As long as the above conditions are met, whether four or more switches are connected in this way or not.
The word switch is interpreted as on and off. It also refers to electronic components that can break the circuit, interrupt the current or make the current flow to other circuits. The most common switch is an electromechanical device operated by a person, which has one or several electronic contacts. Contact "closed" means that the electronic contact is on, allowing current to flow; The "open" of the switch means that the electronic contacts are not conductive to form an open circuit and no current is allowed to flow.
Basic classification
Divide by purpose
Waveform switch, band switch, recording and playback switch, power switch, preselection switch, limit switch, control switch, changeover switch, isolating switch, travel switch, wall switch, intelligent fire-fighting switch, etc.
Divide by structure
Micro switch, ship switch, toggle switch, toggle switch, button switch, key switch, membrane switch, intelligent fire switch, safer steel frame switch, etc.
Press the switch to count the points.
Single control switch
double control switch
Multi-control switch
Dimming switch
Speed regulating switch
Splash box
doorbell switch
inductive switch
touch switch
remote switch
Intelligent switch
Plug-in switch
Yuba special switch
network switch
Basic structure
The simplest switch has two pieces of metal called contacts. When two contacts are in contact, the current forms a loop, and when two contacts are not in contact, the current is disconnected. The corrosion resistance should be considered when selecting the contact metal, because most metals will form insulating oxides after oxidation, which will make the contact unable to work normally. The selection of contact metal should also consider its conductivity, hardness, mechanical strength, cost and toxicity.
Corrosion-resistant metals are sometimes electroplated on contacts. Generally, it will be plated on the contact surface of the contact to avoid the influence of oxide on its performance. Sometimes nonmetallic conductive materials, such as conductive plastics, are used for contact surfaces.
In addition to the contacts, there will be moving parts to make the contacts conductive or non-conductive. Switches can be divided into toggle switches, key switches and rocker switches. According to the different movable parts, the movable parts can also be other types of mechanical links.
Delay switch
Delay switch is a kind of switch that delays the switching circuit by using the electronic component relay installed in the switch. Delay switches are divided into voice-controlled delay switches, light-controlled delay switches and touch-type delay switches. The principle of delay switch is the principle of electromagnetic relay. The working principle of relay is that when the relay coil is energized, the iron core in the coil generates strong electromagnetic force, which attracts the armature to drive the reed, so that the contacts 1 and 2 are disconnected and 1 and 3 are connected. When the coil is powered off, the spring resets the reed, so that the contacts 1 and 2 are connected, and 1 and 3 are disconnected. As long as we connect the circuit to be controlled between the contacts 1 and 2 (1 and 2 are called normally closed contacts) or between the contacts 1 and 3 (called normally open contacts), we can use relays to achieve some control purpose.
principle of operation
Turn off the power switch K2, and then press the button switch K 1. At this time, the crystal diodes V 1 and V2 are turned on, and the relay is attracted. At the same time, the power supply charges the capacitor C. When K 1 is turned off, because C has been charged, it will discharge through R and V 1V2, thus keeping the transistor on and the relay on. After a period of discharge, when the voltage between the two poles of C drops to a certain value, it is not enough to keep the triode on, and the relay is released. The time interval from K 1 disconnection to relay release is called delay time. Depending on the size of R and C, when C is generally 100 microfarad, the delay time of 10 to 90 seconds can be obtained by adjusting the adjustable resistor R, and if C is 1000 microfarad, 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 the high voltage generated by self-induction when the relay is powered off and released.
Specification for printed circuit boards and components
The printed circuit board of the delay switch circuit is shown in Figure 3-26(A). See Figure 3-26 (b) for the physical map.
Component specifications:
J relay 4098 working voltage 6V 1V2 transistor 90 14v crystal diode 2CP 10 or 1N400 1 R adjustable resistor 100k C electrolytic capacitor100U/6Kk/kl.
Tact Switch
Touch switch touch switch can be turned on by lightly clicking the switch button when in use, and turned off by releasing the hand. Its internal structure is opened and closed by the elasticity of metal shrapnel. Such as IKI series touch switches.
Because of its small size and light weight, touch switch has been widely used in the field of electrical appliances, such as audio-visual products, digital products, remote control, communication products, household appliances, security products, toys, computer products, medical devices, car buttons and so on.
Double-control switches are generally used in two different places, such as the upper and lower floors of stairs or the two ends of walkways, which can independently control the lighting or extinguishing of the same lamp. As shown in the figure, three different connections are provided. S 1 and S2 are 1×2 SPDT switches, which can independently control the turn-on or turn-off of the lamp e. The connection in Figure (b) is easy to install, because each switch has a phase line and a zero line of the power supply, but special attention should be paid to the short circuit at both ends of the phase line and the zero line during maintenance.