Many people who are not majors in electronics and structure often mistake themselves for language masters, and foolishly think that micro switches and tact switches are actually the same thing. We have a great responsibility for the seller of the switch. Today we will take you to a good understanding of the difference between the micro switch and the tact switch.
What is a tact switch?
Before we understand the principle of the tact switch, let's first understand what a tact switch is. The tact switch is a common electronic switch and belongs to the category of mechanical action. It is composed of plastic parts, base, slingshot shrapnel, handle button and cover plate. When using it, it is a kind of component that can be connected to the circuit by lightly pressing it, and it will be disconnected when the hand is released
The micro switch is a contact mechanism with a small contact interval and a snap-action mechanism, and a contact mechanism that performs the switching action with a specified stroke and a specified force. Small, hence the name micro switch, also called sensitive switch.
Also known as sensitive switch, snap switch. Pressure actuated quick switch. For door switches in anti-theft systems, etc.
The working principle of the tact switch is to press the inner shrapnel through the button handle, so that the inner shrapnel contacts the contact point of the base, so that the switch is turned on; The contact mechanism of the switch action is covered by the outer casing, with a driver outside, and the shape is small; the mechanical principle of the two is the same, so they are both called switches.
A brief description of the tact switch:
(1) Touch switch is also called key switch, English name: TOUCH SWITCH, TCAT SWITCH. Generally, it is called by its external dimensions: such as 6*6*5, which is its length, width and height. It belongs to a kind of electronic switch, which is different from the wall switch for household use. The difference lies in the difference in the application field and the structural function of itself, so it is called an electronic switch. Divided into: push type and surface mount touch type. The difference between the two is the volume and the welding form. The push type is mainly a plug-in type switch with a larger volume; the surface mount touch type is mainly a SMD ultra-thin type. The tact switch is to press the handle to press the shrapnel to conduct the contact stroke between the shrapnel and the gun point. Therefore, it can be divided into three forms, one is normally open type, one is normally closed type, and the other is double action type. There are also three types of switch pins: one is a two-foot switch, a three-foot switch, a four-foot switch, and a five-foot switch.
(2) The switch is evolved from the dome, which is the first membrane switch to be used. Its structure is single and the production speed is fast. However, the product has a short lifespan and single performance cannot meet market demands. According to the higher and higher demand for product performance, simple dome slices have been gradually eliminated from the market. What follows is that we touch the switch, and the principle of its use is the same. It is an upgraded version of Dome Pie, and its heart is the Dome Pie. Looks like Iron Man.
At the beginning of use, consumers only have requirements for the quality and performance of products. With the improvement of products in the market and the improvement of consumption levels, the quality and performance of products also begin to fail to satisfy consumers. Anyone who is familiar with this switch knows that the switch has its feel, which is simply the strength of the switch. Tact, key, toggle, and micro-motion are all strength parameters. Industry standard: micro power 30-100gf, key strength 250-400gf, dial power 200-400gf, light touch 50-400gf. The quality of the hand is directly related to the quality of the strength. The smaller the positive and negative tolerance range of the force, the better the hand feel. The positive and negative tolerance range of the domestically produced shrapnel is larger, and the value is plus or minus 50; the positive and negative tolerance range of the shrapnel produced in South Korea is relatively medium, and the value is plus or minus 30; imported from Japan The shrapnel of Pinzan is also the best in the world. The range of positive and negative tolerances of the Japanese ternary shrapnel used by Pinzan is very small, and the value is plus or minus 10. Summary: The higher the precision of the shrapnel, the better the touch switch feels.
The working principle of the switch: press the switch button during work to turn on the switch, and when the button is released, the switch is turned off, and its internal structure is realized by the force of the metal shrapnel. The metal shrapnel mentioned in the working principle is referred to as shrapnel, and there are two kinds of materials for the shrapnel. The shrapnel is made of phosphor bronze and stainless steel. The electroplating process is silver-plated and gold-plated. The gold-plated and silver-plated processes of Pinzan are both above 0.3um. The electroplating process directly affects the electrical performance of the product and the oxidation resistance of the product.
