The key switch mainly refers to the light-touch key switch, also known as the touch switch. The key switch is an electronic switch and belongs to electronic components. It first appeared in Japan. When in use, press the switch in the operating direction to meet the operating force. When the pressure is released, the switch is closed, and its internal structure is switched on and off through the stress change of the metal spring. The key switch consists of an insert, a base, an elastic sheet, a button and a cover. A layer of polyimide film is added to the elastic sheet of the waterproof key switch.

Function of key switch: Generally, key switch does not directly control the on and off of the main circuit (high current circuit), but only sends out command signals in the control circuit (low current circuit) to control electrical appliances such as contactors and relays, and then control the on and off of the main circuit, function conversion or electrical interlocking. Usually, the button consists of a button cap, a reset spring, a bridge-type moving contact, a static contact, a support rod and a shell. When the button is not subjected to external force (i.e. static), the on and off state of the contact can be divided into a stop button (i.e. a moving breaking button), a start button (i.e. a moving closing button) and a composite button (i.e. a button that combines the moving closing and moving breaking contacts into one).

Precautions for key switch installation: 1. When key switches are installed on the panel, they should be arranged reasonably and neatly. According to the starting sequence of the motor, they can be arranged from top to bottom or from left to right. 2. The button switch should be installed firmly and the wiring should be reliable. Usually the red button means stop, and the green or black button means start or power on. Do not make mistakes during installation. 3. Since the distance between the contacts of the push-button switch is small, once it is stained with oil, short circuit failure is easy to occur, so keep the contacts clean. 4. The button plate and button box should be made of metal, and try to connect them to the main grounding busbar of the machine tool. For the hanging button, a special grounding wire should be provided, and the metal tube should not be used as the grounding wire. 5. When the button is used in high temperature occasions, it is easy to deform, and the plastic ages, resulting in looseness, causing a short circuit between the connecting screws. Insulated plastic tubes can be added to the connecting screws to prevent short circuits. 6. The push-button switch with an indicator light is easy to deform the plastic lampshade due to the heat of the bulb. The bulb voltage should be reduced to extend the service life. 7. The "stop" button should be red, the "emergency stop" button should be a red mushroom head, and the "start" button should be equipped with a protective retaining ring. The protective retaining ring should be higher than the button head to avoid accidental touch and cause malfunction of the electrical equipment.

The push-button switch may be a simpler component in the electrical circuit, but it does control the lifeblood of the entire control circuit, so it is also called the "master switch". As a novice, understanding various push-button switches and using them skillfully and flexibly can achieve twice the result with half the effort.