What is a Reed Switch?

A reed switch is a type of electrical switch that is operated by a magnetic field. It consists of two thin ferromagnetic reeds that are hermetically sealed within a glass tube containing a low-pressure inert gas. The reeds are positioned alongside each other in the tube, with a small gap between them. When a magnetic field is applied to the switch, the reeds are attracted to each other and make contact, completing a circuit.

Reed switches were first developed in the 1930s and are widely used in various applications today. They are typically small in size, inexpensive, and reliable. Reed switches have a long life span, can operate in harsh environments, and can be used in low-power circuits.

How Does a Reed Switch Work?

A reed switch operates on the principle of magnetism. When a magnetic field is applied to the switch, the ferromagnetic reeds become magnetized and attract each other, closing the circuit. When the magnetic field is removed, the reeds demagnetize and return to their original position, opening the circuit.

Reed switches can be operated by either a permanent magnet or an electromagnet. When an electromagnet is used, the switch is called a “magnetic switch”. The strength of the magnetic field required to operate the switch depends on the sensitivity of the reed switch and the distance between the reeds.

Applications of Reed Switches

Reed switches are used in a wide range of applications, including:

• Security systems: Reed switches are used in door and window sensors to detect when they are opened or closed. They are also used in burglar alarms and other security systems.
• Automotive industry: Reed switches are used in automotive applications such as speedometers, fuel level sensors, and brake light switches.
• Medical equipment: Reed switches are used in medical equipment such as infusion pumps, ventilators, and blood analyzers.
• Telecommunications: Reed switches are used in telecommunication applications such as telephone relays, modems, and fax machines.
• Robotics: Reed switches are used in robotics for position sensing and limit switches.
• Consumer electronics: Reed switches are used in various consumer electronics such as cameras, laptops, and mobile phones.

Example Uses of Reed Switches

One example use of reed switches is in water level sensing. A reed switch is placed inside a plastic or metal float that moves up and down with the water level. As the float rises, it activates the reed switch, which in turn activates a pump or other device to control the water level.

Another example use of reed switches is in security systems. Reed switches are used in door and window sensors to detect when they are opened or closed. When the switch is activated, it sends a signal to the security system to trigger an alarm or alert.

In the automotive industry, reed switches are used in fuel level sensors. A reed switch is placed inside a float that moves up and down with the fuel level. When the float reaches a certain level, it activates the reed switch, which in turn sends a signal to the fuel gauge to display the fuel level.