What is Magnetic Switch : Working & Its Applications

The magnetic switch is an electromechanical switch that operates through an applied magnetic field. This switch was invented at Leningrad Electrotechnical University by Professor Valentin Kovalenkov in 1922 & later developed by Walter B in 1936 at Bell Telephone Laboratories. This switch includes two parts; the magnet & a magnetically sensitive switch. These types of switches may be either NO (normally open) or NC (normally closed). These switches are mainly used for detecting the opening of windows & doors. So, this article discusses an overview of a Magnetic Switch – working with applications.


What is a Magnetic Switch?

An electrical switch that is used to make or break contact within a magnetic field is known as a magnetic switch. Usually, the magnetic switch function is to stay activated if a strong magnetic field is there sufficiently & deactivated once the magnetic field is removed. Magnet switch is used where moving elements is not possible or not desirable to make direct contact through the switch like in unstable environments, submerged within liquids, etc. The magnetic switch symbol is shown below.

Switch Symbol
Magnetic Switch Symbol

These switches are enclosed in glass material for maintaining the integrity of the magnetic field & components. So this material also protects the switch from external conditions. When selecting or designing a switch, it is necessary to consider these parameters like type of application, power requirements, circuitry magnetic sensitivity, and operating environment.

The contact rating of the magnetic switch is the maximum power in watts a contact can switch. The contact rating of this switch is the product of switching voltage & current that will flow throughout the switch.

How Does a Magnetic Switch Work?

A magnetic switch uses a movable magnet and these switches are used in many applications, from electric car charging stations to automated street lights. But how do they work?

The basic principle of a magnetic switch is that an electromagnet (coil of wire) is energized by electricity and then de-energized. When the current is flowing through the coil, it creates a magnetic field which attracts other magnets in its vicinity. When the coil is de-energized and no longer has current running through it, the magnetic field collapses and releases all of its energy at once — something like releasing a rubber band after holding it stretched for some time.

In practical terms, this means that when you turn off an electric device like a lamp or appliance, there’s still some current flowing through the wires inside it for just enough time for them to release their stored energy before everything stops completely. This gives off enough heat (and sometimes sparks) to cause problems with delicate electronics such as computers and TVs if not properly protected by fuses or circuit breakers.

These switches are not affected by water, oil, ice, dirt, etc. So these are flexible electrical switches. The best example of these switches is electromechanical relays, Hall effect sensors, and reed switches.

Types of Magnetic Switches

There are three types of magnetic switches reed switches, hall effect switches, and Triac or Transistor switches.

Reed Switches

Reed switches are very responsive to magnetic fields and customizable. These switches are fairly low-cost as compared to other types of switches. These types of switches are normally used in limit or proximity switch applications like cell phones, doors in household appliances, security alarms, heavy machinery, and doors on vehicles.

Reed Switches
Reed Switches

Reed switches are obtainable in varying magneto motive forces, measured in AT (Ampere-Turns). These switches may vary based on the dimension of the reed, adjacent environmental factors & the applied magnetic field strength.

Hall Effect Switches

The semiconductor devices like Hall Effect switches have no mechanical contact. So they are less prone to break because of the mechanical shock. These switches are normally utilized as limit switches within actuators used in elevator cars, factory automation equipment, vehicles, etc.

Hall Effect Switches
Hall Effect Switches

These switches offer extra options for application configurations because they are available with Unipolar or Omnipolar options. Omnipolar devices can notice either the South or North poles of a magnet, whereas Unipolar devices detect simply one pole. The Hall Effect switches magnetic sensitivity mainly depends on the applied electric current & the kind of magnetic field generated.

Triac or Transistor switches

Transistor or Triac switches are the most complex switches because they include additional circuitry to the switch. Triac switches are mainly designed to use in power control & switching applications within AC voltage systems, whereas Transistor switches are mainly designed for power control & switching applications within DC voltage systems.

Triac or Transistor Switch
Triac or Transistor Switch

These types of switches are strong, so ideal for higher-current switching and more heavy-duty applications. These switches are normally used for controlling motors, relays, or other types of inductive loads. The current-carrying ability of Transistor or Triac switches may be increased by using them in combination with Hall Effect or Reed switches.

