knocking system

Discussion in 'Embedded Systems and Microcontrollers' started by lihle, Jul 19, 2010.

  1. lihle

    Thread Starter Active Member

    Apr 12, 2009
    83
    3
    guys

    i need your advice here. i want to incoparate my security system with a knocking sysytem and i would like to know if what i am thinking is possible. i want to include a knocking system and i have thought of using a electrect microphone element as a speaker to listen to a special sequence on knocking. the thing is you knock lets say 3 times then the microcontroller would have to count if its three then the system has to unlock a deadbolt and if not light a red indicator.

    lihle
     
  2. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    It could work, if the mic was placed on the surface the knock has to be detected from...

    You can try a simple MIC pre amp circuit to see if that would be sensitive enough for a UC to detect...

    [​IMG]


    Or

    You could try a piezo element, you can usually get those out of toys and even greeting cards (The little copper disc shaped speaker)...

    [​IMG]

    [​IMG]

    B. Morse
     
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,769
    969
    You need to use a "secret" knock pattern though... Not just 3 knocks.. I do that all the time..
     
  4. Vaughanabe13

    Active Member

    May 4, 2009
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    5
  5. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    I am missing something here. If it is for you, just use a key. If it is for other people you know, then it won't be a secret.

    Consider also that while many attacks are random (i.e., attacks of opportunity), there is strong evidence a lot of home invasions are planned, and the victim has been watched. Someone watching your house would see individuals come and use the "secret" knock. I suggest incorporating a simplified "rolling code." A formula based on the date or hour (etc.) might be hard for the average criminal to decipher and give some added protection.

    John
     
  6. BMorse

    Senior Member

    Sep 26, 2009
    2,675
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    This can't be any worse than those blue tooth enabled door locks... or the ones where you can access them over the Internet like these >> http://www.cepro.com/article/schlage_plans_z_wave_web_enabled_door_locks/

    and actually, the normal deadbolts and locks didn't stop people from coming into your house anyways, so if it saves you money from having to replace a window or a door after they broke in, why not?:D


    B. Morse
     
  7. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Actually, I was trying to be helpful. A system based on the date could be known by friends, but not easily deciphered by a bad guy. The OP had another thread on a similar subject and wants to use a microcontroller in her project. An MCU could easily calculate the day's code. "Knock Three Times" (Tony Orlando and Dawn) is not a good system.

    As for dead bolts, I will keep them in place. If the door gets broken, it is easier to justify the use of a few 380 rounds.

    John
     
  8. lihle

    Thread Starter Active Member

    Apr 12, 2009
    83
    3
    John

    i am trying to desire the project for my personal use only.i agree that i have to try and come up with a way of making it not the usually knocking pattern that we normally use at home.

    lihle
     
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