What Is a Detection Switch?
A detection switch is a switch used to detect the position of an object and turn it on and off or switch circuits.
They operate by detecting infrared, microwave, magnetism, light, vibration, or pressure. When a switch is used to detect contact, infrared, magnetism, light, or heat, the switch is operated by the change in electrons or resistance emitted when the built-in sensing element detects light, etc. The switch is operated by the change in electrons or resistance emitted when the built-in detection element detects light, etc.
Applications of Detection Switches
Detection switches are used in stores, residences, products, production plants, and experimental equipment. When selecting a detector switch, it is necessary to consider size, detection accuracy, noise immunity, and durability.
The following are examples of detection switches in use.
- Automatic door systems that detect the approach of a person using infrared rays and activate the system
- Systems in factories that detect the passage of objects and sound an alarm
- Detection systems for IC cards and magnetic strip cards at entrance gates
Principle of Detection Switches
Among detection switches, this section explains the detection methods of switches that operate by contact, switches that operate by magnetism, switches that operate by light, and switches that operate by temperature change.
- Contact type: In the case of contact sensing, the change in pressure due to contact is measured by the amount of change in resistance of the sensing element using a diaphragm or the like, and the switch is operated. Other methods include mechanical contact actuation by contact.
- Magnetic type: Detects the amount of change in magnetism using a sensing element such as a reed switch, Hall element, or magnetoresistive element to drive the switch. Depending on the type of sensing element used, there are switches that do not require a power supply, switches that can respond quickly, and switches with high sensitivity.
- Optical type: Switches are operated by detecting light using a sensing element called a photodiode. A photodiode is a sensing element that converts light into electricity.
- Thermal type: A thermal resistive element, whose resistance changes with temperature, is used as a sensing element to operate the switch. A diaphragm or the like is used to detect the amount of resistance changed by temperature.
Types of Detection Switches
There are two types of detection switches: “contact type” and “non-contact type” as the first type of detection method.
1. contact-type detection switch
Contact-type detection switches are a method that switches the contact points by the action of a physical force. Since the sensing body directly contacts the switch to switch the circuit, there is no error in detection, but there is a disadvantage that the physical contact causes the detection switch to malfunction and deteriorate over time.
2. non-contact detection switches
Non-contact detection switches are detection switches activated by magnetism or light. Unlike contact-type switches, there is no direct contact with the sensing element, so the main body of the sensing switch has a long service life. However, they tend to be more expensive than simple contact-type detection switches.