Magnetic lock and buzzer with DPDT relay

Discussion in 'Homework Help' started by questteck, Jul 20, 2013.

  1. questteck

    Thread Starter New Member

    Mar 22, 2013

    I'm trying to wire a buzzer to a magnetic lock, the magnetic lock controls a door, and as long as the lock has power the door remains locked. I would like to wire a buzzer that sounds when the door is released and the magnetic lock looses power. I understand a DPDT relay will do it, but do not know how to wire it.

    The purpose of the buzzer is to let people know that the door is released and open and to enter.

    I'm using an ALTRONIX RBSN 12V DPDT...

    Any help would be greatly appreciated.
  2. elec_mech

    Senior Member

    Nov 12, 2008
    Welcome to AAC.

    Is this a homework assignment or something you're doing for yourself?

    A relay will do this, but whether the one you called out will work depends on the voltage of the magnetic lock. What is the voltage feeding the magnetic lock? Also, is it AC or DC?

    As long as the coil voltage of the relay is a match to the voltage powering the lock, you're golden. Once verified, you connect one end of the relay coil to GND and the other to +V feeding the lock. If the buzzer is powered by DC, then the negative lead goes to GND and the positive goes to the normally closed (NC) contact. Power to the buzzer is then connected to the common pin (labeled C or COM). When the coil is energized (magnetic lock on), the NC contact will be open and the buzzer will be off. When the lock is off, the coil is de-energized and power will go from COM to NC turning the buzzer on.

    Do you have a schematic or a link to the magnetic lock used?

    Do you have a schematic or a link to the buzzer used? What is voltage of the buzzer?

    Do you push a switch to deactivate the door lock?

    Also note, as you've described it, the buzzer will sound for as long as the door lock is off. Is this acceptable? If not, you could add a timing circuit so the buzzer only goes off for a second or two, much like you see on TV and in the movies.
    amiya.tripathy likes this.
  3. sheldons

    Well-Known Member

    Oct 26, 2011
    heres a schematic for you to have a play with-the buzzer timer section....
  4. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    So, if I cut the power to the store ... it will be easy to open the door and rob the joint. Nice.

    Get lots of insurance if this isn't a homework problem.
  5. sheldons

    Well-Known Member

    Oct 26, 2011
    let me know when you are up for the job joe and ill carry the bag.....
  6. thestuauduio

    New Member

    Dec 7, 2015
    Hi, I have a similar question.

    I am designing an audio patchbay to trigger a mag-lock. When the patchbay is not patched, the mag-lock has a full circuit and keeps the door locked. When the patchbay is patched correctly, it creates a full circuit, thus breaking the other circuit to the mag-lock, opening the door.

    Would the same relay work?
  7. JohnInTX


    Jun 26, 2012
    Please do not hijack a thread by posting your own question in someone else's thread.
    You already have a thread open here.
    Last edited: Dec 7, 2015
  8. amiya.tripathy

    New Member

    Jul 16, 2016

    I was trying the suggested connection with an EM lock with buzzer, and it works in the same way you have described. Now I have an issue with the delay.

    As the em lock is open, the buzzer goes on. I want a delay of 10-15 seconds. As the lock is connected to a biometric machine of a door and the traffic is high through the door, there is an unwanted noise.

    Can you please suggest, if anything can be programmed or how to introduce the delay.