay coil resistance.

  4. redls1bird

    redls1bird Guest

    thanks guys
  5. John Fields

    John Fields Guest

    On Thu, 06 Oct 2005 03:35:24 -0500,
    Do you want the relay to:

    1. Turn on some LEDs immediately after you turn the switch
    on and then drop out even if the switch is still on?

    2. Wait for a while after the switch is turned on before it (the
    relay) turns the LEDs on and then turns the LEDs off as soon as
    the switch is turned off?

    3. Something else.?

    If you'd tell us exactly what you want we'd be in a much better
    position to give you what you need.
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