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Basic Magnetic Door Lock System

Tom has 17 years experience as a commercial locksmith and over 20 years in door hardware distribution.

Electromagnetic Locks

Electromagnetic locks are widely used in commercial and industrial applications. The lock is usually mounted on the header above the door and the armature is usually mounted on the door (see drawing below). Different arrangements can be made for inswing or outswing doors, and different holding forces, monitoring switches, and other variations and options are available. In this article I will discuss only the basics.

As with any locking system, use of electromagnetic locks may be restricted by local authorities such as your local building inspector and/or fire marshall. It is wise to check with these authorities before installing an electromagnetic lock.

basic-magnetic-lock-system

System Overview

To install the most basic electromagnetic locking system on an out-swinging hollow metal commercial door and frame you need the following:

  1. The electromagnetic lock
  2. A way in
  3. A way out
  4. A power supply

The electromagnetic lock is an appliance. It unlocks when you shut off the power. Therefore the means of entry and egress will be swtiches of some form or other.

Means of entry could be:

  • A key switch
  • An access control device like a card reader or keypad
  • A remote as for a garage door opener

Your choices for means of egress are limited by national, state and local life safety code. They could be:

  • A mechanical push bar with a mechanical switch inside
  • A pushbutton with pneumatic time delay clearly marked "Push to Exit" right next to the door
  • An exit sensor with redundant pushbutton

Your local Authority Having Jurisdiction (AHJ) may require that your power supply be connected to the building fire alarm so that in the event of an alarm, the panel can unlock the electromagnet. In any case you need a power supply with sufficient capacity to power your electromagnet.

System Examples

A simple electromagnetic locking system using products by Schlage Electronics might include:

  • 1 each M490 electromagnetic lock
  • 1 each PS902 power supply
  • 1 each 653-05 key switch
  • 1 each 621RD EX DA exit pushbutton

A simple electromagnetic locking system by Securitron might consist of:

  • 1 each M62 electromagnetic lock
  • 1 each BPS-24-1 power supply
  • 1 each DK-26SS keypad
  • 1 each XMS exit sensor
  • 1 each EEB2 redundant exit pushbutton

Simple Wiring Diagram

Basic mag wiring diagram

Basic mag wiring diagram

Wiring the Electromagnetic Locking System

In the simple diagram above, you can see that the electricity travels in an unbroken loop. It starts at the "+" (positive) terminal of the power supply, travels through the exit and entry switches, into the positive terminal of the magnetic lock, and out through the negative (-) terminal of the mag back in through the negative terminal of the power supply. Because the loop in unbroken, we know the magnet is locked. If the loop is broken anywhere along the line, the magnet will be unlocked. When either of the switches is activated it breaks the loop and deprives the magnet of power, leaving it unlocked.

NOTE: ALWAYS turn the magnet on and off via the positive terminal. Using the negative terminal could cause residual magnetism, a situation where the magnet does not immediately release when powered down.

The exit switch could be a palm button, touch bar or motion sensor. The entry switch could be a key switch, keypad or other access control device. You could also use a wireless receiver and transmitter to control break or make the loop.

Using a wireless transmitter and receiver to release an electromagnetic lock.

Using a wireless transmitter and receiver to release an electromagnetic lock.

Controlling an Electromagnetic Lock Wirelessly

In the above illustration I have substituted a wireless receiver and transmitter for the exit and entry switches in the previous drawing. Following the loop that powers the lock, electricity travels from the positive terminal of the power supply to the Common (C) terminal on the wireless receiver, then out of the receiver through the Normally Closed (NC) terminal to the positive terminal of the magnet. ("Normally Closed" means that the switch is in the closed position unless it is told to open by the wireless transmitter.) The electricity completes its loop by exiting the magnet by the negative terminal (-) and making its way back to the power supply.

Notice that an additional pair of wires is needed to power the wireless receiver.

When the wireless transmitter is activated the state of the relay on the wireless receiver is changed - that is, the normally closed terminal is changed to open.

NOTE: ALWAYS turn the magnet on and off via the positive terminal. Using the negative terminal could cause residual magnetism, a situation where the magnet does not immediately release when powered down.

Comments

Mark Chen from Queens New York on December 05, 2015:

Great information

Tom rubenoff (author) from United States on October 28, 2013:

Yes, if one uses a magnetic shear lock that is installed concealed in the door and header with a power supply that has a fire alarm interface that is connected to the fire alarm. Web search GF3000 to see an example of the shear lock and ALT175ULX for a power supply with fire alarm interface.

Of course, before you begin, the door must already swing both ways. One consideration is that the door must work very well so that the mag lock lines up consistently.

nn on October 27, 2013:

Is it possible to arrange it so the door opens both ways in case of a fire?

Tom rubenoff (author) from United States on August 26, 2013:

Thanks for the vote up, Toptenluxury!

Adrian Cloute from Cedartown, GA on August 26, 2013:

I think that I'm going to get one of these. There is nothing like feeling protected. Voted up!

Tom rubenoff (author) from United States on May 30, 2013:

A biometric lock is simply a switch that opens and closes a circuit. Think of it as an actuator for the automatic door. Usually the automatic door will have inputs for actuators and sensors, or a separate relay may coordinate these components. Here is a link to BEA's download page where you will find many wiring diagrams. Thinking of the biometric lock as an actuator, you should be able to use one of these diagrams.

http://www.beainc.com/beainc/Downloads/Download.ph...

redgarlic73 on May 29, 2013:

i would like to request to your company a wiring diagram from automatic door going to biometric lock with sensor.thanks

Tom rubenoff (author) from United States on November 17, 2012:

Well, you know, they are not hard to find:

http://www.sdcsecurity.com/system-library.htm

vic on November 12, 2012:

I would like to see a diagram of wiring for a single magnetic door lock system with connections to power supply, on-off switch,exit button and magnet at door.

Tom rubenoff (author) from United States on May 02, 2012:

The diagram would depend on what reader and system you are using. You mention a data connection, so I suggest you start at the HID web site located here:

http://www.hidglobal.com/technology.php?tech_cat=1...

ronald@natalia@db.com on May 02, 2012:

Hi,

do you have a diagram which shows the reader on both sides of the door and data connection and how it looks like so I and our supplier can understand each other?

Mohan on October 12, 2010:

Good info! Thanks.

himachal from himachal on September 22, 2008:

very informative hub

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