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Thread: RC Time Delay Circuit

  1. #1
    Suraj143 Newbie
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    Talking RC Time Delay Circuit

    I need a circuit, when it get triggers it will turn the output after a delay.Delay determine by the values of R & C.

    Is this circuit works?
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    Last edited by Suraj143; 11th November 2009 at 02:58 AM.


  2. #2
    MikeMl Excellent MikeMl Excellent MikeMl Excellent MikeMl Excellent MikeMl Excellent MikeMl Excellent MikeMl Excellent
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    Does the trigger stay high longer than the desired delay, or is it a momentary pulse?
    Mike ML.

  3. #3
    Suraj143 Newbie
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    Trigger comes from the door contact unit (dry output)

    When the door open after the delay it will sound the buzzer.

    But if the door open & close suddenly it won't sound the buzzer.
    Last edited by Suraj143; 11th November 2009 at 06:35 AM.

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    MikeMl Excellent MikeMl Excellent MikeMl Excellent MikeMl Excellent MikeMl Excellent MikeMl Excellent MikeMl Excellent
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    Quote Originally Posted by Suraj143 View Post
    Trigger comes from the door contact unit (dry output)

    When the door open after the delay it will sound the buzzer.

    But if the door open & close suddenly it won't sound the buzzer.
    Is the door contact normally-closed (contact opens when door is opened)?
    Mike ML.

  5. #5
    AllVol Good AllVol Good AllVol Good
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    Quote Originally Posted by Suraj143 View Post
    I need a circuit, when it get triggers it will turn the output after a delay.Delay determine by the values of R & C.

    Is this circuit works?
    Here's a litlle circuit that might do the job.

    It uses just about any comparator (LM324, 339, etc.) and any SPST switch that operates with the opening and closing of your door.

    When the door is closed, the closed switch allows the capacitor in the positive input of the comparator to charge and hold. When the door is opened, voltage is cut off from the cap, and it begins to discharge. When the + input voltage falls below that of the - input, the comparator turns on and activates the buzzer.

    The R*C combination can be adjusted to allow a desired delay time.

    If the door is closed before the comparator is activated, voltage is reapplied to the cap and nothing happens.

    The attached schematic is a bare bones idea to go by, if you are interested.
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  6. #6
    Suraj143 Newbie
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    Hi AllVol that's really what I looking out.Perfect.
    Thanks for your idea.

  7. #7
    AllVol Good AllVol Good AllVol Good
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    Quote Originally Posted by Suraj143 View Post
    Hi AllVol that's really what I looking out.Perfect.
    Thanks for your idea.
    Glad I could help. Hope it works out for you.
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  8. #8
    vernon2009 Newbie
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    Default motor power on/off

    Hi,

    Can anyone help me with a circuit diagram for my requirement? My requirement is I need to switch ON a motor (6V -DC) for 2 - 3 seconds every 14 days. The rest of the time the motor is OFF.

    I would highly appreciate if I can get this

  9. #9
    Gayan Soyza Excellent Gayan Soyza Excellent Gayan Soyza Excellent Gayan Soyza Excellent Gayan Soyza Excellent Gayan Soyza Excellent
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    Quote Originally Posted by vernon2009 View Post
    Hi,

    Can anyone help me with a circuit diagram for my requirement? My requirement is I need to switch ON a motor (6V -DC) for 2 - 3 seconds every 14 days. The rest of the time the motor is OFF.

    I would highly appreciate if I can get this
    You need to apply a trigger signal to a monostable circuit on every 2 weeks.2 weeks period is pretty higher.Easiest way is to use a RTC with a micro controller with lots of battery backup.

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