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Reed switch
A Reed switch is a type of electrical switch that is activated by a magnetic field. It consists of two ferromagnetic reeds inside a glass tube, which are hermetically sealed and separated by a small gap. When a magnet is brought close to the switch, the magnetic field causes the reeds to come together, completing the electrical circuit.
Reed switches are commonly used in a variety of applications, such as in security systems to detect the opening of doors or windows, in level sensors to detect the level of liquids, in flow sensors to measure the flow of fluids, and in automotive systems to control lighting and other functions.
Reed switches have the advantage of being very reliable and durable, since they have no moving parts other than the reeds themselves. They are also very sensitive and can be used to detect very small magnetic fields. However, they do have some limitations, such as a relatively low maximum switching current and a limited number of switching cycles.
What is the working principle of reed switch?
The working principle of a reed switch is based on the interaction between magnetic fields and the ferromagnetic material of the switch. A reed switch consists of two thin, flat ferromagnetic reeds, typically made of nickel-iron or a similar alloy, which are positioned in a hermetically sealed glass tube.
When no external magnetic field is present, the reeds are separated by a small air gap and the switch is open, meaning that no current can flow through it.
However, when a magnetic field is applied to the switch, the ferromagnetic material of the reeds becomes magnetized and attracts each other, causing the reeds to come into contact and complete the electrical circuit. When the magnetic field no longer influences the switch, the reeds move back and close the switch.
The sensitivity of a reed switch depends on the strength of the magnetic field, the distance between the magnet and the switch, and the orientation of the magnetic field with respect to the reeds. Permanent magnets, electromagnets, and moving objects with magnetic fields trigger the use of Reed switches in applications.
How reed switch work?
Reed switches work on the principle of magnetism. They consist of two ferromagnetic reeds inside a glass tube, which are hermetically sealed and separated by a small gap. When a magnetic field is applied to the switch, the ferromagnetic material of the reeds becomes magnetized and attracts each other, causing the reeds to come into contact and complete the electrical circuit.
When no external magnetic field is present, the reeds are separated by a small air gap, and the switch is open, meaning that no current can flow through it.
However, when a magnetic field is brought close to the switch, it causes the reeds to come together, completing the electrical circuit.
When the magnetic field is removed, the reeds return to their original position, and the switch opens again, breaking the circuit.
Reed switches are widely used in various applications, such as in security systems to detect the opening of doors or windows, in level sensors to detect the level of liquids, in flow sensors to measure the flow of fluids, and in automotive systems to control lighting and other functions.
They have the advantage of being very reliable and durable, since they have no moving parts other than the reeds themselves.
Type of reed switch
There are several different types of reed switches, including normally open (NO) reed switches, normally closed (NC) reed switches, and changeover reed switches. Normally open reed switches are open when no magnetic field is present, and close when a magnetic field is applied.
Normally closed reed switches are the opposite – they are closed when no magnetic field is present, and open when a magnetic field is applied. Changeover reed switches have both a normally open and normally closed contact.
Reed switches can also be classified by their size, sensitivity, and power rating. Some common types of reed switches include miniature reed switches, high power reed switches, and surface mount reed switches.
Advantages of reed switch
Reliable: Reed switches are very reliable and durable, as they have no moving parts other than the reeds themselves.
Low Power Consumption: Reed switches are very efficient and consume very little power.
Simple Operation: Reed switches are simple to use and operate, requiring only the presence or absence of a magnetic field to turn them on or off.
Compact Size: Small devices and systems can easily incorporate compact Reed switches.
Fast Response Time: Reed switches have a fast response time and can detect changes in magnetic fields almost instantly.
Disadvantages of reed switch
Limited Switching Cycles: Reed switches have a limited number of switching cycles, typically around 10 million cycles, after which the switch may fail.
Limited Current Handling: Reed switches may not be able to handle high-power applications due to their limitation to switching low current loads.
Sensitivity to Magnetic Fields: Magnetic fields can strongly affect Reed switches, causing them to trigger.
Limited Operating Temperature: Reed switches have limited operating temperatures, and extreme temperatures can cause the reed switch to malfunction.
Application
Reed switches have many applications in various industries. Some common uses of reed switches include:
Security Systems: Security systems commonly use Reed switches to detect the opening of doors or windows. When you open the door or window, you trigger the reed switch and activate the alarm by disrupting the magnetic field.
Proximity Sensors: Reed switches can detect magnetic fields as proximity sensors. Active voice: Industrial applications commonly use them to detect the position of moving objects or the presence of metallic objects.
Level Sensors: Level sensors can use Reed switches to detect the levels of liquids in tanks or reservoirs. When a float with a magnet attached to it moves up or down with the liquid level, it triggers the reed switch, indicating the level of the liquid.
Flow Sensors: Flow sensors can use Reed switches to measure the flow of fluids. Water meters frequently detect the flow of water through a pipe.
Automotive Applications: In automotive applications, Reed switches control lighting and other functions.
Medical Devices: Medical devices, including implantables, use Reed switches to detect magnetic fields and elicit a response.
Consumer Electronics: Consumers electronics devices, such as smartphones, can use Reed switches to detect the presence of a magnetic cover and turn the devices on or off.
FAQ
What does a reed switch sensor do?
Reed sensors make it easy to open and close automatic doors.
What is a reed switch example?
Magnet-actuated reed switches are commonly used in mechanical systems as proximity sensors. Some examples are door and window sensors in burglar alarm systems and tamper protection methods.
What size is a reed switch?
Over the years, the reed switch size has shrunk from about 50 mm (2 inches) to 3.9 mm (0.153 inches) or less.
How far away does the reed switch detect?
Proximity Reed switch BN 32
actuating magnet, the BN 32 magnetic reed switch is capable of actuating distances of up to 55 mm.
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