Part 1 : Key point requirement for keyboard testing device Solenoid  

1.1 Magnetic field requirements

In order to effectively drive keyboard keys, keyboard testing device Solenoids need to generate sufficient magnetic field strength. The specific magnetic field strength requirements depend on the type and design of keyboard keys.  Generally speaking, the magnetic field strength should be able to generate sufficient attraction so that the key press stroke meets the trigger requirements of the keyboard design. This strength is usually in the range of tens to hundreds of Gauss (G).

1.2 Response speed requirements

The keyboard testing deviceneeds to test each key quickly, so the response speed of the solenoidis crucial. After receiving the test signal, the solenoid should be able to generate sufficient magnetic field in a very short time to drive the key action. The response time is usually required to be at the millisecond (ms) level. the rapid pressing and releasing of the keys can be accurately simulated, thereby effectively detecting the performance of the keyboard keys, including its parameters without any delay.

1.3 Accuracy requirements

The action accuracy of the solenoidis crucial for accurately。The keyboard testing device. It needs to accurately control the depth and force of the key press. For example, when testing some keyboards with multi-level trigger functions, such as some gaming keyboards, the keys may have two trigger modes: light press and heavy press. The solenoid must be able to accurately simulate these two different trigger forces. Accuracy includes position accuracy (controlling the displacement accuracy of the key press) and force accuracy. The displacement accuracy may be required to be within 0.1mm, and the force accuracy may be around ±0.1N according to different test standards to ensure the accuracy and reliability of the test results.

1.4  Stability requirements

Long-term stable operation is an important requirement for the solenoidof the The keyboard testing device. During the continuous test, the performance of the solenoidcannot fluctuate significantly. This includes the stability of the magnetic field strength, the stability of the response speed, and the stability of the action accuracy. For example, in large-scale keyboard production testing, the solenoid may need to work continuously for several hours or even days. During this period, if the performance of the electromagnet fluctuates, such as the weakening of the magnetic field strength or the slow response speed, the test results will be inaccurate, affecting the evaluation of product quality.

1.5  Durability requirements

Due to the need to frequently drive the key action, the solenoidmust have high durability. The internal solenoid coils and plungermust be able to withstand frequent electromagnetic conversion and mechanical stress. Generally speaking, Keyboard testing device solenoid need to be able to withstand millions of action cycles, and in this process, there will be no problems that affect performance, such as solenoid coil burnout and core wear. For example, using high-quality enameled wire to make coils can improve their wear resistance and high temperature resistance, and choosing a suitable core material (such as soft magnetic material) can reduce the hysteresis loss and mechanical fatigue of the core.

Part 2 :. Structure of keyboard tester solenoid

2.1 Solenoid Coil

• Wire material: Enameled wire is usually used tomakethe solenoid coil. There is a layer of insulating paint on the outside of the enameled wire to prevent short circuits between the solenoid coils. Common enameled wire materials include copper, because copper has good conductivity and can effectively reduce resistance, thereby reducing energy loss when passing current and improving the efficiency of the electromagnet.
• Turns design: The number of turns is the key affecting the magnetic field strength of the tubular solenoid for Keyboard testing device Solenoid. The more turns, the greater the magnetic field strength generated under the same current. However, too many turns will also increase the resistance of the coil, leading to heating problems. Therefore, it is very important to reasonably design the number of turns according to the required magnetic field strength and power supply conditions. For example, for a Keyboard testing device Solenoidthat requires a higher magnetic field strength, the number of turns may be between hundreds and thousands.
• Solenoid Coil shape: The solenoid coil is generally wound on a suitable frame, and the shape is usually cylindrical. This shape is conducive to the concentration and uniform distribution of the magnetic field, so that when driving the keyboard keys, the magnetic field can act more effectively on the driving components of the keys.

2.2  Solenoid Plunger 

• Plungermaterial: The plungeris an important component of solenoid, and its main function is to enhance the magnetic field. Generally, soft magnetic materials such as electrical pure carbon steel and silicon steel sheets are selected. The high magnetic permeability of soft magnetic materials can make it easier for the magnetic field to pass through the core, thereby enhancing the magnetic field strength of the electromagnet. Taking silicon steel sheets as an example, it is a silicon-containing alloy steel sheet. Due to the addition of silicon, the hysteresis loss and eddy current loss of the core are reduced, and the efficiency of the electromagnet is improved.
• Plungershape: The shape of the core usually matches the solenoid coil, and is mostly tubular. In some designs, there is a protruding part at one end of the plunger, which is used to directly contact or approach the driving components of the keyboard keys, so as to better transmit the magnetic field force to the keys and drive the key action.

2.3 Housing

• Material selection: The housing of keyboard testing device Solenoidmainly protects the internal coil and iron core, and can also play a certain electromagnetic shielding role. Metal materials such as stainless steel or carbon steelare usually used.  Carbon steel housing has higher strength and corrosion resistance, and can adapt to different test environments.
• Structural design: The structural design of the shell should take into account the convenience of installation and heat dissipation. There are usually mounting holes or slots to facilitate the fixing of the electromagnet to the corresponding position of the keyboard tester. At the same time, the shell may be designed with heat dissipation fins or ventilation holes to facilitate the heat generated by the coil during operation to dissipate and prevent damage to the electromagnet due to overheating.

