The Ultimate Guide: How to Choose a High-Quality DC Latching Solenoid

There are several key factors to consider when selecting a quality latching solenoid. Understanding the travel requirements is essential to determining the right solenoid for your specific needs. Force requirements are a key aspect to consider as it directly impacts the performance of the solenoid. Additionally, the amount of energy produced by the holding solenoid plays a major role in its function. Turn-on and turn-off times are also important considerations as well as the operating environment and application operating frequency. Let’s delve deeper into these factors to help you make an informed decision when selecting a holding solenoid.

Part 1  Introduce :

1.1 what is a latching solenoid

A latching solenoid is a specialized electromechanical device known for its unique ability to maintain its position even after power is interrupted. These solenoids integrate permanent magnets into their flux path, providing unique advantages in energy savings and operating efficiency. This introduction takes an in-depth look at the working principles, types, and features of latching solenoids to gain a comprehensive understanding of their properties and applications.

1.2  How it works

Central to the functionality of a self-locking solenoid is its unique ability to utilize a permanent magnet. During operation, the plunger of the solenoid is pulled into the solenoid body by the electromagnetic force generated by the energized coil. Permanent magnets embedded in the flux path significantly assist this process, enhancing the electromagnetic force. Once the plunger is pulled to the retracted position, it will remain there even if the power is cut off. This is due to the magnetic field generated by the integrated permanent magnet, which continues to exert a force on the plunger, ensuring its position is maintained. Therefore, self-locking solenoids are very energy efficient, requiring power only during initial activation.

1.3 Types of latching solenoids

Single latching solenoid and double latching solenoid are two types of latching solenoid devices. The description of 2 types of latching solenoid as below:

Single Latching Solenoid

How it works: It usually built in only one solenoid coil and one latching mechanism. When the solenoid coil is energized, the plunger moves to a specific position, and then the latching mechanism holds it in that position. When the power is cut off, the plunger returns to its original position by  a spring. For example, in some simple door lock systems, a single latching solenoid is used. When the user operates the switch to energize the solenoid, the plunger tongue extends to lock the door. Once the power is removed, the bolt of plunger retracts under the action of the spring, unlocking the door.

Double latching solenoid

Working Principle: Also called a bistable latching solenoid, it has two solnoid coils inside, usually labeled Coil A and Coil B. When Coil A is energized and Coil B is not energized, the plunger moves to one position. Even if solenoid coil A is later de-energized, the plunger will remain in that position. To move the plunger back to its original position or another position, Coil B needs to be energized. For example, in some industrial control valves, dual latching solenoids are used to control the open and closed states of the valve.

The Comparison     

Structural design

Single-holding latching solenoid:  a permanent magnet is set at one end of the frame based on an ordinary frame type solenoid. The solenoid coil structure is simple..

Double-holding latching solenoid: It adopts a double-coil structure, with the permanent magnet located between the two coils, and the structure is more complex.

Working principle

Single-holding latching solenoid: When powered on, the coil create a magnetic field to move the plunger toward the core to the end position; after power is off, the slide bar remains in this position by the action of the permanent magnet. If the slide bar is to return, a reverse voltage or current needs to be applied.

Double-holding latching solenoid: When one of the coils is powered on, a magnetic field is generated to move the plunger to the corresponding position and hold it in the position; after power is off, the plunger remains in this position by the action of the permanent magnet and the magnetic field. To move the plunger to the other side, the other coil needs to be powered on.

Retention force characteristics

Single-holding latching solenoid: Only one end has retention force, there is force when pushing out, and there is no additional retention force except the rebound force of the spring when pulling back.

Double holding latching solenoid: Both ends can provide holding force, and the stroke and holding force at both ends are the same. The push-pull force in the self-holding state is usually twice that of the single holding type.

Control method

Single holding latching solenoid : The control is relatively simple. It only needs to control the power on, power off and reverse power on of the coil to realize the push, hold and reset of the plunger.

Double holding latching solenoid: It is necessary to control the power on and power off of the two solenoid coils separately to accurately control the switching of the plunger between two different positions. The control is relatively complex.

Application

Single holding latching electromagnet: It is suitable for occasions where the position or state only needs to be maintained in one direction, such as door openers, simple locks, automatic door devices, etc. These applications are cost-sensitive and have no demand for bidirectional holding functions.

Double holding latching electromagnet: It is often used in automation equipment, robots, and precision instruments that have high requirements for position control accuracy and need to be accurately maintained in two different positions, such as automatic sorting systems and positioning devices for CNC equipment.

