time delay circuit

Discussion in 'Homework Help' started by aq_rules, Oct 28, 2009.

  1. aq_rules

    Thread Starter Member

    Oct 28, 2009
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    hello guyz i am new to electronic field i want to make sum time delay circuits...
    At first i want to know that the ground symbols in the schematic are connected to sum kinda electric source or what...
    i guess it is connected to the negative (-ve) wire of 12dc v adapter
    ryt??
    if no plzz help
    and tell me that all ground symbols are to br connected to this wire or any other source...
     
  2. aq_rules

    Thread Starter Member

    Oct 28, 2009
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    Plz help me with a time relay time out circuit...
    basically the idea is a 12Dc v(connected to a Battery) circuit operating the 12 dc v alarm
    whenever the MAIN line disconnects (maybe converted to 12 dc v) from the circuit the relay is activated for 5 to 10 seconds (changeable with Variable resistor) and then goes off again...
    The alarm will alert me for 5 to 10 seconds to switch on my generator...
    i hope you guys understood what i want...


    thanks in advance
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
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  4. SgtWookie

    Expert

    Jul 17, 2007
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    aq_rules,
    Two things you should understand about the AAC Forums is:
    1) The Forums are not interactive. It may take many hours for you to receive a reply.
    2) It is considered "bad manners" to post a new request for help in a thread that someone else started. This can cause a great deal of confusion, and makes it harder for everyone, particularly the AAC Moderators. If you have a new request for help, please start a new thread using the "New Thread" button at the top of every page. If you don't know where to start a thread, the General Electronics Discussion area is a good place; if necessary a Moderator will move it to the most appropriate forum.

    It takes time to develop an idea to help you with your particular situation. Posting new requests every 5 to 10 minutes only makes a reply take longer.
     
  5. aq_rules

    Thread Starter Member

    Oct 28, 2009
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    ohhh m really sorry guyz....i signed up today on this forum...m sorry...
     
  6. aq_rules

    Thread Starter Member

    Oct 28, 2009
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    but plz help...its urgent...
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    In a given schematic, all ground symbols are considered to be connected together, and all at a potential of zero volts. All voltage measurements in the circuit are using ground as a reference by default, unless an alternate reference point is specified.

    For instance, If a circuit is designed to be operated from a 12v battery, it is most common to see references of +12v and GND; any GND references are connected to the negative terminal of the battery.
     
  8. SgtWookie

    Expert

    Jul 17, 2007
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    Why is this so urgent? Is this for a homework assignment that you need to complete very soon?
     
  9. SgtWookie

    Expert

    Jul 17, 2007
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    The first part is pretty easy. A 12v power supply could be plugged into an outlet that keeps a relays' coil energized, that has normally closed contacts. As long as the relay coil is energized, the contacts stay open.

    If the power goes off, the contacts will close, supplying power to the timer that controls the alarm buzzer/timer.

    Do you want the alarm to sound right when the power goes off, or wait for a while? How long to wait?

    How long do you want the alarm to sound, and how long do you want it to be quiet before it sounds again?
     
  10. aq_rules

    Thread Starter Member

    Oct 28, 2009
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    Yes :(
    and today i am going to the market to buy all the stuff needed for this circuit...do u have any related schematic??
     
  11. SgtWookie

    Expert

    Jul 17, 2007
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    How long have you had this homework assignment?

    No, I don't have a schematic tailor made to your specifications.

    However, I've already given you the 1st part of it.

    The rest of it you could do using a 555 timer and appropriate timing components.

    Download a datasheet for an LM555 timer from National Semiconductor, http://www.national.com and look at the astable multivibrator configuration.
     
  12. aq_rules

    Thread Starter Member

    Oct 28, 2009
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    Yea...i want the alarm to sound right when the power goes off and it shall sound for 5 or 10 second...
    it should not sound again

    it shall sound again next time when the power goes off...
     
    Last edited: Oct 29, 2009
  13. aq_rules

    Thread Starter Member

    Oct 28, 2009
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    thanks for your support...i would love to be a friend of yours...
     
  14. aq_rules

    Thread Starter Member

    Oct 28, 2009
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    i have hardly 2 days to complete this assignment:(:(
     
  15. SgtWookie

    Expert

    Jul 17, 2007
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    You don't even need a timer then.
    Fuse & fuse holder.
    Low-voltage transformer.
    Full wave bridge.
    Capacitor.
    Relay that will operate from the low-voltage transformer and that has either SPST NC contacts or SPDT contacts.
    A buzzer that will run from DC that is about 1.4 times higher than the AC output of the transformer.
     
    Last edited: Oct 28, 2009
  16. SgtWookie

    Expert

    Jul 17, 2007
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    Don't you have any ideas on how to do something like this?
     
  17. aq_rules

    Thread Starter Member

    Oct 28, 2009
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    can u draw me a schematic for this...'cuz i dint got wat u r trying to say...
    will it sound for 5 or 10 seconds...??
    it is necessary for the alarm to sound for only 5 or 10 secs and i have to fit an external alarm....
     
  18. aq_rules

    Thread Starter Member

    Oct 28, 2009
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    I wasted 3 days thinking and searching about this kinda circuit....lmao
     
  19. aq_rules

    Thread Starter Member

    Oct 28, 2009
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    huh!! okay i shall not ask for id's again:D
     
    Last edited: Oct 28, 2009
  20. SgtWookie

    Expert

    Jul 17, 2007
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    Post the diagram that you've come up with so far.
     
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