A push button switch, also known as a control button, is a common mechanical low-voltage electrical switch used to control circuits. Press the button manually to start or stop. It is often used to control equipment such as lights and electrical appliances to control small currents of 5A and below. It can be used as an instruction to implement functions on electrical equipment. They come in various shapes and sizes depending on the application scenario and design requirements. The main features of push button switches are easy to use, simple appearance and straightforward functions.
The push button switch consists of a button cap, a return spring, a bridge movable contact, a static contact and a terminal. In addition to buttons, push button switches also come in the form of knobs. According to different design requirements, the push button switch can control the circuit to be connected continuously or temporarily.
When the button is pressed, the movable contact will disconnect the upper static contact and connect to the lower static contact. The status of the two pairs of contacts changes. The normally closed contact opens and the normally open contact closes.
According to application scenarios and design requirements, common button categories include the following:
Open type: usually installed on the panel of control cabinets and consoles.
Protective type: There is a shell to protect the internal parts from damage.
Waterproof type: The shell is sealed to prevent water.
Anti-corrosion type: It can prevent corrosive gas from causing damage to the internal parts of the button.
Explosion-proof type: It will not be affected and cause explosions in explosive areas.
Knob type: The operating contact is realized by rotating the button during use.
Key type: It requires a key rotation to operate. It is usually used to prevent unauthorized personnel from misoperation or the button is operated by a dedicated person.
Emergency type: This type of button is larger and red and is used for emergency power disconnection in hazardous areas.
Self-sustaining type: generally installed on the panel for operators to implement instructions.
Illuminated type: There is a ring of light around the button for signal indication and aesthetics.
Combined type: Use multiple buttons in combination.
Interlocking type: Multiple contacts are interconnected and locked.
Push button switches are widely used, and choosing high-quality push button switches is the priority. We can choose the appropriate product based on the function of the equipment and the needs of the environment, as well as the purchase budget and manufacturer qualifications.
There are four elements for selecting a push button switch: switch type, contact capacity, operation mode and protection level.
Switch type: Choose the appropriate switch type according to the function and application scenario of the device, normally open switch or normally closed switch, etc.
Contact capacity: Select the appropriate contact capacity according to the load on the circuit to ensure that the switch can withstand the current.
Operation mode: Choose the appropriate operation mode according to the actual use needs of the button switch.
Protection level: Confirm the appropriate protection level according to the environment in which the equipment is located, especially in harsh environments.
When the button is pressed, the circuit is connected and the button switch is a normally open switch. When the button is pressed, the circuit is disconnected and the button switch is a normally closed switch. Using a multimeter to measure is also a method, Set the multimeter to the on-off position and use two test leads to touch different contacts. If the multimeter beeps, it means that the contact is a normally closed point. If there is no buzzing sound, it means that this contact is a normally open point. Of course, it is also possible that the internal parts of the button are damaged.
The symbol for a normally open switch is “NO”, which means “Normally Open”.
Normally open switches are the most common type of switch. When normally open switches are not in use, they are in an inactive state. When normally open switches are used, they connect and activate a circuit. A light switch is a typical normally open switch that connects the circuit to allow current to flow through a series of connected light bulbs. Examples of normally open switches include juicers, ovens, sewing machines, optical instruments and some industrial machine tools.
The symbol of a normally closed switch is “NC”, which means “Normally Closed”.
When there is only a normally closed switch in a circuit, current is always flowing through the circuit. When a normally closed switch is used, the contacts will separate, the current will be interrupted, and the load equipment will stop working. For example, some large machines are usually equipped with emergency stop buttons, which are eye-catching red mushroom-shaped buttons. They are normally closed switches. Press the emergency stop button and the machine will stop. Examples of normally closed switches include water heater temperature control switch, water level switch and fire alarm switch.
During use, push button switches will always experience some failures due to external factors or the influence of time.
The circuit does not connect or remains connected after pressing the button switch: it may be caused by the internal components of the button switch being stuck, having poor contact, or falling off.
The circuit status does not reset after releasing the push button switch: This may be because the return spring inside the push button switch is damaged.
The service life of push button switches can usually reach hundreds of thousands of times. Regular maintenance can extend the service life of push button switches.
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