The working principle of the latching switch function
Abstract: The simplest switch has two pieces of metal called “contacts”. When two contacts are in contact, the current forms a loop, and when the two contacts are not in contact, the current opens. When using contact metal, it is necessary to consider the degree of corrosion resistance, because most of the metal will form insulation after oxidation.
The simplest switch has two pieces of metal called “contacts”. When two contacts are in contact, the current forms a loop, and when the two contacts are not in contact, the current opens. When using contact metal, it is necessary to consider its anti-corrosion degree, because most of the metal will form an insulating oxide after oxidation, causing the contact to fail to work properly. The use of contact metal also needs to consider factors such as its electrical conductivity, hardness, mechanical strength, cost and whether it contains toxicity. Occasionally, corrosion-resistant metal is plated on the contact, and it is generally plated on the contact surface of the contact to avoid affecting its performance due to oxides. Sometimes non-metallic conductive materials, such as conductive plastics, are also used on the contact surface. In addition to the contacts of the push button switch, there are also movable parts that make the contacts conductive or non-conductive. The switches can be divided into lever switches, key switches, rocker switches, etc. depending on the movable parts, and movable parts can also be another type of mechanical connection.
Close the power switch K2, and then press the button switch K1. At this time, the crystal diodes V1 and V2 are turned on, and the relay is closed. At the same time, the power supply charges the capacitor C. When K1 is disconnected, because C has been charged, it will discharge through R and V1V2, thereby maintaining the transistor to continue to conduct, and the relay is still closed. After a period of discharging, when the voltage between the two poles of C drops to a certain value, it is not enough to maintain the transistor to continue to conduct, and then the relay is released. The time interval from K1 disconnection to relay release is called delay time. It depends on the size of R and C. Generally, when C is 100 microfarads, a delay time of 10 seconds to 90 seconds can be obtained by adjusting the adjustable resistor R. If C is 1000 microfarads, the delay time can reach more than 5 minutes.
The diode connected in parallel on the relay plays a protective role to prevent the transistor from being damaged by high voltage due to self-inductance when the relay is released from power failure.
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