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AS 1325 B DC Linear Push and Pull Solenoid Tubular type for keyboard lifespan testing device

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

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.

product details

Product Description

Brand	Dr. Solenoid	Model Number	AS 1325 B
Rated Voltage (V)	DC 24 V	Rated Power(W)	5--7 W
Work Model	Tubular Push and PUll Type	Holding Force (N)	2 N
Stroke(mm)	3-5 MM	Reset Time(s)	1 S
Service Life	300 Thousand Times	Certification	CE,ROHS,ISO9001,
Material	Carbon Steel Housing with Zinc Plated Coating	Lead Wire Length(mm)	200
Install Style	Adjustable Screw	Tolerance of Dimension	+/- 0.1 MM
Water-proof	None	Insulation Class	F 155 Cel. Degree
Hi-Pot Test	AC 600V 50/60Hz 2s	Non-excitation Holding Force	0
Working Temperature	-10°C-100°C	Duty Cycle	1-100%
Thread Depth(mm)	/	Payment Term	TT, or LC At Sight
Sample Order	Yes	Warranty	1 Year
MOQ	500 pcs	Supply Ability	5000 pcs per Week
Delivery Time	30 Days	Port of Loading	shenzhen

Part 1 : How to design a keyboard tester solenoid according to requirements/

1.1. Test keyboard type

First, determine the type of keyboard to be tested, such as mechanical keyboard, membrane keyboard or capacitive keyboard. Different types of keyboard keys have different structures and trigger mechanisms. For example, mechanical keyboard keys have a shaft structure and a relatively large trigger force, generally between 45-70cN (centinewon), requiring the electromagnet to generate a strong magnetic field force to drive the key. The membrane keyboard key has a smaller trigger force, usually around 30-50cN, and the magnetic field force requirements of the electromagnet are relatively low.

1.2. At the same time, the layout and size of the keyboard keys must also be considered. The size and spacing of keyboard keys of different brands and models may be different, which will affect the size and installation position design of the electromagnet. For example, some compact keyboards have small key spacing, which requires the electromagnet to be not too large to avoid interfering with adjacent keys during testing.

2. Test parameter requirements

2.1. Test speed: If a large number of keyboard keys need to be tested in a short time, such as in the quality inspection link of an automated production line, the test speed may be required to be faster. This requires the electromagnet to have a high response speed and be able to complete the pressing and releasing of the keys in milliseconds. Generally speaking, for high-speed testing, the response time of the electromagnet should be less than 10ms.

2.2. Test accuracy: Test accuracy includes the accuracy of the key pressing depth and the trigger force. If you want to test high-end gaming keyboards or professional typing keyboards, these keyboards have high requirements for key triggering accuracy. For example, for gaming keyboards with multi-gear triggering functions, the electromagnet may need to accurately simulate the trigger force of different gears, with a force accuracy requirement of about ±0.1N, and the key pressing depth accuracy may need to be within 0.1mm.

2.3. Test function diversity: Consider whether you need to test special functions of the keyboard, such as key combinations (such as Ctrl + C, Ctrl + V and other shortcut keys), multimedia key functions, etc. If these functions need to be tested, the design of the electromagnet may need to be able to drive multiple keys at the same time or drive the keys in a specific order.

3 Keyboard testing device Solenoid specification consideration

3.1. Magnetic field strength design

According to the trigger force requirements of the test keyboard keys, the required magnetic field strength is calculated by the formula (Ampere force formula, where is Ampere force, is magnetic field strength, is current, is wire length, and is the angle between the current direction and the magnetic field direction). In actual design, the attraction required for key triggering is usually determined first, and then the required magnetic field strength is reversed based on the selected current, number of coil turns (related to wire length), etc.

3.2 solenoid coil design

3.2.1. Turn selection: The number of turns is related to magnetic field strength and resistance. According to the magnetic field strength requirements calculated above, combined with Ampere's loop theorem (where is the vacuum permeability, is the number of turns, is the current), the number of turns can be determined. At the same time, the coil resistance (is the wire resistivity, is the wire length, is the wire cross-sectional area) should be considered. Too many turns will increase the resistance and cause serious heating. Generally, on the premise of meeting the magnetic field strength requirements, the number of turns should be minimized to reduce the resistance.

