How To Select And Install A Magnetic Switch?

Magnetic switches are widely used in cylinder motion control due to their simplicity, reliability, and ease of use.But there are various installation methods for magnetic switches. How to choose the correct magnetic switch? How to correctly install magnetic switches?

The motion control of a cylinder relies on solenoid valve and magnetic switches to detect the position of the cylinder. Together, these components work in coordination to complete the cylinder's movement.

The main function of a magnetic switch is to detect whether the cylinder has extended or retracted to the specified position. Therefore, when installing magnetic switches, they are generally installed in pairs at both ends of the cylinder.

 When the piston inside the cylinder reaches the designated position, it sends an electrical signal, and the indicator light turns on.

Working Principle of Magnetic Switches

Magnetic switches can be classified into contact type and non-contact type. Contact type magnetic switches mainly include reed switches or magnetic reed switches, while non-contact magnetic switches include Hall effect switches, proximity switches, and magnetic field sensors, among others.

The characteristic of contact type switches is their simplicity and reliability, along with a low cost, but they can be affected by high-frequency vibrations. Non-contact magnetic switches, on the other hand, have better shock resistance but are more expensive.

In practical applications, contact type switches are used in the vast majority of cases, which is why magnetic switches are often referred to as reed switches.

A reed switch typically consists of a reed switch tube and a light-emitting diode (LED). The basic structure of the reed switch tube involves placing two metallic reeds inside a glass tube filled with inert gas. When a magnet is brought near, the reeds close the circuit, and when the magnet is removed, the reeds open the circuit.

When the piston inside the cylinder moves to the specified position, the magnetic ring on the piston affects the reed switch, causing the reeds to make contact, completing the circuit and causing the LED to light up. The solenoid valve then switches positions, and the piston stops moving. Once the piston leaves the position, the switch opens again.

It’s important to note that magnetic switches must be used in conjunction with cylinders equipped with magnetic rings.

Selection and Installation of Magnetic Switches

Based on practical experience, to choose the right magnetic switch, the type of cylinder must first be determined, as different types of cylinders have different installation methods, the corresponding magnetic switch models are different too.

Common installation methods include bracket mounting, band mounting, and rail mounting.

Next, consider the voltage specifications of the load. Common load specifications include DC 24V and AC 220V.

Finally, choose the type of switch wiring. Two-wire and three-wire switches each have their characteristics:

◆ Two-wire magnetic switches have a simple structure with physical contacts, are easy to use, and are commonly used for simple on/off control.

◆ Three-wire magnetic switches do not have physical contacts, are generally used for low-voltage DC loads, and provide additional signal output. They are often used in situations where a signal output is needed and must be linked with other electronic devices.

The two-wire magnetic switch has two colored wires: brown and blue.

Three-wire magnetic switches are further divided into PNP and NPN types, each with three colored wires: brown, blue, and black. The difference is that the PNP type has a 24V output on the black wire, while the NPN type has a 0V output on the black signal wire.

Magnetic Switches Installation Demonstration

Here, we will use the example of installing a two-wire type magnetic switch with a bracket for a SI cylinder tube:

First, place the magnetic switch into the slot on the bracket and tighten the fastening screws.

Next, install the bracket at the appropriate position on the cylinder and tighten the positioning screws on the other side.

Finally, connect the brown wire to the positive power terminal, the blue wire to the negative terminal, and install a magnetic switch at the other end of the cylinder tube to complete the installation.

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