What is the meaning of the normally open/normally closed contact of the key switch? What is the difference?

The key switch has the advantages of small contact resistance load, accurate operating force error, and diversified specifications, and has been widely used in electronic equipment and white goods. Because of the environmental conditions of the key switch (elastic force with pressure less than 2 times/environmental temperature and humidity conditions and electrical performance), large equipment and high-load buttons are directly replaced by conductive rubber or dome switch hardware shrapnel, such as medical equipment, TV. machine remote control, etc. So do you know what the normally open/normally closed contact of the key switch means? What's the difference?

Key switch NO/NC contact introduction
First, the terminal color distinguishes normally open and normally closed contacts
Some key switches can be distinguished from the color of the terminals. This is to avoid operation errors. Generally, the button caps are made of different colors. Green (or blue) is a normally open contact, and red (or pink) is a normal contact. Close the contact.
Second, the terminals distinguish between normally open and normally closed contacts
Normally open and normally closed contacts can be directly distinguished from the terminals. Generally speaking, the upper end is a normally closed contact, and the lower end is a normally open contact. This is the easiest way to distinguish, but not all can be distinguished by this method. Normally open and normally closed contacts also have certain errors.
Third, use a multimeter to accurately measure normally open and normally closed contacts
1. First, adjust the multimeter to the on-off position, that is, the diode beeping position, and then use two test pens to separate the two contacts of the contact button. If the beeping sound, it means that the contact is normally closed (NC), otherwise it is normal. Open (NO). We can press the button to measure the test again, and we will find that the result is exactly the opposite of the above.
2. First, adjust the multimeter to resistance torsion, which is 1K, and use two test pens to separate the two contacts of the contact button. The resistance value is the normally closed point (the resistance value is very small, between 0.2-1 under normal conditions, This is the internal resistance of the multimeter), the non-resistance value is the normally open point. We can press the button to measure the test again, and we will find that the result is exactly the opposite of the above.
What is the use of the two contacts of the normally open and normally closed switch key switch: the normally closed contact is used to connect the circuit when you press it down, and the normally open contact is to start used, normally closed contacts are not used.

Under normal conditions, there will be a holding relay in this circuit to keep the circuit connected. In this way, when you release the button, the circuit still maintains the power state through the maintenance relay, so that the system can operate normally. Until a termination signal such as a closed button or an emergency stop arrives. Because some occasions need to use normally open contacts, and some occasions need to use normally closed contacts, for example, the start button should be normally open, and the stop button should be normally closed. A contact (constituting a normally open contact and a normally closed contact), it is different from our lighting panel switch, the difference is that once the button is released, the contact will return to the state when it is not pressed (there are also buttons that can be held). The keys do not function for maintenance. The lighting panel switch is a circuit breaker, which plays the role of overload protection and short-circuit protection. After it is closed, if there is no fault condition, it will remain closed until someone pulls it open.

The main uses of key switches are color TV sets, black and white TV sets, audio equipment, video recorders, video cameras, computers, game consoles, fax machines, walkie-talkies, batons, machine tool control devices, copiers, printers, electronic instruments, meters and other household appliances.

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