3.2.2. Selection of wire material and wire diameter: Copper is usually used as the wire material because copper has low resistivity and good conductivity. The selection of wire diameter should consider the current passing through. According to the current density (is the current density, is the current, is the wire cross-sectional area), the current density generally does not exceed the allowable value to prevent the wire from overheating. For example, for larger currents (such as), it may be necessary to select thicker wires, such as copper wires with a wire diameter of about .

3.3.3. Coil shape design: The coil shape is generally cylindrical, which is conducive to the concentration and uniform distribution of the magnetic field. The diameter and length of the coil should be determined according to the size of the keyboard keys and the installation position of the electromagnet. For example, if the diameter of the keyboard key to be tested is, the outer diameter of the electromagnet coil may be designed to be about 8-9mm so that the magnetic field can be effectively applied to the key.

4. Plunger design

4.1 Plunger material selection: The plunger material is made of soft magnetic materials, such as electrical pure iron, silicon steel sheets, etc. Electrical pure iron has high magnetic permeability, but the hysteresis loss is relatively large; silicon steel sheets can effectively reduce hysteresis loss and eddy current loss. If the efficiency and stability of the electromagnet are required to be high, especially under high-frequency working conditions, silicon steel sheets are a better choice.

4.2 plunger shape and size design: The core shape is usually cylindrical, which matches the coil. The size of the core is determined according to the magnetic field strength requirements and the coil size. The length of the core is generally slightly smaller than the coil length, and the diameter is slightly smaller than the inner diameter of the coil to ensure that the coil can be tightly wound around the core and the magnetic field can be effectively concentrated around the core. For example, if the inner diameter of the coil is, the plunger diameter can be designed to be about 5-5.5mm.

5. Structural design

5.1. housing design : Material selection: The shell material can be aluminum or stainless steel. Aluminum shell is light and has good heat dissipation; stainless steel shell is strong and corrosion-resistant. If the working environment of the electromagnet is relatively harsh, such as in a humid or corrosive gas environment, a stainless steel shell is more suitable.

5.2. Structural design: The shell should be designed with mounting holes or slots to facilitate the fixing of the electromagnet to the corresponding position of the keyboard tester. At the same time, heat dissipation design should be considered, such as setting heat dissipation fins or ventilation holes on the shell. If the heat generated by the electromagnet is large during operation, the heat dissipation fins can increase the heat dissipation area and improve the heat dissipation efficiency. For example, for a high-power electromagnet, the shell can be designed with multiple ventilation holes, and the size and number of the ventilation holes should be calculated and determined according to the heat dissipation requirements.

6. Interface design with the keyboard

6.1. Design the contact part between the electromagnet and the keyboard key to ensure that the magnetic field force can be accurately transmitted to the key. For different types of keyboard keys, the shape and material of the contact part may be different. For example, for a mechanical keyboard key, the contact part can be designed as a small metal column that can make good contact with the metal part of the key shaft; for a membrane keyboard, the contact part can be designed as a flat shape to evenly apply pressure on the key surface.

6.2. At the same time, it is necessary to consider that the movement stroke of the electromagnet matches the trigger stroke of the keyboard key. According to the trigger depth requirements of the keyboard key, design the movement range of the electromagnet when driving the key. For example, the keyboard key trigger depth is 2-3mm, and the movement stroke of the electromagnet should also be designed within this range to ensure that the pressing and releasing of the key can be accurately simulated.

Part 3 : Common problems with keyboard tester electromagnets?

Magnetic field strength related issues

Insufficient magnetic field strength

· Reasons:

· Coil turns problem: There may be too few coil turns. According to the law of electromagnetic induction, the magnetic field strength is proportional to the number of coil turns. If the number of turns is lower than expected during the design or manufacturing process, the magnetic field strength will be insufficient. For example, during the production process, due to winding equipment failure or human error, the actual number of turns is much less than the design requirements.

·Current problem: The current passing through the electromagnet is less than the design requirements. This may be due to insufficient power supply, such as the power output of the power supply is reduced, the line resistance is too large, etc., resulting in a decrease in current. For example, the transformer inside the power supply is aging, causing the output voltage to decrease.