(3) There are many reasons for the poor hand feel. The structure of the switch itself is unreasonable, the material of the shrapnel and the electroplating process are not up to standard, the shrapnel is deformed, and the error range of the shrapnel is large. How do we ensure its feel, develop and produce a reasonable structure, use stainless steel shrapnel, control the shrapnel error and the shrapnel defect rate. The quality of the feel will directly depend on the sales and reputation of the product. A good brand and a good product have very high requirements on the switch feel. The quality of hand feel has a great influence on the life of the switch itself. The life of domestic shrapnel is between 3-5W times; the life of Korean shrapnel is between 5-8W times; the life of Japanese ternary shrapnel used by Pinzan is 10- Between 100W times. A good shrapnel directly affects the feel, life and quality of the switch.
The height of the button handle can be customized according to the requirements. The general surface of the thin patch has no button handle and is covered by the film. The principle is the same. The height of the plug-in handle is 1.0, 1.5, 2.5, 3.5-28mm, and it is customized according to customer product requirements. It has two kinds of internal structures, one is silent and the other is sound. The general-purpose type is sound, and there is a "tick" sound. There are many kinds of button strengths: 70gf, 90gf, 120gf, 160gf, 180gf, 200gf, 250gf, 300gf, 400gf and other customized strengths. The selection of button strength is based on different products. For example, mouse products, children's products, medical products, and smart home products generally use light strength, and household appliances, automobiles, air purifiers, and sports equipment generally use heavy strength. Positioned according to the market demand of the product. There is a great relationship between the key strength and the mechanical life of the tact switch. The lighter the strength, the higher the lifespan. Life: 3W-5W, 5W-8W, 8W-10W, 10W, 20W, 30W, 50W, 100W times life. The life span has a lot to do with the choice of shrapnel of the switch. The life of domestic shrapnel is 3W-5W, 5W-8W; the life of Korean imported shrapnel is 8W-10W; the life of Japanese imported ternary shrapnel is 10W, 20W, 30W, 50W, 100W.
(4) The switch is turned on and off by the force of the internal metal shrapnel, and the distance between the metal piece and the base bubble point is called the stroke. The stroke is divided into long stroke, short stroke and medium stroke, and its stroke is determined according to the structural size and performance requirements of the switch itself. The shortest lower limit of the short stroke is 0.8mm, which is called a small stroke, and an ultra-thin type is generally used. The middle stroke is between 0.13-0.3mm, which is generally used in plug-in type. The long stroke is between 3.0 and 0.5, and is generally used in silicone buttons and gravity products. The smaller the stroke, the quieter the sound of the keys, and the higher the stroke, the louder the sound and the shorter the life. The stroke can be set according to the mechanism of the switch itself, and sound and silent effects can be achieved. Factors affecting the product: The most direct factor affecting the length of the stroke is the action force. The action force is usually divided into: light force (below 120g), heavy force (above 300g) and standard force (150-250g). The lighter the stroke, the longer its lifespan; on the contrary, the greater the stroke, the greater the strength and the longer its lifespan; the middle stroke is the most standard stroke, and its lifespan is moderate and very ergonomic, so it is widely used.
Basic internal structure analysis of micro switch:
What is the difference between a micro switch and a tact switch?
A brief description of the micro switch:
(1) General terms
Micro switch: A switch with a small contact interval and a snap-action mechanism, a contact structure that performs switching action with a specified stroke and a specified force, covered with a shell, and has a drive rod outside. (hereinafter referred to as switch) with contact: In the switch type, compared with the semiconductor switch with switching characteristics, the function of the switch is realized by the mechanical switch of the contact. Contact form : Electrical input and output circuits [shown in (16)] that form contacts according to various applications.
Rated value: generally refers to the value that is used as a guaranteed reference for switching characteristics and performance, such as rated current, rated voltage, etc., on the premise of specific conditions (type of load, current, voltage, frequency, etc.).
Resin fixation (molded terminal): After wiring the terminal area with lead wires, fill the area with resin to fix the area and eliminate the exposed live parts to improve the drip resistance.
Insulation resistance: refers to the resistance value between non-connected terminals, between each terminal and non-charged metal parts, and between each terminal and ground.
Withstand voltage: the critical value that does not cause insulation damage after applying high voltage to the specified measurement site for 1 minute.
Contact resistance: Indicates the resistance of the contact portion of the contact, but generally indicates the resistance value including the resistance of the spring and the conductor at the terminal portion.
Vibration resistance: Malfunction vibration When the microswitch is in use, the vibration range within which the contacts closed due to vibration will not be separated within a specified time.
Impact resistance: Durable impact means that the micro switch will not be damaged by the mechanical impact during transportation or installation, and the impact within the range that meets the operating characteristics.
