Basic Electronics Help

Discussion in 'General Electronics Chat' started by dhogan, Oct 27, 2008.

  1. dhogan

    Thread Starter New Member

    Oct 27, 2008
    2
    0
    Hello, I was hoping you all could help me out.

    I'm looking for some basic electronics help. Let me describe the application first.

    So we have a door with a magnetic strike that is connected to our phone system. We can open the door by typing a code on the phone, the only problem is the strike is silent when it opens, so people don't know when to pull on the door. I would like to place a buzzer inbetween the switching mechanism and the strike that sounds when the door opens. But since the strike is open for say 5 seconds and I don't want the buzzer sounding for 5 seconds I run into a problem.

    So what do I need to do to add a buzzer that will only give a short buzz? The circuit the strike is on is 12 volts.

    Help is greatly appreciated!
     
  2. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
    230
    Don't know how much you want to built...from a schematic...kit...or off the shelf? Basically you are looking for a monostable circuit...and there a lot of them out there. LM555 integrated circuit versions are very common if you want to start from scratch. Velleman MK111 is a nice ~$5 kit version of the LM555 timer. SSAC makes commercial modules that will do On-Interval timing modules...~$30. This can also be done with a 12v SPST relay, a resistor and an electrolytic capacitor....and a 12v buzzer.

    Ken
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    An old-fashioned "ding dong" type doorbell might work for this purpose.
    http://home.howstuffworks.com/doorbell3.htm
    Just connect in parallel with the striker.

    However, for security reasons, you would want it mounted on the inside. Otherwise, a clever crook could energize your striker by using a portable power source (such as a battery) and gain entrance.
     
  4. dhogan

    Thread Starter New Member

    Oct 27, 2008
    2
    0
    Ken, thanks for the help. I'm looking for something idiot proof. :D It's been a while since I've done electronics, I honestly do not remember much, if anything. I was hoping for someone to say buy a and b and add to the circuit, but sounds like it may not be that simple. Help is appreciated.


    I'll take a look, thanks.
     
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