Part 3 : The operation of the keyboard testing device solenoid is mainly based on the principle of electromagnetic induction.

3.1.Basic electromagnetic principle

When current passes through the solenoid coil of the solenoid, according to Ampere's law (also called the right-hand screw law), a magnetic field will be generated around the electromagnet. If the solenoid coil is wound around the iron core, since the iron core is a soft magnetic material with high magnetic permeability, the magnetic field lines will be concentrated inside and around the iron core, causing the iron core to be magnetized. At this time, the iron core is like a strong magnet, generating a strong magnetic field.

3.2. For example, taking a simple tubular solenoid as an example, when the current flows into one end of the solenoid coil, according to the right-hand screw rule, hold the coil with four fingers pointing in the direction of the current, and the direction pointed by the thumb is the north pole of the magnetic field. The strength of the magnetic field is related to the current size and the number of coil turns. The relationship can be described by the Biot-Savart law. To a certain extent, the larger the current and the more turns, the greater the magnetic field strength.

3.3Driving process of keyboard keys

3.3.1. In keyboard testing device, when the keyboard testing device solenoid is energized, a magnetic field is generated, which will attract the metal parts of the keyboard keys (such as the shaft of the key or metal shrapnel, etc.). For mechanical keyboards, the key shaft usually contains metal parts, and the magnetic field generated by the electromagnet will attract the shaft to move downward, thereby simulating the action of the key being pressed.

3.3.2. Taking the common blue axis mechanical keyboard as an example, the magnetic field force generated by the electromagnet acts on the metal part of the blue axis, overcoming the elastic force and friction of the axis, causing the axis to move downward, triggering the circuit inside the keyboard, and generating a signal of key pressing. When the electromagnet is powered off, the magnetic field disappears, and the key axis returns to its original position under the action of its own elastic force (such as the elastic force of the spring), simulating the action of releasing the key.

3.3.3 Signal control and test process

1. The control system in the keyboard tester controls the power-on and power-off time of the electromagnet to simulate different key operation modes, such as short press, long press, etc. By detecting whether the keyboard can correctly generate electrical signals (through the keyboard's circuit and interface) under these simulated key operations, the function of the keyboard keys can be tested.

What is a tubular Solenoid ?

Tubular solenoid comes in two types: push and pull type. A push solenoid operates by pushing the plunger out of the copper coil when power on, while a pull solenoid works by pulling the plunger into the solenoid coil when power is applied.
Pull solenoid is generally more common product, as they tend to have a longer stroke length (the distance the plunger can move) compared to push solenoids. They are often found in applications like door locks, where the solenoid needs to pull a latch into place.
Push solenoids, on the other hand, are typically used in applications where a component needs to be moved away from the solenoid. For example, in a pinball machine, a push solenoid might be used to propel the ball into play.

Unit Features:- DC 12V 60N Force 10mm Pull Type Tube Shape Solenoid Electromagnet

GOOD DESIGN- Push pull Type, linear motion, open frame, plunger spring return, DC solenoid electromagnet. Less power consumption, low temperature rise, no magnetism when power off.

ADVANTAGES:- Simple structure, small volume, high adsorption force.copper coil inside, has good temperature stability and insulation, high electrical conductivity. It can be installed flexibly and quickly, which is very convenient.

NOTED:  As an actuating element of equipment ,because the current is large, the single cycle can not be electrified for a long time.The best operate time is in 49 seconds.

Dimension: φ 45 * 45 mm / 1.93 * 3.94 Inches.  Stroke Distance:  Mm ; 8-10 MM 

Principle of Tubular Solenoid 

The tubular solenoids ‘s structure is a direct-acting push and pull movement with a unique tubular shell design. The stable and smooth product surface ensures its softness and flexibility during operation.  We can make The diameter of tubular shell from 11mm to 70mm, Its characteristics are: long lifespan with 300,000 cycle time, quiet operation, fast response, stable action, and no radial vibration

Features :  

Unit Housing: Stainless steel housing enclosure, high shining and smooth surface, RoHs and Reach compliance. 
Plunger: φ10 mm  Carbon steel material
Voltage: DC24 V 
Stroke:  4 mm (adjustable according to the requirement) 
Force:  3 Kg
Power: 32 W
Current: 1.33 A
Resistance: 13.8 Ω
Lifespan cycles: ≥200,000 strokes
Temperature rise: max 65 degrees . Cel. 
Working Cycle: 1 s On, 3s Of

Application: 

It is suitable for all kinds of electric toys, office equipment, household appliances, etc. It can be designed into three structures: pull-type electromagnet/push-type electromagnet/push-pull electromagnet. It has the characteristics of simple structure and reliable action. The movable iron core connection part can be designed into various types to match your project. It is also called tubular electromagnet and tubular solenoid. Push-type means that the slide bar is attracted when the product is powered on, and the top rod on the slide bar is used to push the object. Pull-type means that the slide bar pulls the object when the product is powered on. It is designed according to the actual needs of the customer, and the push-pull force can generally be achieved. Usually, the small push-pull round tube electromagnet T2045 is used in life test equipment, electronic toys, etc.