Magnetic Switch Circuit

The magnetic switch circuit is shown below which can be built with different electronic components like a magnetic switch, 3V battery, 470 ohms resistor, and a LED. The circuit is connected as per the diagram shown below. This is a two-terminal switch that is activated once a magnet is brought into the surrounding area of the switch.

Magnetic Switch Circuit
Magnetic Switch Circuit

Generally, these switches are available in two types normally opened & normally closed.  Normally open magnet switches are switches that open the electric circuit when there is no magnet in its surrounding area as a result there is no flow in the circuit. Similarly, when the magnet is arranged near the switch then it circuit will be closed; as a result, current flows throughout the circuit which turns ON a load.

In the above circuit, we use a magnetic switch that is connected to an LED to demonstrate how this switch works.

A normally closed magnetic switch is quite opposite because this switch will be closed without a magnet in its surrounding area. So without a magnet near the switch, electricity can be conducted across the magnetic switch & turn on a load. Once a magnet is arranged near the switch, then it opens the circuit then the load will be turned off.

In this example circuit, we use normally an open switch so that the LED will be turned ON simply when a magnet is in its surrounding area.

These switches usually handle over 1Amp of current & 100V. The working of this circuit is, for a NO (normally open) switch, the circuit will be turned off when there is no magnet. When the magnet is arranged near the surrounding area of the circuit, the circuit will turn on & the LED will be turned ON. So this switch is called a magnetically-driven device.

For a normally closed (NC) switch, the electronic circuit will be turned on when there is no magnet, as a result, the LED will be turned ON. When the magnet is arranged near the surrounding area of the circuit, then the circuit will be turned off & the load-like LED will be turned off.

Advantages

The advantages of the magnetic switch include the following.

  • These switches are simple, reliable, and have actuation capabilities.
  • These are integrated into space-constrained environments due to low-profile designs.
  • Less weight & not expensive.
  • These switches are ON/OFF very quickly.
  • Contact resistance is less.
  • Its lifespan is longer.
  • Lower maintenance.
  • More difficult to override.
  • It has high performance.
  • They are simple and have reliable operation.
  • Extra components are not required apart from a magnet for its function.
  • It can switch both AC & DC.
  • This switch can be used by a magnet within open or closed conditions indefinitely without any power utilization.
  • Like an optical switch, this switch’s performance is not affected because of dirt or dust.

Disadvantages

The disadvantages of the magnetic switch include the following.

  • It uses a separate magnet for its function.
  • If the magnet is away above a few millimeters from the switch part, then it doesn’t work properly.
  • The glass envelope of this switch can be damaged easily.
  • Arcing may happen in between contacts.
  • This switch can be accidentally turned ON through other magnetic fields.

Applications

The magnetic switch applications include the following.

  • This switch is used to make or break the contacts in the magnetic field. So this switch is activated as long as there is a magnetic field & the switch is deactivated when the magnetic field is removed.
  • These switches help in detecting the opening of windows & doors.
  • These are used in battery-powered applications
  • This switch is used to measure the magnitude of the magnetic field.
  • It is normally used in tachometers, anti-lock braking systems, etc.
  • These are used in Heavy-duty vehicles like road construction equipment and road maintenance trucks for various systems like fuel level indicators, security switches, power steering, ignition systems, equipment consoles, etc.
  • These switches are used in control consoles & Instrumentation panels for different applications.
  • These types of switches are used in a wide range of ground transportation applications due to their versatility.
  • These are used in Private buses for safety systems, fuel systems & ignition systems, etc.
  • These switches are useful in avoiding wasting energy whenever the refrigeration door opens & closes from running.

Thus, this is an overview of a magnetic switch – working, advantages, disadvantages & its applications. This switch includes contacts that are formed by two movable, thin, and magnetically activated metal vanes otherwise reed arranged in a normally open (NO) position in a sealed glass envelope. Here is a question for you, the magnetic switch is also called?

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