A magnetic switch, also known as a reed switch, is a line switch device controlled using magnetic field signals.
Principle of Magnetic Switch
A magnetic switch has two main components: a permanent magnet and a reed switch. The reed switch, also known as a tongue switch, is constructed from two or more metal reeds sealed in a glass tube filled with inert gas. When the magnetic switch is in different electrical states, the reeds inside the glass tube do not touch each other.
The gap between the reeds is very small. When an external magnetic field is applied, the reeds become magnetized, generating opposite magnetic polarities that attract each other. When the magnetic field strength reaches a certain level, the reeds close and complete the circuit; when the magnetic field is removed, the magnetism of the reeds weakens, and they return to their original state, opening the circuit.
Types of Magnetic Switches
Magnetic switches can be categorized as normally open or normally closed, depending on their design and application needs.
Normally Open Magnetic Switch: In its default state (i.e., without magnetic field influence), the switch contacts are open. When a magnetic field approaches and affects the switch, the contacts close, resulting in a signal output or control of the circuit’s on/off state.
Normally Closed Magnetic Switch: Conversely, in its default state, the switch contacts are closed. When a magnetic field approaches and affects the switch, the contacts open, causing a change in signal output or the circuit’s status.
Characteristics of Magnetic Switches
Advantages
| High Reliability: The glass tube of the reed switch is usually filled with inert gas, which protects the reeds from moisture or oxidation, ensuring long-life performance and high stability.
| Fast Response Speed: Due to the small mass of the reeds, they generally respond 5 to 10 times faster than relays. Their non-contact working principle makes them especially suitable for non-contact circuit control.
|Miniaturized Design: Small size makes them suitable for tight spaces.
Disadvantages
Although compact and lightweight magnetic switches have a small switching capacity; they can only be directly packaged for small-capacity circuits. Larger capacities require the use of amplification circuits or small relays to enhance them.
Selecting a Magnetic Switch
| Based on Space: Choose the appropriate switch size and installation method according to the installation space and requirements.
| Based on Switch Type: Select between electronic or reed-type magnetic switches based on needs. Electronic magnetic switches typically offer higher sensitivity and speed, while reed-type switches may be more suitable for cost-sensitive applications.
Magnets in Magnetic Switches
Role of the Magnet
The magnet triggers the switch action. When it approaches the magnetic sensing element, it alters the magnetic field around the element, leading to an electrical signal or a change in its state. This electrical signal or change is subsequently converted into a switch signal to control the circuit.
When the magnet moves from left to right parallel to the reed switch, it can control the magnetic switch’s on and off states in the following manner.
Types of Magnets
| Neodymium Magnets: A high-performance permanent magnetic material with high energy density and coercivity, widely used in applications requiring strong magnetic fields.
| Ferrite Magnets: Traditional permanent magnetic materials, with relatively lower magnetic performance but are more economical, and suitable for applications with less stringent magnetic requirements.
| Rubber Magnets: Made from a composite material of magnetic powder and rubber, known for its flexibility, bendability, and ease of processing, suitable for installations requiring flexibility or complex shapes.
Generally, neodymium magnets and ferrite magnets are more commonly used.
Installation of Magnet
According to the principle of magnetic switches, the magnetic field must act on the two reeds, magnetizing them to opposite polarities and attracting each other to complete the switch action. To ensure the magnetic field effectively acts on the reeds, the magnetic field lines must pass through both reeds.
When using a bar magnet, the north and south poles of the magnet should be aligned parallel to the direction of the reed switch. In this case, when the magnet approaches, the reed switch will close; when it moves away, the switch will open. If the magnet moves vertically, it may not generate enough magnetic field variation, causing both reeds to have the same magnetic polarity and preventing the switch from activating.
Applications of Magnetic Switches
| Position Detection and Feedback: Magnetic switches are commonly used for detecting piston positions in cylinders or the movement state of mechanical components. When the magnetic switch approaches a magnet or magnetic material, its internal circuit changes, producing a corresponding signal. This signal can indicate whether the mechanical component has reached a predetermined position or can control the actions of other related devices.
| Safety Protection: Magnetic switches are often employed in safety protection mechanisms. For example, in machinery, when an abnormal situation or dangerous state is detected, a magnetic switch can quickly cut off power or trigger a safety device to prevent equipment damage or personal injury.
| Electrical Control: Magnetic switches function to turn circuits on and off, controlling the flow of current.
Magnet Manufacturer
At Tengye, we’re thrilled to be early participants in your new projects. Our passion for magnets extends from material selection and design optimization to providing magnetic solutions. We hope to bring our knowledge and experience to the forefront by actively engaging in your upcoming projects. Work with our magnet experts to get the right magnet solution.
Image Source: Hw2sw & Instrumentationtools & Magnelinkinc & Misensor & Rochestermagnet
