A switch is an element used in electronic equipment to make contact, break, and convert circuits.
Principle of switch
The principle of a switch is that the “closed” state of a contact indicates that the electronic contact is conducting and allows current to flow; the “open” state indicates that the electronic contact is not conducting and forms an open circuit, and current is not allowed to flow.
Main parameters of switch components
Rated voltage: It refers to the safe voltage allowed when the switch is in normal operation. Applying a voltage greater than this value across the switch will cause arcing and breakdown between the two contacts.
Rated current: Refers to the maximum safe current allowed when the switch is turned on. When this value is exceeded, the contacts of the switch will be burned due to excessive current.
Insulation resistance: Refers to the resistance value between the conductor part and the insulation part of the switch. The insulation resistance value should be above 100 MΩ.
Contact resistance: Refers to the resistance value between each pair of contacts when the switch is in the on state. Generally, it is required to be below 0.1 - 0.5 Ω. The smaller this value, the better.
Characteristics of switch
Also known as a switching power supply or switch converter, it is a high-frequency power conversion device and a type of power supply. Its function is to convert a voltage of a certain level into the voltage or current required by the user end through different forms of architecture. The input of a switching power supply is mostly AC power (such as mains power) or DC power, and the output is mostly equipment that requires DC power, such as a personal computer. The switching power supply performs the conversion of voltage and current between the two.
The switching power supply is different from the linear power supply. The switching transistors used in the switching power supply mostly switch between the full-on mode (saturation region) and the full-off mode (cut-off region). Both of these modes have the characteristics of low dissipation. The conversion between switching has relatively high dissipation but for a very short time. Therefore, it is more energy-saving and generates less waste heat. Ideally, the switching power supply itself does not consume electrical energy.
Voltage stabilization is achieved by adjusting the conduction and cut-off time of the transistor. In contrast, in the process of generating the output voltage, the transistor in a linear power supply works in the amplification region and also consumes electrical energy itself. The high conversion efficiency of the switching power supply is one of its major advantages. Moreover, because the switching power supply operates at a high frequency, a small-sized and lightweight transformer can be used. Therefore, the switching power supply will also be smaller in size and lighter in weight than the linear power supply.
If high efficiency, volume, and weight of the power supply are key considerations, the switching power supply is better than the linear power supply. However, the switching power supply is relatively complex. The internal transistors will switch frequently. If the switching current is not properly handled, it may generate noise and electromagnetic interference that affects other equipment. Moreover, if the switching power supply is not specially designed, its power factor may not be high.
Function of switch
Push-button switches can achieve manual control of electrical equipment, thereby changing its on/off state. It mainly has the following functions:
Turn on/off electrical equipment: Control the turning on and off of electrical equipment by pressing the button. For example, the switch button on the TV remote control we use is a kind of push-button switch.
Control the operating mode of electrical equipment: Some push-button switches also have the function of selecting the operating mode of electrical equipment. For example, the wind speed switch on a fan and the cleaning program button on a washing machine.
Realize equipment linkage: Through the combination of multiple push-button switches, the linkage control of multiple electrical equipment can be achieved. For example, we can use the push-button switches in a smart home system to control all lights, curtains, audio equipment, etc. with one button.
Main classification of switches
Classification by use: Toggle switch, band switch, recording and playback switch, power switch, preselection switch, limit switch, control switch, transfer switch, isolation switch, travel switch, wall switch, intelligent fireproof switch, etc.
Classification by structure: Microswitch, rocker switch, toggle switch, slide switch, push-button switch, keypad switch, and the fashionable and trendy membrane switch and dot switch.
Classification by contact type: Switches can be classified into three types according to contact type: type A contact, type B contact, and type C contact. Contact type refers to the relationship between the operation status (“pressing” the switch and the contact is closed) and the contact state. A switch with an appropriate contact type needs to be selected according to the use.
Classification by number of switches: Single-control switch, double-control switch, multi-control switch, dimming switch, speed control switch, splash-proof box, doorbell switch, induction switch, touch switch, remote control switch, intelligent switch, card access power switch, and special switch for bathroom heater.
Address switch Limit switch Temperature switch SW-520D Ball Switch
Common types of switches
Delay switch is a kind of switch in a delay switch circuit where an electronic component relay is installed in the switch. Delay switches are further divided into sound-controlled delay switches, light-controlled delay switches, touch-type delay switches, etc.
Tactile switch. When in use, simply press the switch button lightly to turn on the switch. When you release your hand, the switch is disconnected. Its internal structure realizes on/off through the forceful bouncing of a metal dome.
Photoelectric switch is a member of the large family of sensors. It converts the change in light intensity between the transmitting end and the receiving end into a change in current to achieve the detection purpose. Because the output circuit and input circuit of the photoelectric switch are electrically isolated (i.e., electrically insulated), it can be applied in many occasions.
A new generation of photoelectric switch devices manufactured by adopting integrated circuit technology and SMT surface mount technology has intelligent functions such as delay, broadening, external synchronization, anti-interference, high reliability, stable working area, and self-diagnosis.
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