Malfunction shock? Refers to the impact range that the contacts closed due to impact do not separate within a specified time when the micro switch is in use.
(2) Terms related to lifespan
Mechanical life: The switch life when the finger contacts are not energized and the overtravel (OT) is set to the specified value at the specified operating frequency.
Electrical life: The switching life when the rated load is connected to the contact and the overtravel (OT) is set to the specified value at the specified operating frequency.
(3) Standard test status
The test conditions for the switch are as follows.
Ambient temperature: 20±2℃, relative humidity: 65±5%RH, air pressure: 101.3kPa
(4) N level reference value
Indicates the failure level at a reliability of 60% (λ60).
λ60=0.5×10-6/time means that the failure rate is below times when the reliability is 60%.
(5) Shape and type of contact
(6) Contact interval
Four types of contact intervals are specified: 0.25mm, 0.5mm, 1.0mm, and 1.8mm. Contact spacing is a design goal. When using, if the minimum contact interval is required, please confirm and select separately. The general standard for contact spacing is 0.5mm. For the same switch mechanism, the smaller the contact interval, the smaller the MD, the higher the sensitivity, and the longer the mechanical life (life), but the DC breaking performance, vibration resistance and shock resistance are disadvantageous. The micro switch will lose contacts due to current switching, the contact interval becomes larger, and the sensitivity decreases as the MD increases. Therefore, in order to achieve high sensitivity, when using a micro switch with a contact interval of 0.25mm, it is necessary to maintain a small switching current to reduce the current. Contact loss due to switching. Products with large contact spacing, good vibration resistance, shock resistance and breaking performance.
(7) Snap-action mechanism
The snap action mechanism can make the movable contact move quickly from one fixed contact to the other fixed contact without being affected by the operating speed as much as possible. For example, even for a guillotine switch, if the handle is operated quickly, the action will become faster. However, the mechanism in which the speed of the handle is related to the speed of the contact movement is not called a quick-action type, but a slow-action type. The faster the contacts switch, the shorter the duration of arcing between the contacts.
In this way, the consumption and damage of the contacts are reduced, and stable characteristics can be maintained. However, in this switching speed, in addition to the speed limit (economic speed) that effectively reduces the amount of arcing, there is also a limit to mechanical problems. In particular, if the switching speed is too fast during closed circuit, the impact energy of the movable contact and the fixed contact will be reduced. If it becomes larger, the jumping phenomenon (vibration or friction closure) formed by the impact will generate an arc, which will seriously wear the contacts and sometimes fail to open the circuit, causing the contacts to melt. A spring mechanism having a dead point (a critical point of action when jumping from one state to another state) is generally used for a mechanism that performs such a rapid action.
The figure below shows an example of a microswitch snap action mechanism formed by combining a tension spring and a compression spring.
The operation principle of the double-throw (Z) snap-action mechanism is explained below.
As shown in the figure below, is the force relationship of the switch. In the free position where no external force is applied to the actuator, the reaction force F1 of the compression spring is in a balanced state due to the influence of two forces - F2 and F0. F0 is the pressure that pushes the movable contact c to the fixed contact b.
Then, a force is applied to a part of the tension spring through the actuator to displace the tension spring. At this time, the forces F1 and F2 at point N will increase in turn, and the included angle will be close to 180°. Soon, only F1 and F2 will be in a state of equilibrium. That is, F0=0. There is a sliding action from the free position to F0 = 0, which moves the contact horizontally and further bends the compression spring. From the position of F0=0, by further applying external force, the tension spring is slightly displaced, and a force -F0 in the opposite direction is generated, and the movable contact c is pressed out from the downward direction with the maximum force of the bending compression spring, and the movable contact c will move through the space to the opposite fixed contact a.
Using this principle of action, the micro switch switches contacts at the switch's inherent switching speed (leaving speed), regardless of the speed at which the external force is generated when the tension spring is pressed. The position when F0=0 is called the action position, which is basically the same as the position where a part of the tension spring passes through the dead center.
When the reset operation is performed by eliminating the external force, it is also based on the same principle, and the bending reaction force of the spring at this time is the reset motive force.
The difference between the application scope of micro switch and tact switch:
1. Micro switches are divided into small current, medium current and large current, so they are widely used in harsh environments such as electronics, machinery, medical care, automobiles, and aviation;
2. The tact switch has only a small current, and currently there is no product with a large current, so it is widely used in low-current control boards such as consumer electronics.