Power consumption and efficiency

Single holding  latching solenoid: In the holding state, since only the permanent magnet at one end is working, the power consumption is relatively low, especially compared with ordinary electromagnets that need to be continuously powered to maintain the position.

Dual holding  latching solenoid: Although it does not need to be continuously powered in the holding state, due to the dual coil structure, a larger current may be required to overcome the magnetic field force when switching positions, and the power consumption may be relatively high in some cases. However, it has high efficiency and reliability when realizing the bidirectional holding function.

Part 2 : Characteristics of latching solenoid

Self-locking solenoids are known for their unique properties that make them widely used in various industries. One of the most outstanding features is its bistable operation. This means that the solenoid can maintain two stable positions without any powered. This feature reduces energy consumption and heat generation, making the latching solenoids ideal for battery-powered or energy-sensitive applications.

Another key feature is its robust construction. Latching solenoids are typically made from high-quality materials and are designed to withstand harsh operating environments while providing long-term reliability. Permanent magnets integrated into the structure ensure a strong and consistent magnetic flux, which is essential for maintaining the plunger's position. Additionally, many latching solenoids are designed with low power consumption in mind, requiring only minimal electrical input to actuate. This, combined with the solenoid’s ability to remain in place without continuous power, can result in significant savings in long-term operating costs.

Force requirements , This force is the amount of suction or thrust that the electromagnet produces from a distance when energized. Whether it is for a sliding door or other application, understanding the force requirements will ensure that the electromagnet is effective for the task at hand.

Energy is another important consideration when choosing a holding electromagnet. The energy required to push an object from one location to another is directly related to the power of the electromagnet. The greater the energy, the more powerful the electromagnet is, and therefore suitable for applications that require higher levels of force and performance.

Keeping the electromagnet powered on and off is also an important factor to consider. The longer the electromagnet is powered on, the higher its temperature will be, which will affect its power and kinetic energy. Knowing these time parameters will help select an electromagnet that can withstand the required operating time without affecting its performance.

The operating environment of the holding solenoid is equally important. Factors such as average temperature, relative humidity, and the thermal resistance rating of the materials used in the solenoid design are crucial to ensuring its durability and reliability under specific environmental conditions.

Finally, the application operating frequency and the power supply and distribution system are critical considerations. Understanding the operating frequency and power requirements will ensure that the electromagnet can be seamlessly integrated into the intended application without any supply and demand conflicts.

Part 3 :  Applications and Benefits

The unique properties and characteristics of latching solenoids make them very useful in a variety of applications. They are widely used in **automotive systems** for functions such as locking mechanisms, throttle control and valve operation. The ability to maintain its position without continuous power makes it ideal for these applications, helping to improve energy efficiency and system reliability. Additionally, they are used in **medical equipment** to provide precise control and reliability in applications such as fluid control valves and diagnostic machinery.

In the industrial sector, self-locking solenoids are essential for automation processes, providing reliable and energy-efficient solutions for machine controls, conveyor systems and safety mechanisms. The benefits of using self-locking solenoids in these applications include reduced energy costs, improved operating efficiency, and enhanced system reliability. Its robust construction ensures a long service life, reducing maintenance costs and downtime. By choosing self-locking solenoids, the industry can achieve more sustainable and cost-effective operations.

Single latching solenoid is commonly used in simple automatic door locks, some single-action pneumatic control systems, and low-power control devices in some household appliances.

Double latching solenoid are widely applied in aerospace solenoid valve control systems, satellite antenna positioning mechanisms, ventilators and other medical equipment that require precise control, high-precision industrial automation production lines, etc.

Part 4  Conclusion

Latching solenoids offer significant advantages in energy savings and operating efficiency with their unique combination of permanent magnet integration, bistable operation, and rugged construction. Understanding how it works, its various types, and its unique characteristics can help in selecting the right solenoid for a specific application. Their ability to maintain position without continuous power supply makes them indispensable in a variety of fields, from automotive systems to industrial automation, resulting in more energy-efficient and economical solutions. By leveraging the unique properties of latching solenoids, industries can improve the performance and sustainability of their operations.

In summary, when selecting a high-quality latching or holding solenoid, you must consider force requirements, energy, power-on and power-off times, operating environment, application operating frequency, and power supply and distribution systems. By carefully evaluating these factors, you can select an solenoid that meets the specific needs of your application and ensures optimal performance and reliability.